Desert sand polyvinyl alcohol fiber cement-based composite material and preparation method thereof

Abstract

The application relates to the technical field of concrete, in particular to a desert sand polyvinyl alcohol fiber cement-based composite material and a preparation method thereof. The raw materials of the desert sand polyvinyl alcohol fiber cement-based composite material include the following in parts by mass: cement 50-100 parts, desert sand 20-40 parts, fly ash 40-60 parts, gamma-aminopropyl triethoxysilane 1-3 parts, activated fiber 5-15 parts, polyvinyl alcohol fiber 5-15 parts, water reducing agent 1.5-3 parts, thickening agent 0.5-2 parts and water 40-60 parts. The cement consumption can be reduced, the waste is reused, the desert sand resource is reasonably developed and the waste is reused, the preparation method is simple, and the method is suitable for large-scale popularization and application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, in particular to a desert sand polyvinyl alcohol fiber cement-based composite material and a preparation method thereof. BACKGROUND

[0002] For a long time, concrete is an important building material widely used in industrial structures and civil construction projects, and has a large demand. Sand is one of the important components of concrete, and is mainly derived from natural river sand and artificial machine-made sand at present. Most sandstone enterprises have small production scale, quite backward production processing technology and management, and low equipment and machinery efficiency, so that the performance indicators of medium sand cannot meet the specification requirements. Therefore, there are serious problems in terms of production quantity, quality, grading requirements, economic benefits and environmental protection. At the same time, the use of sand in construction projects is complex, which has a direct impact on the quality of engineering construction.

[0003] In recent years, the super high performance of polyvinyl alcohol (Polyvinyl Alcohol, PVA for short) fiber cement-based composite material has attracted the attention of many experts and scholars at home and abroad. The PVA fiber cement-based composite material is usually based on cement or cement plus filler, or adding small particle size fine aggregate on the basis, and using PVA fiber as reinforcing material. Compared with carbon fiber and steel fiber, PVA fiber has small density, high adhesion, good dispersibility and easy stirring; compared with other synthetic fibers, PVA fiber has good hydrophilicity, high elastic modulus, large specific surface area, good compatibility with cement and obvious reinforcing effect. In addition, the PVA fiber cement-based composite material also has the characteristics of high temperature resistance, wear resistance, fatigue resistance and no pollution to the environment.

[0004] Therefore, using PVA fiber cement-based composite material to replace traditional concrete, using desert sand to replace silica sand or river sand in PVA fiber cement-based composite material, improving the compressive and tensile strength of desert sand PVA fiber cement-based composite material, and enhancing the tensile strain performance of desert sand PVA fiber cement-based composite material have excellent research prospects. SUMMARY

[0005] The present application aims at solving the problems in the prior art, and provides a desert sand polyvinyl alcohol fiber cement-based composite material and a preparation method thereof.

[0006] A desert sand polyvinyl alcohol fiber cement-based composite material, raw materials of which include, by mass fraction: cement 50-100 parts, desert sand 20-40 parts, fly ash 40-60 parts, gamma-aminopropyl triethoxysilane 1-3 parts, activated fiber 5-15 parts, polyvinyl alcohol fiber 5-15 parts, water reducing agent 1.5-3 parts, thickening agent 0.5-2 parts, and water 40-60 parts.

[0007] Preferably, the cement is Portland cement or / and fast-hardening sulphoaluminate cement.

[0008] Preferably, the cement is composed of Portland cement and fast-hardening sulphoaluminate cement in a mass ratio of 10:1-2.

[0009] Preferably, the water reducing agent is polycarboxylic high-performance water reducing agent.

[0010] Preferably, the thickening agent is hydroxypropyl methyl cellulose or / and polyacrylamide.

[0011] Preferably, the activated fiber is prepared by the following steps: basalt fiber is added into a mixed acid solution, ultrasonic treatment is carried out at 50-60 DEG C for 2-4h, centrifugation, washing, vacuum drying; added into a Tris solution, adjusting the pH value of the system to 8-9, adding dopamine hydrochloride, stirring at 50-60 DEG C for 1-2h, centrifugation, washing, vacuum drying.

[0012] More preferably, the mass ratio of basalt fiber and dopamine hydrochloride is 5-15:1-2.

[0013] More preferably, in the mixed acid solution, the concentration of phosphoric acid is 2-4mol / L, and the concentration of sodium nitrate is 1-2mol / L.

