CN114940602A - Self-curing multi-gradient temperature-control early-strength anti-cracking concrete and preparation method thereof - Google Patents
Self-curing multi-gradient temperature-control early-strength anti-cracking concrete and preparation method thereof Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 8
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- 238000000034 method Methods 0.000 claims abstract description 25
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- 238000003756 stirring Methods 0.000 claims abstract description 8
- 238000001723 curing Methods 0.000 claims description 85
- 239000012782 phase change material Substances 0.000 claims description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
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- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 2
- 150000001335 aliphatic alkanes Chemical class 0.000 claims description 2
- 150000002148 esters Chemical class 0.000 claims description 2
- 229910017053 inorganic salt Inorganic materials 0.000 claims description 2
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/0028—Aspects relating to the mixing step of the mortar preparation
- C04B40/0039—Premixtures of ingredients
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/0068—Ingredients with a function or property not provided for elsewhere in C04B2103/00
- C04B2103/0071—Phase-change materials, e.g. latent heat storage materials used in concrete compositions
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/34—Non-shrinking or non-cracking materials
- C04B2111/343—Crack resistant materials
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
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- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The invention discloses self-curing multi-gradient temperature-control early-strength anti-crack concrete and a preparation method thereof, wherein the concrete consists of a self-curing temperature-control material and concrete, and comprises 2-25 parts of the self-curing multi-gradient temperature-control material and 75-98 parts of the concrete by mass. And fully mixing and stirring the materials, and curing to obtain the self-curing multi-gradient temperature-control early-strength anti-cracking concrete with the designed strength grade of C30-C55. The self-curing or temperature-control material containing various different heat absorption and release intervals is applied to mass concrete to realize multi-gradient temperature control, multi-gradient heat absorption and temperature control are formed in the process of heating and cooling the concrete, the heating and cooling duration of the concrete is prolonged, and the generation of cracks is reduced; the self-curing mortar is applied to prefabricated parts, can realize self-curing, accelerates the early-stage hardening rate, reduces the curing difficulty, and improves the construction efficiency or the product delivery frequency.
Description
Technical Field
The invention belongs to the field of building materials, and particularly relates to self-curing multi-gradient temperature-control early-strength anti-cracking concrete and a preparation method thereof.
Background
With the continuous expansion and deepening of construction scale, modern concrete structural engineering develops towards high, large, deep and complex structures. However, the structure size is large, in the construction process, a large amount of heat generated by cement hydration is not easy to dissipate, the surface heat dissipation is fast, and when the temperature difference between the inside and the outside of the concrete is large, uneven temperature deformation and temperature stress can be caused, so that cracks are generated. The cracks not only affect the appearance quality of the structure, but also cause the problems of strength reduction and durability, and affect the safety and normal use of the structure.
In the actual construction process, it is very difficult to reduce the maximum temperature rise of the concrete, and the following methods are generally used: 1. from the aspect of raw materials, the consumption of cement in unit volume is reduced or coarse and fine aggregates are precooled by ice slag; 2. pre-burying a water pipe in the concrete and introducing cooling water; 3. and covering a heat insulation material on the outer side of the structure by adopting a heat insulation method. However, the measures are complicated in the actual construction process, the engineering cost is increased, the construction time and the construction efficiency are delayed, and the anti-cracking effect of the concrete is influenced once the construction process has slight deviation. Therefore, the improvement of the anti-cracking performance of the concrete from the composition and the proportion of the concrete has important significance for modern building construction engineering.
The phase change material can absorb or emit a large amount of heat during the phase change process, and keep the temperature relatively stable during the process. The phase-change material with proper phase-change temperature is used for absorbing heat generated by hydration of cement, so that the temperature stress of concrete can be reduced, and further the formation of concrete temperature cracks is inhibited. Patent CN 111533500A directly adds the phase change material into the slurry, and the concrete prepared has the temperature control effect, but the effect is limited and the phase change material directly contacts with the matrix, and the physical property of the concrete is greatly reduced. Patent CN 112028572 a adopts an adsorption method to soak a porous material in a liquid phase-change material to obtain phase-change energy-storage particles. However, the adsorption performance of the phase change energy storage particles prepared by the method is limited, and the temperature control effect is not obvious. Patent CN 111253136A adopts phase change microcapsule to prepare concrete, though this method can solve the energy transfer problem, has higher phase change accuse temperature characteristic and better work cycle stability, but the manufacturing process is complicated, and is with high costs, and can only satisfy single phase transition interval. Many researchers have conducted a lot of research, but the research mainly focuses on the encapsulation, preparation and temperature control performance research of the phase-change material, and the applied phase-change material has less consideration of other performances and is difficult to apply to practical engineering.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide concrete with multiple temperature control gradients, self-curing effect, high early strength and excellent crack resistance and a preparation method thereof.
