Cement mortar suitable for summer high-temperature construction and preparation method thereof

Abstract

The invention relates to the technical field of cement mortar, in particular to cement mortar suitable for summer high-temperature construction and a preparation method thereof. The cement mortar is prepared by the preparation method. The preparation method comprises the following steps: preparing dry powder and mixed liquid; the mixed solution comprises the following raw material components in parts by weight: 0.5-2 parts of a water reducing agent, 1-3 parts of a water retaining agent, 0.2-6 parts of a retarder and 60-110 parts of water; wherein the retarder comprises at least one of white sugar and sodium gluconate; uniformly mixing the raw material components in the mixed solution to obtain the mixed solution; and uniformly mixing the dry powder with the mixed solution to obtain the cement mortar suitable for high-temperature construction in summer. The prepared cement mortar can prolong the setting time, reduce the shrinkage rate of the cement mortar, reduce the cracking risk and enhance the compressive strength and shrinkage resistance of the cement mortar.

Description

Technical Field

[0001] The invention relates to the technical field of cement mortar, and in particular to a cement mortar suitable for high-temperature construction in summer and a preparation method thereof. Background Art

[0002] Cement mortar is easily affected by temperature during construction, especially during high-temperature construction in summer. High temperature will accelerate the hydration reaction of cement, shorten the setting time of cement mortar, cause the cement mortar to solidify quickly, and shorten its operability time. At the same time, high temperature causes the water in cement mortar to evaporate faster, reducing the wetness and fluidity of the mortar, leading to construction difficulties. In order to make cement mortar adapt to the needs of high-temperature construction in summer, the industry usually adopts the method of increasing the amount of water reducer. Although increasing the amount of water reducer can delay the loss of mortar and extend its working time to a certain extent, excessive use of water reducer may cause segregation and water seepage problems in cement mortar, seriously affecting the quality of cement mortar.

[0003] In addition, as a brittle engineering material, cement mortar is prone to cracking and has a large shrinkage rate. It is easily affected by complex environments and cracks will form during long-term use. Although small cracks may not affect the bearing capacity of the cement mortar structure, they will damage its impermeability and durability, causing cement mortar underground structures and hydraulic structures to fail due to water seepage.

[0004] In summary, it is necessary to develop a cement mortar suitable for high-temperature construction in summer and a preparation method thereof, which can solve the problem that the existing cement mortar is easily affected by temperature during the construction process, resulting in shortened operating time and construction difficulties, and solve the problem that the existing cement mortar is easy to crack and has a large shrinkage rate. Summary of the invention

[0005] The object of the present invention is to provide a cement mortar suitable for high temperature construction in summer and a preparation method thereof. The specific technical scheme is as follows:

[0006] In a first aspect, the present invention provides a method for preparing cement mortar suitable for high temperature construction in summer, comprising:

[0007] Preparation of dry powders and mixed solutions;

[0008] The mixed solution comprises the following raw material components in parts by weight: 0.5-2 parts of a water reducing agent, 1-3 parts of a water retaining agent, 0.2-6 parts of a retarder and 60-110 parts of water; wherein the retarder comprises at least one of white sugar and sodium gluconate; the raw material components in the mixed solution are mixed uniformly to obtain the mixed solution;

[0009] The dry powder comprises the following raw material components in parts by weight: 200-300 parts of cement, 50-150 parts of admixture and 500-700 parts of medium sand; the raw material components in the dry powder are mixed uniformly to obtain the dry powder;

[0010] The dry powder is mixed with the mixed liquid to obtain cement mortar suitable for high temperature construction in summer.

[0011] Optionally, the water reducer includes a polycarboxylate water reducer; the water reduction rate of the polycarboxylate water reducer is 25%-30%.

[0012] Optionally, the water retaining agent includes hydroxypropyl methylcellulose ether.

[0013] Optionally, the cement is ordinary Portland cement with a strength grade of 42.5-52.5 MPa.

[0014] Optionally, the admixture includes fly ash and / or slag; the grade of the fly ash is grade I; the grade of the slag is grade S95.

[0015] Optionally, the fineness modulus of the medium sand is 2.3-3; the mud content of the medium sand is not more than 1.0%; and the maximum particle size of the medium sand is not more than 4.75 mm.

[0016] Optionally, the dry powder further comprises the following raw material components in parts by weight: 2-6 parts of basalt fiber and / or 4-10 parts of steel fiber.

[0017] Optionally, the basalt fiber has a monofilament diameter of 15-18 μm, a fiber length of 3-9 mm, and a density of 2.8-3.3 g / cm 3 .

[0018] Optionally, the steel fiber is a copper-plated steel fiber with a diameter greater than or equal to 0.2 mm, a length of 12-15 mm, an aspect ratio of 60-70, and a tensile strength greater than or equal to 3000 MPa.

[0019] In a second aspect, the present invention provides a cement mortar suitable for high-temperature construction in summer, which is prepared by the method for preparing the cement mortar suitable for high-temperature construction in summer.

