Powder dispersion-reinforced concrete of a new generation. A method for preparing a self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties and a method for manufacturing concrete products from the resulting mixture
Reaction powder concreteREACTION POWDER CONCRETE
New generation reaction-powder concretes (RPCs) are specific concretes of the future, not
having in its composition coarse-grained and lumpy aggregates. This distinguishes them from
fine-grained (sandy) and crushed stone concretes. Dry reaction powder concrete mixtures
(SRPBS), designed to obtain crushed-stone self-compacting concrete for
monolithic and prefabricated construction, can become a new, main type of composite binder
for the production of many types of concrete. High fluidity of reaction-powder concrete mixes
allows you to additionally fill them with crushed stone while maintaining fluidity and use them for
self-compacting high-strength concretes; when filling with sand and gravel - for vibrating
molding, vibropressing and calendering technologies. At the same time, concretes obtained by
vibration and vibro-force compaction technologies, may have higher strength than
cast concrete. At a higher degree, concretes for general construction purposes of classes are obtained
B20-B40.
Reactive powder concrete
REACTION POWDER CONCRETEDue to the fact that in powder concrete the volume concentration of cement is 22-25%, the particles
cement, in accordance with the previously proposed formula, do not contact each other, but are separated
water nanosized particles of microsilica, micrometric particles of ground sand and
fine grained sand. In such conditions, unlike conventional sandy and crushed stone concrete,
the topochemical mechanism of solidification is inferior to the through-solution, ion-diffusion
hardening mechanism. This is confirmed by simple but original control experiments.
hardening of composite systems consisting of small amounts of coarsely ground clinkers and
granular slag and a significant amount of fine marble at 10-12% water. IN
powdered concrete cement particles are separated by microsilica particles and stone flour.
Due to the thinnest shells of water on the surfaces of particles, the processes of hardening of powder
concrete flows very quickly. Their daily strength reaches 40-60 MPa and more.
The dispersed part of reaction-powder concrete, consisting of Portland cement, stone flour and
MK, responsible for high gravitational fluidity, has a significant water demand
without the addition of SP. With a composition with a ratio of C: KM: MK: Fri as 1: 0.5: 0.1: 1.5, the gravitational current
is implemented at a water-solid ratio equal to 0.095-0.11, depending on the type of MK. the largest
MK has water demand. Its suspension with water begins to spread at a water content of 110-120% by weight of the MC. Only in the presence of cement and SP does MK become a reactive component in an aqueous medium.
binder (SRPV)
ADVANTAGES OF DRY REACTION POWDERBINDER (SRPV)
1. Extremely high strength RPV, reaching 120-160 MPa., Significantly exceeding
strength of superplasticized Portland cement due to the transformation of "ballast" lime into
cementing hydrosilicates.
2. The multifunctionality of the physical and technical properties of concrete with the introduction of short
dispersed steel fibers: low water absorption (less than 1%), high frost resistance (more
1000 cycles), high axial tensile strength (10-15 MPa) and bending tensile strength (40-50
MPa), high impact strength, high resistance to carbonate and sulfate corrosion, etc.;
3. High technical and economic indicators of the production of SRPB at cement plants,
having a complex of equipment: drying, grinding, homogenization, etc.;
4. The widespread occurrence of quartz sand in many regions of the world, as well as stone
flour from ferrous and non-ferrous metals beneficiation technology by magnetic separation and flotation;
ADVANTAGES OF DRY REACTION POWDER
BINDER (SRPV)
5. Huge reserves of screenings of stone crushing during their complex processing into fine-grained
crushed stone and stone flour;
6. Possibilities of using the technology of joint grinding of the reaction filler, cement and
superplasticizer;
7. Possibilities of using SRPB for the manufacture of high-strength, extra-high-strength
crushed stone and sandy concrete of a new generation, as well as concrete for general construction purposes
by varying the ratio of aggregate and binder;
8. Possibilities of obtaining high-strength lightweight concretes on non-absorbent microglass and
microsolspheres with the implementation of high strength of the reaction-powder binder;
9. Possibilities of manufacturing high-strength adhesive and ligaments for repair work.
(SRPW)
The use of dry reaction-powder binder (RPB)
APPLICATION OF DRY REACTION POWDER BINDER(SRPW)
Dry reaction-powder concrete mixes (SRPBS) intended for obtaining crushed-stone-free
self-compacting concrete for monolithic and prefabricated construction, can become a new, basic
type of composite binder for the production of many types of concrete. High fluidity
reaction-powder concrete mixes allows you to additionally fill them with crushed stone while maintaining
fluidity and use them for self-compacting high-strength concretes; when filled with sand
crushed stone - for vibration technologies of molding, vibropressing and calendering. Wherein
concretes obtained using vibration and vibro-force compaction technologies may have more
higher strength than cast concrete. At a higher degree, concretes are obtained
general construction purposes of classes B20-B40.
Compressive strength, MPa
Compound
reaction powder
concrete with 0.9% Melflux 2641 F
V/T
0,1
V/C
Consistency
cone blur
0,31
Higermann
290 mm
Raft
Water absorption
o-shchenie
ness
by weight
,
%
kg/m3
2260
0,96
after
steaming
under normal
conditions
hardening
through
1 day
through
28 days
through
1 day
through
28 days
119
149
49,2
132
Efficient use of reaction-powder concrete mix
EFFICIENT USE OF REACTION POWDERCONCRETE MIXTURE
When filling the reaction-powder concrete mix with sand and high-strength crushed stone,
concrete with a strength of 120-130 MPa with cement costs in terms of heavy concrete equal to 300-350
kg/m3. These are just a few examples of the rational and efficient use of SRPBS. Promising
the possibility of using SRPBS for the manufacture of foam concrete and aerated concrete. They use
portland cement, the strength of which is lower than that of RPB, and the structural processes of self-hardening during
time flows more fully with the latter.
An increase in the operational reliability of products and structures made of such concretes is achieved
dispersed reinforcement with thin short steel fibers, glass and basalt fibers.
This allows you to increase the axial tensile strength by 4-5 times, the tensile strength in bending
6-8 times, impact strength 15-20 times compared to concrete grades 400-500.
01.06.2008 16:51:57
The article describes the properties and capabilities of high-strength powder concretes, as well as areas and technologies for their application.
High rates of construction of residential and industrial buildings with new and unique architectural forms and especially special especially loaded structures (such as large-span bridges, skyscrapers, offshore oil platforms, tanks for storing gases and liquids under pressure, etc.) required the development of new effective concretes. Significant progress in this has been especially noted since the late 1980s. Modern high-quality concretes (HKB) classify a wide range of concretes for various purposes: high-strength and ultra-high-strength concretes [see. Bornemann R., Fenling E. Ultrahochfester Beton-Entwicklung und Verhalten.// Leipziger Massivbauseminar, 2000, Bd. 10; Schmidt M. Bornemann R. Möglichkeiten und Crensen von Hochfestem Beton.// Proc. 14, Jbausil, 2000, Bd. 1], self-compacting concretes, highly corrosion resistant concretes. These types of concrete meet the high requirements for compressive and tensile strength, crack resistance, impact strength, wear resistance, corrosion resistance, and frost resistance.
Undoubtedly, the transition to new types of concrete was facilitated, firstly, by revolutionary achievements in the field of plasticizing concrete and mortar mixtures, and secondly, the emergence of the most active pozzolanic additives - silica fume, dehydrated kaolins and fine ash. Combinations of superplasticizers and especially environmentally friendly hyperplasticizers based on polycarboxylate, polyacrylate and polyglycol base make it possible to obtain superfluid cement-mineral dispersed systems and concrete mixes. Thanks to these achievements, the number of components in concrete with chemical additives reached 6–8, the water-cement ratio decreased to 0.24–0.28 while maintaining plasticity, characterized by a cone draft of 4–10 cm. flour (KM) or without it, but with the addition of MK in highly workable concretes (Ultrahochfester Beton, Ultra hochleistung Beton) on hyperplasticizers, in contrast to those cast on traditional joint ventures, the perfect fluidity of concrete mixes is combined with low sedimentation and self-compacting with spontaneous removal of air.
"High" rheology with a significant water reduction in superplasticized concrete mixtures is provided by a fluid rheological matrix, which has different scale levels of the structural elements that make it up. In crushed stone concrete for crushed stone, the cement-sand mortar serves as a rheological matrix at various micro-mesolevels. In plasticized concrete mixtures for high-strength concretes for crushed stone as a macrostructural element, the rheological matrix, the proportion of which should be much higher than in ordinary concretes, is a more complex dispersion consisting of sand, cement, stone flour, microsilica and water. In turn, for sand in conventional concrete mixtures, the rheological matrix at the micro level is a cement-water paste, the proportion of which can be increased to ensure fluidity by increasing the amount of cement. But this, on the one hand, is uneconomical (especially for concretes of classes B10 - B30), on the other hand, paradoxically, superplasticizers are poor water-reducing additives for Portland cement, although they were all created and are being created for it. Almost all superplasticizers, as we have shown since 1979, "work" much better on many mineral powders or on their mixture with cement [see. Kalashnikov V.I. Fundamentals of plasticization of mineral dispersed systems for production building materials: Dissertation in the form of a scientific report for the degree of Dr. tech. Sciences. - Voronezh, 1996] than on pure cement. Cement is an unstable in water, hydrating system that forms colloidal particles immediately after contact with water and quickly thickens. And colloidal particles in water are difficult to disperse with superplasticizers. An example is clay slurries that are difficult to superfluidize.
Thus, the conclusion suggests itself: it is necessary to add stone flour to the cement, and it will increase not only the rheological effect of the joint venture on the mixture, but also the proportion of the rheological matrix itself. As a result, it becomes possible to significantly reduce the amount of water, increase the density and increase the strength of concrete. The addition of stone powder will practically be equivalent to an increase in cement (if the water-reducing effects are significantly higher than with the addition of cement).
It is important here to focus not on replacing part of the cement with stone flour, but on adding it (and a significant proportion - 40–60%) to Portland cement. Based on the polystructural theory in 1985–2000. all works on changing the polystructure were aimed at replacing 30–50% of Portland cement with mineral fillers to save it in concrete [see. Solomatov V.I., Vyrovoy V.N. et al. Composite building materials and structures of reduced material consumption. - Kyiv: Budivelnik, 1991; Aganin S.P. Concretes of low water demand with modified quartz filler: Abstract for the competition of an account. degree cand. tech. Sciences. - M, 1996; Fadel I. M. Intensive separate technology of concrete filled with basalt: Abstract of the thesis. cand. tech. Sciences - M, 1993]. The strategy of saving Portland cements in concretes of the same strength will give way to the strategy of saving concrete with 2–3 times higher strength not only in compression, but also in bending and axial tension, and impact. Saving concrete in more openwork structures will give a higher economic effect than saving cement.
Considering the compositions of rheological matrices at different scale levels, we establish that for sand in high-strength concretes, the rheological matrix at the micro level is a complex mixture of cement, flour, silica, superplasticizer and water. In turn, for high-strength concretes with microsilica for a mixture of cement and stone flour (equal dispersity) as structural elements, another rheological matrix appears with a smaller scale level - a mixture of silica fume, water and superplasticizer.
For crushed concrete, these scales of the structural elements of rheological matrices correspond to the scales of the optimal granulometry of the dry components of concrete to obtain its high density.
Thus, the addition of stone flour performs both a structural-rheological function and a matrix-filling one. For high-strength concretes, the reactive-chemical function of stone flour is no less important, which is performed with a higher effect by reactive microsilica and microdehydrated kaolin.
The maximum rheological and water-reducing effects caused by the adsorption of SP on the surface of the solid phase are genetically characteristic of finely dispersed systems with a high interface.
Table 1.
Rheological and water-reducing action of SP in water-mineral systems
Type of dispersed powder and plasticizer | Dosage SP,% | ||
CaCO3 (Mg 150) | |||
BaCO3 (Melment) | |||
Ca(OH)2 (LST) | |||
Cement PO "Volskcement" (C-3) | |||
Opoka of the Penza deposit (S-3) | |||
Ground glass TF10 (S-3) |
Table 1 shows that in Portland cement casting slurries with SP, the water-reducing effect of the latter is 1.5–7.0 times (sic!) Higher than in mineral powders. For rocks, this excess can reach 2–3 times.
Thus, the combination of hyperplasticizers with microsilica, stone flour or ash made it possible to raise the level of compressive strength to 130–150, and in some cases to 180–200 MPa or more. However, a significant increase in strength leads to an intensive increase in brittleness and a decrease in Poisson's ratio to 0.14–0.17, which leads to the risk of sudden destruction of structures in emergency situations. Getting rid of this negative property of concrete is carried out not so much by reinforcing the latter with rod reinforcement, but by combining rod reinforcement with the introduction of fibers from polymers, glass and steel.