[0014] The preparation method of the desert sand polyvinyl alcohol fiber cement-based composite material described above comprises the following steps:

[0015] S1, the cement, desert sand and fly ash are stirred for 10-20min to obtain a premix a;

[0016] S2, gamma-aminopropyl triethoxysilane is added into an aqueous ethanol solution, the pH value of the system is adjusted to 8-9, stirring is carried out for 1-2h, activated fiber is added, reflux stirring is carried out at 60-80 DEG C under nitrogen protection for 1-2h, filtration, washing, vacuum drying, the premix a is added and stirred for 5-10min to obtain a premix b;

[0017] S3, polyvinyl alcohol fiber, water reducing agent, thickening agent and water are added into the premix b and stirred for 1-5min.

[0018] Beneficial effects: the present application utilizes low-cost desert sand mixed with polyvinyl alcohol fiber, fully utilizes desert sand resources and high-content fly ash, and cooperates with the action of activated fiber to ensure that the concrete has sufficient compressive strength, and has high tensile strength and excellent strain capacity.

[0019] The application covers basalt fiber with a polydopamine layer as a loading layer, optimizes the interface of the polydopamine layer, makes the product have high dispersion uniformity with the premix a, and comprehensively improves the mechanical properties of the product; the polyvinyl alcohol fiber has poor flowability due to the long chain, and direct blending with the basalt fiber will cause mechanical strength degradation, the application activates and grafts the basalt fiber, further controls the mass ratio of the basalt fiber and the polyvinyl alcohol fiber, so that the cement-based composite material has high mechanical strength, and has excellent inhibitory effect on crack propagation of mortar.

[0020] The application can reduce the cement dosage, reuse waste, reasonably develop desert sand resources, and reuse waste, and has a simple preparation method and is suitable for large-scale popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0021] Fig. 1 A comparison chart of compressive strength of samples prepared by using the cement-based composite materials obtained in Example 5 and Comparative Examples 1-2.

[0022] Fig. 2 A comparison chart of tensile strength of samples prepared by using the cement-based composite materials obtained in Example 5 and Comparative Examples 1-2.

[0023] Fig. 3 A comparison chart of tensile strain of samples prepared by using the cement-based composite materials obtained in Example 5 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0024] The application will be further described in combination with specific examples.

[0025] The cement used below is from a local cement manufacturer in Ordos. The desert sand used below is collected from the Kubuqi Desert in Ordos, has a clay content of ≤2.05%, and a particle size of 100-400 μm. The polyvinyl alcohol fiber used below is purchased from Inner Mongolia Shuanggeng Environmental Protection Material Co., Ltd., has a length of 6 mm, and a diameter of 30 μm. The basalt fiber used below is from Inner Mongolia Daceng New Material Co., Ltd., and has a length of 6 mm.

[0026] Example 1: A desert sand polyvinyl alcohol fiber cement-based composite material, raw materials of which include: P.O 42.5 ordinary portland cement 500 g, desert sand 200 g, I-grade fly ash 400 g, γ-aminopropyl triethoxysilane 10 g, activated fiber 50 g, polyvinyl alcohol fiber 50 g, polycarboxylic acid high-performance water reducing agent 15 g, polyacrylamide 5 g, and water 400 g.

[0027] The activated fiber is prepared by the following steps: 50g basalt fiber is added into 300g mixed acid solution (the concentration of phosphoric acid is 2mol / L and the concentration of sodium nitrate is 1mol / L), ultrasonic treatment is carried out at 50℃ for 2h, the ultrasonic frequency is 40kHz, centrifugal separation is carried out, deionized water is used for washing once, vacuum drying is carried out, 300g Tris solution is added, the pH value of the system is adjusted to 8-9, 10g dopamine hydrochloride is added, stirring is carried out at 50℃ for 1h, centrifugal separation is carried out, washing is carried out, and vacuum drying is carried out.

[0028] The preparation method of the desert sand polyvinyl alcohol fiber cement-based composite material comprises the following steps:

[0029] S1, P.O 42.5 ordinary portland cement, desert sand and I-class fly ash are added into a stirrer, stirred at a speed of 200r / min for 10min, and a premix a is obtained;

[0030] S2, γ-aminopropyl triethoxysilane is added into 300g ethanol solution with a mass fraction of 40%, 1mol / L sodium hydroxide solution is used to adjust the pH value of the system to 8-9, stirring is carried out for 1h, activated fiber is added, reflux stirring is carried out at 60℃ for 1h under nitrogen protection, filtration is carried out, washing is carried out, vacuum drying is carried out, the premix a is added and stirred for 5min at a stirring speed of 100r / min, and a premix b is obtained;

[0031] S3, polyvinyl alcohol fiber, polycarboxylate high-performance water reducing agent, polyacrylamide and water are added into the premix b and stirred for 1min.

