A large volume concrete hydration heat inhibitor and its preparation method and application

Abstract

The present invention discloses a large-volume concrete hydration heat inhibitor, its preparation method and application, and belongs to the technical field of concrete admixtures. The hydration heat inhibitor includes a dissolving heat absorbing material, a temperature-controlling heat absorbing material, an intelligent heat-controlling material and a hydration reaction regulating material; wherein, the dissolving heat absorbing material includes at least one of calcium nitrate, ammonium nitrate and potassium nitrate; the temperature-controlling heat absorbing material includes sodium thiosulfate, paraffin and barium hydroxide octahydrate; the intelligent heat-controlling material is obtained by wrapping the dissolving heat absorbing material with polyethylene glycol; the hydration reaction regulating material is a calcium-complexed sulfonated dextrin. Under the joint action of the dissolving heat absorbing material, the temperature-controlling heat absorbing material, the intelligent heat-controlling material and the hydration reaction regulating material, the large-volume concrete hydration heat inhibitor of the present invention can realize step-by-step regulation of the hydration heat of large-volume concrete, significantly reduce the hydration heat of large-volume concrete, and effectively control the temperature cracks of large-volume concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete admixtures, and more particularly to a large-volume concrete hydration heat inhibitor, a preparation method thereof, and an application thereof. Background Art

[0002] During the pouring process of large-volume concrete, due to the hydration heat release of cement and other cementitious materials and the simultaneous heat dissipation on the surface, the temperature of the concrete itself changes continuously in time and space, thereby generating temperature stress; and concrete itself is a poor conductor of heat, and most of the hydration heat cannot be dissipated to the surrounding environment in a short time. The temperature of the core area of ​​large-volume concrete is generally higher than 50°C, and can even reach above 80°C. During the cooling stage, the large-volume concrete is constrained by the foundation or adjacent parts, and tensile stress is generated inside. Then, as the size of the concrete increases, the temperature difference between the inside and outside causes inconsistent volume deformation, which can easily lead to the surface temperature stress caused by the temperature difference between the inside and outside exceeding the maximum allowable tensile stress of the concrete. Once the tensile stress is greater than the tensile limit of the concrete, cracks will expand from the surface to the inside, that is, cracks will occur in the constrained area, which increases the risk of cracking of large-volume concrete.

[0003] At present, it is necessary to take appropriate temperature control measures during large-volume concrete pouring construction to ensure the concrete temperature and improve the quality of concrete pouring. The traditional methods mainly include: (1) reducing the heat release of cement hydration in concrete, such as reducing the amount of adhesive, using admixtures such as fly ash and mineral powder, or using low- and medium-heat cement; (2) increasing the heat dissipation rate, such as pre-buried cooling water pipes, reducing the structural size, etc.; (3) reducing the mold entry temperature, pre-cooling raw materials, etc. These methods have the disadvantages of reducing concrete performance and greatly increasing construction difficulty and cost; adding concrete hydration temperature rise inhibitors has become the simplest and most effective method. Adding hydration temperature rise inhibitors not only reduces the cost of cooling aggregates and pre-buried cooling water pipes, but also can more effectively reduce cement hydration heat release and reduce the temperature difference between the inside and outside of concrete compared to optimizing concrete mix ratio. It has the advantages of convenience, economy and high controllability. For example, Chinese patent application CN111377652A provides a large-volume concrete hydration temperature rise inhibitor, which is composed of porous ceramsite, phase change material and starch-based hydration heat control material. The phase change material paraffin and / or barium hydroxide octahydrate is mixed evenly with the porous ceramsite, cooled and added with starch-based hydration heat control material (starch polysaccharide obtained by starch hydrolysis or enzymatic hydrolysis), and mixed evenly to form a hydration temperature rise inhibitor. This inhibitor absorbs the heat generated by the hydration of large-volume concrete, reduces the cement hydration heat release rate, delays the temperature rise rate of large-volume concrete, reduces the temperature peak of large-volume concrete, and ultimately reduces the phenomenon of non-penetrating surface cracking. However, the hydration temperature rise inhibitor provided in this patent has limited effect on the regulation of the hydration heat reaction of large-volume concrete, especially in an environment with high temperature, where the temperature rise during the concrete casting and molding process is still relatively fast, which ultimately affects the compressive strength and other properties of large-volume concrete.

