Low-alkali masonry cement with high fly ash content and preparation method of low-alkali masonry cement

Abstract

The invention relates to the technical field of masonry cement, and particularly discloses low-alkali masonry cement with high fly ash content and a preparation method of the low-alkali masonry cement. The low-alkali masonry cement is mainly prepared from the following raw materials in parts by weight: 55-65 parts of low-alkali cement clinker, 35-45 parts of fly ash, 4-6 parts of modified calcium sulfate whiskers, 2-4 parts of redispersible latex powder, 3-5 parts of desulfurized gypsum, 0.3-0.7 part of a retarder and 0.3-0.7 part of an early strength agent. The modified calcium sulfate whiskers are obtained by treating calcium sulfate whiskers with chitosan, starch sodium octenylsuccinate and sodium trimetaphosphate. According to the low-alkali masonry cement, the fly ash is recycled, the resource utilization rate is increased, the low-alkali masonry cement has the advantages of high compressive strength, high breaking strength and good cracking resistance, the durability is improved, the service life is prolonged, and market requirements are met.

Description

Technical Field

[0001] The present application relates to the technical field of masonry cement, and more specifically, to a low-alkali masonry cement with a high content of fly ash and a preparation method thereof. Background Art

[0002] Fly ash is the fine ash collected from the flue gas after coal combustion, and is also one of the main solid wastes discharged by coal-fired power plants. With the development of the power industry, the amount of fly ash discharged by coal-fired power plants has increased year by year, and the amount of fly ash discharged is relatively large. If a large amount of fly ash is not treated, it will not only cause waste of resources, but also cause environmental pollution, and at the same time, there are potential safety hazards to human body and organisms. Therefore, how to achieve the recycling of fly ash has become one of the problems to be solved in order to achieve sustainable development. At present, some researchers apply fly ash to cement to obtain cement doped with fly ash, thereby solving the problem of fly ash recycling. However, the applicant found in actual application that adding a small amount of fly ash to cement clinker, for example, the amount of fly ash added is less than 30% of the total weight of cement clinker, can improve the strength of cement, but when the amount of fly ash added is large, for example, the amount of fly ash added is more than 50% of the total weight of cement clinker, it will reduce the strength of cement and affect the use of cement. Summary of the invention

[0003] On the basis that the addition amount of fly ash is more than 50% of the total weight of low-alkali cement clinker, in order to improve the compressive strength of low-alkali masonry cement, the present application provides a low-alkali masonry cement with a high amount of fly ash and a preparation method thereof.

[0004] In the first aspect, the present application provides a low-alkali masonry cement with a high content of fly ash, adopting the following technical scheme: a low-alkali masonry cement with a high content of fly ash, the low-alkali masonry cement is mainly made of the following raw materials in parts by weight: 55-65 parts of low-alkali cement clinker, 35-45 parts of fly ash, 4-6 parts of modified calcium sulfate whiskers, 2-4 parts of redispersible latex powder, 3-5 parts of desulfurized gypsum, 0.3-0.7 parts of retarder, and 0.3-0.7 parts of accelerator; the modified calcium sulfate whiskers are obtained by treating calcium sulfate whiskers with chitosan, sodium starch octenyl succinate, and sodium trimetaphosphate.

[0005] The low-alkali masonry cement with high fly ash content of the present application replaces part of the low-alkali cement clinker with fly ash, which not only realizes the recycling of fly ash and reduces environmental pollution. Moreover, the fly ash of the present application is Class III fly ash, which has a lower grade and is added to the low-alkali cement clinker in a larger amount. The amount of fly ash added is more than 50% of the total weight of the cement clinker, which increases the recycling rate of fly ash. At the same time, through the mutual coordination between the raw materials, the 28d compressive strength is greater than 53MPa, the 28d flexural strength is greater than 10MPa, and the cracking index is less than 100mm, showing the characteristics of high compressive strength, high flexural strength, and good cracking resistance, improving durability and service life, having good comprehensive performance, and meeting market demand.