The fundamentals of plasticizing and water reduction of mineral and cement dispersed systems were formulated in the doctoral dissertation of Kalashnikov V.I. [cm. Kalashnikov VI Fundamentals of plasticization of mineral dispersed systems for the production of building materials: Dissertation in the form of a scientific report for the degree of Doctor of Science. tech. Sciences. - Voronezh, 1996] in 1996 on the basis of previously completed work in the period from 1979 to 1996. [Kalashnikov V. I., Ivanov I. A. On the structural-rheological state of extremely liquefied highly concentrated disperse systems. // Proceedings of the IV National Conference on Mechanics and Technology of Composite Materials. - Sofia: BAN, 1985; Ivanov I. A., Kalashnikov V. I. Efficiency of plasticization of mineral disperse compositions depending on the concentration of the solid phase in them. // Rheology of concrete mixes and its technological tasks. Tez. report of the III All-Union Symposium. - Riga. - RPI, 1979; Kalashnikov V. I., Ivanov I. A. On the nature of plasticization of mineral dispersed compositions depending on the concentration of the solid phase in them.// Mechanics and technology of composite materials. Materials of the II National Conference. - Sofia: BAN, 1979; Kalashnikov VI On the reaction of various mineral compositions to naphthalene-sulfonic acid superplasticizers and the effect of instant alkalis on it. // Mechanics and technology of composite materials. Materials of the III National Conference with the participation of foreign representatives. - Sofia: BAN, 1982; Kalashnikov VI Accounting for rheological changes in concrete mixes with superplasticizers. // Proceedings of the IX All-Union Conference on Concrete and Reinforced Concrete (Tashkent, 1983). - Penza. - 1983; Kalashnikov VI, Ivanov IA Peculiarities of rheological changes in cement compositions under the action of ion-stabilizing plasticizers. // Collection of works "Technological mechanics of concrete". – Riga: RPI, 1984]. These are the prospects for the directed use of the highest possible water-reducing activity of the joint venture in finely dispersed systems, the features of quantitative rheological and structural-mechanical changes in superplasticized systems, which consist in their avalanche-like transition from solid-state to fluid states with a super-small addition of water. These are the developed criteria for gravitational spreading and post-thixotropic flow resource of highly dispersed plasticized systems (under the action of its own weight) and spontaneous leveling of the day surface. This is the advanced concept of the limiting concentration of cement systems with finely dispersed powders from rocks of sedimentary, magmatic and metamorphic origin, selective in terms of high water reduction to SP. The most important results obtained in these works are the possibility of a 5–15-fold reduction in water consumption in dispersions while maintaining gravitational spreadability. It was shown that by combining rheologically active powders with cement, it is possible to enhance the effect of the joint venture and obtain high-density castings. It is these principles that are implemented in reaction-powder concretes with an increase in their density and strength (Reaktionspulver beton - RPB or Reactive Powder Concrete - RPC [see Dolgopolov N. N., Sukhanov M. A., Efimov S. N. new type cement: structure of cement stone. // Construction Materials. - 1994. - No. 115]). Another result is an increase in the reducing action of the joint venture with an increase in the dispersion of the powders [see. Kalashnikov VI Fundamentals of plasticization of mineral dispersed systems for the production of building materials: Dissertation in the form of a scientific report for the degree of Doctor of Science. tech. Sciences. – Voronezh, 1996]. It is also used in powdered fine-grained concretes by increasing the proportion of finely dispersed constituents by adding microsilica to the cement. A novelty in the theory and practice of powdered concrete was the use of fine sand with a fraction of 0.1–0.5 mm, which made the concrete fine-grained, in contrast to ordinary sandy sand with a fraction of 0–5 mm. Our calculation of the average specific surface of the dispersed part of powder concrete (composition: cement - 700 kg; fine sand fr. 0.125–0.63 mm - 950 kg; basalt flour Ssp = 380 m2/kg - 350 kg; kg - 140 kg) with its content of 49% of the total mixture with fine-grained sand of a fraction of 0.125–0.5 mm shows that with a dispersion of MK Smk = 3000m2 / kg, the average surface of the powder part is Svd = 1060m2 / kg, and with Smk = 2000 m2 /kg - Svd = 785 m2 / kg. It is on such finely dispersed components that fine-grained reaction-powder concretes are made, in which the volume concentration of the solid phase without sand reaches 58–64%, and together with sand - 76–77% and is slightly inferior to the concentration of the solid phase in superplasticized heavy concretes (Cv = 0, 80–0.85). However, in crushed concrete, the volume concentration of the solid phase minus crushed stone and sand is much lower, which determines the high density of the dispersed matrix.
High strength is ensured by the presence of not only microsilica or dehydrated kaolin, but also a reactive powder from ground rock. According to the literature, fly ash, baltic, limestone or quartz flour are mainly introduced. Wide opportunities in the production of reactive powder concretes opened up in the USSR and Russia in connection with the development and research of composite binders of low water demand by Yu. M. Bazhenov, Sh. T. Babaev, and A. Komarom. A., Batrakov V. G., Dolgopolov N. N. It was proved that the replacement of cement in the process of grinding VNV with carbonate, granite, quartz flour up to 50% significantly increases the water-reducing effect. The W / T ratio, which ensures the gravitational spreading of crushed stone concrete, is reduced to 13–15% compared to the usual introduction of joint venture, the strength of concrete on such VNV-50 reaches 90–100 MPa. In essence, on the basis of VNV, microsilica, fine sand and dispersed reinforcement, modern powder concretes can be obtained.
Dispersion-reinforced powder concretes are very effective not only for load-bearing structures with combined reinforcement with prestressed reinforcement, but also for the production of very thin-walled, including spatial, architectural details.
According to the latest data, textile reinforcement of structures is possible. It was the development of textile-fiber production of (fabric) three-dimensional frames made of high-strength polymer and alkali-resistant threads in developed foreign countries that was the motivation for the development more than 10 years ago in France and Canada of reaction-powder concretes with joint ventures without large aggregates with extra fine quartz aggregate filled with stone powders and microsilica. Concrete mixtures from such fine-grained mixtures spread under the action of their own weight, filling the completely dense mesh structure of the woven frame and all filigree-shaped interfaces.
"High" rheology of powder concrete mixes (PBS) provides with a water content of 10–12% of the mass of dry components, the yield strength?0= 5–15 Pa, i.e. only 5-10 times higher than in oil paints. With such a value of 0, it can be determined using the miniareometric method developed by us in 1995. The low yield strength is ensured by optimal thickness layers of rheological matrix. From the consideration of the topological structure of the PBS, the average thickness of the interlayer X is determined by the formula:
where is the average diameter of sand particles; is the volume concentration.
For the composition below, with W/T = 0.103, the thickness of the interlayer will be 0.056 mm. De Larrard and Sedran found that for finer sands (d = 0.125–0.4 mm) the thickness varies from 48 to 88 µm.
An increase in the interlayer of particles reduces the viscosity and ultimate shear stress and increases fluidity. Fluidity can be increased by adding water and introducing SP. In general, the effect of water and SP on the change in viscosity, ultimate shear stress, and yield strength is ambiguous (Fig. 1).
The superplasticizer reduces the viscosity to a much lesser extent than the addition of water, while the yield strength reduction due to SP is much greater than that due to the influence of water.
Rice. 1. Effect of SP and water on viscosity, yield strength and yield strength
The main properties of superplasticized ultimate filled systems are that the viscosity can be quite high and the system can flow slowly if the yield strength is low. For conventional systems without SP, the viscosity may be low, but the increased yield strength prevents them from spreading, because they do not have a post-thixotropic flow resource [see. Kalashnikov VI, Ivanov IA Peculiarities of rheological changes in cement compositions under the action of ion-stabilizing plasticizers. // Collection of works "Technological mechanics of concrete". – Riga: RPI, 1984].
The rheological properties depend on the type and dosage of the joint venture. The influence of three types of joint ventures is shown in fig. 2. The most effective joint venture is Woerment 794.
Rice. 2 Influence of the type and dosage of SP on?o: 1 - Woerment 794; 2 - S-3; 3 – Melment F 10
At the same time, it was not the domestic SP S-3 that turned out to be less selective, but the foreign SP based on the melamine Melment F10.
The spreadability of powdered concrete mixtures is extremely important in the formation of concrete products with woven volumetric mesh frames laid in a mold.
Such voluminous openwork-fabric frames in the form of a tee, an I-beam, a channel and other configurations allow for quick reinforcement, which consists in installing and fixing the frame in a mold, followed by pouring suspension concrete, which easily penetrates through the frame cells with a size of 2–5 mm (Fig. 3) . Fabric scaffolds make it possible to radically increase the crack resistance of concrete under the influence of alternating temperature fluctuations and significantly reduce deformations.
The concrete mixture should not only easily pour locally through the mesh frame, but also spread when filling the form by "reverse" penetration through the frame with an increase in the volume of the mixture in the form. To assess the fluidity, powder mixtures of the same composition were used in terms of the content of dry components, and the spreadability from the cone (for the shaking table) was controlled by the amount of SP and (partially) water. Spreading was blocked with a mesh ring 175 mm in diameter.
Rice. 3 Fabric scaffold sample
Rice. 4 Splashes of the mixture with free and blocked spreading
The mesh had a clear dimension of 2.8 × 2.8 mm with a wire diameter of 0.3 × 0.3 mm (Fig. 4). Control mixtures were made with melts of 25.0; 26.5; 28.2 and 29.8 cm. As a result of the experiments, it was found that with an increase in the fluidity of the mixture, the ratio of the diameters of free dc and blocked flow db decreases. On fig. 5 shows the change in dc/dbotdc.
Rice. 5 Change dc/db from free spread dc
As follows from the figure, the difference in mixture spreads dc and db disappears at fluidity characterized by a free spread of 29.8 cm. At dc.= 28.2, the spread through the mesh decreases by 5%. Particularly large deceleration during spreading through the mesh is experienced by a mixture with a spread of 25 cm.
In this regard, when using mesh frames with a cell size of 3–3 mm, it is necessary to use mixtures with a spread of at least 28–30 cm.
Physical and technical properties of dispersed-reinforced powder concrete, reinforced by 1% by volume with steel fibers with a diameter of 0.15 mm and a length of 6 mm, are presented in table 2
Table 2.
Physical and technical properties of powder concrete on a binder of low water demand using domestic SP S-3
Property name | Unit | Indicators |
|
Density | |||
Porosity | |||
Compressive strength | |||
Flexural tensile strength | |||
Axial tensile strength | |||
Elastic modulus | |||
Poisson's ratio | |||
Water absorption | |||
Frost resistance | number of cycles |
According to foreign data, with 3% reinforcement, the compressive strength reaches 180–200 MPa, and with axial tension - 8–10 MPa. Impact strength increases more than tenfold.
The possibilities of powdered concrete are far from being exhausted, given the effectiveness of hydrothermal treatment and its influence on the increase in the proportion of tobermorite, and, accordingly, xonotlite.
- Was the information helpful? yes partly no
- 15444
CHAPTER 1 MODERN VIEWS AND BASIC
PRINCIPLES OF OBTAINING HIGH-QUALITY POWDER CONCRETE.
1.1 Foreign and domestic experience in the use of high-quality concrete and fiber-reinforced concrete.
1.2 The multicomponent nature of concrete as a factor in ensuring functional properties.
1.3 Motivation for the emergence of high-strength and extra-high-strength reaction-powder concretes and fiber-reinforced concretes.
1.4 High reactivity of dispersed powders is the basis for obtaining high-quality concretes.
CONCLUSIONS ON CHAPTER 1.
CHAPTER 2 SOURCE MATERIALS, RESEARCH METHODS,
INSTRUMENTS AND EQUIPMENT.
2.1 Characteristics of raw materials.
2.2 Research methods, instruments and equipment.
2.2.1 Technology of preparation of raw materials and assessment of their reactive activity.
2.2.2 Technology for the manufacture of powder concrete mixes and me
Tody of their tests.
2.2.3 Research methods. Devices and equipment.
CHAPTER 3 TOPOLOGY OF DISPERSIVE SYSTEMS, DISPERSIVELY
REINFORCED POWDER CONCRETE AND
THE MECHANISM OF THEIR HARDENING.
3.1 Topology of composite binders and mechanism of their hardening.
3.1.1 Structural and topological analysis of composite binders. 59 P 3.1.2 The mechanism of hydration and hardening of composite binders - as a result of the structural topology of the compositions.
3.1.3 Topology of dispersed-reinforced fine-grained concretes.
CONCLUSIONS ON CHAPTER 3.
CHAPTER 4 RHEOLOGICAL STATE OF SUPERPLASTICIZED DISPERSIVE SYSTEMS, POWDER CONCRETE MIXTURES AND THE METHODOLOGY OF ITS EVALUATION.
4.1 Development of a methodology for evaluating the ultimate shear stress and fluidity of dispersed systems and fine-grained powder concrete mixtures.
4.2 Experimental determination of the rheological properties of disperse systems and fine-grained powder mixtures.
CONCLUSIONS ON CHAPTER 4.
CHAPTER 5 EVALUATION OF REACTIVE ACTIVITY OF ROCKS AND INVESTIGATION OF REACTION POWDER MIXTURES AND CONCRETE.
5.1 Reactivity of rocks mixed with cement.-■.
5.2 Principles for selecting the composition of powder dispersion-reinforced concrete, taking into account the requirements for materials.
5.3 Recipe for fine-grained powder dispersion-reinforced concrete.
5.4 Preparation of concrete mix.
5.5 Influence of compositions of powder concrete mixtures on their properties and axial compressive strength.
5.5.1 Influence of the type of superplasticizers on the spreadability of the concrete mixture and the strength of concrete.