[0020] The application of the technical solution of the present invention has at least the following beneficial effects:

[0021] (1) The present invention provides a method for preparing cement mortar suitable for high-temperature construction in summer. The use of a retarder can extend the setting time, thereby solving the problem that the existing cement mortar is easily affected by temperature during the construction process, resulting in a shortened operating time and difficult construction. Specifically, the retarder used includes at least one of white sugar and sodium gluconate, wherein the molecules of white sugar and sodium gluconate can be adsorbed on the surface of cement particles to form a negatively charged hydrophilic film, resulting in mutual repulsion between adjacent cement particles. This repulsive effect slows down the aggregation of cement particles, thereby hindering the hydration process of cement, extending the setting time of cement, and providing a longer operating window for construction.

[0022] (2) The water reduction rate of the polycarboxylate water reducer used in the present invention is 25%-30%. It has a steric hindrance effect and a wetting and lubricating effect, and can form a thicker adsorption layer on the surface of cement particles, increasing the steric repulsion between adjacent cement particles, which is beneficial to the dispersion of cement particles, thereby promoting the fluidity of cement mortar; at the same time, the formed adsorption layer contains a hydration film, which greatly promotes the sliding and dispersion between cement particles, making it difficult for cement particles to agglomerate, thereby further improving the fluidity of cement mortar. In addition, the use of polycarboxylate water reducer can also reduce the shrinkage rate of cement mortar and reduce the risk of cracking, thereby improving its durability.

[0023] (3) The basalt fiber and / or steel fiber used in the dry powder of the present invention can form an effective skeleton structure in the cement mortar, thereby enhancing the compressive strength and shrinkage resistance of the cement mortar. The combined use of basalt fiber and steel fiber can synergistically improve the compressive strength and shrinkage resistance of the cement mortar, reduce the risk of cracking, and improve its durability. DETAILED DESCRIPTION

[0024] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0025] Embodiment 1:

[0026] A method for preparing cement mortar suitable for high-temperature construction in summer, comprising:

[0027] Preparation of dry powders and mixed solutions;

[0028] The mixed liquid comprises the following raw material components in parts by weight: 1 part of water reducing agent, 1 part of water retaining agent, 1 part of retarder (specifically white sugar) and 100 parts of water; the raw material components in the mixed liquid are mixed at a stirring speed of 200 r / min to obtain the mixed liquid;

[0029] The dry powder comprises the following raw material components in parts by weight: 300 parts of cement, 50 parts of admixture, 650 parts of medium sand and 2 parts of basalt fiber; the raw material components in the dry powder are mixed at a stirring speed of 200 r / min to obtain the dry powder;

[0030] The dry powder and the mixed liquid are mixed at a stirring speed of 200 r / min to obtain cement mortar suitable for high temperature construction in summer.

[0031] The water reducing agent is a polycarboxylate water reducing agent; the water reducing rate of the polycarboxylate water reducing agent is 25%-30%, and 27.8% is used in this embodiment 1.

[0032] The water retaining agent is hydroxypropyl methylcellulose ether with a viscosity of 200,000.

[0033] The cement is ordinary Portland cement, and its strength grade is 42.5MPa.

[0034] The admixture includes fly ash and / or slag; the grade of the fly ash is grade I; the grade of the slag is grade S95. The admixture selected in this embodiment 1 is fly ash.

[0035] The fineness modulus of the medium sand is 2.3-3; the mud content of the medium sand is not more than 1.0%; and the maximum particle size of the medium sand is not more than 4.75 mm.

[0036] The basalt fiber has a monofilament diameter of 15-18 μm, a fiber length of 3-9 mm, and a density of 2.8-3.3 g / cm 3 , tensile strength is 4100MPa, and elastic modulus is 100GPa. Considering the small size of basalt fiber products, it is difficult for manufacturers to produce basalt fiber products of fixed size. Therefore, the size of the basalt fiber product provided in Example 1 fluctuates, but its corresponding tensile strength and elastic modulus can reach a fixed value level.

[0037] Embodiment 2:

[0038] The difference from Example 1 is that the weight percentage of the retarder is 3 parts and the weight percentage of water is 90 parts.

[0039] Embodiment 3:

[0040] The difference from Example 1 is that the weight parts of the retarder are 5 parts and the weight parts of water are 80 parts.

[0041] Embodiment 4:

[0042] The difference from Example 1 is that the retarder is sodium gluconate and the weight proportion of water is 110 parts.

[0043] Embodiment 5:

[0044] The difference from Example 1 is that the retarder is sodium gluconate, and its weight proportion is 3 parts.

[0045] Embodiment 6:

[0046] The difference from Example 1 is that the retarder is sodium gluconate, and its weight portion is 6 parts, and the weight portion of water is 90 parts.

[0047] Embodiment 7:

[0048] The difference from Example 6 is that the weight proportion of basalt fiber is 5 parts.

[0049] Embodiment 8:

[0050] Different from Example 6, the weight portion of basalt fiber is 2 parts; steel fiber is added, and the weight portion of steel fiber is 5 parts. The steel fiber is a copper-plated steel fiber, with a diameter greater than or equal to 0.2 mm, a length of 12-15 mm, an aspect ratio of 60-70, and a tensile strength of 3000 MPa. Considering the small size of steel fiber products, it is difficult for manufacturers to produce steel fiber products of fixed size. Therefore, the size of the steel fiber product provided in this Example 8 fluctuates, but its corresponding tensile strength can reach a fixed value level.