[0004] Commonly used hydration heat control materials include starch dextrin polymers, inorganic salts, and endothermic phase change materials. Dextrin and protein materials associate with water molecules through hydroxyl groups to form a stable solvated water film that wraps around the surface of cement particles, hindering the cement hydration reaction. The physical reaction of inorganic salt hydration temperature rise inhibitors when dissolved in water or the chemical reaction with water are both endothermic reactions. They can absorb a large amount of heat released by cement hydration and inhibit cement hydration. However, the use of dextrin has a significant adverse effect on the setting time and mechanical properties of concrete, causing severe retarding of concrete setting and a significant decrease in strength. In addition, inorganic salts dissolve during the concrete mixing process. At this time, the cement has not yet begun to hydrate and no significant hydration heat is generated. Therefore, the dissolution of inorganic salts cannot achieve the actual heat control effect. Summary of the Invention

[0005] In response to the deficiencies of the above-mentioned prior art, the present invention provides a large-volume concrete hydration heat inhibitor, which can achieve step-by-step regulation to address the problem of large hydration heat release of large-volume concrete, significantly reduce the hydration heat of large-volume concrete, and greatly reduce the risk of concrete temperature difference shrinkage cracks.

[0006] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0007] A large volume concrete hydration heat inhibitor, comprising a dissolving heat absorbing material, a temperature controlling heat absorbing material, an intelligent heat controlling material and a hydration reaction regulating material;

[0008] Among them, the dissolving endothermic material includes at least one of calcium nitrate, ammonium nitrate, and potassium nitrate; the temperature-controlling endothermic material includes sodium thiosulfate, paraffin, and barium hydroxide octahydrate; the intelligent heat-control material is obtained by wrapping the dissolving endothermic material with polyethylene glycol; and the hydration reaction regulating material is calcium-complexed sulfonated dextrin.

[0009] In the mass concrete hydration heat inhibitor of the present invention, the dissolving heat absorbing material absorbs a large amount of heat generated by cement hydration when it dissolves; in the temperature control heat absorbing material, sodium thiosulfate melts at 48°C and absorbs a large amount of heat, paraffin melts at 50-55°C and absorbs a large amount of heat, and barium hydroxide octahydrate melts at 78°C and absorbs a large amount of heat. By melting and absorbing heat step by step, sodium thiosulfate, paraffin and barium hydroxide octahydrate can achieve full step-by-step control within the range of 48-78°C; the intelligent heat control material is obtained by wrapping the dissolving heat absorbing material with polyethylene glycol, and has a capsule structure. The material will not dissolve during the concrete mixing process. When the cement hydration releases a large amount of heat, the temperature reaches the melting point of polyethylene glycol, the capsule dissolves, and the material inside begins to dissolve and absorb heat, achieving the effect of intelligent regulation; calcium complex type sulfonated dextrin forms a wrapping structure on the surface of cement particles. As the cement hydration reaction proceeds, when a large amount of cement reacts concentratedly, calcium ions react with silicate and sulfonate to generate needle-shaped calcium aluminate crystals that pierce the water-soluble dextrin film, allowing the cement particles to further undergo hydration reaction, which can avoid the hydration rate being too fast, and at the same time, it can avoid dextrin from causing serious slow setting of concrete. The mass concrete hydration heat inhibitor of the present invention can realize step-by-step regulation of the hydration heat of mass concrete under the joint action of dissolving endothermic material, temperature control endothermic material, intelligent heat control material and hydration reaction regulating material, significantly reducing the hydration heat of mass concrete and greatly reducing the risk of concrete temperature difference shrinkage cracks.