5.5.2 Influence of superplasticizer dosage.
5.5.3 Influence of microsilica dosage.
5.5.4 Influence of the share of basalt and sand on strength.
CONCLUSIONS ON CHAPTER 5.
CHAPTER 6 PHYSICAL AND TECHNICAL PROPERTIES OF CONCRETE AND THEIR
TECHNICAL AND ECONOMIC ASSESSMENT.
6.1 Kinetic features of the formation of the strength of RPB and fibro-RPB.
6.2 Deformative properties of fiber-RPB.
6.3 Volumetric changes in powdered concrete.
6.4 Water absorption of dispersion-reinforced powder concretes.
6.5 Feasibility study and production implementation of the RPM.
Recommended list of dissertations
Composition, topological structure and rheotechnological properties of rheological matrices for the production of new generation concretes 2011, candidate of technical sciences Ananyev, Sergey Viktorovich
Steamed sandy concrete of a new generation on a reaction-powder binder 2013, candidate of technical sciences Valiev, Damir Maratovich
High-strength fine-grained basalt fiber-reinforced concrete 2009, candidate of technical sciences Borovskikh, Igor Viktorovich
Powder-activated high-strength sand concrete and fiber-reinforced concrete with low specific consumption of cement per unit of strength 2012, Candidate of Technical Sciences Volodin, Vladimir Mikhailovich
Powder-activated high-strength concrete and fiber-reinforced concrete with low specific consumption of cement per unit of strength 2011, Ph.D. Khvastunov, Alexey Viktorovich
Introduction to the thesis (part of the abstract) on the topic "Fine-grained reaction-powder dispersed-reinforced concrete using rocks"
Relevance of the topic. Every year in the world practice of concrete and reinforced concrete production, the production of high-quality, high- and extra-high-strength concretes is rapidly increasing, and this progress has become an objective reality, due to significant savings in material and energy resources.
With a significant increase in the compressive strength of concrete, crack resistance inevitably decreases and the risk of brittle fracture of structures increases. Dispersed reinforcement of concrete with fiber eliminates these negative properties, which makes it possible to produce concrete of classes above 80-100 with a strength of 150-200 MPa, which has a new quality - the viscous nature of destruction.
The analysis of scientific works in the field of dispersion-reinforced concretes and their production in domestic practice shows that the main orientation does not pursue the goals of using high-strength matrices in such concretes. The class of dispersion-reinforced concrete in terms of compressive strength remains extremely low and is limited to B30-B50. This does not allow to ensure good adhesion of the fiber to the matrix, to fully use the steel fiber even with low tensile strength. Moreover, in theory, concrete products with freely laid fibers with a degree of volumetric reinforcement of 5-9% are being developed, and in practice, concrete products are produced; they are shed under the action of vibration with unplasticized "fat" highly shrinkable cement-sand mortars of the composition: cement-sand -1: 0.4 + 1: 2.0 at W / C = 0.4, which is extremely wasteful and repeats the level of work in 1974 .Significant scientific achievements in the field of creating superplasticized VNV, microdispersed mixtures with microsilica, with reactive powders from high-strength rocks, made it possible to bring the water-reducing effect to 60% using superplasticizers of oligomeric composition and hyperplasticizers polymer composition. These achievements did not become the basis for the creation of high-strength reinforced concrete or fine-grained powder concretes from cast self-compacting mixtures. Meanwhile, advanced countries are actively developing new generations of reaction-powder concretes reinforced with dispersed fibers, woven shed volumetric fine-mesh frames, their combination with rod or rod with dispersed reinforcement.
All this determines the relevance of creating high-strength fine-grained reaction-powder, dispersed-reinforced concrete grades 1000-1500, which are highly economical not only in the construction of responsible unique buildings and structures, but also for general-purpose products and structures.
The dissertation work was carried out in accordance with the programs of the Institute of Building Materials and Structures of the Technical University of Munich (Germany) and the initiative work of the Department of TBKiV PGUAS and the scientific and technical program of the Ministry of Education of Russia "Scientific research of higher education in priority areas of science and technology" under the subprogram "Architecture and construction" 2000-2004
Purpose and objectives of the study. The purpose of the dissertation work is to develop compositions of high-strength fine-grained reaction-powder concretes, including dispersed-reinforced concretes, using crushed rocks.
To achieve this goal, it was necessary to solve a set of the following tasks:
Reveal the theoretical prerequisites and motivations for the creation of multicomponent fine-grained powder concretes with a very dense, high-strength matrix obtained by casting at an ultra-low water content, providing the production of concretes with a ductile character during destruction and high tensile strength in bending;
To reveal the structural topology of composite binders and dispersed-reinforced fine-grained compositions, to obtain mathematical models of their structure for estimating the distances between coarse filler particles and between the geometric centers of reinforcing fibers;
Develop a methodology for assessing the rheological properties of water-dispersed systems, fine-grained powder dispersion-reinforced compositions; to investigate their rheological properties;
To reveal the mechanism of hardening of mixed binders, to study the processes of structure formation;
Establish the necessary fluidity of multi-component fine-grained powder concrete mixtures, which ensures the filling of molds with a mixture with low viscosity and ultra-low yield strength;
To optimize the compositions of fine-grained dispersed-reinforced concrete mixes with fiber d = 0.1 mm and / = 6 mm with a minimum content sufficient to increase the extensibility of concrete, the preparation technology and establish the effect of the recipe on their fluidity, density, air content, strength and others physical and technical properties of concretes.
Scientific novelty of the work.
1. Scientifically substantiated and experimentally confirmed the possibility of obtaining high-strength fine-grained cement powder concretes, including dispersed-reinforced, made from concrete mixtures without crushed stone with fine fractions of quartz sand, with reactive rock powders and microsilica, with a significant increase the effectiveness of superplasticizers to the water content in the cast self-compacting mixture up to 10-11% (corresponding to semi-dry mixture for pressing without joint venture) of the mass of dry components.
2. Theoretical foundations of methods for determining the yield strength of superplasticized liquid-like disperse systems have been developed and methods for assessing the spreadability of powder concrete mixtures with free spreading and blocked with a mesh fence have been proposed.
3. The topological structure of composite binders and powder concretes, including dispersed reinforced ones, was revealed. Mathematical models of their structure are obtained, which determine the distances between coarse particles and between the geometric centers of fibers in the body of concrete.
4. Theoretically predicted and experimentally proven mainly through the solution diffusion-ion mechanism of hardening of composite cement binders, which increases with the increase in the content of the filler or a significant increase in its dispersion in comparison with the dispersion of cement.
5. The processes of structure formation of fine-grained powder concretes have been studied. It has been shown that powder concretes made from superplasticized cast self-compacting concrete mixtures are much denser, their strength growth kinetics are more intense, and the normative strength is significantly higher than that of concretes without SP, pressed at the same water content under a pressure of 40-50 MPa. Criteria for evaluating the reactive-chemical activity of powders have been developed.
6. The compositions of fine-grained dispersed-reinforced concrete mixtures with fine steel fiber 0.15 in diameter and 6 mm long, the technology of their preparation, the sequence of introduction of components and the duration of mixing have been optimized; the influence of the composition on the fluidity, density, air content of concrete mixtures, and compressive strength of concrete has been established.
7. Some physical and technical properties of dispersed-reinforced powder concretes and the main regularities of the influence of various prescription factors on them have been studied.
The practical significance of the work lies in the development of new cast fine-grained powder concrete mixtures with fiber for pouring molds for products and structures, both without and with combined rod reinforcement or without fiber for pouring molds with ready-made volumetric woven fine-mesh frames. With the use of high-density concrete mixtures, it is possible to produce highly crack-resistant bending or compression reinforced concrete structures with a viscous nature of destruction under the action of limit loads.
A high-density, high-strength composite matrix with a compressive strength of 120-150 MPa was obtained to increase adhesion to metal in order to use thin and short high-strength fiber 0 0.040.15 mm and a length of 6-9 mm, which makes it possible to reduce its consumption and resistance to flow of concrete mixtures for injection molding technology production of thin-walled filigree products with high tensile strength in bending.
New types of fine-grained powder dispersion-reinforced concretes expand the range of high-strength products and structures for various kinds construction.
The raw material base of natural fillers from screenings of stone crushing, dry and wet magnetic separation during the extraction and enrichment of ore and non-metallic minerals has been expanded.
The economic efficiency of the developed concretes consists in a significant reduction in material consumption by reducing the cost of concrete mixtures for the manufacture of high-strength products and structures.
Implementation of research results. The developed compositions have been tested in production at LLC "Penza Concrete Concrete Plant" and at the production base of precast concrete CJSC "Energoservice" and are used in Munich in the manufacture of balcony supports, slabs and other products in housing construction.
Approbation of work. The main provisions and results of the dissertation work were presented and reported at the International and All-Russian scientific and technical conferences: "Young science - the new millennium" (Naberezhnye Chelny, 1996), "Issues of planning and urban development" (Penza, 1996, 1997, 1999 G), " Contemporary Issues building materials science" (Penza, 1998), " modern building"(1998), International scientific and technical conferences" Composite building materials. Theory and practice "(Penza, 2002,
2003, 2004, 2005), “Resource and energy saving as a motivation for creativity in the architectural construction process” (Moscow-Kazan, 2003), “Actual issues of construction” (Saransk, 2004), “New energy and resource-saving high-tech technologies in the production of building materials "(Penza, 2005), the All-Russian scientific and practical conference "Urban planning, reconstruction and engineering support for the sustainable development of cities in the Volga region" (Tolyatti, 2004), Academic readings of the RAASN "Achievements, problems and promising directions development of the theory and practice of building materials science” (Kazan, 2006).
Publications. Based on the results of the research, 27 papers were published (2 papers in journals according to the HAC list).
Structure and scope of work. The dissertation work consists of an introduction, 6 chapters, main conclusions, applications and a list of used literature of 160 titles, presented on 175 pages of typewritten text, contains 64 figures, 33 tables.
Similar theses in the specialty "Building materials and products", 05.23.05 VAK code
Rheotechnological characteristics of plasticized cement-mineral dispersed suspensions and concrete mixtures for the production of effective concretes 2012, candidate of technical sciences Gulyaeva, Ekaterina Vladimirovna
High-strength dispersion-reinforced concrete 2006, candidate of technical sciences Simakina, Galina Nikolaevna
Methodological and technological bases for the production of high-strength concretes with high early strength for non-heating and low-heating technologies 2002, Doctor of Technical Sciences Demyanova, Valentina Serafimovna
Dispersion-reinforced fine-grained concrete on technogenic sand KMA for bending products 2012, Candidate of Technical Sciences Klyuev, Alexander Vasilyevich
Self-compacting fine-grained concretes and fiber-reinforced concretes based on highly filled modified cement binders 2018, Candidate of Technical Sciences Balykov, Artemy Sergeevich
Dissertation conclusion on the topic "Building materials and products", Kalashnikov, Sergey Vladimirovich
1. Analysis of the composition and properties of dispersed reinforced concrete produced in Russia indicates that they do not fully meet the technical and economic requirements due to the low compressive strength of concrete (M 400-600). In such three-, four- and rarely five-component concretes, not only dispersed reinforcement of high strength, but also of ordinary strength, is underused.
2. Based on theoretical concepts of the possibility of achieving maximum water-reducing effects of superplasticizers in dispersed systems that do not contain coarse-grained aggregates, high reactivity of silica fume and rock powders, which jointly enhance the rheological effect of the joint venture, the creation of a seven-component high-strength fine-grained reaction-powder concrete matrix for thin and relatively short dispersed reinforcement d = 0.15-0.20 μm and / = 6 mm, which does not form "hedgehogs" in the manufacture of concrete and slightly reduces the fluidity of PBS.
3. It is shown that the main criterion for obtaining high-density PBS is the high fluidity of a very dense cementing mixture of cement, MK, rock powder and water, provided by the addition of SP. In this regard, a methodology has been developed for assessing the rheological properties of disperse systems and PBS. It has been established that high fluidity of PBS is ensured at a limiting shear stress of 5–10 Pa and a water content of 10–11% of the mass of dry components.
4. The structural topology of composite binders and dispersed-reinforced concretes is revealed and their mathematical models of the structure are given. An ion-diffusion through-mortar mechanism of hardening of composite filled binders has been established. Methods for calculating the average distances between sand particles in PBS, the geometric centers of the fiber in powder concrete are systematized according to various formulas and for various parameters //, /, d. The objectivity of the author's formula is shown in contrast to the traditionally used ones. The optimal distance and thickness of the cementing slurry layer in PBS should be within 37-44 + 43-55 microns at a sand consumption of 950-1000 kg and its fractions of 0.1-0.5 and 0.14-0.63 mm, respectively.
5. The rheotechnological properties of dispersed-reinforced and non-reinforced PBS were established according to the developed methods. Optimal spread of PBS from a cone with dimensions D = 100; d=70; h = 60 mm should be 25-30 cm. The coefficients of decrease in spreading depending on the geometrical parameters of the fiber and the decrease in the flow of PBS when blocking it with a mesh fence were revealed. It is shown that for pouring PBS into molds with volume mesh woven frames, the spread should be at least 28-30 cm.
6. A technique has been developed for assessing the reactive-chemical activity of rock powders in low-cement mixtures (C:P - 1:10) in samples pressed under extrusion molding pressure. It has been established that with the same activity, estimated by strength after 28 days and during long hardening jumps (1-1.5 years), preference when used in RPBS should be given to powders from high-strength rocks: basalt, diabase, dacite, quartz.