The technical scheme is as follows: the self-curing multi-gradient temperature-control early-strength anti-cracking concrete comprises a self-curing temperature-control material and common concrete components, wherein the self-curing temperature-control material accounts for 2% -25% of the total mass, and comprises an encapsulation material and a phase-change material. The phase change material at least comprises a solid material and a liquid material; wherein the solid material is wrapped as an inner layer material and the liquid material is incorporated into the packaging material for use.
Further, the phase change material comprises one or two of a normal-temperature phase change material and a medium-temperature phase change material; the phase-change temperature of the phase-change material is 10-60 ℃.
Further, the phase-change material comprises any two or more of paraffin, alcohol, ester, alkane and hydrated inorganic salt.
Further, the packaging material comprises a liquid phase-change material, a cementing material and water.
Furthermore, the mass ratio of the liquid phase-change material, the cementing material and the water is (2-5): 60-80): 18-35.
Furthermore, the mass ratio of the cementing material cement to various admixtures is (50-100) to (0-50).
The invention also discloses a preparation method of the self-curing multi-gradient temperature-control early-strength anti-cracking concrete, which comprises the following steps:
(1) pretreating the weighed phase-change materials, uniformly mixing all the materials, placing the mixture into balling granulation equipment for granulation and molding, and preparing the self-curing temperature-control material through curing;
(2) fully stirring and mixing the prepared self-curing temperature control material and concrete according to a proportion, and pouring the mixture into a member or a mold;
(3) and removing the mould after natural curing or standard curing to obtain the self-curing multi-gradient temperature-control early-strength anti-cracking concrete.
Further, in the step (3), the curing time is 1 d-5 d.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages:
(1) the invention uses the self-maintenance temperature control material with various phase change intervals, and the temperature control range is wider. When the cement hydration temperature rise method is applied to mass concrete, when the temperature in the cement hydration temperature rise process reaches corresponding phase change temperature points, multi-gradient temperature control can be formed, heat generated by hydration is stored with high efficiency, the peak temperature and the temperature rise rate of the concrete are greatly reduced, the internal and external temperature difference of the concrete is reduced, the cracking risk is further reduced, and the strength grade of the concrete reaches C30-C55.
(2) The self-curing temperature control material with various phase change intervals is adopted, and when the temperature is reduced to a corresponding phase change temperature point in the concrete cooling stage, the absorbed heat can be gradually released, the stable internal and external temperature of the concrete is maintained, the concrete cooling rate is slowed down, the generation of cracks is reduced, and the curing of a matrix is enhanced.
(3) The invention effectively solves the problem of concrete performance reduction caused by the doping of the phase-change material, and the prepared concrete has excellent working performance and mechanical property and can be applied to actual engineering.
(4) The invention has simple process, and the prepared concrete has stable performance. When the curing agent is applied to prefabricated parts, due to the self-curing effect, the early hardening rate can be accelerated, the curing difficulty is reduced, and the construction efficiency or the product delivery frequency is improved.
Drawings
FIG. 1 shows the adiabatic temperature rise test results of concrete of example 1 of the present invention;
FIG. 2 shows the dry shrinkage test results of concrete in example 1 of the present invention;
FIG. 3 shows the results of the concrete adiabatic temperature rise test of example 2 of the present invention;
FIG. 4 shows the dry shrinkage test results of concrete of example 2 of the present invention;
FIG. 5 shows the adiabatic temperature rise test results of the concrete of example 3 of the present invention;
FIG. 6 shows the dry shrinkage test results of concrete of example 3 of the present invention.
