High-crack resistance low-heat portland cement and preparation method thereof

Abstract

The application discloses a high-crack-resistance low-heat Portland cement and a preparation method thereof. The application belongs to the technical field of building materials and comprises, by weight, 81-92 parts of cement clinker, 2-7 parts of gypsum, 1-4 parts of an activator, and 5-17 parts of an adjusting material. Mineral components in the cement clinker comprise, by weight percentage, 30-40% of tricalcium silicate, 35-45% of dicalcium silicate, 3-8% of tricalcium aluminate and 14-17% of tetracalcium aluminoferrite. The adjusting material comprises, by weight percentage, 35-46% of bentonite, 31-40% of superabsorbent resin, 10-23% of hollow glass microbeads and 6-18% of alcohol amine auxiliary agent. The application can significantly improve the comprehensive performance of the low-heat Portland cement, so as to reduce the cracking risk of concrete in a severe and complex environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a high-anti-cracking low-heat Portland cement and a preparation method thereof. BACKGROUND

[0002] The low-heat Portland cement takes dicalcium silicate (C2S) as a dominant mineral, has the performance characteristics of low hydration heat, high later strength, high erosion resistance, and is suitable for water conservancy mass concrete engineering construction, has a remarkable effect on reducing the adiabatic temperature rise of concrete, and has been applied on a large scale in the construction of water conservancy dams such as Wudongde and Baihetan, and the low-heat Portland cement is also suitable for bridge pier, abutment and tower column, tunnel lining and other mass concrete structures in railway and highway engineering.

[0003] With the extension of major engineering construction in China to the western plateau and high-altitude areas, the engineering sites are gradually harsh and complex, the day and night temperature difference is large, the solar radiation is strong, and the environment is dry all year round, and under such complex conditions, the concrete of water conservancy, railway and highway is prone to have large volume shrinkage deformation, fast water loss, and other engineering problems such as easy cracking of concrete structure and poor durability. Therefore, how to comprehensively improve the comprehensive performance of low shrinkage and water retention of low-heat Portland cement, and thus improve the anti-cracking performance of concrete under complex environmental conditions, to meet the high-quality and high-durability construction requirements of major engineering in China, has become a technical problem to be solved in the field. SUMMARY

[0004] The application provides a high-anti-cracking low-heat Portland cement and a preparation method thereof, which can significantly reduce the cracking risk of concrete under harsh and complex environments.

[0005] The technical scheme of the application is: including, by weight, 81-92 parts of cement clinker, 2-7 parts of gypsum and 1-4 parts of an activator, and further including 5-17 parts of an adjusting material;

[0006] The mineral components in the cement clinker include, by weight percentage, 30-40% of tricalcium silicate, 35-45% of dicalcium silicate, 3-8% of tricalcium aluminate and 14-17% of tetracalcium aluminoferrite,

[0007] The adjusting material includes, by weight percentage, 35-46% of bentonite, 31-40% of superabsorbent resin, 10-23% of hollow glass microspheres and 6-18% of alcohol amine auxiliary agent.

[0008] Further, the gypsum is one or more of natural gypsum, desulfurization gypsum and phosphogypsum.

[0009] Further, the activator is one or more of nano-Al2O3 and nano-SiO2, and the size range is 20-80 nm.

[0010] Further, the specific surface area of the bentonite is ≥ 600 m 2 / kg.

[0011] Further, the effective water retention rate of the superabsorbent resin is ≥ 90%, and the liquid absorption ratio is ≥ 25.

[0012] Further, the mass ratio of the bentonite and the superabsorbent resin is 1.2-1.5.

[0013] Further, the true density of the hollow glass microsphere is 0.3~0.6g / cm 3 , the particle size is 50~150μm, and the compressive strength is ≥ 60MPa.

[0014] Further, the alcohol amine additive is one or more of diethanolamine, dimethyl ethanolamine, diisopropanolamine, and triethanolamine.

[0015] Further, the 3d hydration heat of the high crack resistance low heat Portland cement is ≤ 200kj / kg, the 7d hydration heat is ≤ 230kj / kg, the 3d compressive strength is ≥ 22MPa, the 7d compressive strength is ≥ 30MPa, the 28d compressive strength is ≥ 50MPa, and the 28d dry shrinkage rate is ≤ 0.045%.

[0016] The application discloses a preparation method of high crack resistance low heat Portland cement.

[0017] 1), bentonite, superabsorbent resin, hollow glass microsphere and alcohol amine additive are added to deionized water in weight percentage, and stirred uniformly to obtain a mixed solution;

[0018] 2), the mixed solution obtained in step 1 is heated and evaporated, and then placed in a vacuum drying box for full drying to obtain the required adjusting material;

[0019] 3), the adjusting material obtained in step 2 is taken in weight parts, and cement clinker, gypsum and activator are collectively ground to a specific surface area of 300-350 m 2 / kg to obtain high crack resistance low heat Portland cement.