[0010] Preferably, the preparation method of the hydration reaction regulating material comprises the following steps: adding dextrin to water, then adding sulfuric acid, stirring evenly, adding calcium hydroxide suspension dropwise until the pH of the solution is 9 to 11, and then drying the solution until the water content is less than 0.5%, thereby obtaining the hydration reaction regulating material.

[0011] Preferably, in the temperature-controlling endothermic material, the mass ratio of sodium thiosulfate, paraffin wax and barium hydroxide octahydrate is (40-50): (30-40): (15-25).

[0012] Preferably, the preparation method of the intelligent heat control material is as follows: polyethylene glycol with a molecular weight of 2000 to 4000 is heated to a liquid state, a dissolving heat absorbing material is added, and the mixture is stirred evenly and then spray granulated to obtain the intelligent heat control material.

[0013] Preferably, the mass ratio of the polyethylene glycol to the dissolved endothermic material is 100:(22-28).

[0014] Preferably, the nanoscale crystallization agent includes at least one of silicon phosphate, aluminum phosphate or calcium phosphate.

[0015] Preferably, the particle size of the dissolved heat absorbing material is 80 to 120 meshes.

[0016] Preferably, the mass concrete hydration heat inhibitor includes the following components in the following mass percentages: 20% to 30% of dissolved heat absorbing material, 20% to 30% of temperature control heat absorbing material, 40% to 50% of intelligent heat control material, and 5% to 15% of hydration reaction regulating material.

[0017] Another object of the present invention is to provide a method for preparing the mass concrete hydration heat inhibitor, comprising the following steps: weighing the dissolving heat-absorbing material, the temperature-control heat-absorbing material, the intelligent heat-control material and the hydration reaction regulating material in proportion, dry-mixing and stirring them uniformly to obtain the mass concrete hydration heat inhibitor.

[0018] Another object of the present invention is to provide a use of a large volume concrete hydration heat inhibitor in concrete, wherein the dosage of the hydration heat inhibitor is 1% of the mass of the cementitious material.

[0019] Compared with the prior art, the present invention is beneficial in that:

[0020] (1) The temperature-controlled heat-absorbing material of the present invention melts and absorbs heat step by step, and can achieve full-process step-by-step regulation within the range of 48 to 78°C; the intelligent heat-control material of the present invention begins to dissolve and absorb heat when the cement reacts in a concentrated manner, achieving the effect of intelligent regulation; the calcium-complexed sulfonated dextrin of the present invention can prevent the dextrin from causing severe slow setting of concrete while preventing the cement from hydrating too quickly.

[0021] (2) The present invention makes full use of dissolution endothermicity, melting endothermicity, intelligent regulation and hydrophilic calcium sulfonated membrane technology to achieve the effect of inhibiting the hydration heat of large-volume concrete, significantly reducing the hydration heat of large-volume concrete, and effectively controlling the temperature cracks of concrete. DETAILED DESCRIPTION

[0022] The technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] In the following examples and comparative examples, calcium nitrate, ammonium nitrate and potassium nitrate were all analytically pure, with a content of ≥99%.

[0024] Example 1

[0025] This embodiment provides a mass concrete hydration heat inhibitor, comprising the following components in the following mass percentages: 25% dissolving heat absorbing material, 23% temperature control heat absorbing material, 43% intelligent heat control material, and 9% hydration reaction regulating material;

[0026] The dissolving heat absorbing material is obtained by grinding calcium nitrate crystal powder into 80 mesh under low temperature nitrogen conditions at 5°C;

[0027] The temperature-control heat-absorbing material is composed of sodium thiosulfate, C22-C26 paraffin wax, and barium hydroxide octahydrate in a mass ratio of 45:35:20;

[0028] The preparation method of the intelligent thermal control material is as follows: polyethylene glycol with a molecular weight of 2000-4000 is heated to 70°C to form a uniform liquid, and then calcium nitrate is added at a mass ratio of calcium nitrate to polyethylene glycol of 25:100. The mixture is stirred at 70°C and 2000 rpm / min for 30 minutes. The mixture is then sprayed and granulated at a speed of 5 m / s in a cavity at 20±1°C using a medium-pressure spray gun to obtain the intelligent thermal control material.