7. The processes of structure formation of powder concretes have been studied. It has been established that cast mixes emit up to 40-50% of entrained air in the first 10-20 minutes after pouring and require coating with a film that prevents the formation of a dense crust. Mixtures begin to actively set 7-10 hours after pouring and gain strength after 1 day 30-40 MPa, after 2 days - 50-60 MPa.
8. The main experimental and theoretical principles for selecting the composition of concrete with a strength of 130-150 MPa are formulated. Quartz sand to ensure high fluidity of PBS should be fine-grained fraction
0.14-0.63 or 0.1-0.5 mm with a bulk density of 1400-1500 kg/m3 at a flow rate of 950-1000 kg/m. The thickness of the interlayer of suspension of cement-stone flour and MF between sand grains should be in the range of 43-55 and 37-44 microns, respectively, with the content of water and SP, providing the spread of mixtures of 2530 cm. The dispersion of PC and stone flour should be approximately the same, the content MK 15-20%, the content of stone flour is 40-55% by weight of cement. When varying the content of these factors, the optimal composition is selected according to the required flow of the mixture and the maximum compressive strength after 2.7 and 28 days.
9. The compositions of fine-grained dispersed-reinforced concretes with a compressive strength of 130-150 MPa were optimized using steel fibers with a reinforcement coefficient // = 1%. Optimal technological parameters have been identified: mixing should be carried out in high-speed mixers of a special design, preferably evacuated; the sequence of loading the components and the modes of mixing, "rest", are strictly regulated.
10. The influence of the composition on the fluidity, density, air content of dispersed-reinforced PBS, on the compressive strength of concrete was studied. It was revealed that the spreadability of mixtures, as well as the strength of concrete, depend on a number of prescription and technological factors. During optimization, mathematical dependences of fluidity, strength on individual, most significant factors were established.
11. Some physical and technical properties of dispersed reinforced concretes have been studied. It is shown that concretes with a compressive strength of 120l
150 MPa have a modulus of elasticity (44-47) -10 MPa, Poisson's ratio -0.31-0.34 (0.17-0.19 - for unreinforced). Air shrinkage of dispersion-reinforced concrete is 1.3-1.5 times lower than that of unreinforced concrete. High frost resistance, low water absorption and air shrinkage testify to the high performance properties of such concretes.
12. Production approbation and feasibility study testify to the need to organize production and widely introduce fine-grained reaction-powder dispersed-reinforced concrete into construction.
List of references for dissertation research candidate of technical sciences Kalashnikov, Sergey Vladimirovich, 2006
1. Aganin S.P. Concretes of low water demand with modified quartz filler. step. Ph.D., M, 1996.17 p.
2. Antropova V.A., Drobyshevsky V.A. Properties of modified steel fiber concrete // Concrete and reinforced concrete. No. 3.2002. C.3-5
3. Akhverdov I.N. Theoretical basis concrete science.// Minsk. Higher School, 1991, 191 p.
4. Babaev Sh.T., Komar A.A. Energy-saving technology of reinforced concrete structures made of high-strength concrete with chemical additives.// M.: Stroyizdat, 1987. 240 p.
5. Bazhenov Yu.M. Concrete of the XXI century. Resource and energy saving technologies of building materials and structures. scientific tech. conferences. Belgorod, 1995. p. 3-5.
6. Bazhenov Yu.M. High-quality fine-grained concrete//Building materials.
7. Bazhenov Yu.M. Improving the efficiency and cost-effectiveness of concrete technology // Concrete and reinforced concrete, 1988, No. 9. With. 14-16.
8. Bazhenov Yu.M. Concrete technology.// Publishing house of the Association of higher educational institutions, M.: 2002. 500 p.
9. Bazhenov Yu.M. Concrete of increased durability // Construction materials, 1999, No. 7-8. With. 21-22.
10. Bazhenov Yu.M., Falikman V.R. New century: new effective concretes and technologies. Materials of the I All-Russian Conference. M. 2001. p. 91-101.
11. Batrakov V.G. and other Superplasticizer-thinner SMF.// Concrete and reinforced concrete. 1985. No. 5. With. 18-20.
12. Batrakov V.G. Modified concrete // M.: Stroyizdat, 1998. 768 p.
13. Batrakov V.G. Concrete modifiers new opportunities // Proceedings of the I All-Russian Conference on Concrete and Reinforced Concrete. M.: 2001, p. 184-197.
14. Batrakov V.G., Sobolev K.I., Kaprielov S.S. High-strength low-cement additives // Chemical additives and their application in the technology of prefabricated reinforced concrete production. M.: Ts.ROZ, 1999, p. 83-87.
15. Batrakov V.G., Kaprielov S.S. Evaluation of ultrafine wastes of metallurgical industries as additives to concrete // Beton and reinforced concrete, 1990. No. 12. p. 15-17.
16. Batsanov S.S. The electronegativity of the elements and chemical bond.// Novosibirsk, publishing house SOAN USSR, 1962,195 p.
17. Berkovich Ya.B. Study of the microstructure and strength of cement stone reinforced with short-fiber chrysotile asbestos: Abstract of the thesis. Dis. cand. tech. Sciences. Moscow, 1975. - 20 p.
18. Bryk M.T. Destruction of filled polymers M. Chemistry, 1989 p. 191.
19. Bryk M.T. Solid surface polymerization inorganic substances.// Kyiv, Naukova Dumka, 1981,288 p.
20. Vasilik P.G., Golubev I.V. The use of fibers in dry building mixes. // Building materials №2.2002. S.26-27
21. Volzhensky A.V. Mineral binders. M.; Stroyizdat, 1986, 463 p.
22. Volkov I.V. Problems of using fiber-reinforced concrete in domestic construction. //Building materials 2004. - №6. pp. 12-13
23. Volkov I.V. Fiber-reinforced concrete - the state and prospects of application in building structures // Construction materials, equipment, technologies of the 21st century. 2004. No. 5. P.5-7.
24. Volkov I.V. Fiber concrete structures. Review inf. Series "Building structures", no. 2. M, VNIIIS Gosstroy of the USSR, 1988.-18s.
25. Volkov Yu.S. The use of heavy-duty concrete in construction // Concrete and reinforced concrete, 1994, No. 7. With. 27-31.
26. Volkov Yu.S. Monolithic reinforced concrete. // Concrete and reinforced concrete. 2000, no. 1, p. 27-30.
27. VSN 56-97. "Design and basic provisions of technologies for the production of fiber-reinforced concrete structures." M., 1997.
28. Vyrodov IP On some basic aspects of the theory of hydration and hydration hardening of binders // Proceedings of the VI International Congress on Cement Chemistry. T. 2. M.; Stroyizdat, 1976, pp. 68-73.
29. Glukhovsky V.D., Pokhomov V.A. Slag-alkaline cements and concretes. Kyiv. Budivelnik, 1978, 184 p.
30. Demyanova B.C., Kalashnikov S.V., Kalashnikov V.I. Reaction activity of crushed rocks in cement compositions. News of TulGU. Series "Building materials, structures and facilities". Tula. 2004. Issue. 7. p. 26-34.
31. Demyanova B.C., Kalashnikov V.I., Minenko E.Yu., Shrinkage of concrete with organomineral additives // Stroyinfo, 2003, No. 13. p. 10-13.
32. Dolgopalov N.N., Sukhanov M.A., Efimov S.N. A new type of cement: the structure of cement stone/Building materials. 1994 No. 1 p. 5-6.
33. Zvezdov A.I., Vozhov Yu.S. Concrete and reinforced concrete: Science and practice // Materials of the All-Russian conference on concrete and reinforced concrete. M: 2001, p. 288-297.
34. Zimon A.D. Liquid adhesion and wetting. Moscow: Chemistry, 1974. p. 12-13.
35. Kalashnikov V.I. Nesterov V.Yu., Khvastunov V.L., Komokhov P.G., Solomatov V.I., Marusentsev V.Ya., Trostyansky V.M. Clay building materials. Penza; 2000, 206 p.
36. Kalashnikov V.I. On the predominant role of the ion-electrostatic mechanism in the liquefaction of mineral dispersed compositions.// Durability of structures made of autoclaved concrete. Tez. V Republican Conference. Tallinn 1984. p. 68-71.
37. Kalashnikov V.I. Fundamentals of plasticization of mineral dispersed systems for the production of building materials.// Dissertation for the degree of Doctor of Technical Sciences, Voronezh, 1996, 89 p.
38. Kalashnikov V.I. Regulation of the thinning effect of superplasticizers based on ion-electrostatic action.//Production and application to chemical additives in construction. Collection of abstracts of NTC. Sofia 1984. p. 96-98
39. Kalashnikov V.I. Accounting for rheological changes in concrete mixtures with superplasticizers.// Proceedings of the IX All-Union Conference on Concrete and Reinforced Concrete (Tashkent 1983), Penza 1983 p. 7-10.
40. Kalashnikov V L, Ivanov I A. Peculiarities of rheological changes in cement compositions under the action of ion-stabilizing plasticizers// Collection of works "Technological mechanics of concrete" Riga RPI, 1984 p. 103-118.
41. Kalashnikov V.I., Ivanov I.A. The role of procedural factors and rheological indicators of dispersed compositions.// Technological mechanics of concrete. Riga FIR, 1986. p. 101-111.
42. Kalashnikov V.I., Ivanov I.A., On the structural-rheological state of extremely liquefied highly concentrated disperse systems.// Proceedings of the IV National Conference on Mechanics and Technology of Composite Materials. BAN, Sofia. 1985.
43. Kalashnikov V.I., Kalashnikov S.V. To the theory of "hardening of composite cement binders.// Proceedings of the international scientific and technical conference "Actual issues of construction" TZ Publishing house of Mordovian State University, 2004. P. 119-123.
44. Kalashnikov V.I., Kalashnikov S.V. On the theory of hardening of composite cement binders. Materials of the international scientific and technical conference "Actual issues of construction" T.Z. Ed. Mordovian state. University, 2004. S. 119-123.
45. Kalashnikov V.I., Khvastunov B.JI. Moskvin R.N. Formation of the strength of carbonate-slag and causticized binders. Monograph. Deposited in VGUP VNIINTPI, Issue 1, 2003, 6.1 p.s.
46. Kalashnikov V.I., Khvastunov B.JL, Tarasov R.V., Komokhov P.G., Stasevich A.V., Kudashov V.Ya. Effective heat-resistant materials based on modified clay-slag binder// Penza, 2004, 117 p.
47. Kalashnikov S. V. et al. Topology of composite and dispersed-reinforced systems // Materials of MNTK composite building materials. Theory and practice. Penza, PDZ, 2005, pp. 79-87.
48. Kiselev A.V., Lygin V.I. Infrared spectra of surface compounds.// M.: Nauka, 1972,460 p.
49. Korshak V.V. Heat-resistant polymers.// M.: Nauka, 1969,410 p.
50. Kurbatov L.G., Rabinovich F.N. On the effectiveness of concrete reinforced with steel fibers. // Concrete and reinforced concrete. 1980. L 3. S. 6-7.
51. Lankard D.K., Dickerson R.F. Reinforced concrete with reinforcement from scraps of steel wire// Building materials abroad. 1971, No. 9, p. 2-4.
52. Leontiev V.N., Prikhodko V.A., Andreev V.A. On the possibility of using carbon fiber materials for reinforcing concrete / / Building materials, 1991. No. 10. pp. 27-28.
53. Lobanov I.A. Structural features and properties of dispersed-reinforced concrete // Manufacturing technology and properties of new composite building materials: Mezhvuz. subject. Sat. scientific tr. L: LISI, 1086. S. 5-10.
54. Mailyan DR, Shilov Al.V., Dzhavarbek R Effect of fiber reinforcement with basalt fiber on the properties of light and heavy concrete // New research of concrete and reinforced concrete. Rostov-on-Don, 1997. S. 7-12.
55. Mailyan L.R., Shilov A.V. Curved claydite-fiber-reinforced concrete elements on coarse basalt fiber. Rostov n/a: Rost. state builds, un-t, 2001. - 174 p.
56. Mailyan R.L., Mailyan L.R., Osipov K.M. and other Recommendations for the design of reinforced concrete structures made of expanded clay concrete with fiber reinforcement with basalt fiber / Rostov-on-Don, 1996. -14 p.
57. Mineralogical encyclopedia / Translation from English. L. Nedra, 1985. With. 206-210.
58. Mchedlov-Petrosyan O.P. Chemistry of inorganic building materials. M.; Stroyizdat, 1971, 311s.
59. S. V. Nerpin and A. F. Chudnovsky, Physics of Soil. M. Science. 1967, 167p.
60. Nesvetaev G.V., Timonov S.K. Shrinkage deformations of concrete. 5th Academic Readings of RAASN. Voronezh, VGASU, 1999. p. 312-315.
61. Pashchenko A.A., Serbia V.P. Reinforcement of cement stone with mineral fiber Kyiv, UkrNIINTI - 1970 - 45 p.
62. Pashchenko A.A., Serbia V.P., Starchevskaya E.A. Astringent substances. Kyiv. Vishcha school, 1975,441 p.
63. Polak A.F. Hardening of mineral binders. M.; Publishing house of literature on construction, 1966,207 p.
64. Popkova A.M. Structures of buildings and structures made of high-strength concrete // A series of building structures // Survey information. Issue. 5. Moscow: VNIINTPI Gosstroya USSR, 1990, 77 p.