[0020] The application changes the composition mode of traditional Portland cement,

[0021] Firstly, a nanoscale activator is adopted to effectively induce the activity of cement clinker minerals and accelerate the hydration reaction, thereby significantly improving the strength of the cement.

[0022] Secondly, the "multi-dimensional regulator" of cement material is innovatively developed, that is, the regulating material composed of "bentonite, superabsorbent resin, hollow glass microsphere and alcohol amine additive". By using the adsorption performance of bentonite, water is effectively locked, the loss rate of water in the dry environment is reduced, and the shrinkage of cement caused by drying water loss is reduced; by using the water absorption and "water storage" characteristics of superabsorbent resin, the role of water retention in the early stage and water release in the later stage in the cement slurry solution is played; by using the characteristics of low thermal conductivity and high strength of hollow glass microspheres, one is to adsorb on the cement particles to realize the strength effect, and two is to reduce the heat exchange between the inside and the outside environment of cement mortar or concrete when the temperature and humidity of the environment change greatly, effectively reducing the water loss of cement mortar or concrete caused by large temperature difference and dry environment; by using the complexation of alcohol amine additive, the hydration reaction of cement minerals is promoted, the early strength is improved, and the surface tension of the cement slurry pore solution is also reduced, thereby reducing the shrinkage stress caused by the reduction of cement hydration pore solution, and further reducing the drying shrinkage rate of cement.

[0023] Finally, in the preparation process of the present application, when the regulating material is ground together with the cement clinker and the activator, the three-dimensional structure of the regulating material will be destroyed into a semi-three-dimensional structure, and can be uniformly distributed around the cement particles to form a four-dimensional double-scale (micron-nanometer) close-packed structure. When preparing cement mortar or concrete, after the cement is mixed with water, a part of the water will be adsorbed and locked by the bentonite and superabsorbent resin according to a certain proportion, and a part of the water will be free in the pores. With the promotion of the activator and alcohol amine additive to the hydration reaction of cement, the strength of cement is continuously developed. When the cement mortar or concrete is in a large temperature difference and dry environment, the hollow glass microspheres will close the channels to reduce water loss. In the case of insufficient water, the 1.2-1.5 mass ratio of bentonite and superabsorbent resin will adjust according to the hydration rate of the clinker minerals, release water at a certain rate for the cement to continue to hydrate and harden, and the strength of the cement will continue to increase.

[0024] The present application can significantly improve the comprehensive performance of low-heat Portland cement to reduce the risk of concrete cracking in harsh and complex environments. DETAILED DESCRIPTION

[0025] The high-anti-cracking low-heat Portland cement of the present application comprises, by weight: 81-92 parts of cement clinker, 2-7 parts of gypsum and 1-4 parts of activator, and further comprises 5-17 parts of regulating material.

[0026] The mineral components in the cement clinker comprise, by weight percentage: 30-40% of tricalcium silicate, 35-45% of dicalcium silicate, 3-8% of tricalcium aluminate and 14-17% of tetracalcium aluminoferrite.

[0027] The adjusting material comprises, by weight percentage, 35-46% bentonite, 31-40% superabsorbent resin, 10-23% hollow glass microbeads and 6-18% alcohol amine auxiliary.

[0028] The gypsum is one or more of natural gypsum, desulfurization gypsum and phosphogypsum.

[0029] The activator is one or more of nano-Al2O3 and nano-SiO2, and the size range is 20-80 nm. The nano-sized activator has a nano effect, high surface activity, can effectively induce the cement clinker minerals to accelerate the hydration reaction with water, and thus significantly improve the cement strength.

[0030] The specific surface area of the bentonite is ≥600 m 2 / kg. The bentonite has good physical and chemical properties, and its strong adsorption property can effectively lock water and reduce the water loss rate in a dry environment, and reduce the shrinkage of cement caused by drying and water loss.

[0031] The effective water retention rate of the superabsorbent resin is ≥90%, and the liquid absorption rate is ≥25. The superabsorbent resin is a polymer with a certain degree of crosslinking, has a hydrophilic group, can absorb a large amount of water and swell, and can keep the water from flowing out. In an alkaline environment, it can slowly release water, so it can play a role in water retention in the early stage and water release in the later stage in the cement slurry solution.

[0032] The mass ratio of the bentonite to the superabsorbent resin is 1.2-1.5. Although the mass percentage ratio of the bentonite, the superabsorbent resin, the hollow glass microbeads and the alcohol amine auxiliary in the adjusting material is limited in the basic scheme of the application, the inventors have further found that when the mass ratio of the bentonite to the superabsorbent resin is 1.2-1.5, the prepared adjusting material can adjust the hydration rate of the main mineral dicalcium silicate of the low-heat portland cement clinker, and release the water required for cement hydration at a certain rate.

