CN111377653A - Efficient anti-cracking agent for cement concrete and preparation method and application thereof - Google Patents
Efficient anti-cracking agent for cement concrete and preparation method and application thereof Download PDFInfo
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- CN111377653A CN111377653A CN201811651786.8A CN201811651786A CN111377653A CN 111377653 A CN111377653 A CN 111377653A CN 201811651786 A CN201811651786 A CN 201811651786A CN 111377653 A CN111377653 A CN 111377653A
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Abstract
The invention discloses an efficient anti-cracking agent for concrete and a preparation method and application thereof. The efficient crack resistance agent for cement concrete comprises a calcareous expansion component and a zeolite component which forms a film on the surface and contains cement hydration heat regulating material liquid in holes. The mass ratio of the calcareous expansion component to the zeolite component which forms a film on the surface and contains cement hydration heat regulating material liquid in the pores is 40: 60-20: 80. The high-efficiency anti-cracking agent for the cement concrete, which is prepared by the invention, overcomes the adverse effect of internal curing materials on the workability of the concrete; the expansion performance of calcium oxide is improved; the internal pores of the zeolite release water, so that the internal humidity of the concrete is regulated and controlled; the internal pores obstruct the contact area of the cement alkaline substances and the hydration heat regulating material, the cement hydration heat regulating material is slowly released, the regulating and controlling efficiency of the cement hydration heat regulating material is improved, the coordinated control of temperature and humidity deformation is realized, and the anti-cracking performance of concrete is improved.
Description
Technical Field
The invention belongs to the technical field of building material concrete additives, and particularly relates to a high-efficiency anti-cracking agent for cement concrete as well as a preparation method and application thereof.
Background
The cement concrete is a hydraulic cementing material, is a cement concrete structure which is in a natural environment from the beginning of casting and forming, has self-shrinkage, drying shrinkage and temperature reduction shrinkage due to self hydration reaction and a water loss process to a surrounding environment medium in a hydration hardening process, and is a main cause of engineering quality accidents due to the cracking of the concrete caused by the shrinkage under a constraint condition. The drying shrinkage refers to irreversible shrinkage caused by drying due to the fact that the tension of the inner surface of a capillary hole is increased to cause the negative pressure of a cement capillary after the water absorbed by the capillary hole in concrete is lost in an unsaturated environment after the concrete is hardened. Self-shrinkage refers to that the relative humidity in the sealed concrete is reduced along with the hydration process of cement, and during the process, water is consumed during the hydration of the cement to cause the pores of the gel to descend to form a meniscus, so that the self-shrinkage occurs. The relative humidity of the concrete body is reduced, so that the volume is relatively reduced, and the self-shrinkage of the high-strength concrete is generally larger than that of common concrete due to the large using amount of the cementing material. The temperature reduction shrinkage refers to that after concrete is poured, the temperature of the concrete is raised due to a large amount of hydration heat generated by hydration of cement, the volume thermal expansion is generated, and after the highest temperature is reached, the temperature of the concrete is reduced to the ambient temperature from the highest value along with the dissipation of heat to the external environment, so that the shrinkage of the concrete is caused. Under constraint conditions, self-shrinkage, drying shrinkage and temperature drop shrinkage are the main causes of concrete non-load cracks.
How to take effective measures to reduce or even eliminate various kinds of shrinkage and avoid cracking from the source is always a problem which is sought by engineers. At present, the shrinkage of concrete is compensated by adding a concrete expanding agent at home and abroad, and the mixing amount is 6-12%. In the construction process, the requirement is that the sufficient moisture preservation and maintenance are required to achieve a certain shrinkage compensation effect. Generally, the use effect of the underground engineering bottom plate is good, but the side wall and the top plate are greatly restrained and difficult to maintain in a moisture-preserving manner, so that the structural concrete is easy to crack under the combined action of self-shrinkage, dry shrinkage and temperature-reduction shrinkage.