[0051] Comparative Example 1:

[0052] The difference from Example 1 is that the weight percentage of the water reducing agent is 0 parts, and the weight percentage of water is 150 parts.

[0053] Comparative Example 2:

[0054] The difference from Example 1 is that the weight percentage of the retarder is 0 parts, and the weight percentage of water is 120 parts.

[0055] All raw material components used in Examples 1-8 and Comparative Examples 1-2 are commercially available raw materials. The cement mortars prepared in Examples 1-8 and Comparative Examples 1-2 were sampled for performance testing. The test was based on JGJ / T 70-2009 "Standard for Basic Performance Test Methods of Building Mortar". The test results are shown in Table 1.

[0056] Table 1 Performance test results

[0057]

[0058] In the data in Table 1:

[0059] It can be seen from Comparative Example 2 and Examples 1-3 that, with the increase in the amount of white sugar, the fluidity loss of cement mortar over time is significantly reduced, and the setting time is extended, providing a longer operating window for construction. It is known from Examples 1-2 and 4-5 that, under the same dosage, sodium gluconate has a better effect on the fluidity of cement mortar than white sugar, but the setting time is relatively shortened. This is because white sugar molecules are larger than sodium gluconate molecules, and are adsorbed on the surface of cement particles to form a relatively thick hydrophilic film, resulting in an enhanced mutual repulsion between adjacent cement particles, further hindering the hydration process of cement and extending the setting time of cement.

[0060] Comparison between Example 6 and Example 7 shows that the compressive strength of cement mortar increases with the increase in the amount of basalt fiber used. Comparison between Example 6 and Example 8 shows that the combination of basalt fiber and steel fiber can significantly improve the compressive strength of cement mortar.

[0061] From the comparison between Comparative Example 1 and Comparative Example 2, it can be seen that not using a water reducing agent will lead to a significant increase in the fluidity loss of cement mortar over time. This is because without using a water reducing agent, an adsorption layer with steric hindrance effect and wetting and lubrication effect cannot be formed on the surface of cement particles, and cement particles are prone to agglomeration, resulting in a decrease in the fluidity of cement mortar.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing cement mortar suitable for high temperature construction in summer, characterized in that: include: Preparation of dry powders and mixed solutions; The mixed solution comprises the following raw material components in parts by weight: 0.5-2 parts of a water reducing agent, 1-3 parts of a water retaining agent, 0.2-6 parts of a retarder and 60-110 parts of water; wherein the retarder comprises at least one of white sugar and sodium gluconate; the raw material components in the mixed solution are mixed uniformly to obtain the mixed solution; The dry powder comprises the following raw material components in parts by weight: 200-300 parts of cement, 50-150 parts of admixture and 500-700 parts of medium sand; the raw material components in the dry powder are mixed uniformly to obtain the dry powder; The dry powder is mixed with the mixed liquid to obtain cement mortar suitable for high temperature construction in summer.

2. The method for preparing cement mortar suitable for high temperature construction in summer according to claim 1, characterized in that: The water reducing agent includes a polycarboxylate water reducing agent; the water reducing rate of the polycarboxylate water reducing agent is 25%-30%.

3. The method for preparing cement mortar suitable for high temperature construction in summer according to claim 1, characterized in that: The water retaining agent includes hydroxypropyl methylcellulose ether.

4. The method for preparing cement mortar suitable for high temperature construction in summer according to claim 1, characterized in that: The cement is ordinary Portland cement, and its strength grade is 42.5-52.5MPa.

5. The method for preparing cement mortar suitable for high temperature construction in summer according to claim 1, characterized in that: The admixture includes fly ash and / or slag; the grade of the fly ash is grade I; the grade of the slag is grade S95.

6. The method for preparing cement mortar suitable for high temperature construction in summer according to claim 1, characterized in that: The fineness modulus of the medium sand is 2.3-3; the mud content of the medium sand is not more than 1.0%; and the maximum particle size of the medium sand is not more than 4.75 mm.

7. The method for preparing cement mortar suitable for high temperature construction in summer according to any one of claims 1 to 6, characterized in that: The dry powder further comprises the following raw material components in parts by weight: 2-6 parts of basalt fiber and / or 4-10 parts of steel fiber.

8. The method for preparing cement mortar suitable for high temperature construction in summer according to claim 7, characterized in that: The basalt fiber has a monofilament diameter of 15-18 μm, a fiber length of 3-9 mm, and a density of 2.8-3.3 g / cm 3 .

9. The method for preparing cement mortar suitable for high temperature construction in summer according to claim 7, characterized in that: The steel fiber is a copper-plated steel fiber with a diameter greater than or equal to 0.2 mm, a length of 12-15 mm, an aspect ratio of 60-70, and a tensile strength greater than or equal to 3000 MPa.

10. A cement mortar suitable for high temperature construction in summer, characterized in that: The cement mortar suitable for high-temperature construction in summer is prepared by the method for preparing the cement mortar according to claim 7.

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