[0029] The preparation method of the hydration reaction regulating material is as follows: dextrin and water are mixed in a mass ratio of 10:90, and then a sulfuric acid solution (0.1 mol / L) accounting for 10% of the total mass of the dextrin and water is added. After stirring at a speed of 2000 rpm / min for 60 minutes, a 10% calcium hydroxide suspension is added dropwise until the pH value of the solution reaches 10. Finally, the solution is dried at 105°C to make the moisture content of the powder less than 0.5%, thereby obtaining a calcium complex sulfonated dextrin, which is the hydration reaction regulating material.

[0030] The preparation method of the mass concrete hydration heat inhibitor of this embodiment is as follows: a dissolving heat-absorbing material, a temperature-control heat-absorbing material, an intelligent heat-control material, and a hydration reaction regulating material are weighed according to mass percentage and placed in a forced mixer. The mixture is stirred at a speed of 120 rpm / min for 30 minutes to obtain the mass concrete hydration heat inhibitor.

[0031] Example 2

[0032] This embodiment provides a large-volume concrete hydration heat inhibitor, comprising the following components in the following mass percentages: 22% dissolving heat absorbing material, 21% temperature control heat absorbing material, 45% intelligent heat control material, and 12% hydration reaction regulating material:

[0033] The dissolved heat-absorbing material is obtained by grinding ammonium nitrate crystal powder into 100 mesh under low-temperature nitrogen conditions at 5°C;

[0034] The temperature-control heat-absorbing material is composed of sodium thiosulfate, C22-C26 paraffin wax, and barium hydroxide octahydrate in a mass ratio of 40:40:20;

[0035] The preparation method of the intelligent thermal control material is as follows: polyethylene glycol with a molecular weight of 2000-4000 is heated to 65°C to form a uniform liquid, and then calcium nitrate is added at a mass ratio of calcium nitrate to polyethylene glycol of 22:100. The mixture is stirred at 2000 rpm / min while maintaining the temperature at 65°C for 30 minutes. The mixture is then sprayed and granulated at a speed of 5 m / s in a cavity at 20±1°C using a medium-pressure spray gun to obtain the intelligent thermal control material.

[0036] The preparation method of the hydration reaction regulating material is as follows: dextrin and water are mixed in a mass ratio of 10:90, and then a sulfuric acid solution (0.1 mol / L) accounting for 10% of the total mass of the dextrin and water is added. After stirring at a speed of 2000 rpm / min for 60 minutes, a 10% calcium hydroxide suspension is added dropwise until the pH value of the solution reaches 9. Finally, the solution is dried at 105° C. to reduce the moisture content of the powder to less than 0.5%, thereby obtaining the hydration reaction regulating material.

[0037] The preparation method of the mass concrete hydration heat inhibitor of this embodiment is as follows: a dissolving heat-absorbing material, a temperature-control heat-absorbing material, an intelligent heat-control material, and a hydration reaction regulating material are weighed according to mass percentage and placed in a forced mixer. The mixture is stirred at a speed of 120 rpm / min for 30 minutes to obtain the mass concrete hydration heat inhibitor.