65. Puharenko, Yu.V. Scientific and practical foundations for the formation of the structure and properties of fiber-reinforced concrete: dis. doc. tech. Sciences: St. Petersburg, 2004. p. 100-106.
66. Rabinovich F.N. Concrete, dispersed-reinforced with fibers: Review of VNIIESM. M., 1976. - 73 p.
67. Rabinovich F.N. Dispersion-reinforced concretes. M., Stroyizdat: 1989.-177 p.
68. Rabinovich F.N. Some issues of dispersed reinforcement of concrete materials with fiberglass // Dispersed reinforced concretes and structures made of them: Abstracts of reports. Republican conferred Riga, 1 975. - S. 68-72.
69. Rabinovich F.N. On the optimal reinforcement of steel-fiber-concrete structures // Concrete and reinforced concrete. 1986. No. 3. S. 17-19.
70. Rabinovich F.N. On the levels of dispersed reinforcement of concrete. // Construction and architecture: Izv. universities. 1981. No. 11. S. 30-36.
71. Rabinovich F.N. The use of fiber-reinforced concrete in the construction of industrial buildings // Fiber-reinforced concrete and its use in construction: Proceedings of NIIZhB. M., 1979. - S. 27-38.
72. Rabinovich F.N., Kurbatov L.G. The use of steel fiber concrete in the construction of engineering structures // Concrete and reinforced concrete. 1984.-№12.-S. 22-25.
73. Rabinovich F.N., Romanov V.P. On the limit of crack resistance of fine-grained concrete reinforced with steel fibers // Mechanics of Composite Materials. 1985. No. 2. pp. 277-283.
74. Rabinovich F.N., Chernomaz A.P., Kurbatov L.G. Monolithic bottoms of tanks made of steel fiber concrete//Concrete and reinforced concrete. -1981. No. 10. pp. 24-25.
76. Solomatov V.I., Vyroyuy V.N. and others. Composite building materials and structures of reduced material consumption.// Kyiv, Budivelnik, 1991.144 p.
77. Steel fiber reinforced concrete and structures made of it. Series "Building materials" Vol. 7 VNIINTPI. Moscow. - 1990.
78. Glass fiber reinforced concrete and structures made of it. Series "Building materials". Issue 5. VNIINTPI.
79. Strelkov M.I. Changes in the true composition of the liquid phase during hardening of binders and the mechanisms of their hardening // Proceedings of the meeting on the chemistry of cement. M.; Promstroyizdat, 1956, pp. 183-200.
80. Sycheva L.I., Volovika A.V. Fiber-reinforced materials / Translation ed.: Fibrereinforced materials. -M.: Stroyizdat, 1982. 180 p.
81. Toropov N.A. Chemistry of silicates and oxides. L.; Nauka, 1974,440s.
82. Tretyakov N.E., Filimonov V.N. Kinetics and catalysis / T .: 1972, No. 3,815-817 p.
83. Fadel I.M. Intensive separate technology of concrete filled with basalt.// Abstract of the thesis. Ph.D. M, 1993.22 p.
84. Fiber concrete in Japan. Express information. Building structures”, M, VNIIIS Gosstroy USSR, 1983. 26 p.
85. Filimonov V.N. Spectroscopy of phototransformations in molecules.//L.: 1977, p. 213-228.
86. Hong DL. Properties of concrete containing silica fume and carbon fiber treated with silanes // Express information. Issue No. 1.2001. pp.33-37.
87. Tsyganenko A.A., Khomenia A.V., Filimonov V.N. Adsorption and adsorbents.//1976, no. 4, p. 86-91.
88. Shvartsman A.A., Tomilin I.A. Advances in Chemistry//1957, Vol. 23 No. 5, p. 554-567.
89. Slag-alkaline binders and fine-grained concretes based on them (under the general editorship of V.D. Glukhovsky). Tashkent, Uzbekistan, 1980.483 p.
90. Jurgen Schubert, Kalashnikov S.V. Topology of mixed binders and the mechanism of their hardening // Sat. Articles MNTK New energy and resource-saving science-intensive technologies in the production of building materials. Penza, PDZ, 2005. p. 208-214.
91. Balaguru P., Najm. High-performance fiber-reinforced mixture with fiber volume fraction//ACI Materials Journal.-2004.-Vol. 101, No. 4.-p. 281-286.
92. Batson G.B. State-the-Art Reportion Fiber Reinforced Concrete. Reported by ASY Committee 544. ACY Journal. 1973,-70,-№ 11,-p. 729-744.
93. Bindiganavile V., Banthia N., Aarup B. Impact response of ultra-high-strength fiber-reinforced cement composite. // ACI Materials Journal. 2002. - Vol. 99, no.6. - P.543-548.
94. Bindiganavile V., Banthia., Aarup B. Impact response of ultra-high-strength fiber-reinforced cement compsite // ACJ Materials Journal. 2002 - Vol. 99, no. 6.
95. Bornemann R., Fenling E. Ultrahochfester Beton-Entwicklung und Verhalten.//Leipziger Massivbauseminar, 2000, Bd. 10, s 1-15.
96. Brameschuber W., Schubert P. Neue Entwicklungen bei Beton und Mauerwerk. // Oster. Jngenieur-und Architekten-Zeitsehrieft., s. 199-220.
97. Dallaire E., Bonnean O., Lachemi M., Aitsin P.-C. Mechanical Behavior of Consined Reactive Powder Concrete.// American Societe of Givil Eagineers Materials Engineering Coufernce. Washington. DC. November 1996 Vol. 1, p.555-563.
98. Frank D., Friedemann K., Schmidt D. Optimisierung der Mischung sowie Verifizirung der Eigenschaften Saueresistente Hochleistungbetone.// Betonwerk+Fertigteil-Technik. 2003. No. 3. S.30-38.
99. Grube P., Lemmer C., Riihl M Vom Gussbeton zum Selbstvendichtenden Beton. s. 243-249.
100. Kleingelhofer P. Neue Betonverflissiger auf Basis Policarboxilat.// Proc. 13. Jbasil Weimar 1997, Bd. 1, s 491-495.
101. Muller C., Sehroder P. Schlif3e P., Hochleistungbeton mit Steinkohlenflugasche. Essen VGB Fechmische Vereinigung Bundesveband Kraftwerksnelenprodukte.// E.V., 1998-Jn: Flugasche in Beton, VGB/BVK-Faschaugung. 01 December 1998, Vortag 4.25 seiten.
102. Richard P., Cheurezy M. Composition of Reactive Powder Concrete. Scientific Division Bougies.// Cement and Concrete Research, Vol. 25. No. 7, pp. 1501-1511,1995.
103. Richard P., Cheurezy M. Reactive Powder Concrete with High Ducttility and 200-800 MPa Compressive Strength.// AGJ SPJ 144-22, p. 507-518, 1994.
104. Romualdy J.R., Mandel J.A. Tensile strength of Concrete Affected by Uniformly Distributed and Glosely Spaced Lengths of Wire Reinforcement "ACY Journal". 1964, - 61, - No. 6, - p. 675-670.
105. Schachinger J., Schubert J., Stengel T., Schmidt PC, Hilbig H., Heinz DL Ultrahochfester Beton-Bereit fur die Anwendung? Schriftenzeihe Baustoffe.// FestSchrift zum 60. Geburgstag Von Prof.-Dr. Jng. Peter Schliessl. heft. 2003, s. 189-198.
106. Schmidt M. Bornemann R. Moglichkeiten und Crensen von Hochfestem Beton.// Proc. 14, Jbausil, 2000, Bd. 1, s 1083-1091.
107 Schmidt M. Jahre Entwicklung bei Zement, Zusatsmittel und Beton. Ceitzum Baustoffe und Materialpriifung. Schriftenreihe Baustoffe.// Fest-schrift zum 60. Geburgstag von Prof. Dr. Jng. Peter Schiesse. Heft 2.2003 s 189-198.
108. SchmidM,FenlingE.Utntax;hf^
109. Schmidt M., Fenling E., Teichmann T., Bunjek K., Bornemann R. Ultrahochfester Beton: Perspective fur die Betonfertigteil Industrie.// Betonwerk+Fertigteil-Technik. 2003. No. 39.16.29.
110. Schnachinger J, Schuberrt J, Stengel T, Schmidt K, Heinz D, Ultrahochfester Beton Bereit Fur die Anwendung? Scnriftenreihe Baustoffe. Fest - schrift zum 60. Geburtstag von Prof. Dr.-ing. Peter Schliessl. Heft 2.2003, C.267-276.
111. Scnachinger J., Schubert J., Stengel T., Schmidt K., Heinz D. Ultrahochfester Beton Bereit Fur die Anwendung? Scnriftenreihe Baustoffe.// Fest - schrift zum 60. Geburtstag von Prof. Dr. - ing. Peter Schlissl. Heft 2.2003, C.267-276.
112. Stark J., Wicht B. Geschichtleiche Entwichlung der ihr Beitzag zur Entwichlung der Betobbauweise. // Oster. Jngenieur-und Architekten-Zeitsehrieft., 142.1997. H.9.125. Taylor //MDF.
113. Wirang-Steel Fibraus Concrete.//Concrete construction. 1972.16, No. l, s. 18-21.
114. Bindiganavill V., Banthia N., Aarup B. Impact response of ultra-high-strength fiber-reinforced cement composite // ASJ Materials Journal. -2002.-Vol. 99, No. 6.-p. 543-548.
115. Balaguru P., Nairn H., High-performance fiber-reinforced concrete mixture proportion with high fiber volume fractions // ASJ Materials Journal. 2004, Vol. 101, No. 4.-p. 281-286.
116. Kessler H., Kugelmodell fur Ausfallkormengen dichter Betone. Betonwetk + Festigteil-Technik, Heft 11, S. 63-76, 1994.
117. Bonneau O., Lachemi M., Dallaire E., Dugat J., Aitcin P.-C. Mechanical ProPerties and Durability of Two Industrial Reactive Powder Cohcrete // ASJ Materials Journal V.94. No.4, S.286-290. Juli-August, 1997.
118. De Larrard F., Sedran Th. Optimization of ultrahigh-performance concrete by the use of a packing model. Cem. Concrete Res., Vol. 24(6). S. 997-1008, 1994.
119. Richard P., Cheurezy M. Composition of Reactive Powder Concrete. Cem. Coner.Res.Vol.25. No.7, S.1501-1511, 1995.
120. Bornemann R., Sehmidt M., Fehling E., Middendorf B. Ultra Hachleistungsbeton UHPC - Herstellung, Eigenschaften und Anwendungsmoglichkeiten. Sonderdruck aus; Beton und Stahlbetonbau 96, H.7. S.458-467, 2001.
121. Bonneav O., Vernet Ch., Moranville M. Optimization of the Reological Behavior of Reactive Powder Coucrete (RPC). Tagungsband International Symposium of High-Performance and Reactive Powder Concretes. Shebroke, Canada, August, 1998. S.99-118.
122. Aitzin P., Richard P. The Pedestrian/Bikeway Bridge of scherbooke. 4th International Symposium on Utilization of High-strength/ High-Performance, Paris. S. 1999-1406, 1996.
123. De Larrard F., Grosse J.F., Puch C. Comparative study of Various Silica Fumes as Additives in High-Performance Cementious Materials. Materials and Structures, RJLEM, Vol. 25, S. 25-272, 1992.
124. Richard P. Cheyrezy M.N. Reactive Powder Concretes with High Ductility and 200-800 MPa Compressive Strength. ACI, SPI 144-24, S. 507-518, 1994.
125. Berelli G., Dugat I., Bekaert A. The Use of RPC in Gross-Flow Cooling Towers, International Symposium on High-Performance and Reactive Powder Concretes, Sherbrooke, Canada, S. 59-73,1993.
126. De Larrard F., Sedran T. Mixture-Proportioning of High-Performance Concrete. Cem. Concr. Res. Vol. 32, S. 1699-1704, 2002.
127. Dugat J., Roux N., Bernier G. Mechanical Properties of Reactive Powder Concretes. Materials and Structures, Vol. 29, S. 233-240, 1996.
128. Bornemann R., Schmidt M. The Role of Powders in Concrete: Proceedings of the 6th International Symposium on Utilization of High Strength/High Performance Concrete. S. 863-872, 2002.
129. Richard P. Reactive Powder Concrete: A New Ultra-High Cementitius Material. 4th Internanional Symposium on Utilization of High-Strength/ High-Performance Concrete, Paris, 1996.
130. Uzawa, M; Masuda, T; Shirai, K; Shimoyama, Y; Tanaka, V: Fresh Properties and Strength of Reactive Powder Composite Material (Ductal). Proceedings of the est fib congress, 2002.
131 Vernet, Ch; Moranville, M; Cheyrezy, M; Prat, E: Ultra-High Durability Concretes, Chemistry and Microstructure. HPC Symposium, Hong Kong, December 2000.