Because the concrete structure is compact, the film covering, the water spraying and the like only carry out maintenance on the concrete surface layer, and the external moisture is difficult to effectively diffuse inside the structure for moisturizing and maintaining. The most suitable method is to provide water source from the inside of the concrete for self-curing by means of the internal curing material. The internal curing material has certain water absorption and storage capacity, and can release water at proper time when the relative humidity in the concrete begins to reduce, promote the hydration of cement and improve the internal humidity of cement stone. The currently used internal curing materials include organic polymers and inorganic porous solids, typically represented by super absorbent resins (SAPs) and lightweight aggregates, respectively. The SAP absorbs water by means of hydrophilic groups on polymer chains, but the dispersibility of SAP particles is difficult to control, the SAP particles are easy to bond into a cluster, and a large cavity is left after water is released, so that the working performance, the mechanical property, the volume deformation, the durability and the like of concrete are influenced. Inorganic porous materials, such as light aggregate, expanded shale, rice hull ash and the like, can obviously improve the internal relative humidity of the high-strength concrete and relieve early shrinkage deformation. However, the inorganic materials can affect the workability of the concrete if the inorganic materials do not absorb water in advance, the risk of bleeding of the concrete is increased if the inorganic materials absorb water in advance, and the strength and the elastic modulus of the concrete are reduced along with the increase of the mixing amount of the lightweight aggregate. How to prepare the anti-cracking agent which can obviously improve the internal humidity of hardened concrete, control the temperature rise of the concrete and compensate the shrinkage is a problem which needs to be solved urgently in the field of building materials.
Natural zeolite is a kind of porous aluminosilicate material with unique silicon-oxygen tetrahedron SiO4]Structure, can be made of alundum [ AlO4]And (4) replacement. The chemical general formula is as follows: a. thex/n(SiO2)(AlO2)x·mH2O and A are cations. Zeolite has the characteristics of adsorptivity, ion exchange property, acid resistance and the like. Large amount of active SiO in zeolite2And Al2O3OH in concrete high alkaline solution-The volcanic ash reaction is generated, a large amount of hydrated silicate and aluminate gel is formed, the later strength of the concrete is improved, and the porosity is reduced; on the other hand natural zeolites havingThe pore structure has larger specific surface area after being levigated, can adsorb a large amount of water and gas, and can regulate and control the internal humidity of the concrete. In the process of popularizing and applying the zeolite powder, the zeolite is added into concrete to obtain the same slump, and the dosage of a concrete water reducing agent is increased; and the slump loss of the fresh concrete is easy to accelerate, the fresh concrete loses fluidity within half an hour in serious cases, the requirement of normal construction is difficult to meet, and the popularization and the application of the technology in the construction engineering are seriously influenced.
Chinese patent CN103058549B discloses a concrete anti-cracking siliceous waterproofing agent. The composite material is prepared by mixing 75-85% of activated modified zeolite powder, 1-3% of defoaming agent and 13-19% of high-alumina clinker. The activated modified zeolite powder is prepared by modifying 77-85% of roasted composite zeolite powder, 0.1-0.5% of silane coupling agent, 2-6% of stearic acid, 1.5-5% of acetone and 2-6% of emulsified silicone oil. The anti-cracking siliceous waterproofing agent can improve the anti-permeability performance of concrete, but has no anti-cracking function and limited humidity control function. The concrete with the strength grade of C30 does not crack, has extremely low permeability coefficient, and can completely meet the requirement of impermeability; but once cracked, groundwater and the like will start to leak from the crack.
Chinese patent CN 108751777B, CN 108774015B discloses a temperature-inhibiting anti-cracking waterproof agent for concrete, a zeolite-based hydration heat slow-release material and a preparation method thereof. The zeolite-based hydration heat slow-release material is obtained by mixing and finely crushing the phase-change material, the organic acid and the boiling powder. The zeolite-based hydration heat slow-release material is compounded with a plastic expanding agent and a double-source expanding agent to obtain the temperature-inhibiting anti-cracking waterproof agent. The organic acid adopts citric acid or tartaric acid, only influences the induction period of cement, plays a role in retarding coagulation, and has no effect on temperature control. The temperature-inhibiting anti-cracking waterproof agent is difficult to regulate and control the internal humidity of concrete.
Chinese patent CN 108774016B discloses a dual expansion source for concrete and a method for preparing the same. The double-source expanding agent is composed of 30-40 wt% of modified zeolite powder, calcium oxide clinker, alumina and sulphoaluminate. After the zeolite is modified by acetone, although the influence on the workability of concrete is small, the water absorption capacity of the concrete in the later period is limited. Therefore, the modified zeolite powder prepared by the method has limited effect of improving the expansion performance of the calcium oxide-sulphoaluminate expanded clinker.
Chinese patent CN 108069633B discloses a preparation method of zeolite powder modified magnesia expansive agent. The zeolite powder modified magnesium oxide expanding agent is prepared by mixing 50-90% of light-burned MgO and 10-50% of zeolite powder. The MgO particles are a porous material, and the zeolite powder also has a porous structure. The two materials have larger specific surface area after being ground, can absorb a large amount of water, and can absorb a large amount of water when being mixed into concrete, so that the workability of the concrete is seriously deteriorated, and the construction is difficult.
