CN111377648B - Magnesium-based temperature-control humidity-control efficient anti-cracking agent for cement concrete and preparation method and application thereof - Google Patents
Magnesium-based temperature-control humidity-control efficient anti-cracking agent for cement concrete and preparation method and application thereof Download PDFInfo
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- CN111377648B CN111377648B CN201811651823.5A CN201811651823A CN111377648B CN 111377648 B CN111377648 B CN 111377648B CN 201811651823 A CN201811651823 A CN 201811651823A CN 111377648 B CN111377648 B CN 111377648B
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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Abstract
The invention discloses a magnesium-based temperature and humidity control efficient anti-cracking agent for cement concrete and a preparation method and application thereof. The invention relates to a magnesium-based temperature-control humidity-control efficient anti-cracking agent for cement concrete, which comprises a magnesium expansion component, a zeolite component containing water in pores, and a layer of temperature-sensitive material coated on the surfaces of magnesium and zeolite. The mass ratio of the magnesium expansion component to the zeolite component containing water in the pores to the temperature-sensitive material coated on the surface is 40:55: 5-80: 10: 10. The magnesium-based temperature-control humidity-control efficient anti-cracking agent for the cement concrete overcomes the adverse effects of internal curing materials and magnesium oxide on the workability of the concrete; the temperature drop compensation effect of the magnesium oxide is improved; the internal pores of the zeolite release water, so that the internal humidity of the concrete is regulated and controlled; the temperature sensitive material can dissolve and absorb heat along with the temperature rise of the concrete, reduce the temperature rise of the concrete, realize the coordination effect of compensation shrinkage and temperature control, and improve the anti-cracking performance of the concrete.
Description
Technical Field
The invention belongs to the technical field of building material concrete additives, and particularly relates to a magnesium-based temperature and humidity control efficient crack resistance agent for cement concrete, and 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, the natural zeolite has a porous structure, has a large specific surface area after being ground, 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 expansion material compensates the shrinkage of the concrete, and a certain shrinkage compensation effect can be achieved only by fully moisturizing and curing in the construction process.
In the technology, compared with the traditional expanding agent taking ettringite and calcium hydroxide as expansion sources, the MgO expanding agent has the advantages of less water requirement, good effect of compensating temperature drop shrinkage, stable physical and chemical properties of hydration products, adjustable expansion process and the like in the expanding material for compensating shrinkage, can meet the requirements of concrete shrinkage compensation in different types of structures, and has important engineering application value. However, MgO is a porous material and can adsorb the water reducing agent of concrete. When MgO is doped into concrete, the problems that the working performance of the concrete is influenced by the increase of the using amount of a water reducing agent, the acceleration of the slump loss of the concrete and the like exist. Therefore, it is necessary to solve the above problems, improve the influence of MgO on the workability of concrete, and prepare an anti-cracking agent capable of significantly improving the internal humidity of hardened concrete, controlling temperature and temperature rise, and significantly compensating for temperature drop and shrinkage.
Disclosure of Invention
Aiming at the problems that the workability is influenced by the increase of the using amount of a water reducing agent under the same slump condition, the acceleration of the slump loss of concrete and the like when a MgO expanding agent (particularly high-activity MgO) is doped into the concrete in the prior art; the invention also provides a magnesium-based temperature and humidity control efficient anti-cracking agent for cement concrete, and a preparation method and application thereof, aiming at the problems of insufficient temperature drop shrinkage compensation, weak later expansion capability and the like of concrete caused by insufficient internal humidity of the concrete in the prior art.
The magnesium-based temperature and humidity control high-efficiency anti-cracking agent for cement concrete does not adsorb a concrete water reducing agent, improves the workability of concrete, and has the functions of obviously improving the internal humidity of hardened concrete, controlling the temperature rise of concrete and obviously compensating shrinkage.