132 Cheyrezy, M; Maret, V; Frouin, L: Microstructural Analysis of RPC (Reactive Powder Concrete). Cem.Coner.Res.Vol.25, No. 7, S. 1491-1500, 1995. ,
133. Bouygues Fa: Juforniationsbroschure zum betons de Poudres Reactives, 1996.
134. Reineck. K-H., Lichtenfels A., Greiner. St. Seasonal storage of solare "of energy in hot-Water tanks made out high performance concrete. 6 th International Symposium on high Strength / High Performance. Leipzig, June, 2002.
135. Babkov B.V., Komokhov P.G. and others. Volumetric changes in the reactions of hydration and recrystallization of mineral binders / Science and Technology, -2003, No. 7
136. Babkov V.V., Polok A.F., Komokhov P.G. Aspects of the durability of cement stone / Cement-1988-№3 pp. 14-16.
137. Alexandrovsky S.V. Some features of shrinkage of concrete and reinforced concrete, 1959 No. 10 pp. 8-10.
138. Sheikin A.V. Structure, strength and crack resistance of cement stone. M: Stroyizdat 1974, 191 p.
139. Sheikin A.V., Chekhovsky Yu.V., Brusser M.I. Structure and properties of cement concretes. M: Stroyizdat, 1979. 333 p.
140. Tsilosani Z.N. Shrinkage and creep of concrete. Tbilisi: Publishing House of the Academy of Sciences of Georgia. SSR, 1963. p. 173.
141. Berg O.Ya., Shcherbakov Yu.N., Pisanko T.N. High strength concrete. M: Stroyizdat. 1971. from 208.i?6
Please note the above scientific texts posted for review and obtained through recognition of original texts of dissertations (OCR). In this connection, they may contain errors related to the imperfection of recognition algorithms. There are no such errors in the PDF files of dissertations and abstracts that we deliver.
The present invention relates to the building materials industry and is used for the manufacture of concrete products: highly artistic openwork fences and gratings, pillars, thin paving slabs and curb stone, thin-walled tiles for interior and exterior cladding of buildings and structures, decorative items and small architectural forms. The method for preparing a self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture consists in sequential mixing of the components until a mixture with the required fluidity is obtained. Initially, water and a hyperplasticizer are mixed in the mixer, then cement, microsilica, stone flour are poured and the mixture is stirred for 2-3 minutes, after which sand and fiber are introduced and mixed for 2-3 minutes. A self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties is obtained, which contains the following components: Portland cement PC500D0, sand fraction from 0.125 to 0.63, hyperplasticizer, fibers, microsilica, stone flour, strength gain accelerator and water. The method for manufacturing concrete products in molds consists in preparing a concrete mixture, feeding the mixture into molds and then holding it in a curing chamber. The inner, working surface of the mold is treated with a thin layer of water, then a self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties is poured into the mold. After filling the mold, a thin layer of water is sprayed onto the surface of the mixture and the mold is covered with a technological pallet. EFFECT: obtaining a self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, high strength characteristics, low cost and making it possible to manufacture openwork products. 2 n. and 2 z.p. f-ly, 1 tab., 3 ill.
The present invention relates to the building materials industry and is used for the manufacture of concrete products: highly artistic openwork fences and gratings, pillars, thin paving slabs and curbstones, thin-walled tiles for internal and external cladding of buildings and structures, decorative products and small architectural forms.
A known method of manufacturing decorative building products and/or decorative coatings by mixing with water a binder containing Portland cement clinker, a modifier, including an organic water-reducing component and a certain amount of a hardening accelerator and gypsum, pigments, aggregates, mineral and chemical (functional) additives, and the resulting mixture is kept until bentonite clay is saturated (functional additive mixture stabilizer) propylene glycol (an organic water-reducing component), fixing the resulting complex with hydroxypropyl cellulose gelling agent, laying, shaping, compacting and heat treatment. Moreover, the mixing of dry components and the preparation of the mixture is carried out in different mixers (see RF patent No. 2084416, MPK6 SW 7/52, 1997).
The disadvantage of this solution is the need to use different equipment for mixing the components of the mixture and subsequent compaction operations, which complicates and increases the cost of technology. In addition, when using this method it is impossible to obtain products with thin and openwork elements.
A known method of preparing a mixture for the production of building products, including the activation of the binder by joint grinding of Portland cement clinker with dry superplasticizer and subsequent mixing with filler and water, and first the activated filler is mixed with 5-10% mixing water, then the activated binder is introduced and the mixture is stirred, after which 40 - 60% mixing water is introduced and the mixture is stirred, then the remaining water is introduced and final mixing is carried out until a homogeneous mixture is obtained. Stepwise mixing of the components is carried out for 0.5-1 min. Products made from the resulting mixture must be kept at a temperature of 20°C and a humidity of 100% for 14 days (see RF patent No. 2012551, MPK5 C04B 40/00, 1994).
The disadvantage of the known method is the complex and expensive operation for the joint grinding of the binder and superplasticizer, which requires high costs on the organization of the mixing and grinding complex. In addition, when using this method, it is impossible to obtain products with thin and openwork elements.
Known composition for the preparation of self-compacting concrete, containing:
100 wt. parts of cement
50-200 wt. parts of mixtures of sands from calcined bauxites of different granulometric composition, the finest sand of average granulometric composition is less than 1 mm, the largest sand of average granulometric composition is less than 10 mm;
5-25 wt. parts of ultra-fine particles of calcium carbonate and white soot, and the content of white soot is not more than 15 wt. parts;
0.1-10 wt. parts of a defoamer;
0.1-10 wt. parts of the superplasticizer;
15-24 wt. fiber parts;
10-30 wt. parts of water.
The mass ratio between the amount of ultra-fine particles of calcium carbonate in concrete and the amount of white soot can reach 1:99-99:1, preferably 50:50-99:1 (see RF patent No. 111/62 (2006.01), 2009, para. 12).
The disadvantage of this concrete is the use of expensive calcined bauxite sands, usually used in aluminum production, as well as an excess amount of cement, which leads, respectively, to an increase in the consumption of other very expensive concrete components and, accordingly, to an increase in its cost.
The conducted search showed that no solutions have been found that provide the production of reaction-powder self-compacting concrete.
There is known a method for preparing concrete with the addition of fibers, in which all concrete components are mixed until concrete with the required fluidity is obtained, or dry components are first mixed, such as cement, different types sand, ultrafine particles of calcium carbonate, white soot and possibly superplasticizer and antifoam agent, after which water, and if necessary superplasticizer and antifoam agent if present in liquid form, and if necessary fibers are added to the mixture, and mixed until concrete with the required fluidity. After mixing, for example, for 4-16 minutes, the resulting concrete can be easily molded due to its very high fluidity (see RF patent No. ., item 12). This decision was taken as a prototype.
The resulting ultra-high performance self-compacting concrete can be used to make prefabricated elements such as posts, crossbeams, beams, ceilings, tiles, artistic structures, prestressed elements or composite materials, material for sealing gaps between structural elements, elements of sewage systems or in architecture.
The disadvantage of this method is the high consumption of cement for the preparation of 1 m3 of the mixture, which entails an increase in the cost of the concrete mixture and products from it due to an increase in the consumption of other components. In addition, the method described in the invention for using the resulting concrete does not carry any information on how, for example, artistic openwork and thin-walled concrete products can be produced.
Widely known methods for the manufacture of various products from concrete, when the concrete poured into the mold is subsequently subjected to vibrocompaction.
However, using such known methods, it is impossible to obtain artistic, openwork and thin-walled concrete products.
A known method for the manufacture of concrete products in packaging forms, which consists in the preparation of a concrete mixture, feeding the mixture into molds, hardening. An air and moisture insulating form is used in the form of packaging thin-walled multi-chamber forms, coated after the mixture is supplied to them with an air and moisture insulating coating. Hardening of products is carried out in sealed chambers for 8-12 hours (see the patent for the invention of Ukraine No. UA 39086, MPK7 V28V 7/11; V28V 7/38; S04V 40/02, 2005).
The disadvantage of the known method is the high cost of the molds used for the manufacture of concrete products, as well as the impossibility of manufacturing artistic, openwork and thin-walled concrete products in this way.
The first task is to obtain the composition of a self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture with the required workability and the necessary strength characteristics, which will reduce the cost of the obtained self-compacting concrete mixture.
The second task is to increase the strength characteristics at a daily age with optimal mix workability and improve the decorative properties of the front surfaces of concrete products.
The first task is solved due to the fact that a method has been developed for preparing a self-compacting extra high-strength reaction-powder fiber-reinforced concrete mixture, which consists in mixing the components of the concrete mixture until the required fluidity is obtained, in which the mixing of the components of the fiber-reinforced concrete mixture is carried out sequentially, and initially water and a hyperplasticizer are mixed in the mixer, then cement, microsilica, stone flour are poured and the mixture is stirred for 2-3 minutes, after which sand and fiber are introduced and mixed for 2-3 minutes until a fiber-reinforced concrete mixture is obtained containing components, wt.%:
The total preparation time of the concrete mixture is from 12 to 15 minutes.
The technical result from the use of the invention is to obtain a self-compacting extra high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, improving the quality and spreadability of the fiber-reinforced concrete mixture, due to a specially selected composition, sequence of introduction and mixing time of the mixture, which leads to a significant increase in fluidity and strength characteristics concrete up to M1000 and above, reducing the required thickness of products.
Mixing the ingredients in a certain sequence, when initially a measured amount of water and a hyperplasticizer are mixed in the mixer, then cement, microsilica, stone flour are added and mixed for 2-3 minutes, after which sand and fiber are introduced and the resulting concrete mixture is mixed for 2- 3 minutes allows for a significant improvement in the quality and flow characteristics (workability) of the resulting self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture.
The technical result from the use of the invention is to obtain a self-compacting extra high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, high strength characteristics and low cost. Compliance with the given ratio of the components of the mixture, wt.%:
allows to obtain a self-compacting, extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, high strength characteristics and low cost.
The use of the above components, while observing the specified proportion in a quantitative ratio, makes it possible, when obtaining a self-compacting extra high-strength reaction-powder fiber-reinforced concrete mixture with the required fluidity and high strength properties, to ensure the low cost of the resulting mixture and thus increase its consumer properties. The use of components such as microsilica, stone flour, allows you to reduce the percentage of cement, which entails a decrease in the percentage of other expensive components (hyperplasticizer, for example), as well as to abandon the use of expensive sands from calcined bauxites, which also leads to a decrease in the cost of concrete mixture, but does not affect its strength properties.
The second task is solved due to the fact that a method has been developed for manufacturing products in molds from a fiber-reinforced concrete mixture prepared as described above, which consists in feeding the mixture into molds and subsequent holding for curing, and initially a thin layer of water is sprayed onto the inner, working surface of the mold, and after filling the mold with the mixture, a thin layer of water is sprayed on its surface and the mold is covered with a technological pallet.
Moreover, the mixture is fed into the molds sequentially, covering the filled mold from above with a technological pallet, after installing the technological pallet, the process of manufacturing products is repeated many times, placing the next form on the technological pallet above the previous one.
The technical result from the use of the invention is to improve the quality of the front surface of the product, a significant increase in the strength characteristics of the product, due to the use of a self-compacting fiber-reinforced concrete mix with very high flow properties, special processing of molds and organization of concrete care at a daily age. The organization of concrete care at a daily age consists in ensuring sufficient waterproofing of the molds with concrete poured into them by covering the upper layer of concrete in the mold with a water film and covering the molds with pallets.
The technical result is achieved through the use of a self-compacting fiber-reinforced concrete mixture with very high flow properties, which allows the production of very thin and openwork products of any configuration, repeating any textures and types of surfaces, eliminates the process of vibration compaction when molding products, and also allows the use of any shape (elastic, fiberglass , metal, plastic, etc.) for the production of products.
Pre-wetting the mold with a thin layer of water and the final operation of spraying a thin layer of water on the surface of the poured fiber-reinforced concrete mix, covering the mold with concrete with the next technological pallet in order to create an airtight chamber for better maturation of the concrete makes it possible to exclude the appearance of air pores from trapped air, to achieve high quality of the front surface of the products , reduce the evaporation of water from hardening concrete and increase the strength characteristics of the resulting products.
The number of molds poured simultaneously is selected based on the volume of the obtained self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture.
Obtaining a self-compacting fiber-reinforced concrete mixture with very high flow properties and, due to this, with improved workability qualities, makes it possible not to use a vibrating table in the manufacture of artistic products and to simplify the manufacturing technology, while increasing the strength characteristics of artistic concrete products.
The technical result is achieved due to the specially selected composition of the fine-grained self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mix, the mode of the sequence of introducing the components, the method of processing the forms and organizing the care of concrete at a daily age.
The advantages of this technology and the concrete used:
The use of sand module fineness fr. 0.125-0.63;
The absence of large aggregates in the concrete mix;
The possibility of manufacturing concrete products with thin and openwork elements;
Ideal surface of concrete products;
The possibility of manufacturing products with a given roughness and surface texture;
High grade concrete compressive strength, not less than M1000;
High brand strength of concrete in bending, not less than Ptb100;
The present invention is explained in more detail below with the help of non-restrictive examples.
Fig. 1 (a, b) - scheme for manufacturing products - pouring the resulting fiber-reinforced concrete into molds;
Fig. 2 is a top view of a product obtained using the claimed invention.