Detailed Description
The technical scheme of the invention is further explained by combining the attached drawings.
In the following examples, the self-curing temperature control material includes a phase change material and an encapsulation material. The phase change material comprises paraffin with a phase change point of 58 ℃ and polyethylene glycol with a temperature of 20 ℃, the paraffin is wrapped as an inner layer material, and the liquid polyethylene glycol is doped into the packaging material for use.
The mass ratio of the liquid polyethylene glycol to the cementing material to the water is 5:70: 25.
The cementing material is cement and various admixtures, and the mass ratio of the cementing material to the admixtures is 60: 40.
And uniformly mixing all the materials in pelletizing and granulating equipment, granulating and forming, and curing to obtain the self-curing temperature-control material.
Example 1
The large-volume C55 concrete is prepared from the raw materials including, by mass, water, cement, fly ash, mineral powder, sand, stone and a water reducing agent, wherein the mass ratio of the raw materials is 1:1.7:0.9:0.4:4.9:7.3:0.03, in order to ensure consistent volume, a self-curing temperature control material with the total mass ratio of 4% of concrete is used to replace the same-volume stone in the experimental group 1, a self-curing temperature control material with the total mass ratio of 15% of concrete is used to replace the same-volume stone in the experimental group 2, and a self-curing temperature control material with the total mass ratio of 28% of concrete is used to replace the same-volume stone in the experimental group 3. Adding the materials into a concrete mixer in proportion, fully mixing and stirring, pouring into a member or a mould, and naturally curing for 3d to remove the mould to obtain the self-curing multi-gradient temperature-control early-strength anti-cracking concrete. The performance pairs are shown in table 1 and fig. 1.
TABLE 1 comparison of the properties of the concretes
As can be seen from Table 1, the working performance of the concrete is improved after the self-curing temperature control material is added. Due to the addition of the self-curing temperature control material, the early-age compression resistance and splitting tensile strength of the experimental group 1 and the experimental group 2 are improved by 13-21%, the early-stage hardening rate is obviously accelerated, and the curing difficulty in actual construction is reduced. The early-age strength of the experimental group 3 is not obviously improved, the 28d compressive strength is reduced by 12%, the split tensile strength is reduced by about 17%, and when the doping amount of the self-curing temperature control material is too high, the volume of a weak item in the concrete is increased, so that the long-term mechanical property of the concrete is reduced.
In an adiabatic temperature rise experiment, the multi-gradient self-curing temperature control material has an obvious temperature control effect on concrete, multi-gradient heat absorption temperature control is formed in the temperature rise process of the concrete, the temperature rise duration of the concrete is prolonged, and the duration of the temperature rise is prolonged at about 20 ℃; the maximum temperature rise of the concrete is reduced, the time for reaching the maximum temperature rise is prolonged, and the slope of the temperature rise curve is reduced. The maximum temperature rise of the experimental group 1 is reduced by 4.3 ℃ compared with that of the reference group 1, the maximum temperature rise of the experimental group 2 is reduced by 7.6 ℃ and the maximum temperature rise of the experimental group 3 is reduced by 11.1 ℃. Meanwhile, in the cooling process, the cooling rate can be delayed, the generation of cracks is reduced, and the multi-gradient temperature control of the large-volume concrete in the heating/cooling process is realized.
The drying shrinkage results of the concretes of different ages are shown in figure 2. The results show that after the self-curing temperature control material is added, the drying shrinkage of the concrete of the experimental group 1 and the experimental group 2 in each age period is reduced, wherein the drying shrinkage of 56d of the experimental group 1 is reduced by 5% compared with that of the reference group 1, and the drying shrinkage of the experimental group 2 is reduced by about 10%, which shows that the self-resistance of the concrete structure can be improved by adding a proper amount of the self-curing temperature control material, and the cracking risk of the concrete is greatly reduced by combining the reduction of the maximum temperature rise. Due to the effect of early self-curing, the early drying shrinkage of the experimental group 3 is smaller than that of the reference group 1, but the shrinkage of 56d is increased by about 6 percent compared with that of the reference group 1, and when the doping amount of the self-curing temperature control material is too high, the long-term deformation resistance of the concrete is reduced.