The magnesia temperature-control humidity-control efficient anti-cracking agent for cement concrete utilizes the porosity of zeolite powder particles, and pre-absorbs water and stores the water in the pores of the zeolite particles in a physical adsorption and chemical reaction mode; the temperature sensitive material is coated on the surfaces of the magnesium oxide particles and the zeolite powder particles with pre-absorbed water through a fluidized bed preparation process to form a film.
The magnesia temperature and humidity control high-efficiency anti-cracking agent for the cement concrete overcomes the adverse effect of internal curing materials and magnesium oxide on the workability of the concrete; the temperature drop compensation effect of the magnesium oxide is improved; the internal pores of the zeolite release water, so that the internal humidity of the concrete is regulated and controlled; the temperature sensitive material can dissolve and absorb heat along with the temperature rise of the concrete, reduce the temperature rise of the concrete, realize the coordination effect of compensation shrinkage and temperature control, and improve the anti-cracking performance of the concrete.
The magnesium-based temperature-control humidity-control efficient anti-cracking agent for cement concrete comprises a magnesium expansion component, a zeolite component containing water in pores, and a layer of temperature-sensitive material coated on the surfaces of magnesium and zeolite. The mass ratio of the magnesium expansion component to the zeolite component containing water in the pores to the temperature-sensitive material coated on the surface is 40:55: 5-80: 10: 10.
The magnesium expansion component is prepared from magnesium-rich minerals by adopting a suspension kiln calcination technology, wherein the magnesium-rich minerals are any one or more than two of magnesite, magnesite tailings and serpentine which are mixed in any proportion.
The MgO content in the magnesium expansion component is more than or equal to 80 wt%, the hydration activity value is 35s-200s, and the screen residue of a 80 mu m square-hole sieve is less than or equal to 5.0%.
The zeolite containing water in the pores consists of 10-40 wt% of water and 90-60 wt% of zeolite. The zeolite component is natural zeolite with 800 meshes, and preferably mordenite powder with ammonia absorption value more than or equal to 135mmol/100 g. The water content is concrete water meeting JGJ 63-2006 concrete water standard, and drinking water is preferred.
The surface of the magnesium and the zeolite is coated with a layer of temperature sensitive material, preferably paraffin with the phase transition temperature of 45-60 ℃.
The specific surface area of the magnesium-based temperature-control humidity-control efficient anti-cracking agent for cement concrete is 150-300m2/kg。
The invention relates to a preparation method of a magnesium high-efficiency anti-cracking agent for cement concrete, which comprises the following steps:
(1) calcining suspension kilnThe specific surface area of the sintered material is 200-400m2Adding/kg of magnesium expansion component into a powder feeder of a fluidized bed, conveying the magnesium expansion component into the fluidized bed through compressed air with the pressure of 0.3-0.8 MPa, and uniformly dispersing the magnesium expansion component in hot air flow through hot air in the fluidized bed;
(2) slowly adding zeolite powder containing water in the holes into a powder feeder of the fluidized bed, adding a zeolite component into the fluidized bed through compressed air with the pressure of 0.3-0.8 MPa, and uniformly dispersing a magnesium expansion component into hot air flow through hot air in the fluidized bed. Sealing the equipment to form a closed space in the fluidized bed, and fully boiling the components.
(3) The spraying device in the fluidized bed is started. And atomizing the paraffin liquid into micro liquid beads with the diameter of 5-50 mu m. The paraffin micro liquid beads which are fully boiled in the fluidized bed are adsorbed on the surfaces of magnesium and zeolite particles by physical adsorption and chemical reaction by taking a magnesium expansion component and a zeolite component containing water in pores as carriers.
(4) And (3) quickly separating the zeolite which is quickly formed into a film in the airflow and contains water in the pores and the magnesium oxide which is formed into a film on the surface to obtain the efficient anti-cracking agent for the cement concrete.
The internal temperature of the fluidized bed is controlled at 45-70 ℃, preferably 60-70 ℃.
The magnesium high-efficiency anti-cracking agent for cement concrete is suitable for: the temperature of the mold is above 25 ℃, the temperature rise value is above 20 ℃, and the concrete structure has strength grade of C50 and above for side walls, bottom plates and top plates with the requirements of shrinkage compensation, crack resistance, permeability resistance and temperature control.