[0032] Example 2: A desert sand polyvinyl alcohol fiber cement-based composite material, the raw materials of which comprise: R.SAC 42.5 fast hardening sulphoaluminate cement 1000g, desert sand 400g, I-class fly ash 600g, γ-aminopropyl triethoxysilane 30g, activated fiber 150g, polyvinyl alcohol fiber 150g, polycarboxylate high-performance water reducing agent 30g, polyacrylamide 20g and water 600g.

[0033] The activated fiber is prepared by the following steps: 150g basalt fiber is added into 600g mixed acid solution (the concentration of phosphoric acid is 4mol / L and the concentration of sodium nitrate is 2mol / L), ultrasonic treatment is carried out at 60℃ for 4h, the ultrasonic frequency is 60kHz, centrifugal separation is carried out, deionized water is used for washing once, vacuum drying is carried out, 600g Tris solution is added, the pH value of the system is adjusted to 8-9, 20g dopamine hydrochloride is added, stirring is carried out at 60℃ for 2h, centrifugal separation is carried out, washing is carried out, and vacuum drying is carried out.

[0034] The preparation method of the desert sand polyvinyl alcohol fiber cement-based composite material comprises the following steps:

[0035] S1, R.SAC 42.5 fast hardening sulphoaluminate cement, desert sand, I-class fly ash are added into a mixer, stirred at a speed of 300 r / min for 20 min to obtain premix a;

[0036] S2, γ-aminopropyl triethoxysilane is added into a 500 g ethanol solution with a mass fraction of 60%, a 2 mol / L sodium hydroxide solution is used to adjust the pH value of the system to 8-9, stirring is performed for 2 h, activated fiber is added, reflux stirring is performed at a temperature of 80℃ under nitrogen protection for 2 h, filtration, washing, vacuum drying, premix a is added and stirred for 10 min at a stirring speed of 500 r / min to obtain premix b;

[0037] S3, polyvinyl alcohol fiber, polycarboxylate high-performance water reducing agent, polyacrylamide, and water are added into premix b and stirred for 5 min.

[0038] Example 3: A desert sand polyvinyl alcohol fiber cement-based composite material, raw materials of which include: cement 700 g, desert sand 350 g, I-class fly ash 450 g, γ-aminopropyl triethoxysilane 25 g, activated fiber 80 g, polyvinyl alcohol fiber 120 g, polycarboxylate high-performance water reducing agent 20 g, hydroxypropyl methyl cellulose 16 g, and water 450 g. The cement is composed of P.O 42.5 ordinary portland cement and R.SAC 42.5 fast hardening sulphoaluminate cement at a mass ratio of 10:2.

[0039] The activated fiber is prepared by the following steps: 80 g of basalt fiber is added into a 500 g mixed acid solution (the concentration of phosphoric acid is 2.5 mol / L, and the concentration of sodium nitrate is 1.7 mol / L), ultrasonic treatment is performed at a temperature of 52℃ for 3.5 h at an ultrasonic frequency of 45 kHz, centrifugation is performed, deionized water is used for washing twice, vacuum drying is performed, and the product is added into a 500 g Tris solution, the pH value of the system is adjusted to 8-9, 12 g of dopamine hydrochloride is added, stirring is performed at a temperature of 58℃ for 80 min, centrifugation is performed, washing is performed, and vacuum drying is performed.

[0040] The preparation method of the above-mentioned desert sand polyvinyl alcohol fiber cement-based composite material includes the following steps:

[0041] S1, cement, desert sand, and I-class fly ash are added into a mixer, stirred at a speed of 360 r / min for 12 min to obtain premix a;

[0042] S2, γ-aminopropyl triethoxysilane is added to 450 g of an ethanol solution with a mass fraction of 45%, a 1.8 mol / L sodium hydroxide solution is used to adjust the pH value of the system to 8-9, stirring is performed for 80 min, activated fiber is added, stirring is performed under reflux at a temperature of 75°C for 80 min under nitrogen protection, filtration, washing, vacuum drying, pre-mixed material a is added, stirring is performed for 9 min at a stirring speed of 200 r / min, and pre-mixed material b is obtained;

[0043] S3, polyvinyl alcohol fiber, polycarboxylate high-performance water reducing agent, hydroxypropyl methyl cellulose, and water are added to the pre-mixed material b, and stirring is performed for 4 min.