In the technology, the zeolite powder for regulating and controlling humidity is a porous material, and if the zeolite powder is not modified, the workability of concrete is influenced; such as the modified concrete, the humidity compensation effect on the concrete is weakened. The calcium and sulphoaluminate expansive agents compensate the shrinkage of the concrete, and a certain shrinkage compensation effect can be achieved only by fully moisturizing and maintaining in the construction process. Therefore, it is necessary to solve the above problems and prepare an anti-cracking agent capable of significantly improving the internal humidity of hardened concrete, controlling the temperature rise of the concrete and compensating the shrinkage.
Disclosure of Invention
Aiming at the problems that the workability is influenced, such as the concrete strength is influenced after pre-water absorption, when the internal curing material is doped into the concrete in the prior art, the use amount of a water reducing agent is increased under the same slump condition if the internal curing material does not pre-absorb water, the concrete slump loss is accelerated, and the like; aiming at the problems of low early expansion and weak later expansion capability and the like caused by insufficient humidity of calcium and calcium sulphoaluminate expansion materials in the prior art, the invention provides an efficient anti-cracking agent for cement concrete and a preparation method and application thereof.
The efficient anti-cracking agent for cement concrete is prepared by adding zeolite powder into cement hydration heat regulation material liquid prepared by dextrin, wherein the zeolite powder is used as a carrier of the cement hydration heat regulation material liquid; the cement hydration heat regulating material liquid is absorbed and stored in the pores of the zeolite particles by utilizing the porosity of the zeolite particles and through physical absorption and chemical reaction; forming a film on the surface of zeolite powder particles containing hydration heat regulating material liquid by a fluidized bed preparation process; the zeolite powder with a film formed on the surface and containing a liquid hydration heat regulating material inside is compounded with a calcium oxide expanding agent to form the high-efficiency anti-cracking agent.
The high-efficiency anti-cracking agent for the cement concrete, which is prepared by the invention, overcomes the adverse effect of internal curing materials on the workability of the concrete; the expansion performance of calcium oxide is improved; the internal pores of the zeolite release water, so that the internal humidity of the concrete is regulated and controlled; the internal pores obstruct the contact area of the cement alkaline liquid and the hydration heat regulating material, the cement hydration heat regulating material is slowly released, the regulating efficiency of the cement hydration heat regulating material is improved, the coordinated control of temperature and humidity deformation is realized, and the anti-cracking performance of concrete is improved.
The efficient crack resistance agent for cement concrete comprises a calcareous expansion component and a zeolite component which forms a film on the surface and contains cement hydration heat regulating material liquid in pores. The mass ratio of the calcareous expansion component to the zeolite component which forms a film on the surface and contains cement hydration heat regulating material liquid in the pores is 40: 60-20: 80.
The calcareous expanding component comprises free calcium oxide, sulphoaluminate and anhydrite and mixtures thereof.
The zeolite with the film formed on the surface and containing the cement hydration heat regulating material liquid in the pores is formed by treating 40-60 wt% of zeolite, 28.5-49.5 wt% of cement hydration heat regulating material liquid, 10-20 wt% of calcium carbonate, 0.2-1.0 wt% of pullulan, 0.2-0.5 wt% of sorbitol and 0.01-0.05 wt% of erythritol through a fluidized bed process.
The zeolite is natural zeolite with 800 meshes, and preferably mordenite powder with an ammonia absorption value of more than or equal to 135mmol/100 g.
The cement hydration heat regulating material liquid is dextrin solution with a cement hydration rate regulating function, and the solvent is water. The mass ratio of dextrin and water with the cement hydration heat regulation function is 10: 90-40: 60. The cement hydration heat regulating material preferably has an average molecular weight of 7000-20000 g/mol.
The calcium carbonate is the main component of the zeolite surface film forming, and forms the framework of the film. The calcium carbonate is preferably CaCO in calcium carbonate3The content is not less than85 percent, and the fineness is more than or equal to 1800 meshes.
The pullulan is a water-soluble mucopolysaccharide, and a bonding forming agent is used for forming a film and isolating the air to form a stable and compact film so as to prevent moisture from volatilizing.
The sorbitol can be filled in calcium carbonate to form gaps among frameworks, so that the formed membrane structure is protected from being damaged easily.
The erythritol can promote the internal water retention of zeolite, has high solution heat, and has strong refrigeration and microorganism inhibition effects.
The invention relates to a preparation method of an efficient anti-cracking agent for cement concrete, which comprises the following steps:
(1) limestone, pullulan, sorbitol and erythritol are fully and uniformly mixed according to a certain mass ratio to form a mixture for film formation.
(2) The resulting mixture was slowly fed into the granulation fluidized bed to thoroughly boil the film-forming mixture.