[0006] Modified calcium sulfate whiskers and redispersible latex powder are added to the raw materials of low-alkali masonry cement. The redispersible latex powder can effectively increase fluidity, improve volume density, and also has outstanding adhesion, enhance the bonding strength between raw materials, and improve durability. Calcium sulfate whiskers can fill pores and form a network structure with redispersible latex powder to increase the integrity of low-alkali masonry cement. Further, chitosan and sodium octenyl succinate starch are grafted on the surface of calcium sulfate whiskers to introduce a large number of active groups, which not only greatly increases the interfacial bonding force and dispersibility of modified calcium sulfate whiskers, but also improves the interaction between modified calcium sulfate whiskers and redispersible latex powder, enhances the stability of the network structure, reduces internal defects, and makes low-alkali masonry cement show higher compressive strength, flexural strength and crack resistance, even if low-alkali masonry cement shows better performance and use effect.

[0007] Optionally, the modified calcium sulfate whisker is prepared by the following method: At a temperature of 60-70° C., water, isopropanol and an emulsifier are mixed, calcium sulfate whiskers are added, chitosan, sodium starch octenyl succinate and sodium trimetaphosphate are added, stirred for 3-5 hours, filtered, washed and dried to constant weight to obtain modified calcium sulfate whiskers.

[0008] Optionally, the weight ratio of the calcium sulfate whisker, chitosan, sodium starch octenylsuccinate, and sodium trimetaphosphate is 100:(4-6):(4-6):(0.5-1.5).

[0009] By adopting the above technical scheme, the surface of the calcium sulfate whisker contains a large number of hydroxyl groups, the sodium starch octenyl succinate also contains a large number of hydroxyl groups, and the chitosan contains a large number of hydroxyl groups and amino groups. The calcium sulfate whisker, the sodium starch octenyl succinate, and the chitosan undergo grafting and cross-linking reactions under the action of sodium trimetaphosphate, and a large number of active groups are introduced on the surface of the calcium sulfate whisker, which increases the interaction between the modified calcium sulfate whisker and the redispersible latex powder, improves the interface bonding strength, forms a stable network structure, increases the density, and improves the comprehensive performance of the low-alkali masonry cement.

[0010] Optionally, the weight ratio of the calcium sulfate whisker, water, isopropanol and emulsifier is 10:(70-130):(70-130):(2-4).

[0011] By adopting the above technical scheme, the addition amounts of water, isopropanol and emulsifier are limited, so that the raw materials are fully mixed, which is convenient for grafting and cross-linking reactions, ensures the stability of the preparation of modified calcium sulfate whiskers, ensures the use effect of modified calcium sulfate whiskers, and enhances the compressive strength, flexural strength and crack resistance of low-alkali masonry cement.

[0012] Optionally, the emulsifier is one or more of Tween 40, Tween 60, Tween 80, Span 40, Span 60, and Span 80.

[0013] By adopting the above technical solution, the emulsifier is limited, which is convenient for the selection of the emulsifier. Moreover, the emulsifier can reduce the interfacial tension between the oil phase and the water phase, which is convenient for water, isopropyl ketone, chitosan, sodium octenyl succinate starch, and sodium trimetaphosphate to fully contact and mix, and is also convenient for the reaction between calcium sulfate whiskers, chitosan, sodium octenyl succinate starch, and sodium trimetaphosphate, thereby ensuring the stability of the preparation of modified calcium sulfate whiskers.

[0014] Optionally, the emulsifier is Tween 80 and Span 60, and the weight ratio of Tween 80 to Span 60 is (1-3):(1-3). In multiple embodiments, the weight ratio of Tween 80 to Span 60 is 2:1, and the weight ratio can also be set to 1:1, 1:2, 1:3, 2:3, 3:1, 3:2 as needed, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0015] Optionally, the calcium sulfate whiskers used in the modified calcium sulfate whiskers have an average length of 20-50 μm and an average diameter of 1-4 μm.