Example 2
The large-volume C30 concrete is prepared from the raw materials including, by mass, water, cement, fly ash, mineral powder, sand, stone and a water reducing agent, 1:1.23:0.82:0.4:4.7:7.3:0.02, wherein in order to ensure the volume consistency, a self-curing temperature control material with the total mass ratio of 1% of concrete is used in an experimental group 4 to replace the stone with the same volume, a self-curing temperature control material with the total mass ratio of 10% of concrete is used in an experimental group 5 to replace the stone with the same volume, and a self-curing temperature control material with the total mass ratio of 30% of concrete is used in an experimental group 6 to replace the stone with the same volume. Adding the materials into a concrete mixer in proportion, fully mixing and stirring, pouring into a member or a mould, and naturally curing for 3d to remove the mould to obtain the self-curing multi-gradient temperature-control early-strength anti-cracking concrete. The performance pairs are shown in table 2 and fig. 3.
TABLE 2 comparison of various properties of the concretes
Due to the addition of the self-curing temperature control material, the slump of the concrete is increased, and the working performance is improved. The performance of the concrete of the experimental group 4 doped with a small amount of self-curing temperature control material is similar to that of the reference group 2, and the change is not obvious. Compared with the reference group 2, the 3d compressive strength of the concrete of the experimental group 5 is improved by about 19%, the 3d split strength is improved by about 12%, the early hardening rate of the concrete is obviously accelerated, and the maintenance difficulty in actual construction is reduced. The 3d strength of the experimental group 6 is not obviously improved, the later-stage compressive strength is reduced by about 18%, the split tensile strength is reduced by about 7%, and when the mixing amount of the self-curing temperature control material is too high, the volume of the self-curing temperature control material in the concrete is increased as a weak item, so that the long-term mechanical property of the concrete is reduced.
In the adiabatic temperature rise experiment, the temperature rise curve of the experiment group 4 doped with a small amount of self-curing temperature control material is similar to that of the reference group, and the temperature control effect is not obvious. Whereas the maximum temperature rise of the experimental group 5 was decreased by 7.1 ℃ and the maximum temperature rise of the experimental group 6 was decreased by 11.5 ℃ compared to the reference group 2. The proper amount of self-curing temperature control material has obvious temperature control effect on the concrete, forms multi-gradient heat absorption temperature control in the temperature rise process of the concrete, prolongs the temperature rise duration of the concrete, and prolongs the duration at about 20 ℃; the maximum temperature rise of the concrete is reduced. The time for the concrete to reach the maximum temperature rise is prolonged, and the slope of the temperature rise curve is reduced. In the concrete cooling process, the cooling rate can be delayed, the generation of cracks is reduced, and the multi-gradient temperature control of the large-volume concrete in the heating/cooling process is realized.
The drying shrinkage results of the concretes of different ages are shown in figure 4. The drying shrinkage of the concrete in each age period of the experimental group 4 and the experimental group 5 is reduced, the reduction of the experimental group 4 doped with a small amount of the self-curing temperature control material is not obvious, and the reduction of the experimental group 5 is about 8 percent, and the result shows that the self resistance of the concrete structure can be improved after a proper amount of the self-curing temperature control material is doped, so that the cracking risk of the concrete is reduced. Due to the effect of early self-curing, the early drying shrinkage of the experimental group 6 is smaller than that of the reference group 2, but the shrinkage of 56d is increased by about 8 percent compared with that of the reference group 2, and when the doping amount of the self-curing temperature control material is too high, the long-term deformation resistance of the concrete is reduced.
Example 3
The large-volume C35 concrete is prepared from the raw materials including, by mass, water, cement, fly ash, mineral powder, sand, stone and a water reducing agent, wherein the mass ratio of the raw materials is 1:1.3:0.72:0.48:4.8:7.5:0.02, in order to ensure the volume consistency, a self-curing temperature control material with the total mass ratio of 4% of concrete is used in an experimental group 7 to replace the stone with the same volume, a self-curing temperature control material with the total mass ratio of 8% of concrete is used in an experimental group 8 to replace the stone with the same volume, and a self-curing temperature control material with the total mass ratio of 22% of concrete is used in an experimental group 9 to replace the stone with the same volume. Adding the materials into a concrete mixer in proportion, fully mixing and stirring, pouring into a member or a mould, and naturally curing for 3d to remove the mould to obtain the self-curing multi-gradient temperature-control early-strength anti-cracking concrete. The performance pair ratios are shown in table 3 and fig. 5.