(3) Adding zeolite into cement hydration heat regulating material liquid prepared by dextrin, and uniformly stirring to form suspension. The suspension was uniformly sprayed in the fluidized bed using a spray gun. The liquid inlet speed of the spray gun and the pressure of the spray gun are regulated to control the particle size of the zeolite component of the surface film and the pore containing cement hydration heat regulating material liquid.
(4) Separating out zeolite components which are quickly formed into films in airflow and contain cement hydration heat regulating material liquid in pores, and mixing the zeolite components with calcareous expansion components to obtain the efficient anti-cracking agent for the cement concrete.
The internal temperature of the fluidized bed is controlled at 30-80 ℃, preferably 60-70 ℃.
The high-efficiency anti-cracking agent for the cement concrete disclosed by the invention needs to meet the requirement of the anti-cracking agent on fineness. Preferably, the specific surface area of the efficient anti-cracking agent for cement concrete is 150-300m2/kg。
The high-efficiency anti-cracking agent for the cement concrete is suitable for: the concrete structure and the prefabricated member have strength grades of C50 and above of side walls, bottom plates and top plates with the requirements of shrinkage compensation, crack resistance, permeability resistance and temperature control.
The efficient anti-cracking agent for cement concrete disclosed by the invention is characterized in that the mixing amount of the C50-C100 concrete accounts for 3-10% of the total mass of the adhesive material.
Compared with the prior art, the invention has the beneficial effects that:
(1) the high-efficiency anti-cracking agent for the cement concrete, which is prepared by the invention, overcomes the adverse effect of internal curing materials on the workability of the concrete; the expansion performance of calcium oxide is improved; the internal pores of the zeolite release water, so that the internal humidity of the concrete is regulated and controlled; the internal pores obstruct the contact area of the cement alkaline substances and the hydration heat regulating material, the cement hydration heat regulating material is slowly released, the regulating and controlling efficiency of the cement hydration heat regulating material is improved, the coordinated control of temperature and humidity deformation is realized, and the anti-cracking performance of concrete is improved.
(2) According to the preparation method of the efficient anti-cracking agent for the cement concrete, drying treatment is not needed in the preparation process of the cement hydration heat regulating material, so that the process for preparing the efficient hydration heat regulating material in the prior art is omitted; the preparation process is simple and easy to implement, the production cost is greatly reduced, and the social and economic benefits are remarkable.
Drawings
FIG. 1 shows the adiabatic temperature rise of C50 concrete doped with the efficient crack-resistant agent, the same calcareous expansion component, the same cement hydration heat control material liquid and the same zeolite powder obtained in example 1; 1# is C50 concrete, 2# is calcium expansion component doped with 1.6 wt%, 3# is zeolite powder doped with 3.84 wt%, 4# is cement hydration heat regulating material liquid doped with 1.824 wt%, and 5# is high-efficiency crack-resistant agent for cement concrete doped with 8.0 wt% in example 1 (the ratio of zeolite with surface film-forming and cement hydration heat regulating material liquid contained in pores to calcium expansion component is 80 wt%: 20 wt%).
FIG. 2 is a graph showing the temperature increase rate under adiabatic conditions for C50 concrete doped with the efficient crack resistance agent and the same calcareous expansive component obtained in example 1; 1# standard C50 concrete, 2# concrete doped with 1.6 wt% of calcareous expansion component, and 5# concrete doped with 8.0 wt% of the high-efficiency crack-resistant agent for cement concrete in example 1 (the ratio of zeolite with surface film forming and cement hydration heat regulating material liquid contained in pores to the calcareous expansion component is 80 wt%: 20 wt%).
FIG. 3 shows the temperature rise rate of the C50 concrete doped with the efficient crack-resistant agent and the same cement hydration heat control material liquid obtained in example 1 under adiabatic conditions; 1# standard C50 concrete, 4# cement hydration heat regulating material liquid doped with 1.824 wt%, and 5# cement hydration heat regulating material liquid doped with 8.0 wt% of the high-efficiency crack-resistant agent for cement concrete in example 1 (the ratio of zeolite to calcareous expansion component contained in the cement hydration heat regulating material liquid in the pores, which forms a film on the surface, is 80 wt%: 20 wt%).
Detailed Description
The technical characteristics of the efficient anti-cracking agent for cement concrete, the preparation method and the application thereof are further described below by combining specific examples, but not limited to the examples; in the present invention, all the percentages are mass percentages unless otherwise specified.