[0033] The true density of the hollow glass microbeads is 0.3-0.6 g / cm 3 , the particle size is 50-150 μm, and the compressive strength is ≥60 MPa. The hollow glass microbeads have the advantages of light weight, low thermal conductivity, high strength and good chemical stability. Due to its high compressive and impact resistance, it will not have a negative impact on the sustained development of cement strength. At the same time, due to its much smaller particle size than cement and the electrostatic adsorption effect, when mixed with cement particles, it can be filled between and wrapped around the cement particles. Due to its low thermal conductivity, when the external temperature and humidity change greatly, it can reduce the heat exchange between the inside of the cement mortar or concrete and the external environment, effectively reducing the loss of water in the cement mortar or concrete caused by large temperature difference and dry environment.

[0034] The alcohol amine additive is one or more of diethanolamine, dimethyl ethanolamine, diisopropanolamine, and triethanolamine. The complexation can promote the hydration reaction of cement minerals to improve the early strength of cement, and can also reduce the surface tension of the cement paste pore solution, thereby reducing the shrinkage stress caused by the reduction of the cement hydration pore solution, and further reducing the drying shrinkage rate of the cement.

[0035] The 3d hydration heat of the high crack resistance low heat Portland cement prepared by the method is less than or equal to 200 kj / kg, the 7d hydration heat is less than or equal to 230 kj / kg, the 3d compressive strength is greater than or equal to 22 MPa, the 7d compressive strength is greater than or equal to 30 MPa, and the 28d compressive strength is greater than or equal to 50 MPa, and the 28d drying shrinkage rate is less than or equal to 0.045%.

[0036] The method for preparing the high crack resistance low heat Portland cement comprises the following preparation steps,

[0037] 1. The bentonite, superabsorbent resin, hollow glass microsphere and alcohol amine additive are added to the deionized water in a weight percentage, and stirred uniformly to obtain a mixed solution;

[0038] 2. The mixed solution obtained in step 1 is heated and evaporated to remove water, and then placed in a vacuum drying box for full drying to obtain the required adjusting material;

[0039] 3. The adjusting material obtained in step 2, cement clinker, gypsum and activator are ground together to a specific surface area of 300-350 m 2 / kg to obtain the high crack resistance low heat Portland cement.

[0040] The bentonite, superabsorbent resin, hollow glass microsphere and alcohol amine additive are stirred and mixed uniformly in the deionized water, and then the water is removed, so that the adjusting material with a three-dimensional compact structure can be obtained, that is, the bentonite particles and the superabsorbent resin are in the inner layer, the hollow glass microsphere is in the outer layer, and the alcohol amine additive is filled between the two.

[0041] When the adjusting material is ground together with the cement clinker and the activator, the three-dimensional structure of the adjusting material will be destroyed into a semi-three-dimensional structure, and can be uniformly distributed around the cement particles to form a four-dimensional double-scale (micron-nanometer) compact structure, that is, the cement particles are in the innermost layer, the bentonite particles and the superabsorbent resin are in the middle layer, the hollow glass microsphere is in the outermost layer, and the activator is filled between the cement particles and the bentonite particles and adjacent to the alcohol amine additive.

[0042] When the cement is mixed with water, the hollow glass microspheres open the channels, a part of water is adsorbed and locked by the bentonite and superabsorbent resin according to a certain proportion, and another part of water is free in the pores. With the promotion of the activator and the alcohol amine additive, the cement hydration reaction occurs, and the strength of the cement continuously develops. When the cement mortar or concrete is in an environment with large temperature difference and dry environment, the hollow glass microspheres will close the channels to reduce water loss. In the case of insufficient water, the bentonite and superabsorbent resin with a mass ratio of 1.2-1.5 will adjust the hydration rate of the clinker minerals and release water at a certain rate to continue the hydration and hardening reaction of the cement, and the strength of the cement continuously increases.

[0043] Example 1

[0044] A high-anti-cracking low-heat Portland cement, the composition of which is 90 parts of cement clinker, 5 parts of adjusting material, 3 parts of gypsum and 2 parts of activator, wherein the adjusting material is composed of 43% bentonite, 35% superabsorbent resin, 13% hollow glass microspheres and 9% alcohol amine additive in terms of mass percentage, and is obtained after being uniformly mixed in deionized water and then removing water.