TABLE 3 comparison of various properties of the concrete
After the self-curing temperature control material is added, the slump of the concrete is increased, and the working performance is improved. Due to the addition of the self-curing temperature control material, the 3d compressive strength of the concrete of the experiment group 7 and the experiment group 8 is improved by 6-11%, the 3d split strength is improved by about 7-17%, the early hardening rate of the concrete is obviously accelerated, and the curing difficulty in actual construction is further reduced. The later compressive strength of the experimental group 9 is reduced by about 3%, the split tensile strength is reduced by about 4%, and the strength still meets the requirement of C35 concrete.
In an adiabatic temperature rise experiment, the multi-gradient self-curing temperature control material has an obvious temperature control effect on concrete, multi-gradient heat absorption temperature control is formed in the temperature rise process of the concrete, the temperature rise duration of the concrete is prolonged, and the duration of the temperature rise is prolonged at about 20 ℃; the maximum temperature rise of the concrete is reduced, the maximum temperature rise of the experimental group 7 is reduced by 4.5 ℃, the maximum temperature rise of the experimental group 8 is reduced by 7.4 ℃ and the maximum temperature rise of the experimental group 9 is reduced by 9.7 ℃ compared with the maximum temperature rise of the reference group 3. The time for the concrete to reach the maximum temperature rise is prolonged, and the slope of the temperature rise curve is reduced. In the concrete cooling process, the cooling rate can be delayed, the generation of cracks is reduced, and the multi-gradient temperature control of the large-volume concrete in the heating/cooling process is realized.
The results of the drying shrinkage results of the concretes of different ages are shown in fig. 6, wherein the drying shrinkage of 56d of the experimental group 7 is reduced by 11% compared with that of the reference group 3, and the drying shrinkage of the experimental group 8 is reduced by 17%, and the results show that the self resistance of the concrete structure can be improved after a proper amount of self-curing temperature control material is added, and the cracking risk of the concrete is further reduced. The 56d drying shrinkage of the experimental group 9 is reduced by about 4 percent compared with that of the reference group 3, and when the mixing amount of the self-curing temperature control material is larger, the deformation resistance of the concrete is reduced, but the shrinkage at each age is still smaller than that of the reference concrete.
Example 4
The C40 concrete for the prefabricated part is prepared from the raw materials including, by mass, water, cement, fly ash, sand, stone and a water reducing agent, 1:1.3:1.2:5.3:7.5:0.02, in order to ensure consistent volume, a self-curing temperature control material with the total mass ratio of 15% of concrete is used for replacing the stone with the same volume in the experimental group 10, and a self-curing temperature control material with the total mass ratio of 35% of concrete is used for replacing the stone with the same volume in the experimental group 11. Adding the materials into a concrete mixer according to a certain proportion, fully mixing and stirring to obtain the self-curing multi-gradient temperature-control early-strength anti-cracking concrete, respectively carrying out natural curing and standard curing, and comparing the compressive strength of the concrete at each age. The performance pairs are shown in table 4.
TABLE 4 mechanical Properties of the concretes
It can be seen that the compressive strength of the concrete in the early age is improved after the self-curing temperature control material is doped. Under the condition of natural curing, the 12-hour compressive strength of the experimental group 10 is improved by 2.1MPa, and the 1-day compressive strength is improved by 5.3 MPa; the 12h compressive strength of the experimental group 11 is improved by 1.0MPa, and the 1d compressive strength is improved by 1.4 MPa. The result shows that the early hardening rate of the concrete is obviously accelerated and the early strength is obviously improved by adding the self-curing temperature control material. The experimental group 11 had lower strength at each age than the experimental group 10 and lower late strength than the baseline group 4, with a reduction in 28d compressive strength of 8.5MPa compared to the baseline group 4. When the mixing amount of the self-curing temperature control material is too high, the volume of the self-curing temperature control material serving as a weak item in the concrete is increased, and the mechanical property of the concrete is reduced. The compressive strength of natural curing and standard curing concrete is compared, and it can be found that the compressive strength of the experimental group 10 and the experimental group 11 in the early age period under the natural curing is higher than that of the standard curing, and the self-curing temperature control material absorbs heat when cement is hydrated and releases the heat in the cooling stage, so that the curing of the matrix concrete is enhanced, the early strength of the concrete is improved, the curing difficulty in actual construction is reduced, and the construction efficiency or the product delivery frequency is improved.