Example 1
Preparation of efficient anti-cracking agent for cement concrete
The calcareous expansion component is selected from CaO expanding agent prepared by a rotary kiln by Jiangsu Subo new material company Limited; the zeolite powder is mordenite powder which has an ammonia absorption value of more than or equal to 135mmol/100g and is sold in the market and passes through 800 meshes. The cement hydration heat regulating component is selected from Jiangsu Subo new materials GmbH. The content of dextrin in the cement hydration heat regulating material liquid is 40 wt%, and the number average molecular weight of the dextrin is 7000-20000 g/mol. Calcium carbonate is commercially available as CaCO3The content is more than or equal to 85 percent, and the fineness is more than or equal to 1800 meshes. Pullulan, sorbitol and erythritol are commercially available products.
Limestone, pullulan, sorbitol and erythritol are fully and uniformly mixed according to a certain mass ratio to form a mixture for film formation. Slowly feeding the resulting mixture into a granulation fluidized bed; the skip car is sent into the corresponding position, and the material taking hole is pulled open, so that the material state can be checked in the operation process, and the material can be quickly pumped when being checked. Sealing the equipment to form a closed space in the fluidized bed, determining the material condition through an observation port, controlling the air speed according to the material condition, and adjusting the induced air force to be 25HZ to ensure that the film-formed mixture is fully boiled. Adding zeolite powder into cement hydration heat regulating material liquid prepared by dextrin, and uniformly stirring to form suspension. The particle size of the zeolite component of the liquid containing the cement hydration heat regulating material in the hole, which forms a film on the surface, is controlled by adjusting the liquid inlet speed of the spray gun to be 45rpm and the pressure of the spray gun to be 10 kPa. Adding zeolite into cement hydration heat regulating material liquid prepared by dextrin, and uniformly stirring to form suspension. The suspension is atomized and uniformly sprayed in the fluidized bed by adjusting the spray gun. The particle size of the zeolite component of the surface film and the pore containing cement hydration heat regulating material liquid is controlled to be 10-20 mu m by regulating the liquid inlet speed of the spray gun and the pressure of the spray gun. The temperature inside the fluidized bed is controlled at 60-70 ℃.
The formed zeolite with the surface film and the cement hydration heat regulating material liquid in the pores consists of 60 percent of zeolite, 28.5 percent of hydration heat regulating material liquid, 10 percent of calcium carbonate, 1.0 percent of pullulan, 0.45 percent of sorbitol and 0.05 percent of erythritol. Separating out zeolite components which are quickly formed into films in airflow and contain cement hydration heat regulating material liquid in pores, and mixing the zeolite components with calcareous expansion components to obtain the efficient anti-cracking agent for the cement concrete.
Table 1 shows the ratio of the calcareous expansion component to the zeolite which forms a film on the surface and contains cement hydration heat regulating material liquid in the pores in the prepared high-efficiency anti-cracking agent.
Working performance test of efficient anti-cracking agent for cement concrete
And evaluating the influence of the high-efficiency anti-cracking agent on the fluidity of the cement paste by using a paste cleaning test. The method for testing the net slurry fluidity of the cementing material is carried out according to the relevant regulations of GB80770-2000 concrete admixture homogeneity experimental method; the water-to-gel ratio of the cement paste was 0.35.
Table 2 compares the performance of the high efficiency crack resistance agent with the same untreated zeolite powder.
The test results in table 2 show that the high-efficiency anti-cracking agent for cement concrete prepared by the invention can effectively improve the initial fluidity of the zeolite-containing internal curing material, can remarkably improve the fluidity retention capacity of the cement paste after 60min, and provides guarantee for popularization and application of the zeolite powder internal curing material. The influence of the zeolite component on the fluidity of cement paste cannot be improved by adopting a simple compounding mode of the zeolite component and calcium oxide.
(III) testing of temperature control effect of efficient anti-cracking agent for cement concrete
Table 3 shows the mixing ratio of C50 concrete for a certain project, wherein the mineral powder is replaced by the efficient anti-cracking agent (sample 1-1) for the cement concrete; selecting a calcium expansion Component (CA) which is the same as the high-efficiency anti-cracking agent to replace the mineral powder; selecting the same zeolite powder to replace mineral powder; the same hydration heat regulating material liquid (TRI) is selected to replace the mineral powder.
The cement is conch P.II 42.5 cement; the fly ash comes from Jiangsu Nanjing Huaneng power plant; the mineral powder is from Nanjing Meibao company; the sands are Ganjiang Zhongsha; the stones are produced in Anhui Maanshan and county quarries; the water reducing agent is Jiangsu Subo water reducing agent (without retarding component).
Table 3 shows the mixing ratio (kg/m) of C50 concrete3)
The concrete formulation was tested for adiabatic temperature rise and rate of exothermic hydration heat release under adiabatic conditions according to the method of standard DL/T5150-2001 test procedures for hydraulic concrete (see FIGS. 1, 2 and 3).