[0038] Example 3

[0039] This embodiment provides a large-volume concrete hydration heat inhibitor, comprising the following components in the following mass percentages: 28% dissolving heat absorbing material, 25% temperature control heat absorbing material, 40% intelligent heat control material, and 7% hydration reaction regulating material:

[0040] The dissolving heat absorbing material is obtained by grinding potassium nitrate crystal powder to 120 mesh under low temperature nitrogen conditions at 5°C;

[0041] The temperature-control heat-absorbing material is composed of sodium thiosulfate, C22-C26 paraffin and barium hydroxide octahydrate in a mass ratio of 50:30:20;

[0042] The preparation method of the intelligent thermal control material is as follows: polyethylene glycol with a molecular weight of 2000-4000 is heated to 75°C to form a uniform liquid, and then calcium nitrate is added at a mass ratio of calcium nitrate to polyethylene glycol of 28:100. The mixture is stirred at 75°C and 2000 rpm / min for 30 minutes. The mixture is then sprayed and granulated using a medium-pressure spray gun at a speed of 5 m / s in a cavity at 20±1°C to obtain the intelligent thermal control material.

[0043] The preparation method of the hydration reaction regulating material is as follows: dextrin and water are mixed in a mass ratio of 10:90, and then a sulfuric acid solution (0.1 mol / L) accounting for 10% of the total mass of the dextrin and water is added. After stirring at a speed of 2000 rpm / min for 60 minutes, a 10% calcium hydroxide suspension with a mass concentration is added dropwise until the pH value of the solution reaches 11. Finally, the solution is dried at 105° C. to reduce the moisture content of the powder to less than 0.5%, thereby obtaining the hydration reaction regulating material.

[0044] The preparation method of the mass concrete hydration heat inhibitor of this embodiment is as follows: a dissolving heat-absorbing material, a temperature-control heat-absorbing material, an intelligent heat-control material, and a hydration reaction regulating material are weighed according to mass percentage and placed in a forced mixer. The mixture is stirred at a speed of 120 rpm / min for 30 minutes to obtain the mass concrete hydration heat inhibitor.

[0045] Comparative Example 1

[0046] The mass concrete hydration heat inhibitor of this comparative example is basically the same as that of Example 1, except that the temperature-control heat-absorbing material is composed of C22-C26 paraffin wax and barium hydroxide octahydrate in a mass ratio of 80:20;

[0047] That is, compared with Example 1, the temperature-controlling endothermic material of this comparative example does not contain sodium thiosulfate, and the amount of C22-C26 paraffin wax is adjusted accordingly.

[0048] Comparative Example 2

[0049] The mass concrete hydration heat inhibitor of this comparative example is substantially the same as that of Example 1, except that it comprises the following components in the following mass percentages: 68% of a dissolving heat absorbing material, 23% of a temperature controlling heat absorbing material, and 9% of a hydration reaction regulating material;

[0050] That is, compared with Example 1, this comparative example lacks the intelligent heat control material, and the amount of dissolved heat-absorbing material is increased accordingly.

[0051] Comparative Example 3

[0052] The mass concrete hydration heat inhibitor of this comparative example is basically the same as that of Example 1, except that the hydration reaction regulating material is dextrin.

[0053] Test example

[0054] In accordance with the relevant provisions of JCT 2608-2020 "Concrete Hydration Temperature Rise Inhibitors", the large-volume concrete hydration heat inhibitors of Examples 1 to 3 and Comparative Examples 1 to 3 were added to mortar and concrete. The amount of hydration heat inhibitor was 1% by mass of the cementitious material. The concrete mix ratio is shown in Table 1, and the test results of relevant properties are shown in Table 2.

[0055] Table 1 Concrete mix ratio (kg / m 3 )

[0056] cement river sand gravel water Hydration heat inhibitor 330 748 1123 198 3.3

[0057] Table 2 Performance test results The test results in Table 2 show that the addition of the hydration heat inhibitor of the present invention can reduce the 24-hour hydration heat of the mortar by as much as 49%, and the compressive strength ratio of the concrete by as much as 108%. These indicators far exceed the requirements of JCT 2608-2020. This demonstrates that the hydration heat inhibitor of the present invention can effectively reduce the hydration heat of cement, improve the mechanical properties of concrete, and significantly reduce the risk of thermal shrinkage cracking in concrete.