The magnesium-based temperature-control humidity-control efficient anti-cracking agent for cement concrete disclosed by the invention is characterized in that the mixing amount of C50-C100 concrete accounts for 3-10% of the total mass of a rubber material.
Compared with the prior art, the invention has the beneficial effects that:
(1) the magnesium-based temperature-control humidity-control efficient anti-cracking agent for the cement concrete overcomes the adverse effects of internal curing materials and magnesium oxide on the workability of the concrete; the temperature drop compensation effect of the magnesium oxide is improved; the internal pores of the zeolite release water, so that the internal humidity of the concrete is regulated and controlled; the temperature sensitive material can dissolve and absorb heat along with the temperature rise of the concrete, reduce the temperature rise of the concrete, realize the coordination effect of compensation shrinkage and temperature control, and improve the anti-cracking performance of the concrete.
(2) The efficient anti-cracking agent for the cement concrete provided by the invention has the advantages of easily available raw materials, simple preparation method operation, no need of special process equipment, greatly reduced production cost and remarkable social and economic benefits.
Drawings
FIG. 1 shows the temperature drop deformation of a sample prepared by simply mixing the same magnesium-doped, temperature-controlled, humidity-controlled and high-efficiency anti-cracking agent prepared in example 1, the same MgO expanding material with the same activity value of 100s, the same paraffin powder, 100s MgO expanding material powder and pre-hydrated zeolite powder; the No. 1 is C50 concrete of the benchmark, the No. 2 is a sample prepared by simply mixing 6.4% of 100 s-doped magnesium oxide expansion material, the No. 3 is 10% of homogeneous paraffin powder, 80% of 100 s-doped MgO expansion material powder and 10% of pre-absorbent zeolite powder, and the No. 4 is a sample 1-3 of the sample in the example 1, namely the high-efficiency cracking-resistant agent with magnesium, temperature and humidity control.
FIG. 2 shows the swelling deformation of magnesium oxide after deducting the change of the reference concrete of the sample prepared by simply mixing the magnesium-doped, temperature-controlled, humidity-controlled and high-efficiency anti-cracking agent prepared in example 1, the same MgO expanding material with the same activity value of 100s, the same paraffin powder, 100s MgO expanding material powder and pre-hydrated zeolite powder. The No. 1 sample is prepared by simply mixing 6.4% of 100 s-doped magnesium oxide expansion material, the No. 2 sample is prepared by simply mixing 10% of homogeneous paraffin powder, 80% of 100 s-MgO expansion material powder and 10% of pre-absorbent zeolite powder, and the No. 3 sample is a magnesium-based temperature-control humidity-control high-efficiency anti-cracking agent in example 1.
Detailed Description
The technical characteristics of the efficient anti-cracking agent for cement concrete, the preparation method thereof and the application thereof are further described below with reference to 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 magnesium expansion component is in suspensionThe hydration activity value of the kiln production is 100s (by adopting a DL/T5296-2013 detection method), the MgO content is 90.0 percent, and the specific surface area is 400m2Per kg of a magnesium intumescent material; 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. Paraffin is commercially available, and the phase transition temperature is 50-55 ℃.
The specific surface area prepared by calcining the suspension kiln is 200-400m2Adding/kg of magnesium expansion component into a powder feeder of the fluidized bed, conveying the magnesium expansion component into the fluidized bed through compressed air with the pressure of 0.3MPa, and uniformly dispersing the magnesium expansion component into hot air flow through hot air in the fluidized bed; slowly adding zeolite powder containing water in the pores into a powder feeder of the fluidized bed, adding the zeolite component into the fluidized bed through compressed air with the pressure of 0.8MPa, and uniformly dispersing the magnesium expansion component into hot air flow through hot air in the fluidized bed. 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 wind power of induced air to fully boil the components. The zeolite containing water in the pores consists of 40% water and 60% zeolite.