The method of obtaining a self-compacting extra high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, containing the above components, is carried out as follows.
First, all components of the mixture are weighed. Then, a measured amount of water, a hyperplasticizer, is poured into the mixer. Then the mixer is turned on. In the process of mixing water, hyperplasticizer, the following components of the mixture are sequentially poured: cement, microsilica, stone flour. If necessary, iron oxide pigments can be added to color concrete in mass. After introducing these components into the mixer, the resulting suspension is mixed for 2 to 3 minutes.
At the next stage, sand and fiber are sequentially introduced and the concrete mixture is mixed for 2 to 3 minutes. After that, the concrete mixture is ready for use.
During the preparation of the mixture, an accelerator of curing is introduced.
The resulting self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties is a liquid consistency, one of the indicators of which is the flow of the Hagermann cone on the glass. In order for the mixture to spread well, the spread must be at least 300 mm.
As a result of applying the claimed method, a self-compacting, extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties is obtained, which contains the following components: Portland cement PC500D0, sand fraction from 0.125 to 0.63, hyperplasticizer, fibers, silica fume, stone flour, set accelerator strength and water. When implementing the method for manufacturing a fiber-reinforced concrete mixture, the following ratio of components is observed, wt.%:
Moreover, when implementing the method for manufacturing a fiber-reinforced concrete mix, stone flour is used from various natural materials or wastes, such as, for example, quartz flour, dolomite flour, limestone flour, etc.
The following grades of hyperplasticizer can be used: Sika ViscoCrete, Glenium, etc.
A strength accelerator such as Master X-Seed 100 (X-SEED 100) or similar strength accelerators may be added during the manufacture of the mixture.
The obtained self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties can be used in the production of artistic products with a complex configuration, such as openwork hedges (see Fig. 2). Use the resulting mixture immediately after its manufacture.
A method for manufacturing concrete products from a self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, obtained by the method described above and having the specified composition, is carried out as follows.
For the manufacture of openwork products by pouring a self-compacting, extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, elastic (polyurethane, silicone, mold-plastic) or rigid plastic molds are used circuit simplification. The form is installed on the technological pallet 2. A thin layer of water is sprayed onto the inner, working surface 3 of the form, which further reduces the number of trapped air bubbles on the front surface of the concrete product.
After that, the resulting fiber-reinforced concrete mixture 4 is poured into a mold, where it spreads and self-compacts under its own weight, squeezing out the air in it. After the self-levelling of the concrete mixture in the mold, a thin layer of water is sprayed onto the concrete poured into the mold for a more intensive release of air from the concrete mixture. Then the form filled with fiber-reinforced concrete mixture is covered from above with the next technological pallet 2, which creates closed cell for more intensive curing of concrete (see figure 1 (a)).
A new mold is placed on this pallet, and the manufacturing process is repeated. Thus, from one portion of the prepared concrete mixture, several molds can be filled successively, installed one above the other, which ensures an increase in the efficiency of using the prepared fiber-reinforced concrete mixture. Forms filled with fiber-reinforced concrete mixture are left to cure the mixture for about 15 hours.
After 15 hours, concrete products are demoulded and sent for grinding the back side, and then into a steaming chamber or into a heat-humidity treatment chamber (HMW), where the products are kept until they are fully cured.
The use of the invention makes it possible to produce highly decorative openwork and thin-walled high-strength concrete products of the M1000 and higher grade using a simplified casting technology without the use of vibration compaction.
The invention can be carried out using the listed known components, while observing the quantitative proportions and the described technological regimes. Known equipment can be used in carrying out the invention.
An example of a method for preparing a self-compacting, extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties.
First, all components of the mixture are weighed and measured in the given amount (wt.%):
Then a measured amount of water and Sika ViscoCrete 20 Gold hyperplasticizer are poured into the mixer. Then the mixer is turned on and the components are mixed. In the process of mixing water and hyperplasticizer, the following components of the mixture are sequentially poured: Portland cement ПЦ500 D0, silica fume, quartz flour. The mixing process is carried out continuously for 2-3 minutes.
At the next stage, sand FR is sequentially introduced. 0.125-0.63 and steel fiber 0.22 × 13mm. The concrete mixture is mixed for 2-3 minutes.
Reducing the mixing time does not make it possible to obtain a homogeneous mixture, and increasing the mixing time does not further improve the quality of the mixture, but delays the process.
After that, the concrete mixture is ready for use.
The total manufacturing time of the fiber-reinforced concrete mixture is from 12 to 15 minutes, this time includes additional operations for backfilling the components.
The prepared self-compacting, extra-high-strength, reaction-powder fiber-reinforced concrete mixture with very high flow properties is used for the manufacture of openwork products by pouring into molds.
Examples of the composition of the obtained self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, made by the claimed method, are shown in table 1.
1. A method for preparing a self-compacting extra-high-strength reaction-powder fiber-reinforced concrete mixture with very high flow properties, which consists in mixing the components of the concrete mixture until the required fluidity is obtained, characterized in that the mixing of the components of the fiber-reinforced concrete mixture is carried out sequentially, and initially water and a hyperplasticizer are mixed in the mixer, then cement, microsilica, stone flour are poured and the mixture is stirred for 2-3 minutes, after which sand and fiber are introduced and mixed for 2-3 minutes until a fiber-reinforced concrete mixture is obtained, containing, wt.%:
2. The method according to claim 1, characterized in that the total time for preparing the concrete mixture is from 12 to 15 minutes.
3. A method for manufacturing products in molds from a fiber-reinforced concrete mixture prepared by the method according to claims 1, 2, which consists in feeding the mixture into molds and subsequent heat treatment in a steaming chamber, and initially a thin layer of water is sprayed onto the inner, working surface of the mold, after filling the mold with a mixture a thin layer of water is sprayed on its surface and the form is covered with a technological pallet.
4. The method according to claim 3, characterized in that the mixture is fed into the molds sequentially, covering the filled mold from above with a technological pallet, after installing the technological pallet, the process of manufacturing products is repeated many times, placing the next form on the technological pallet above the previous one and filling it.
www.findpatent.ru
high-performance reaction-powder high-strength and heavy-duty concretes and fiber-reinforced concretes (options) - patent application 2012113330
Applicant: Volodin Vladimir Mikhailovich (RU)
1. Reaction-powder heavy-duty concrete containing Portland cement PC 500 D0 (gray or white), superplasticizer based on polycarboxylate ether, silica fume with a content of amorphous - vitreous silica of at least 85-95%, characterized in that it additionally includes ground quartz sand(microquartz) or ground stone flour from dense rocks with a specific surface of (3-5) 103 cm2 / g, fine-grained quartz sand of a narrow particle size distribution of fraction 0.1-0.5 ÷ 0.16-0.63 mm, has the specific consumption of cement per unit of concrete strength is not more than 4.5 kg/MPa, it has a high density with a new formulation and with a new structural and topological structure, with the following content of components, % of the mass of dry components in the concrete mix:
Microsilica - 3.2-6.8%;
Water - W / T \u003d 0.95-0.12.
2. Reaction-powder heavy-duty fiber-reinforced concrete containing Portland cement PC 500 D0 (gray or white), superplasticizer based on polycarboxylate ether, microsilica with a content of amorphous vitreous silica of at least 85-95%, characterized in that it additionally includes ground quartz sand (microquartz ) or ground stone flour from dense rocks with a specific surface area (3-5) 103 cm2 / g, fine-grained quartz sand of a narrow granulometric composition of the fraction 0.1-0.5 ÷ 0.16-0.63 mm, as well as the content fiber steel cord (diameter 0.1-0.22 mm, length 6-15 mm), basalt and carbon fibers, has a specific consumption of cement per unit of concrete strength of not more than 4.5 kg / MPa, and the specific consumption of fiber per unit of growth tensile strength in bending, does not exceed 9.0 kg / MPa has a high density with a new formulation and with a new structural and topological structure, and concrete has a ductile (plastic) character of destruction with the following content of components,% of the mass of dry components in concrete mixtures:
Portland cement (gray or white) grade not lower than PC 500 D0 - 30.9-34%;
Superplasticizer based on polycarboxylate ether - 0.2-0.5%;
Microsilica - 3.2-6.8%;
Ground quartz sand (microquartz) or stone flour - 12.3-17.2%;
Fine-grained quartz sand - 53.4-41.5%;
Fiber steel cord 1.5-5.0% by volume of concrete;
Basalt fiber and carbon fibers 0.2-3.0% by volume of concrete;
Water - W / T \u003d 0.95-0.12.
www.freepatent.ru
Construction articles
The article describes the properties and capabilities of high-strength powder concretes, as well as areas and technologies for their application.
The high rate of construction of residential and industrial buildings with new and unique architectural forms, and especially special especially loaded structures (such as large-span bridges, skyscrapers, offshore oil platforms, tanks for storing gases and liquids under pressure, etc.) required the development of new effective concretes. Significant progress in this has been especially noted since the late 1980s. Modern high-quality concretes (HKB) classify a wide range of concretes for various purposes: high-strength and ultra-high-strength concretes [see. Bornemann R., Fenling E. Ultrahochfester Beton-Entwicklung und Verhalten.// Leipziger Massivbauseminar, 2000, Bd. 10; Schmidt M. Bornemann R. Möglichkeiten und Crensen von Hochfestem Beton.// Proc. 14, Jbausil, 2000, Bd. 1], self-compacting concretes, highly corrosion resistant concretes. These types of concrete meet the high requirements for compressive and tensile strength, crack resistance, impact strength, wear resistance, corrosion resistance, and frost resistance.
Undoubtedly, the transition to new types of concrete was facilitated, firstly, by revolutionary achievements in the field of plasticizing concrete and mortar mixtures, and secondly, the emergence of the most active pozzolanic additives - silica fume, dehydrated kaolins and fine ash. Combinations of superplasticizers and especially environmentally friendly hyperplasticizers based on polycarboxylate, polyacrylate and polyglycol base make it possible to obtain superfluid cement-mineral dispersed systems and concrete mixes. Thanks to these achievements, the number of components in concrete with chemical additives reached 6–8, the water-cement ratio decreased to 0.24–0.28 while maintaining plasticity, characterized by a cone draft of 4–10 cm. flour (KM) or without it, but with the addition of MK in highly workable concretes (Ultrahochfester Beton, Ultra hochleistung Beton) on hyperplasticizers, in contrast to those cast on traditional joint ventures, the perfect fluidity of concrete mixes is combined with low sedimentation and self-compacting with spontaneous removal of air.
"High" rheology with a significant water reduction in superplasticized concrete mixtures is provided by a fluid rheological matrix, which has different scale levels of the structural elements that make it up. In crushed stone concrete for crushed stone, the cement-sand mortar serves as a rheological matrix at various micro-mesolevels. In plasticized concrete mixtures for high-strength concretes for crushed stone as a macrostructural element, the rheological matrix, the proportion of which should be much higher than in ordinary concretes, is a more complex dispersion consisting of sand, cement, stone flour, microsilica and water. In turn, for sand in conventional concrete mixtures, the rheological matrix at the micro level is a cement-water paste, the proportion of which can be increased to ensure fluidity by increasing the amount of cement. But this, on the one hand, is uneconomical (especially for concretes of classes B10 - B30), on the other hand, paradoxically, superplasticizers are poor water-reducing additives for Portland cement, although they were all created and are being created for it. Almost all superplasticizers, as we have shown since 1979, "work" much better on many mineral powders or on their mixture with cement [see. Kalashnikov VI Fundamentals of plasticization of mineral dispersed systems for the production of building materials: Dissertation in the form of a scientific report for the degree of Doctor of Science. tech. Sciences. - Voronezh, 1996] than on pure cement. Cement is an unstable in water, hydrating system that forms colloidal particles immediately after contact with water and quickly thickens. And colloidal particles in water are difficult to disperse with superplasticizers. An example is clay slurries that are difficult to superfluidize.
Thus, the conclusion suggests itself: it is necessary to add stone flour to the cement, and it will increase not only the rheological effect of the joint venture on the mixture, but also the proportion of the rheological matrix itself. As a result, it becomes possible to significantly reduce the amount of water, increase the density and increase the strength of concrete. The addition of stone powder will practically be equivalent to an increase in cement (if the water-reducing effects are significantly higher than with the addition of cement).
It is important here to focus not on replacing part of the cement with stone flour, but on adding it (and a significant proportion - 40–60%) to Portland cement. Based on the polystructural theory in 1985–2000. all works on changing the polystructure were aimed at replacing 30–50% of Portland cement with mineral fillers to save it in concrete [see. Solomatov V.I., Vyrovoy V.N. et al. Composite building materials and structures of reduced material consumption. - Kyiv: Budivelnik, 1991; Aganin S.P. Concretes of low water demand with modified quartz filler: Abstract for the competition of an account. degree cand. tech. Sciences. - M, 1996; Fadel I. M. Intensive separate technology of concrete filled with basalt: Abstract of the thesis. cand. tech. Sciences - M, 1993]. The strategy of saving Portland cements in concretes of the same strength will give way to the strategy of saving concrete with 2–3 times higher strength not only in compression, but also in bending and axial tension, and impact. Saving concrete in more openwork structures will give a higher economic effect than saving cement.