[0016] By adopting the above technical scheme, the length and diameter of the calcium sulfate whisker are limited, and then the length and diameter of the modified calcium sulfate whisker are limited, so as to ensure that the modified calcium sulfate whisker is evenly dispersed in the low-alkali masonry cement raw material, enhance the uniformity of dispersion, and improve the use effect of the modified calcium sulfate whisker. In multiple embodiments, the average length of the calcium sulfate whisker is 30 μm and the average diameter is 2 μm, and the average length can also be set to 20 μm, 25 μm, 35 μm, 40 μm, 45 μm, 50 μm as needed, and the average diameter can also be set to 1 μm, 3 μm, 4 μm as needed, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0017] Optionally, the redispersible latex powder is one or more of the redispersible latex powder WWJF-8010, the redispersible latex powder WWJF-8020, the redispersible latex powder WWJF-8050, and the redispersible latex powder WWJF-8060.

[0018] By adopting the above technical solution, the redispersible latex powder is limited, which facilitates the selection of the redispersible latex powder.

[0019] Optionally, the C3A content in the low-alkali cement clinker is ≤8wt%, the f-CaO content is ≤1wt%, and the Na2O+0.658K2O content is ≤0.5wt%.

[0020] The contents of C3A, f-CaO and Na2O+0.658K2O in low-alkali cement clinker are too high, which is detrimental to the durability and mechanical properties of low-alkali masonry cement. In this application, the contents of C3A, f-CaO and Na2O+0.658K2O in low-alkali cement clinker are limited to ensure a stable source of low-alkali cement clinker and ensure the stability and quality of low-alkali cement clinker.

[0021] Optionally, the retarder is one or more of tartaric acid, citric acid, sodium phosphate, sodium borate, and glucose; the early strength agent is one or more of calcium chloride, sodium chloride, calcium sulfate, sodium sulfate, triethanolamine, and triisopropanolamine.

[0022] By adopting the above technical solution, the retarder and the early strength agent are limited, which is convenient for the selection of the retarder and the early strength agent. Moreover, the retarder can prolong the hydration speed and hydration heat of low-alkali masonry cement, adjust the setting time, and facilitate construction. The early strength agent can increase the early strength, shorten the maintenance period, and speed up the construction progress.

[0023] Optionally, the retarder is glucose and sodium phosphate, and the weight ratio of glucose to sodium phosphate is (1-3):(1-3). In multiple embodiments, the weight ratio of glucose to sodium phosphate is 2:1, and the weight ratio can also be set to 1:1, 1:2, 1:3, 2:3, 3:1, 3:2 as needed, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0024] Optionally, the early strength agent is calcium chloride and triethanolamine, and the weight ratio of calcium chloride to triethanolamine is (1-3): (1-3). In multiple embodiments, the weight ratio of calcium chloride to triethanolamine is 1:1, and the weight ratio can also be set to 1:2, 1:3, 2:1, 2:3, 3:1, 3:2 as needed, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] In a second aspect, the present application provides a method for preparing the low-alkali masonry cement with a high amount of fly ash, using the following technical solution: A method for preparing low-alkali masonry cement with a high content of fly ash mainly comprises the following steps: Low-alkali cement clinker, fly ash, modified magnesium borate whisker, redispersible latex powder, desulfurized gypsum, retarder and early strength agent are mixed to obtain low-alkali masonry cement.

[0026] By adopting the above technical solution, the preparation of low-alkali masonry cement is facilitated.

[0027] In summary, this application has at least the following beneficial effects: 1. The low-alkali masonry cement with high fly ash content of the present application replaces part of the low-alkali cement clinker with fly ash, realizes the recycling of fly ash and reduces environmental pollution. Modified calcium sulfate whiskers and redispersible latex powder are also added to the raw materials, and the synergistic effect between them is utilized to make the low-alkali masonry cement have the advantages of high compressive strength, high flexural strength and good crack resistance, and the 28d compressive strength is greater than 53MPa, the 28d flexural strength is greater than 10MPa, and the cracking index is less than 100mm, which improves durability and service life and meets market demand.