FIG. 1 shows that the adiabatic temperature rise values of C50 standard concrete, 1.6% of calcium component, 3.84% of zeolite powder, 1.824% of hydration heat control material liquid and 8% of the efficient crack-resistant agent prepared in the above way in the 7d age are 50.68 ℃, 53.07 ℃, 49.31 ℃, 46.58 ℃ and 39.44 ℃. The calcium expansion component is doped into the C50 concrete, so that the early adiabatic temperature rise value of the concrete is increased and is higher than the benchmark 2.39 ℃; the singly-doped hydration heat regulation material can reduce the early adiabatic temperature rise of the concrete by about 4.1 ℃; the high-efficiency anti-cracking agent prepared by the method can obviously reduce the early adiabatic temperature rise value of the concrete to 11.24 ℃.
FIGS. 1 and 3 show that the single admixture of 1.6% calcareous material accelerates the early heat release rate of concrete; the hydration heat regulating material liquid with the content of 1.824% can slow down the early heat release rate of the concrete; however, the high-efficiency anti-cracking agent prepared by the process can obviously slow down the early heat release rate of concrete and has the peak clipping effect.
FIG. 1 shows that the efficient anti-cracking agent prepared by the preparation method obviously improves the regulation and control efficiency of the cement hydration heat regulation and control material.
Expansion performance test of efficient crack resistance agent for cement concrete
According to a test method of a standard GB/T23439-.
Table 4 shows the mortar restrained expansion ratios (unit:%) of the samples and the selected hydration heat control material and the selected calcareous expansion component
The test results in table 4 show that the hydration heat regulating material has no effects of compensating shrinkage and generating expansion; the calcium high-efficiency anti-cracking agent prepared by the process improves the expansion performance of the calcium oxide expansion material.
(V) concrete humidity test of efficient anti-cracking agent for cement-doped concrete
The internal humidity change of the concrete is tested by adopting a commercially available embedded humidity sensor, the prepared concrete humidity is tested, wherein 8 wt% of mineral powder is replaced by the high-efficiency anti-cracking agent, 8 wt% of mineral powder is replaced by the simple mixed sample, the size of the formed concrete test piece is 150mm × 150mm × 150mm, the curing temperature of a curing room is 20 +/-2 ℃, and the relative humidity RH (65 +/-5)%.
Table 5 shows the internal humidity (RH/%) of concrete poured into 3d and 7d sections
The test results in table 5 show that the high-efficiency anti-cracking agent prepared by the process can achieve the effect of regulating and controlling the internal humidity of concrete, and effectively reduce the internal dryness caused by cement hydration.
Example 2
Preparation of efficient anti-cracking agent for cement concrete
The calcareous expansion component is selected from a CaO expanding agent which is commercially available and prepared by adopting a rotary kiln; the zeolite powder is mordenite powder which has an ammonia absorption value of more than or equal to 135mmol/100g and is sold in the market and passes through 800 meshes. The cement hydration heat regulating component is selected from Jiangsu Subo new materials GmbH. The content of dextrin in the cement hydration heat regulating material liquid is 20 wt%, and the number average molecular weight of the dextrin is 7000-20000 g/mol. Calcium carbonate is commercially available as CaCO3The content is more than or equal to 85 percent, and the fineness is more than or equal to 1800 meshes. Pullulan, sorbitol and erythritol are commercially available products.
Limestone, pullulan, sorbitol and erythritol are fully and uniformly mixed according to a certain mass ratio to form a mixture for film formation. Slowly feeding the resulting mixture into a granulation fluidized bed; the skip car is sent into the corresponding position, and the material taking hole is pulled open, so that the material state can be checked in the operation process, and the material can be quickly pumped when being checked. Sealing the equipment to form a closed space in the fluidized bed, determining the material condition through an observation port, controlling the air speed according to the material condition, and adjusting the induced air force to be 35HZ to ensure that the film-formed mixture is fully boiled. Adding zeolite powder into cement hydration heat regulating material liquid prepared by dextrin, and uniformly stirring to form suspension. The particle size of the zeolite component of the liquid containing the cement hydration heat regulating material in the hole, which forms a film on the surface, is controlled by adjusting the liquid inlet speed of the spray gun to be 50rpm and the pressure of the spray gun to be 20 kPa. Adding zeolite into cement hydration heat regulating material liquid prepared by dextrin, and uniformly stirring to form suspension. The suspension is atomized and uniformly sprayed in the fluidized bed by adjusting the spray gun. The particle size of the zeolite component of the surface film and the pore containing cement hydration heat regulating material liquid is controlled to be 10-20 mu m by regulating the liquid inlet speed of the spray gun and the pressure of the spray gun. The temperature inside the fluidized bed is controlled at 30-45 ℃.