[0058] Compared with Example 1, the temperature-control endothermic material of Comparative Example 1 does not contain sodium thiosulfate, and the amount of paraffin is increased accordingly, resulting in a decrease in the 28d compressive strength ratio to 103% and a decrease in the 24h hydration heat reduction rate to 24%; Comparative Example 2 lacks the intelligent heat control material and increases the amount of dissolved endothermic material accordingly, that is, the intelligent heat control material is not wrapped with polyethylene glycol, resulting in a decrease in the 28d compressive strength ratio to 104% and a decrease in the 24h hydration heat reduction rate to 27%; Comparative Example 3 uses dextrin to replace calcium-complexed sulfonated dextrin, which results in a prolonged setting time of the concrete and a significant decrease in the mechanical properties, with a 28d compressive strength ratio of only 94%.

[0059] In summary, the hydration heat inhibitor of the present invention makes full use of dissolution endothermicity, melting endothermicity, intelligent regulation and hydrophilic calcareous sulfonated membrane technology to achieve the effect of inhibiting the hydration heat of large-volume concrete, significantly reducing the hydration heat of large-volume concrete. Changing its components will significantly reduce its effect of inhibiting hydration heat, or cause the problem of severe retarded setting of concrete.

[0060] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A mass concrete hydration heat inhibitor, characterized in that: The invention comprises the following components in the following mass percentages: 20% to 30% of a dissolving heat absorbing material, 20% to 30% of a temperature controlling heat absorbing material, 40% to 50% of an intelligent heat controlling material, and 5% to 15% of a hydration reaction regulating material; Among them, the dissolving endothermic material includes at least one of calcium nitrate, ammonium nitrate, and potassium nitrate; the temperature-controlling endothermic material includes sodium thiosulfate, paraffin, and barium hydroxide octahydrate; the intelligent heat-control material is obtained by wrapping the dissolving endothermic material with polyethylene glycol; and the hydration reaction regulating material is calcium-complexed sulfonated dextrin.

2. The mass concrete hydration heat inhibitor according to claim 1, characterized in that: The preparation method of the hydration reaction regulating material comprises the following steps: adding dextrin to water, then adding sulfuric acid, stirring evenly, dropwise adding calcium hydroxide suspension until the pH value of the solution is 9-11, and then drying the solution until the water content is less than 0.5%, thereby obtaining the hydration reaction regulating material.

3. The mass concrete hydration heat inhibitor according to claim 1, characterized in that: In the temperature-controlling heat-absorbing material, the mass ratio of sodium thiosulfate, paraffin wax and barium hydroxide octahydrate is (40-50): (30-40): (15-25).

4. The mass concrete hydration heat inhibitor according to claim 1, characterized in that: The preparation method of the intelligent heat control material is as follows: polyethylene glycol with a molecular weight of 2000-4000 is heated to a liquid state, a dissolving heat absorbing material is added, and the mixture is stirred evenly and then spray granulated to obtain the intelligent heat control material.

5. The mass concrete hydration heat inhibitor according to claim 4, characterized in that: The mass ratio of the polyethylene glycol to the dissolved heat absorbing material is 100:(22-28).

6. The mass concrete hydration heat inhibitor according to claim 1, characterized in that: The particle size of the dissolved heat-absorbing material is 80 to 120 meshes.

7. The method for preparing the mass concrete hydration heat inhibitor according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: weighing the dissolving heat absorbing material, the temperature controlling heat absorbing material, the intelligent heat controlling material and the hydration reaction regulating material in proportion, dry mixing and stirring them evenly, thereby obtaining the mass concrete hydration heat inhibitor.

8. Use of the mass concrete hydration heat inhibitor according to any one of claims 1 to 6 in concrete, characterized in that: The amount of the hydration heat inhibitor is 1% of the mass of the gelling material.

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