[0028] 2. In the preparation method of the modified calcium sulfate whiskers of the present application, chitosan and sodium starch octenyl succinate are grafted on the surface of the calcium sulfate whiskers by crosslinking with sodium trimetaphosphate, thereby increasing the surface active groups of the modified calcium sulfate whiskers, improving the interfacial bonding force and dispersibility of the modified calcium sulfate whiskers, reducing internal defects, increasing the stability of the network structure, improving the density, enhancing the interaction between the modified calcium sulfate whiskers and the redispersible latex powder, improving the compressive strength and flexural strength, and reducing the cracking index, so that the low-alkali masonry cement exhibits better comprehensive performance. DETAILED DESCRIPTION

[0029] In order to make the present application easier to understand, the present application will be further described in detail below in conjunction with the examples, which are merely illustrative and are not intended to limit the scope of application of the present application. The raw materials or components used in the present application can be obtained through commercial routes or conventional methods unless otherwise specified.

[0030] Preparation Example Preparation Example 1 A modified calcium sulfate whisker is prepared by the following method: At a stirring rate of 400r / min and a temperature of 65°C, add 1000g of isopropanol and 30g of emulsifier to 1000g of water and stir for 2min. Add 100g of calcium sulfate whisker and stir for 5min. Add 5g of chitosan, 5g of sodium octenyl succinate starch, and 1g of sodium trimetaphosphate and stir for 4h. Then filter, wash once with 500g of 30% ethanol aqueous solution, wash once with 500g of water, and dry to constant weight to obtain modified calcium sulfate whisker.

[0031] Among them, the emulsifiers are Tween 80 and Span 60, and the weight ratio of Tween 80 and Span 60 is 2:1; the calcium sulfate whiskers are anhydrous calcium sulfate whiskers, and the average length of the calcium sulfate whiskers is 30μm and the average diameter is 2μm; chitosan and sodium starch octenylsuccinate are both selected from Jiangxi Huayuyuan Biotechnology Co., Ltd.

[0032] Preparation Example 2 A modified calcium sulfate whisker is prepared by the following method: At a stirring rate of 400 r / min and a temperature of 60°C, add 1300 g of isopropanol and 40 g of emulsifier to 700 g of water and stir for 2 min. Add 100 g of calcium sulfate whiskers and stir for 5 min. Add 4 g of chitosan, 6 g of sodium octenyl succinate starch, and 0.5 g of sodium trimetaphosphate and stir for 5 h. Then filter, wash once with 500 g of 30% ethanol aqueous solution, wash once with 500 g of water, and dry to constant weight to obtain modified calcium sulfate whiskers.

[0033] Among them, the emulsifiers are Tween 80 and Span 60, and the weight ratio of Tween 80 and Span 60 is 2:1; the calcium sulfate whiskers are anhydrous calcium sulfate whiskers, and the average length of the calcium sulfate whiskers is 30μm and the average diameter is 2μm; chitosan and sodium starch octenylsuccinate are both selected from Jiangxi Huayuyuan Biotechnology Co., Ltd.

[0034] Preparation Example 3 A modified calcium sulfate whisker is prepared by the following method: At a stirring rate of 400 r / min and a temperature of 70°C, add 700 g of isopropanol and 20 g of emulsifier to 1300 g of water and stir for 2 min. Add 100 g of calcium sulfate whiskers and stir for 5 min. Add 6 g of chitosan, 4 g of sodium octenyl succinate starch, and 1.5 g of sodium trimetaphosphate and stir for 3 h. Then filter, wash once with 500 g of 30% ethanol aqueous solution, wash once with 500 g of water, and dry to constant weight to obtain modified calcium sulfate whiskers.