Considering the compositions of rheological matrices at different scale levels, we establish that for sand in high-strength concretes, the rheological matrix at the micro level is a complex mixture of cement, flour, silica, superplasticizer and water. In turn, for high-strength concretes with microsilica for a mixture of cement and stone flour (equal dispersity) as structural elements, another rheological matrix appears with a smaller scale level - a mixture of silica fume, water and superplasticizer.
For crushed concrete, these scales of the structural elements of rheological matrices correspond to the scales of the optimal granulometry of the dry components of concrete to obtain its high density.
Thus, the addition of stone flour performs both a structural-rheological function and a matrix-filling one. For high-strength concretes, the reactive-chemical function of stone flour is no less important, which is performed with a higher effect by reactive microsilica and microdehydrated kaolin.
The maximum rheological and water-reducing effects caused by the adsorption of SP on the surface of the solid phase are genetically characteristic of finely dispersed systems with a high interface.
Table 1.
Rheological and water-reducing action of SP in water-mineral systems
Table 1 shows that in Portland cement casting slurries with SP, the water-reducing effect of the latter is 1.5–7.0 times (sic!) Higher than in mineral powders. For rocks, this excess can reach 2–3 times.
Thus, the combination of hyperplasticizers with microsilica, stone flour or ash made it possible to raise the level of compressive strength to 130–150, and in some cases to 180–200 MPa or more. However, a significant increase in strength leads to an intensive increase in brittleness and a decrease in Poisson's ratio to 0.14–0.17, which leads to the risk of sudden destruction of structures in emergency situations. Getting rid of this negative property of concrete is carried out not so much by reinforcing the latter with rod reinforcement, but by combining rod reinforcement with the introduction of fibers from polymers, glass and steel.
The fundamentals of plasticizing and water reduction of mineral and cement dispersed systems were formulated in the doctoral dissertation of Kalashnikov V.I. [cm. Kalashnikov VI Fundamentals of plasticization of mineral dispersed systems for the production of building materials: Dissertation in the form of a scientific report for the degree of Doctor of Science. tech. Sciences. - Voronezh, 1996] in 1996 on the basis of previously completed work in the period from 1979 to 1996. [Kalashnikov V. I., Ivanov I. A. On the structural-rheological state of extremely liquefied highly concentrated disperse systems. // Proceedings of the IV National Conference on Mechanics and Technology of Composite Materials. - Sofia: BAN, 1985; Ivanov I. A., Kalashnikov V. I. Efficiency of plasticization of mineral disperse compositions depending on the concentration of the solid phase in them. // Rheology of concrete mixes and its technological tasks. Tez. report of the III All-Union Symposium. - Riga. - RPI, 1979; Kalashnikov V. I., Ivanov I. A. On the nature of plasticization of mineral dispersed compositions depending on the concentration of the solid phase in them.// Mechanics and technology of composite materials. Materials of the II National Conference. - Sofia: BAN, 1979; Kalashnikov VI On the reaction of various mineral compositions to naphthalene-sulfonic acid superplasticizers and the effect of instant alkalis on it. // Mechanics and technology of composite materials. Materials of the III National Conference with the participation of foreign representatives. - Sofia: BAN, 1982; Kalashnikov VI Accounting for rheological changes in concrete mixtures with superplasticizers. // Proceedings of the IX All-Union Conference on Concrete and Reinforced Concrete (Tashkent, 1983). - Penza. - 1983; Kalashnikov VI, Ivanov IA Peculiarities of rheological changes in cement compositions under the action of ion-stabilizing plasticizers. // Collection of works "Technological mechanics of concrete". – Riga: RPI, 1984]. These are the prospects for the directed use of the highest possible water-reducing activity of the joint venture in finely dispersed systems, the features of quantitative rheological and structural-mechanical changes in superplasticized systems, which consist in their avalanche-like transition from solid-state to fluid states with a super-small addition of water. These are the developed criteria for gravitational spreading and post-thixotropic flow resource of highly dispersed plasticized systems (under the action of its own weight) and spontaneous leveling of the day surface. This is the advanced concept of the limiting concentration of cement systems with finely dispersed powders from rocks of sedimentary, magmatic and metamorphic origin, selective in terms of high water reduction to SP. The most important results obtained in these works are the possibility of a 5–15-fold reduction in water consumption in dispersions while maintaining gravitational spreadability. It was shown that by combining rheologically active powders with cement, it is possible to enhance the effect of the joint venture and obtain high-density castings. It is these principles that are implemented in reaction-powder concretes with an increase in their density and strength (Reaktionspulver beton - RPB or Reactive Powder Concrete - RPC [see Dolgopolov N. N., Sukhanov M. A., Efimov S. N. A new type of cement: structure of cement stone. // Building materials. - 1994. - No. 115]). Another result is an increase in the reducing action of the joint venture with an increase in the dispersion of the powders [see. Kalashnikov VI Fundamentals of plasticization of mineral dispersed systems for the production of building materials: Dissertation in the form of a scientific report for the degree of Doctor of Science. tech. Sciences. – Voronezh, 1996]. It is also used in powdered fine-grained concretes by increasing the proportion of finely dispersed constituents by adding microsilica to the cement. A novelty in the theory and practice of powdered concrete was the use of fine sand with a fraction of 0.1–0.5 mm, which made the concrete fine-grained, in contrast to ordinary sandy sand with a fraction of 0–5 mm. Our calculation of the average specific surface of the dispersed part of powder concrete (composition: cement - 700 kg; fine sand fr. 0.125–0.63 mm - 950 kg; basalt flour Ssp = 380 m2/kg - 350 kg; kg - 140 kg) with its content of 49% of the total mixture with fine-grained sand of a fraction of 0.125–0.5 mm shows that with a dispersion of MK Smk = 3000m2 / kg, the average surface of the powder part is Svd = 1060m2 / kg, and with Smk = 2000 m2 /kg - Svd = 785 m2 / kg. It is on such finely dispersed components that fine-grained reaction-powder concretes are made, in which the volume concentration of the solid phase without sand reaches 58–64%, and together with sand - 76–77% and is slightly inferior to the concentration of the solid phase in superplasticized heavy concretes (Cv = 0, 80–0.85). However, in crushed concrete, the volume concentration of the solid phase minus crushed stone and sand is much lower, which determines the high density of the dispersed matrix.
High strength is ensured by the presence of not only microsilica or dehydrated kaolin, but also a reactive powder from ground rock. According to the literature, fly ash, baltic, limestone or quartz flour are mainly introduced. Wide opportunities in the production of reactive powder concretes opened up in the USSR and Russia in connection with the development and research of composite binders of low water demand by Yu. M. Bazhenov, Sh. T. Babaev, and A. Komarom. A., Batrakov V. G., Dolgopolov N. N. It was proved that the replacement of cement in the process of grinding VNV with carbonate, granite, quartz flour up to 50% significantly increases the water-reducing effect. The W / T ratio, which ensures the gravitational spreading of crushed stone concrete, is reduced to 13–15% compared to the usual introduction of joint venture, the strength of concrete on such VNV-50 reaches 90–100 MPa. In essence, on the basis of VNV, microsilica, fine sand and dispersed reinforcement, modern powder concretes can be obtained.
Dispersion-reinforced powder concretes are very effective not only for load-bearing structures with combined reinforcement with prestressed reinforcement, but also for the production of very thin-walled, including spatial, architectural details.
According to the latest data, textile reinforcement of structures is possible. It was the development of textile-fiber production of (fabric) three-dimensional frames made of high-strength polymer and alkali-resistant threads in developed foreign countries that was the motivation for the development more than 10 years ago in France and Canada of reaction-powder concretes with joint ventures without large aggregates with extra fine quartz aggregate filled with stone powders and microsilica. Concrete mixtures from such fine-grained mixtures spread under the action of their own weight, filling the completely dense mesh structure of the woven frame and all filigree-shaped interfaces.
"High" rheology of powder concrete mixes (PBS) provides with a water content of 10–12% of the mass of dry components, the yield strength?0= 5–15 Pa, i.e. only 5-10 times higher than in oil paints. With this value of Δ0, it can be determined using the mini-areometric method developed by us in 1995. The low yield point is ensured by the optimal thickness of the rheological matrix interlayer. From the consideration of the topological structure of the PBS, the average thickness of the interlayer X is determined by the formula:
where is the average diameter of sand particles; is the volume concentration.
For the composition below, with W/T = 0.103, the thickness of the interlayer will be 0.056 mm. De Larrard and Sedran found that for finer sands (d = 0.125–0.4 mm) the thickness varies from 48 to 88 µm.
An increase in the interlayer of particles reduces the viscosity and ultimate shear stress and increases fluidity. Fluidity can be increased by adding water and introducing SP. In general, the effect of water and SP on the change in viscosity, ultimate shear stress, and yield strength is ambiguous (Fig. 1).
The superplasticizer reduces the viscosity to a much lesser extent than the addition of water, while the yield strength reduction due to SP is much greater than that due to the influence of water.
Rice. 1. Effect of SP and water on viscosity, yield strength and yield strength
The main properties of superplasticized ultimate filled systems are that the viscosity can be quite high and the system can flow slowly if the yield strength is low. For conventional systems without SP, the viscosity may be low, but the increased yield strength prevents them from spreading, because they do not have a post-thixotropic flow resource [see. Kalashnikov VI, Ivanov IA Peculiarities of rheological changes in cement compositions under the action of ion-stabilizing plasticizers. // Collection of works "Technological mechanics of concrete". – Riga: RPI, 1984].
The rheological properties depend on the type and dosage of the joint venture. The influence of three types of joint ventures is shown in fig. 2. The most effective joint venture is Woerment 794.
Rice. 2 Influence of the type and dosage of SP on?o: 1 - Woerment 794; 2 - S-3; 3 – Melment F 10
At the same time, it was not the domestic SP S-3 that turned out to be less selective, but the foreign SP based on the melamine Melment F10.
The spreadability of powdered concrete mixtures is extremely important in the formation of concrete products with woven volumetric mesh frames laid in a mold.
Such voluminous openwork-fabric frames in the form of a tee, an I-beam, a channel and other configurations allow for quick reinforcement, which consists in installing and fixing the frame in a mold, followed by pouring suspension concrete, which easily penetrates through the frame cells with a size of 2–5 mm (Fig. 3) . Fabric frames can radically increase the crack resistance of concrete under the influence of alternating temperature fluctuations and significantly reduce deformation.
The concrete mixture should not only easily pour locally through the mesh frame, but also spread when filling the form by "reverse" penetration through the frame with an increase in the volume of the mixture in the form. To assess the fluidity, powder mixtures of the same composition were used in terms of the content of dry components, and the spreadability from the cone (for the shaking table) was controlled by the amount of SP and (partially) water. Spreading was blocked with a mesh ring 175 mm in diameter.
Rice. 3 Fabric scaffold sample
Rice. 4 Splashes of the mixture with free and blocked spreading
The mesh had a clear dimension of 2.8 × 2.8 mm with a wire diameter of 0.3 × 0.3 mm (Fig. 4). Control mixtures were made with melts of 25.0; 26.5; 28.2 and 29.8 cm. As a result of the experiments, it was found that with an increase in the fluidity of the mixture, the ratio of the diameters of free dc and blocked flow db decreases. On fig. 5 shows the change in dc/dbotdc.
Rice. 5 Change dc/db from free spread dc
As follows from the figure, the difference in mixture spreads dc and db disappears at fluidity characterized by a free spread of 29.8 cm. At dc.= 28.2, the spread through the mesh decreases by 5%. Particularly large deceleration during spreading through the mesh is experienced by a mixture with a spread of 25 cm.
In this regard, when using mesh frames with a cell size of 3–3 mm, it is necessary to use mixtures with a spread of at least 28–30 cm.
Physical and technical properties of dispersed-reinforced powder concrete, reinforced by 1% by volume with steel fibers with a diameter of 0.15 mm and a length of 6 mm, are presented in table 2
Table 2.
Physical and technical properties of powder concrete on a binder of low water demand using domestic SP S-3
According to foreign data, with 3% reinforcement, the compressive strength reaches 180–200 MPa, and with axial tension - 8–10 MPa. Impact strength increases more than tenfold.
The possibilities of powdered concrete are far from being exhausted, given the effectiveness of hydrothermal treatment and its influence on the increase in the proportion of tobermorite, and, accordingly, xonotlite.
www.allbeton.ru
Powder reaction concrete
Last update of the encyclopedia: 12/17/2017 - 17:30
Reactive powder concrete is concrete made from finely ground reactive materials with a grain size of 0.2 to 300 microns and is characterized by high strength (more than 120 MPa) and high water resistance.
[GOST 25192-2012. Concrete. Classification and general technical requirements]
Reactive powder concrete reactive powder concrete-RPC] - a composite material with high compressive strength of 200-800 MPa, bending >45 MPa, including a significant amount of highly dispersed mineral components - quartz sand, microsilica, superplasticizer, as well as steel fiber with low W / T (~0.2), using heat and moisture treatment of products at a temperature of 90-200°C.
[Usherov-Marshak A.V. Concrete science: a lexicon. M.: RIF Building Materials. - 2009. - 112 p.]
Copyright holders! If free access to this term is a copyright infringement, the compilers are ready, at the request of the copyright holder, to remove the link, or the term (definition) itself from the site. To contact the administration, use the feedback form.
enciklopediyastroy.ru