[0044] Example 4: A desert sand polyvinyl alcohol fiber cement-based composite material, raw materials of which include: cement 900 g, desert sand 250 g, I-class fly ash 550 g, γ-aminopropyl triethoxysilane 15 g, activated fiber 120 g, polyvinyl alcohol fiber 80 g, polycarboxylate high-performance water reducing agent 24 g, hydroxypropyl methyl cellulose 10 g, and water 550 g. The cement is composed of P.O 42.5 ordinary portland cement and R.SAC 42.5 fast hardening sulphoaluminate cement at a mass ratio of 10:1.

[0045] The activated fiber is prepared by the following steps: 120 g of basalt fiber is added to 400 g of mixed acid solution (phosphoric acid concentration is 3.5 mol / L, and sodium nitrate concentration is 1.3 mol / L), ultrasonic treatment is performed at a temperature of 58°C for 2.5 h at an ultrasonic frequency of 55 kHz, centrifugation is performed, deionized water is used for washing twice, vacuum drying is performed, and the product is added to 400 g of Tris solution, the pH value of the system is adjusted to 8-9, 18 g of dopamine hydrochloride is added, stirring is performed at a temperature of 52°C for 100 min, centrifugation is performed, washing is performed, and vacuum drying is performed.

[0046] The preparation method of the above-mentioned desert sand polyvinyl alcohol fiber cement-based composite material includes the following steps:

[0047] S1, cement, desert sand, and I-class fly ash are added to a stirrer, stirring is performed at a speed of 240 r / min for 18 min, and pre-mixed material a is obtained;

[0048] S2, γ-aminopropyl triethoxysilane is added to 350 g of an ethanol solution with a mass fraction of 55%, a 1.2 mol / L sodium hydroxide solution is used to adjust the pH value of the system to 8-9, stirring is performed for 100 min, activated fiber is added, stirring is performed under reflux at a temperature of 65°C for 100 min under nitrogen protection, filtration, washing, vacuum drying, pre-mixed material a is added, stirring is performed for 7 min at a stirring speed of 400 r / min, and pre-mixed material b is obtained;

[0049] S3, add polyvinyl alcohol fiber, polycarboxylate superplasticizer, hydroxypropyl methyl cellulose and water into the premix b and stir for 2 min.

[0050] Example 5: A desert sand polyvinyl alcohol fiber cement-based composite material, the raw materials of which include: cement 800g, desert sand 300g, I-grade fly ash 500g, γ-aminopropyl triethoxysilane 20g, activated fiber 100g, polyvinyl alcohol fiber 100g, polycarboxylate superplasticizer 22g, hydroxypropyl methyl cellulose 15g, and water 500g. The cement is composed of P.O 42.5 ordinary portland cement and R.SAC 42.5 fast hardening sulphoaluminate cement in a mass ratio of 10:1.5.

[0051] The activated fiber is prepared by the following steps: 100g basalt fiber is added to 450g mixed acid solution (with a phosphoric acid concentration of 3mol / L and a sodium nitrate concentration of 1.5mol / L), ultrasonic treatment is performed at a temperature of 55℃ for 3h, the ultrasonic frequency is 50kHz, centrifugation is performed, deionized water is used for washing twice, vacuum drying is performed, it is added to 450g Tris solution, the pH value of the system is adjusted to 8-9, 15g dopamine hydrochloride is added, stirring is performed at a temperature of 55℃ for 90min, centrifugation is performed, washing is performed, and vacuum drying is performed.

[0052] The preparation method of the above-mentioned desert sand polyvinyl alcohol fiber cement-based composite material includes the following steps:

[0053] S1, cement, desert sand and I-grade fly ash are added to a stirrer, stirring is performed at a speed of 300r / min for 15min, and premix a is obtained;

[0054] S2, γ-aminopropyl triethoxysilane is added to 400g ethanol solution with a mass fraction of 50%, 1.5mol / L sodium hydroxide solution is used to adjust the pH value of the system to 8-9, stirring is performed for 90min, activated fiber is added, reflux stirring is performed under nitrogen protection at a temperature of 70℃ for 90min, filtration is performed, washing is performed, vacuum drying is performed, it is added to the premix a and stirring is performed for 8min at a stirring speed of 300r / min, and premix b is obtained;

[0055] S3, polyvinyl alcohol fiber, polycarboxylate superplasticizer, hydroxypropyl methyl cellulose and water are added to the premix b and stirring is performed for 3min.