[0035] Among them, the emulsifiers are Tween 80 and Span 60, and the weight ratio of Tween 80 and Span 60 is 2:1; the calcium sulfate whiskers are anhydrous calcium sulfate whiskers, and the average length of the calcium sulfate whiskers is 30μm and the average diameter is 2μm; chitosan and sodium starch octenylsuccinate are both selected from Jiangxi Huayuyuan Biotechnology Co., Ltd. Example

[0036] Table 1 Raw material dosage of low-alkali masonry cement (unit: ×10g) Example 1 A low-alkali masonry cement with a high amount of fly ash, the raw materials and raw material ratios of which are shown in Table 1.

[0037] Among them, the C3S content in the low-alkali cement clinker is 53%, the C2S content is 25%, the C4AF content is 13%, the C3A content is 5.5wt%, the f-CaO content is 0.8wt%, and the Na2O+0.658K2O content is 0.4wt%; the fly ash is Class III fly ash; the redispersible latex powder is the redispersible latex powder WWJF-8020; the desulfurized gypsum is selected from Shijiazhuang Deze Mineral Products Co., Ltd.; the retarder is glucose and sodium phosphate, and the weight ratio of glucose to sodium phosphate is 2:1; the early strength agent is calcium chloride and triethanolamine, and the weight ratio of calcium chloride to triethanolamine is 1:1; the modified magnesium borate whisker is prepared by the method of Preparation Example 1.

[0038] A method for preparing low-alkali masonry cement with a high content of fly ash mainly comprises the following steps: At a stirring rate of 400r / min, fly ash, modified magnesium borate whisker, redispersible latex powder, desulfurized gypsum, retarder and early strength agent were added to the low-alkali cement clinker and stirred for 3 minutes to obtain low-alkali masonry cement.

[0039] Example 2 A low-alkali masonry cement with a high amount of fly ash, which is different from Example 1 in that the raw material ratio of the low-alkali masonry cement is different. The raw material ratio is shown in Table 1.

[0040] Example 3 A low-alkali masonry cement with a high amount of fly ash, which is different from Example 1 in that the raw material ratio of the low-alkali masonry cement is different. The raw material ratio is shown in Table 1.

[0041] Example 4 A low-alkali masonry cement with a high amount of fly ash added, which differs from Example 1 in that the source of the modified magnesium borate whisker in the raw materials of the low-alkali masonry cement is different, and the modified magnesium borate whisker is prepared by the method of Preparation Example 2.

[0042] Example 5 A low-alkali masonry cement with a high amount of fly ash added, which differs from Example 1 in that the source of the modified magnesium borate whisker in the raw materials of the low-alkali masonry cement is different, and the modified magnesium borate whisker is prepared by the method of Preparation Example 3.

[0043] Comparative Example Comparative Example 1 A low-alkali masonry cement with a high amount of fly ash, which is different from Example 1 in that modified calcium sulfate whiskers and redispersible latex powder are not added to the raw materials of the low-alkali masonry cement.

[0044] Comparative Example 2 A low-alkali masonry cement with a high amount of fly ash, which is different from Example 1 in that in the raw materials of the low-alkali masonry cement, an equal amount of modified calcium sulfate whiskers is replaced by redispersible latex powder.

[0045] Comparative Example 3 A low-alkali masonry cement with a high amount of fly ash, which is different from Example 1 in that in the raw materials of the low-alkali masonry cement, modified calcium sulfate whiskers and redispersible latex powder are replaced with calcium sulfate whiskers in equal amounts.

[0046] Comparative Example 4 A low-alkali masonry cement with a high amount of fly ash added, which differs from Example 1 in that in the raw materials of the low-alkali masonry cement, an equal amount of modified calcium sulfate whiskers are replaced by calcium sulfate whiskers.

[0047] Comparative Example 5 A low-alkali masonry cement with a high amount of fly ash, which is different from Example 1 in that in the raw materials of the low-alkali masonry cement, in the preparation method of the modified calcium sulfate whisker, chitosan and sodium starch octenyl succinate are replaced by 3-aminopropyl triethoxysilane in equal amounts.