The formed zeolite with the surface film and the cement hydration heat regulating material liquid in the pores consists of 40 percent of zeolite, 38.49 percent of hydration heat regulating material liquid, 20 percent of calcium carbonate, 1.0 percent of pullulan, 0.5 percent of sorbitol and 0.05 percent of erythritol. Separating out zeolite components which are quickly formed into films in airflow and contain cement hydration heat regulating material liquid in pores, and mixing the zeolite components with calcareous expansion components to obtain the efficient anti-cracking agent for the cement concrete.
Table 6 shows the ratio of the calcium expansion component to the zeolite which forms a film on the surface and contains the cement hydration heat regulating material liquid in the pores in the prepared high-efficiency anti-cracking agent.
Working performance test of efficient anti-cracking agent for cement concrete
And evaluating the influence of the high-efficiency anti-cracking agent on the fluidity of the cement paste by using a paste cleaning test. The method for testing the net slurry fluidity of the cementing material is carried out according to the relevant regulations of GB80770-2000 concrete admixture homogeneity experimental method; the water-to-gel ratio of the cement paste was 0.35.
Table 7 comparison of the performance of the high efficiency crack inhibitor with the same untreated zeolite powder
The test result in table 7 shows that the high-efficiency anti-cracking agent for cement concrete prepared by the invention can effectively improve the initial fluidity of the zeolite-containing internal curing material, can remarkably improve the fluidity retention capacity of the cement paste after 60min, and provides guarantee for popularization and application of the zeolite powder internal curing material. The influence of the zeolite component on the fluidity of cement paste cannot be improved by adopting a simple compounding mode of the zeolite component and calcium oxide.
(III) temperature control effect and mechanical property test of efficient anti-cracking agent for cement concrete
Table 8 shows the ratio of C50 concrete for a project, the mineral powder is replaced by the high-efficiency anti-cracking agent, and the same cement hydration heat regulating material is selected to replace the mineral powder. Except for the above, the concrete temperature control effect test was carried out in the same manner as in example 1.
Table 8 shows the C50 reference concrete mixing ratio (kg/m)3)
| Strength grade | Cement | Coal ash | Mineral powder | Sand | Small stone | Large stone | Water (W) | W/C |
| C50 | 245 | 90 | 85 | 756 | 306 | 738 | 145 | 0.33 |
According to the test method DL/T5150-2001 of the standard test procedure for hydraulic concrete, the concrete with the proportion is subjected to the adiabatic temperature rise test.
And Table 9 shows the comparison of the temperature control effect of the sample and the selected hydration heat regulation material powder.
Table 9 shows that the hydration heat regulation material liquid is stored in the pores of the zeolite powder particles with the film-formed surfaces prepared by the method, so that the hydrolysis rate of dextrin is delayed, and the regulation effect of the cement hydration heat regulation material on the cement acceleration period is obviously improved.
Table 10 shows the temperature control effect comparison of the samples with selected hydration heat control materials, zeolite powder and simple compound samples.
The formulation in table 10 was prepared by simply mixing 24% zeolite, 23.07% hydration heat control material liquid, 12% calcium carbonate, 0.6% pullulan, 0.3% sorbitol, 0.03% erythrose, and 40% calcium bulking component. Table 10 shows that the temperature control effect of the cement hydration heat regulating and controlling material cannot be improved by adopting a simple compounding mode.
And (3) testing the compressive strength of the mixture ratio concrete for 28d according to a test method of standard GB/T50081-2002 test method of mechanical property test method of common concrete.
Table 11 shows the compressive strength of the samples with selected hydration heat control material liquid, zeolite powder and simple compounded C50 concrete.
The formulation in table 11 was prepared by simply mixing 24% zeolite, 23.07% hydration heat control material liquid, 12% calcium carbonate, 0.6% pullulan, 0.3% sorbitol, 0.03% erythrose, and 40% calcareous bulking agent. Table 11 shows that the 28d compressive strength of the C50 concrete using the high-efficiency crack inhibitor for cement concrete of samples 2 to 3 in example 2 is improved compared to the compounded sample.
Concrete humidity test of efficient anti-cracking agent for cement-doped concrete
The internal humidity change of the concrete is tested by adopting a commercially available embedded humidity sensor, the prepared concrete humidity is tested, wherein 8 wt% of mineral powder is replaced by the high-efficiency anti-cracking agent, 8 wt% of mineral powder is replaced by the simple mixed sample, the size of the formed concrete test piece is 150mm × 150mm × 150mm, the curing temperature of a curing room is 20 +/-2 ℃, and the relative humidity RH (65 +/-5)%.