[0056] Comparative Example 1: A desert sand polyvinyl alcohol fiber cement-based composite material, the raw materials of which include: cement 800 g, desert sand 300 g, I-class fly ash 500 g, γ-aminopropyl triethoxysilane 20 g, activated fiber 100 g, polyvinyl alcohol fiber 100 g, polycarboxylate high-performance water reducing agent 22 g, hydroxypropyl methyl cellulose 15 g, and water 500 g. The cement is composed of P.O 42.5 ordinary portland cement and R.SAC 42.5 fast hardening sulphoaluminate cement at a mass ratio of 10:1.5.

[0057] The activated fiber is prepared by the following steps: 100 g of basalt fiber is added to 450 g of mixed acid solution (with a phosphoric acid concentration of 3 mol / L and a sodium nitrate concentration of 1.5 mol / L), ultrasonic treatment at a temperature of 55°C for 3 h, ultrasonic frequency of 50 kHz, centrifugation, washing twice with deionized water, and vacuum drying.

[0058] The preparation method of the above-mentioned desert sand polyvinyl alcohol fiber cement-based composite material includes the following steps:

[0059] S1, the cement, desert sand, and I-class fly ash are added to a blender and stirred at a speed of 300 r / min for 15 min to obtain a premix a;

[0060] S2, the γ-aminopropyl triethoxysilane is added to 400 g of an ethanol solution with a mass fraction of 50%, a 1.5 mol / L sodium hydroxide solution is used to adjust the pH value of the system to 8-9, stirring for 90 min, the activated fiber is added, reflux stirring under nitrogen protection at a temperature of 70°C for 90 min, filtration, washing, vacuum drying, adding the premix a and stirring for 8 min at a stirring speed of 300 r / min to obtain a premix b;

[0061] S3, the polyvinyl alcohol fiber, polycarboxylate high-performance water reducing agent, hydroxypropyl methyl cellulose, and water are added to the premix b and stirred for 3 min.

[0062] Comparative Example 2: A desert sand polyvinyl alcohol fiber cement-based composite material, the raw materials of which include: cement 800 g, desert sand 300 g, I-class fly ash 500 g, γ-aminopropyl triethoxysilane 20 g, activated fiber 100 g, polyvinyl alcohol fiber 100 g, polycarboxylate high-performance water reducing agent 22 g, hydroxypropyl methyl cellulose 15 g, and water 500 g. The cement is composed of P.O 42.5 ordinary portland cement and R.SAC 42.5 fast hardening sulphoaluminate cement at a mass ratio of 10:1.5.

[0063] The activated fiber is prepared by the following steps: 100 g of basalt fiber is added to 450 g of mixed acid solution (with a concentration of 3 mol / L of phosphoric acid and 1.5 mol / L of sodium nitrate), ultrasonic treatment at a temperature of 55℃ for 3 h, ultrasonic frequency of 50 kHz, centrifugation, washing twice with deionized water, vacuum drying, adding to 450 g of Tris solution, adjusting the pH value of the system to 8-9, adding 15 g of dopamine hydrochloride, stirring at a temperature of 55℃ for 90 min, centrifugation, washing, and vacuum drying.

[0064] The preparation method of the desert sand polyvinyl alcohol fiber cement-based composite material described above comprises the following steps:

[0065] S1, the cement, desert sand, I-grade fly ash is added to the mixer, and stirred at a speed of 300 r / min for 15 min to obtain a premix a;

[0066] S2, the γ-aminopropyl triethoxysilane and the activated fiber are mixed uniformly, and are added to the premix a and stirred for 8 min at a stirring speed of 300 r / min to obtain a premix b;

[0067] S3, the polyvinyl alcohol fiber, the polycarboxylic acid high-performance water reducing agent, the hydroxypropyl methyl cellulose and the water are added to the premix b and stirred for 3 min.

[0068] The cement-based composite materials obtained in Example 5 and Comparative Examples 1-2 are poured into a mold (40 mm x 40 mm x 160 mm), demolded, and placed in a curing box (temperature 20±2℃, humidity≥95%) for curing for 7-28 days. The performance of each group of concrete samples is tested according to T / CECS 864-2021 “Standard Test Methods for Ultra-High Performance Concrete”.