The spraying device in the fluidized bed is started. And atomizing the paraffin liquid into micro liquid beads with the diameter of 5-50 mu m. The paraffin micro liquid beads which are fully boiled in the fluidized bed are adsorbed on the surfaces of magnesium and zeolite particles by physical adsorption and chemical reaction by taking a magnesium expansion component and a zeolite component containing water in pores as carriers. And (3) quickly separating magnesium oxide formed on the surface of zeolite which is quickly formed into a film in the airflow and contains water in pores, so as to obtain the magnesium-based temperature-controlled humidity-controlled efficient anti-cracking agent for the cement concrete. The temperature inside the fluidized bed is controlled at 60-65 ℃.
Table 1 shows the ratio of the magnesium expansion component, the zeolite component containing water in pores, and the paraffin component coated on the surfaces of the two components in the prepared magnesium, temperature and humidity controlled high-efficiency crack resistance agent.
Working performance test of magnesium-based temperature-control humidity-control efficient anti-cracking agent for cement concrete
And evaluating the influence of the magnesian, temperature and humidity controlled and 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 shows the comparison of the performance of the high-efficiency anti-cracking agent with the same MgO expanding material, zeolite powder and paraffin material with the hydration activity value of 100 s.
The test results in table 2 show that the magnesium-based temperature-control humidity-control efficient anti-cracking agent prepared by the invention can effectively improve the initial fluidity of the cement paste mixed with the magnesium-based expansion material, and can remarkably improve the fluidity retention capacity of the cement paste after 60 min. The influence of the magnesium oxide expansion material on the fluidity of the cement paste cannot be improved by adopting a simple compounding mode of the magnesium oxide expansion component, the zeolite powder and the paraffin.
(III) temperature control effect test of magnesium-based temperature and humidity control efficient anti-cracking agent for cement concrete
Table 3 shows the ratio of C50 concrete for a project, the mineral powder is replaced by a magnesium temperature-controlled anti-cracking agent, and the mineral powder is also replaced by a selected magnesium expansion material.
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 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 | 115 | 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.
Table 4 shows the comparison of the temperature control effects of the sample, the selected hydration heat control material powder and the 100s MgO expansion component.
Table 4 shows that the MgO granules prepared by the method are coated with paraffin and have temperature control effect.
Table 5 shows the comparison of the temperature control effect of the samples with the selected hydration heat control material and the 100s MgO expansion component.
The compound sample in Table 5 was prepared by simply mixing 10% of the same paraffin powder, 80% of 100s MgO expanding material powder and 10% of pre-absorbent zeolite powder. Table 5 shows that the regulation and control efficiency of the cement hydration heat regulation and control material cannot be improved by adopting a simple magnesium oxide expansion component, zeolite powder and paraffin wax compounding mode. The anti-cracking agent prepared by the method can dissolve and absorb heat along with the temperature rise of the concrete, and the temperature rise of the concrete is reduced.
Expansion performance test of magnesium high-efficiency anti-cracking agent for cement concrete
An environment simulation box is adopted, the temperature is controlled to be 23.5 ℃ within 6h of pouring, then the temperature is raised to 75 ℃, and the temperature reduction rate is about 3 ℃/d. PVC pipe of 110mm x 400mm is used to cast concrete and put in environment simulating box. The initial setting is used as a starting point to simulate the reference and the actual temperature history of the concrete doped with the magnesium, temperature-controlled and humidity-controlled efficient anti-cracking agent. And a strain gauge for monitoring temperature and deformation is adopted to test the deformation of the material. The concrete is the reference mixing ratio of example 1 and table 3. Monitoring results of the temperature drop phase (see fig. 1 and 2).
The test results of the figure 1 and the figure 2 show that the prepared magnesium-based temperature and humidity control efficient anti-cracking agent improves the temperature drop compensation effect of MgO.