Example 5
The C40 concrete for large-volume or prefabricated parts is prepared from the raw materials including, by mass, water, cement, fly ash, sand, stone and a water reducing agent, 1:1.7:0.8:4.9:7.2:0.02, in order to ensure the consistency of the volume, a self-curing temperature-control material accounting for 12% of the total mass of the concrete is used for replacing the stone with the same volume in the experimental group 12, and a self-curing temperature-control material accounting for 30% of the total mass of the concrete is used for replacing the stone with the same volume in the experimental group 13. The materials are added into a concrete mixer according to a certain proportion, and after full mixing and stirring, the self-curing multi-gradient temperature-control early-strength anti-cracking concrete is obtained, wherein the anti-cracking performance is shown in the table 5.
TABLE 5 anti-crack Properties of the concretes
The crack number and the total length of the cracks are reduced after the self-curing temperature control material is doped, and the crack resistance of the concrete is obviously improved. Wherein the total cracking area of the experimental group 12 is decreased by about 51% compared to the reference group 5, the experimental group 13 is decreased by about 15%, and the crack resistance of the experimental group 12 is superior to that of the experimental group 13. By comparing the compressive strength, the 28d compressive strength of the experimental group 9 is improved by about 7% compared with that of the reference group 5, and the 28d compressive strength of the experimental group 13 is reduced by about 17%, which indicates that the mixing amount of the self-curing temperature control material has an optimal range, and when the mixing amount is too high, the mechanical property and the crack resistance of the concrete are reduced.
Claims (8)
1. The self-curing multi-gradient temperature-control early-strength anti-cracking concrete is characterized by comprising a self-curing temperature-control material and common concrete components, wherein the self-curing temperature-control material accounts for 2% -25% of the total mass, and comprises an encapsulation material and a phase-change material; the phase change material at least comprises a solid material and a liquid material; wherein the solid material is wrapped as an inner layer material and the liquid material is incorporated into the packaging material for use.
2. The self-curing multi-gradient temperature-control early-strength anti-crack concrete according to claim 1, wherein the phase change material comprises one or two of a normal-temperature phase change material and a medium-temperature phase change material; the phase-change temperature of the phase-change material is 10-60 ℃.
3. The self-curing multi-gradient temperature-control early-strength crack-resistant concrete according to claim 1 or 2, wherein the phase-change material comprises any two or more of paraffin, alcohol, ester, alkane and hydrated inorganic salt.
4. The self-curing multi-gradient temperature-control early-strength crack-resistant concrete according to claim 1, wherein the encapsulating material comprises a liquid phase-change material, a cementing material and water.
5. The packaging material of claim 4, wherein the mass ratio of the liquid phase-change material, the cementing material and the water is (2-5): (60-80): (18-35).
6. The packaging material as claimed in claim 4 or 5, wherein the cement binder and the various admixtures are present in a mass ratio of (50-100) to (0-50).
7. The preparation method of the self-curing multi-gradient temperature-control early-strength anti-crack concrete according to claim 1, which is characterized by comprising the following steps:
(1) pretreating the weighed phase change material, uniformly mixing all the materials, placing the mixture into balling granulation equipment for granulation and molding, and curing to prepare the self-curing temperature control material;
(2) fully stirring and mixing the prepared self-curing temperature control material and concrete according to a proportion, and pouring the mixture into a member or a mold;
(3) and removing the mould after natural curing or standard curing to obtain the self-curing multi-gradient temperature-control early-strength anti-cracking concrete.
8. The method for preparing self-curing multi-gradient temperature-control early-strength anti-crack concrete according to claim 7, wherein in the step (3), the curing time is 1-5 days.
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