[0048] Comparative Example 6 A low-alkali masonry cement with a high amount of fly ash, which is different from Example 1 in that in the raw materials of the low-alkali masonry cement, in the preparation method of the modified calcium sulfate whisker, an equal amount of chitosan is replaced by sodium starch octenyl succinate.

[0049] Comparative Example 7 A low-alkali masonry cement with a high amount of fly ash, which is different from Example 1 in that in the raw materials of the low-alkali masonry cement, in the preparation method of the modified calcium sulfate whisker, an equal amount of sodium starch octenyl succinate is replaced by chitosan.

[0050] Performance Testing The low-alkali masonry cement obtained in Examples 1-5 and Comparative Examples 1-7 was taken respectively, and the following performance tests were performed on the low-alkali masonry cement. The test results are shown in Table 2.

[0051] Among them, GB / T 17671-2021 "Test method for strength of cement mortar (ISO method)" is used to test the 28d compressive strength and 28d flexural strength of low-alkali masonry cement.

[0052] The cracking index of low-alkali masonry cement is tested using JC / T 951-2005 "Test method for crack resistance of cement mortar". The lower the cracking index, the better the crack resistance of low-alkali masonry cement.

[0053] Table 2 Test results As can be seen from Table 2, the low-alkali masonry cement of the present application has high compressive strength and flexural strength, with a 28d compressive strength of 53.64-57.36MPa and a 28d flexural strength of 10.93-12.35MPa, showing the advantages of high compressive strength and high flexural strength. It also has a low cracking index of 56-91mm, showing the advantage of good cracking resistance. The low-alkali masonry cement of the present application, through the mutual coordination between the raw materials, not only realizes the recycling of fly ash and reduces environmental pollution, but also has excellent compressive strength, flexural strength and cracking resistance, improves durability and service life, and meets market demand.

[0054] Comparative Examples 1-4 are compared. In the raw materials of low-alkali masonry cement in Comparative Example 1, no calcium sulfate whisker and redispersible latex powder are added; in the raw materials of low-alkali masonry cement in Comparative Example 2, redispersible latex powder is added; in the raw materials of low-alkali masonry cement in Comparative Example 3, calcium sulfate whisker is added; in the raw materials of low-alkali masonry cement in Comparative Example 4, calcium sulfate whisker and redispersible latex powder are added. It can be seen from this that by adding calcium sulfate whisker and redispersible latex powder to the raw materials of low-alkali masonry cement at the same time and utilizing the synergistic effect therebetween, the compressive strength and flexural strength can be improved, and the cracking index can be reduced.

[0055] Comparative Examples 4-5 are compared. Calcium sulfate whiskers are added to the raw materials of low-alkali masonry cement in Comparative Example 4; modified calcium sulfate whiskers are added to the raw materials of low-alkali masonry cement in Comparative Example 5, and the calcium sulfate whiskers are treated with 3-aminopropyltriethoxysilane and sodium trimetaphosphate to obtain. It can be seen that modifying the calcium sulfate whiskers and increasing the surface active groups of the calcium sulfate whiskers can enhance the interaction between the calcium sulfate whiskers and the redispersible latex powder and improve the use effect. Combined with Comparative Examples 6-7 and Example 1. In comparative example 6, modified calcium sulfate whiskers are added to the raw materials of low-alkali masonry cement, and the calcium sulfate whiskers are treated with sodium starch octenyl succinate and sodium trimetaphosphate to obtain; in comparative example 7, modified calcium sulfate whiskers are added to the raw materials of low-alkali masonry cement, and the calcium sulfate whiskers are treated with chitosan and sodium trimetaphosphate to obtain; in embodiment 1, modified calcium sulfate whiskers are added to the raw materials of low-alkali masonry cement, and the calcium sulfate whiskers are treated with chitosan, sodium starch octenyl succinate and sodium trimetaphosphate to obtain. It can be seen that by grafting chitosan and sodium starch octenyl succinate on the surface of calcium sulfate whiskers and utilizing the interaction between them, the modification effect of calcium sulfate whiskers can be further improved, the compressive strength, flexural strength and crack resistance can be increased, and the modified calcium sulfate whiskers show better use effect.