Example 2
Preparation of efficient anti-cracking agent for cement concrete
The magnesian expansion component is the hydration activity value of 200s (adopting a DL/T5296-2013 detection method) produced by a suspension kiln, the MgO content is 90.0 percent, and the specific surface area is 300m2Per kg of a magnesium intumescent material; 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. Paraffin is commercially available, and the phase transition temperature is 45-50 ℃.
The specific surface area prepared by calcining the suspension kiln is 200-400m2Adding/kg of magnesium expansion component into a powder feeder of the fluidized bed, conveying the magnesium expansion component into the fluidized bed through compressed air with the pressure of 0.8MPa, and uniformly dispersing the magnesium expansion component into hot air flow through hot air in the fluidized bed; slowly adding zeolite powder containing water in the pores into a powder feeder of the fluidized bed, adding the zeolite component into the fluidized bed through compressed air with the pressure of 0.3MPa, and uniformly dispersing the magnesium expansion component into hot air flow through hot air in the fluidized bed. 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 wind power of induced air to fully boil the components. The zeolite with water in the pores consists of 10% of water and 90% of zeolite.
The spraying device in the fluidized bed is started. And atomizing the paraffin liquid into micro liquid beads with the diameter of 5-50 mu m. The paraffin micro liquid beads which are fully boiled in the fluidized bed are adsorbed on the surfaces of magnesium and zeolite particles by physical adsorption and chemical reaction by taking a magnesium expansion component and a zeolite component containing water in pores as carriers. And (3) quickly separating magnesium oxide formed on the surface of zeolite which is quickly formed into a film in the airflow and contains water in pores, so as to obtain the magnesium-based temperature-controlled humidity-controlled efficient anti-cracking agent for the cement concrete. The internal temperature of the fluidized bed is controlled at 50-55 ℃.
Table 6 shows the ratio of the magnesium expansion component, the zeolite component containing water in pores, and the paraffin component coated on the surfaces of the two components in the prepared magnesium-based, temperature and humidity controlled high-efficiency crack inhibitor.
Working performance test of magnesium-based temperature-control humidity-control efficient anti-cracking agent for cement concrete
And evaluating the influence of the magnesian, temperature and humidity controlled and 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 shows the comparison of the performance of the high-efficiency anti-cracking agent and the same MgO expanding material, zeolite powder and paraffin material with the hydration activity value of 200 s.
The test results in Table 7 show that the magnesium-based temperature-control humidity-control efficient anti-cracking agent prepared by the invention can effectively improve the initial fluidity of the cement paste mixed with the magnesium-based expansion material, and can remarkably improve the fluidity retention capacity of the cement paste after 60 min. The influence of the magnesium oxide expansion material on the fluidity of the cement paste cannot be improved by adopting a simple compounding mode of the magnesium oxide expansion component, the zeolite powder and the paraffin.
(III) testing expansion performance of magnesium high-efficiency anti-cracking agent for cement concrete
According to a standard CBMF 19-2017 'magnesium oxide expanding agent for concrete' test method, the prepared efficient anti-cracking agent, the same zeolite powder material and the same 200s MgO expanding material are subjected to a mortar limited expansion rate test under a water-curing condition.
Table 8 mortar limited expansion ratio (unit:%) of the samples with the selected zeolite powder material and 200sMgO expansion component
The test results in Table 8 show that the zeolite powder has no effect of compensating shrinkage and generating expansion; the magnesium high-efficiency anti-cracking agent prepared by the process improves the expansion performance of the magnesium expansion material.