[0069] As shown in Figs. 1 to 3 , the compressive strength, tensile strength and tensile strain of the sample prepared from the cement-based composite material obtained in Example 5 are the highest, which are better than those of Comparative Examples 1-2 (P<0.05).

[0070] The reason for the above result is that the basalt fiber is covered with a polydopamine layer as a loading layer, the interface of the polydopamine layer is optimized, the dispersion uniformity between the product and the premix a is high, and the mechanical properties of the product are comprehensively improved; the polyvinyl alcohol fiber has the problem of poor flowability of long chains, and direct blending with the basalt fiber will cause mechanical strength to deteriorate, the basalt fiber is activated and grafted in the application, the mass ratio of the basalt fiber and the polyvinyl alcohol fiber is further controlled, the cement-based composite material has higher mechanical strength, and has excellent inhibitory effect on crack propagation of the mortar. Meanwhile, the application uses low-cost desert sand mixed with polyvinyl alcohol fiber, fully utilizes desert sand resources and high-content fly ash, and cooperates with the activated fiber to ensure that the concrete has sufficient compressive strength, so that the concrete has higher tensile strength and excellent strain capacity.

[0071] The above is only a preferred specific embodiment of the application, but the protection scope of the application is not limited to this, any person skilled in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the application within the technical range disclosed by the application, which should be covered in the protection scope of the application.

Claims

1. A desert sand polyvinyl alcohol fiber cement-based composite material, characterized in that, Its raw materials, by weight, include: 50-100 parts cement, 20-40 parts desert sand, 40-60 parts fly ash, 1-3 parts γ-aminopropyltriethoxysilane, 5-15 parts activated fiber, 5-15 parts polyvinyl alcohol fiber, 1.5-3 parts water-reducing agent, 0.5-2 parts thickener, and 40-60 parts water. The activated fibers are prepared by the following steps: basalt fibers are added to a mixed acid solution, ultrasonically treated at 50-60℃ for 2-4 hours, centrifuged, washed, and vacuum dried; then added to a Tris solution, the pH of the system is adjusted to 8-9, dopamine hydrochloride is added, stirred at 50-60℃ for 1-2 hours, centrifuged, washed, and vacuum dried. Prepared using the following steps: S1. Mix cement, desert sand and fly ash for 10-20 minutes to obtain premix a; S2. Add γ-aminopropyltriethoxysilane to an aqueous ethanol solution, adjust the pH of the system to 8-9, stir for 1-2 hours, add activated fiber, reflux and stir at 60-80℃ for 1-2 hours under nitrogen protection, filter, wash, vacuum dry, add premix a and stir for 5-10 minutes to obtain premix b. S3. Add polyvinyl alcohol fiber, water reducing agent, thickener and water to premix b and stir for 1-5 minutes.

2. The desert sand polyvinyl alcohol fiber cement-based composite material according to claim 1, characterized in that, The cement is silicate cement and / or rapid-hardening sulfoaluminate cement.

3. The desert sand polyvinyl alcohol fiber cement-based composite material according to claim 1, characterized in that, The cement is composed of silicate cement and rapid-hardening sulfoaluminate cement in a mass ratio of 10:1-2.

4. The desert sand polyvinyl alcohol fiber cement-based composite material according to claim 1, characterized in that, The water-reducing agent is a high-performance polycarboxylate water-reducing agent.

5. The desert sand polyvinyl alcohol fiber cement-based composite material according to claim 1, characterized in that, The thickener is hydroxypropyl methylcellulose and / or polyacrylamide.

6. The desert sand polyvinyl alcohol fiber cement-based composite material according to claim 1, characterized in that, The mass ratio of basalt fiber to dopamine hydrochloride is 5-15:1-2.

7. The desert sand polyvinyl alcohol fiber cement-based composite material according to claim 1, characterized in that, In the mixed acid solution, the concentration of phosphoric acid is 2-4 mol / L and the concentration of sodium nitrate is 1-2 mol / L.

8. A method for preparing a desert sand polyvinyl alcohol fiber cementitious composite material as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Mix cement, desert sand and fly ash for 10-20 minutes to obtain premix a; S2. Add γ-aminopropyltriethoxysilane to an aqueous ethanol solution, adjust the pH of the system to 8-9, stir for 1-2 hours, add activated fiber, reflux and stir at 60-80℃ for 1-2 hours under nitrogen protection, filter, wash, vacuum dry, add premix a and stir for 5-10 minutes to obtain premix b. S3. Add polyvinyl alcohol fiber, water reducing agent, thickener and water to premix b and stir for 1-5 minutes.

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