[0056] It should be noted that the embodiments described above are only used to explain the present application and do not constitute any limitation to the present application. The present application is described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present application may be modified as specified within the scope of the claims of the present application, and the present invention may be revised without departing from the scope and spirit of the present application. Although the present application described therein relates to specific methods, materials and embodiments, it does not mean that the present application is limited to the specific examples disclosed therein. On the contrary, the present application can be extended to all other methods and applications with the same functions.

Claims

1. A low-alkali masonry cement with a high content of fly ash, characterized in that: The low-alkali masonry cement is mainly prepared from the following raw materials in parts by weight: 55-65 parts of low-alkali cement clinker, 35-45 parts of fly ash, 4-6 parts of modified calcium sulfate whiskers, 2-4 parts of redispersible latex powder, 3-5 parts of desulfurized gypsum, 0.3-0.7 parts of retarder and 0.3-0.7 parts of early strength agent; the modified calcium sulfate whiskers are obtained by treating the calcium sulfate whiskers with chitosan, sodium starch octenyl succinate and sodium trimetaphosphate.

2. The low-alkali masonry cement with a high content of fly ash according to claim 1, characterized in that: The modified calcium sulfate whisker is prepared by the following method: At a temperature of 60-70° C., water, isopropanol and an emulsifier are mixed, calcium sulfate whiskers are added, chitosan, sodium starch octenyl succinate and sodium trimetaphosphate are added, stirred for 3-5 hours, filtered, washed and dried to constant weight to obtain modified calcium sulfate whiskers.

3. The low-alkali masonry cement with high fly ash content according to claim 2, characterized in that: The weight ratio of the calcium sulfate whisker, chitosan, sodium starch octenyl succinate and sodium trimetaphosphate is 100:(4-6):(4-6):(0.5-1.5).

4. The low-alkali masonry cement with high fly ash content according to claim 2, characterized in that: The weight ratio of the calcium sulfate whisker, water, isopropanol and emulsifier is 10:(70-130):(70-130):(2-4).

5. The low-alkali masonry cement with high fly ash content according to claim 2, characterized in that: The emulsifier is one or more of Tween 40, Tween 60, Tween 80, Span 40, Span 60 and Span 80.

6. The low-alkali masonry cement with high fly ash content according to claim 1, characterized in that: The calcium sulfate whiskers used in the modified calcium sulfate whiskers have an average length of 20-50 μm and an average diameter of 1-4 μm.

7. The low-alkali masonry cement with high fly ash content according to claim 1, characterized in that: The redispersible latex powder is one or more of the redispersible latex powder WWJF-8010, the redispersible latex powder WWJF-8020, the redispersible latex powder WWJF-8050 and the redispersible latex powder WWJF-8060.

8. The low-alkali masonry cement with high fly ash content according to claim 1, characterized in that: The low-alkali cement clinker has a C3A content of ≤8wt%, an f-CaO content of ≤1wt%, and a Na2O+0.658K2O content of ≤0.5wt%.

9. The low-alkali masonry cement with high fly ash content according to claim 1, characterized in that: The retarder is one or more of tartaric acid, citric acid, sodium phosphate, sodium borate, and glucose; The early strength agent is one or more of calcium chloride, sodium chloride, calcium sulfate, sodium sulfate, triethanolamine, and triisopropanolamine.

10. A method for preparing low-alkali masonry cement with high fly ash content as claimed in any one of claims 1 to 9, characterized in that: The main steps are as follows: Low-alkali cement clinker, fly ash, modified magnesium borate whisker, redispersible latex powder, desulfurized gypsum, retarder and early strength agent are mixed to obtain low-alkali masonry cement.

Images