[0045] Example 2

[0046] A high-anti-cracking low-heat Portland cement, the composition of which is 85 parts of cement clinker, 10 parts of adjusting material, 4 parts of gypsum and 1 part of activator, wherein the adjusting material is composed of 40% bentonite, 33% superabsorbent resin, 15% hollow glass microspheres and 12% alcohol amine additive in terms of mass percentage, and is obtained after being uniformly mixed in deionized water and then removing water.

[0047] Example 3

[0048] A high-anti-cracking low-heat Portland cement, the composition of which is 80 parts of cement clinker, 15 parts of adjusting material, 2 parts of gypsum and 3 parts of activator, wherein the adjusting material is composed of 38% bentonite, 32% superabsorbent resin, 19% hollow glass microspheres and 11% alcohol amine additive in terms of mass percentage, and is obtained after being uniformly mixed in deionized water and then removing water.

[0049] The high-anti-cracking low-heat Portland cement of Examples 1-3 is tested for performance by using conventional testing methods in the art, and the results are shown in Table 1.

[0050] Table 1 Performance test results of high-anti-cracking low-heat Portland cement

[0051]

[0052] It can be seen from the experimental data that the high-anti-cracking low-heat Portland cement has 3d hydration heat of less than or equal to 200 kj / kg, 7d hydration heat of less than or equal to 230 kj / kg, 3d compressive strength of more than or equal to 22 MPa, 7d compressive strength of more than or equal to 30 MPa, 28d compressive strength of more than or equal to 50 MPa and 28d dry shrinkage of less than or equal to 0.045%, which are all better than those of ordinary low-heat Portland cement, and the expected target of the application is achieved.

[0053] The application is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the application, those skilled in the art can make some substitutions and modifications to some technical features according to the disclosed technical content without creative labor, and these substitutions and modifications are all within the protection scope of the application.

Claims

1. A high crack resistance type low heat Portland cement, comprising, in parts by weight: 81-92 parts of cement clinker, 2-7 parts of gypsum and 1-4 parts of activator, characterized in that further comprising 5-17 parts of adjusting material; The mineral components in the cement clinker comprise 30-40% of tricalcium silicate, 35-45% of dicalcium silicate, 3-8% of tricalcium aluminate and 14-17% of tetracalcium aluminoferrite by weight percentage, The adjusting material comprises 35-46% of bentonite, 31-40% of superabsorbent resin, 10-23% of hollow glass microsphere and 6-18% of alcohol amine auxiliary by weight percentage; The activator is one or more of nano-Al2O3 and nano-SiO2.

2. A high crack resistance low heat Portland cement according to claim 1, characterized in that, The gypsum is one or more of natural gypsum, desulfurization gypsum and phosphogypsum.

3. The high crack resistance low heat Portland cement according to claim 1, characterized by, The size range of the activator is 20-80 nm.

4. The high crack resistance low heat Portland cement according to claim 1, characterized by, The specific surface area of the bentonite is > 600 m 2 / kg.

5. The high crack resistance low heat Portland cement according to claim 1, characterized by, The effective water retention rate of the superabsorbent resin is ≥90% and the liquid absorption ratio is ≥25.

6. A high crack resistance low heat Portland cement according to claim 1, characterized in that, The mass ratio of the bentonite to the superabsorbent resin is 1.2-1.

5.

7. A high crack resistance low heat Portland cement according to claim 1, characterized in that, The hollow glass microsphere has a true density of 0.3-0.6 g / cm 3 , a particle size of 50-150 μm, and a compressive strength of ≥ 60 MPa.

8. A high crack resistance low heat Portland cement according to claim 1, characterized in that, The alcohol amine auxiliary is one or more of diethanolamine, dimethyl ethanolamine, diisopropyl alcohol amine and triethanolamine.

9. A high crack resistance low heat Portland cement according to any one of claims 1 to 8, characterized in that, The 3d hydration heat of the high crack resistance low heat Portland cement is ≤200 kj / kg, the 7d hydration heat is ≤230 kj / kg, the 3d compressive strength is ≥22 MPa, the 7d compressive strength is ≥30 MPa, the 28d compressive strength is ≥50 MPa and the 28d dry shrinkage rate is ≤0.045%.

10. A method for producing a high-crack resistance low-heat Portland cement, characterized by, The high crack resistance low heat Portland cement of claim 1 is prepared by the following steps: 1) The bentonite, superabsorbent resin, hollow glass microsphere and alcohol amine auxiliary are added to the deionized water in the weight percentage and stirred uniformly to obtain a mixed solution; 2) The mixed solution obtained in step 1) is heated to evaporate the water, and then placed in a vacuum drying box for sufficient drying to obtain the required adjusting material. 3), take the adjusting material obtained in step 2), cement clinker, gypsum and activator together to grind to specific surface area 300-350m 2 / kg by weight parts, to obtain high-anti-cracking low-heat Portland cement.

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