Claims (9)
1. A kind of magnesia, temperature control and humidity control high-efficient anticracking agent for cement concrete, wherein its composition includes the magnesium expansion component, zeolite component containing water in the hole, and a layer of temperature sensitive material coated on the surface of magnesium and zeolite;
the mass ratio of the magnesium expansion component to the zeolite component containing water in the pores to the temperature-sensitive material coated on the surface is 40:55: 5-80: 10: 10;
the magnesium expansion component is prepared from magnesium-rich minerals by adopting a suspension kiln calcination technology, wherein the magnesium-rich minerals are any one or more than two of magnesite, magnesite tailings and serpentine and are mixed in any proportion;
the zeolite containing water in the pores consists of 10-40 wt% of water and 90-60 wt% of zeolite; the zeolite component is natural zeolite with 800 meshes;
the water is drinking water;
the layer of temperature sensitive material coated on the surfaces of the magnesium and the zeolite is paraffin with the phase transition temperature of 45-60 ℃;
the magnesia temperature-control humidity-control efficient anti-cracking agent for the cement concrete utilizes the porosity of zeolite powder particles, and pre-absorbs water and stores the water in the pores of the zeolite particles in a physical adsorption and chemical reaction mode; the temperature sensitive material is coated on the surfaces of the magnesium oxide particles and the zeolite powder particles with pre-absorbed water through a fluidized bed preparation process to form a film.
2. The magnesia temperature-and humidity-control efficient anti-cracking agent for cement concrete according to claim 1, wherein the content of MgO in the magnesia expansion component is more than or equal to 80 wt%, the hydration activity value is 35s-200s, and the screen residue of a 80-micron square-hole screen is less than or equal to 5.0%.
3. The magnesia temperature-and humidity-control efficient crack resistance agent for cement concrete according to claim 1, wherein the zeolite powder is mordenite powder with an ammonia absorption value of not less than 135mmol/100 g.
4. The magnesia temperature-and humidity-controlled high-efficiency anti-cracking agent for cement concrete as recited in claim 1, wherein the specific surface area is 150-300m2/kg。
5. The preparation method of the magnesium-based temperature and humidity control high-efficiency crack resistance agent for the cement concrete, which is disclosed by any one of claims 1 to 4, is characterized by comprising the following steps of:
(1) the specific surface area prepared by calcining the suspension kiln is 200-400m2Adding/kg of magnesium expansion component into a powder feeder of a fluidized bed, conveying the magnesium expansion component into the fluidized bed through compressed air with the pressure of 0.3-0.8 MPa, and uniformly dispersing the magnesium expansion component in hot air flow through hot air in the fluidized bed;
(2) slowly adding zeolite powder containing water in the holes into a powder feeder of the fluidized bed, adding a zeolite component into the fluidized bed through compressed air with the pressure of 0.3-0.8 MPa, and uniformly dispersing a magnesium expansion component into hot air flow through hot air in the fluidized bed; sealing the equipment to form a closed space in the fluidized bed so as to fully boil the components;
(3) starting a spraying device in the fluidized bed; atomizing the paraffin liquid into micro liquid beads with the diameter of 5-50 mu m; the paraffin micro liquid beads which are fully boiled in the fluidized bed are adsorbed on the surfaces of magnesium and zeolite particles to form a film by taking a magnesium expansion component and a zeolite component containing water in pores as carriers through physical adsorption and chemical reaction;
(4) and (3) quickly separating the zeolite which is quickly formed into a film in the airflow and contains water in the pores and the magnesium oxide which is formed into a film on the surface to obtain the efficient anti-cracking agent for the cement concrete.
6. The method according to claim 5, characterized in that the internal temperature of the fluidized bed of the suspension kiln is controlled between 45 and 70 ℃.
7. The method according to claim 6, wherein the temperature inside the fluidized bed is controlled to be 60-70 ℃.
8. The application of the magnesium temperature and humidity control efficient anti-cracking agent for cement concrete as claimed in any one of claims 1 to 4, wherein the magnesium temperature and humidity control efficient anti-cracking agent for cement concrete is suitable for: the temperature of the mold is above 25 ℃, the temperature rise value is above 20 ℃, and the concrete structure has strength grade of C50 and above for side walls, bottom plates and top plates with the requirements of shrinkage compensation, crack resistance, permeability resistance and temperature control.
9. The application of the cement concrete as claimed in claim 8, wherein the magnesium-based temperature and humidity control efficient crack resistance agent for the cement concrete is added into the C50-C100 concrete in an amount of 3-10% of the total mass of the cement concrete.
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