Table 12 shows the internal humidity (RH/%) of concrete poured into 3d and 7d sections
The test results in table 12 show that the efficient anti-cracking agent prepared by the process can achieve the effect of regulating and controlling the internal humidity of concrete, and effectively reduce internal dryness caused by cement hydration.
Expansion performance test of efficient crack resistance agent for cement concrete
According to a test method of a standard GB/T23439-.
Table 13 shows the data (unit:%) of the mortar limited expansion rate test of the prepared anti-cracking agent, the same cement hydration heat control material, the same zeolite powder and the same calcareous expansion material.
Samples 2-3 in Table 13 were prepared by simply mixing 24% zeolite, 23.07% hydration heat control material liquid, 12% calcium carbonate, 0.6% pullulan, 0.3% sorbitol, 0.03% erythrose, and 40% calcareous bulking agent in the same proportions. The test results in Table 13 show that the hydration heat regulating and controlling material liquid has no effects of compensating shrinkage and generating expansion; the high-efficiency anti-cracking agent prepared by the process has the effect of remarkably improving the expansion performance of the calcium expansion component. The expansion efficiency of the calcium expansion material cannot be obviously improved by adopting a simple compounding mode of the zeolite powder, the hydration heat inhibitor and the calcium expansion material.
Claims (9)
1. The efficient crack resistance agent for cement concrete is characterized by comprising a calcareous expansion component and a zeolite component which forms a film on the surface and contains cement hydration heat regulating material liquid in pores;
the mass ratio of the calcareous expansion component to the zeolite component which forms a film on the surface and contains cement hydration heat regulating material liquid in the pores is 40: 60-20: 80;
the calcareous expansion component is free calcium oxide, sulphoaluminate and/or anhydrous gypsum.
The zeolite with the film formed on the surface and containing the cement hydration heat regulating material liquid in the pores is formed by treating 40-60 wt% of zeolite, 28.5-49.5 wt% of cement hydration heat regulating material liquid, 10-20 wt% of calcium carbonate, 0.2-1.0 wt% of pullulan, 0.2-0.5 wt% of sorbitol and 0.01-0.05 wt% of erythritol through a fluidized bed process;
the zeolite is natural zeolite with 800 meshes;
the cement hydration heat regulating material liquid is dextrin solution, and the solvent is water; the mass ratio of dextrin to water is 10: 90-40: 60.
2. The efficient crack resistance agent for cement concrete according to claim 1, wherein mordenite powder having an ammonia absorption value of not less than 135mmol/100g is preferably used.
3. The efficient crack resistance agent for cement concrete according to claim 1, wherein the molecular weight of the dextrin is 7000 to 20000 g/mol.
4. The highly efficient crack inhibitor for cement concrete according to claim 1, wherein CaCO is a calcium carbonate3The content is more than or equal to 85 percent, and the fineness is more than or equal to 1800 meshes.
5. The efficient anti-cracking agent for cement concrete as claimed in claim 1, wherein the specific surface area of the efficient anti-cracking agent for cement concrete is 150-300m2/kg。
6. The method for preparing the efficient anti-cracking agent for cement concrete according to claims 1 to 5, characterized by comprising the following steps:
(1) sufficiently and uniformly mixing limestone, pullulan, sorbitol and erythritol to form a mixture for film formation;
(2) slowly adding the formed mixture into a granulation fluidized bed to ensure that the film-forming mixture is fully boiled;
(3) adding zeolite into cement hydration heat regulating material liquid prepared by dextrin, and uniformly stirring to form suspension; the suspension was uniformly sprayed in the fluidized bed by adjusting the spray gun. The particle size of zeolite components of surface film and cement hydration heat regulating material liquid in holes is controlled by regulating the liquid inlet speed of a spray gun and the pressure of the spray gun;
(4) separating out zeolite components which are quickly formed into films in airflow and contain cement hydration heat regulating material liquid in pores, and mixing the zeolite components with calcareous expansion components to obtain the efficient anti-cracking agent for the cement concrete.
7. The method according to claim 6, wherein the temperature inside the fluidized bed is controlled to be 30 to 80 ℃.
8. The method according to claim 7, wherein the temperature inside the fluidized bed is controlled at 60-70 ℃.
9. The use of the efficient anti-cracking agent for cement concrete according to claims 1 to 5, wherein the efficient anti-cracking agent for cement concrete is used as an expanding agent in C50-C100 concrete, and the mixing amount of the efficient anti-cracking agent for cement concrete accounts for 3-10% of the total mass of the cement material.
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