Whisker-toughened ultra-early-strength composite mortar and preparation method thereof

Abstract

The application relates to the technical field of building materials, and discloses a super-early-strength composite mortar based on whisker toughening and a preparation method thereof. The prepared composite mortar comprises the following raw materials in parts by weight: cement 200-300 parts, fine aggregate 250-400 parts, fly ash 80-150 parts, whisker reinforcing agent 25-45 parts, water 120-170 parts, water reducing agent 1-2 parts and early-strength agent 2-5 parts. The composite mortar not only has the advantages of super-early strength, but also has excellent compressive strength and bending strength.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to an ultra-early strength composite mortar based on whisker toughening and its preparation method. Background Technology

[0002] Existing ultra-early strength composite mortars mostly use rapid-hardening sulfoaluminate cement, high-alumina cement, or special silicate cement as the base material, and incorporate early-strength agents, accelerators, and high-performance water-reducing components to achieve rapid setting and hardening and early strength development. However, traditional ultra-early strength mortars generally suffer from technical defects such as high brittleness, low flexural strength, and susceptibility to shrinkage cracking. Due to the coarse crystalline morphology of early hydration products and the lack of an effective micro-toughening mechanism within the matrix, microcracks easily initiate and rapidly propagate within the material under constrained shrinkage or dynamic load impact, leading to insufficient structural toughness and deterioration of durability, severely limiting their application in emergency repair projects and under dynamic load service conditions.

[0003] To address these issues, existing technologies often employ polymer emulsion modification or fiber reinforcement. While polymer modification improves bond density and flexibility, it inhibits early strength development. Fiber reinforcement, although enhancing toughness through bridging and crack prevention, suffers from poor dispersibility of conventional micron- or millimeter-sized fibers in ultra-early strength systems, resulting in weak interfacial adhesion with the matrix and difficulty in effectively controlling the growth and accumulation of hydration products at the microscale. Therefore, a composite putty system possessing both ultra-early strength and high toughness is needed to meet practical application requirements. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an ultra-early strength composite mortar based on whisker toughening and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions: An ultra-early strength composite mortar based on whisker toughening comprises the following raw materials in parts by weight: 200-300 parts cement, 250-400 parts fine aggregate, 80-150 parts fly ash, 25-45 parts whisker reinforcing agent, 120-170 parts water, 1-2 parts water-reducing agent, and 2-5 parts early strength agent. Furthermore, the cement is ordinary Portland cement; Furthermore, the fine aggregate is quartz sand with a particle size of 0.1-0.4 mm; Furthermore, the water-reducing agent is a polyether-type polycarboxylate water-reducing agent; Furthermore, the early strength agent is one of sodium carbonate and sodium chloride; The whisker reinforcing agent is prepared by the following steps: Step A1: Under nitrogen atmosphere, 3-isocyanate-propyltrimethoxysilane and dibutyltin dilaurate are added to toluene and mixed evenly. Then, hydroxypropyl acrylate is added and the mixture is heated to 40-50℃ and stirred for 2-3 hours. The solvent is removed by rotary evaporation to obtain the silane modifier. Further, in step A1, the molar ratio of 3-isocyanopropyltrimethoxysilane to hydroxypropyl acrylate is 1:1-1.05, and the amount of dibutyltin dilaurate used is 0.05%-0.1% of the total mass of 3-isocyanopropyltrimethoxysilane and hydroxypropyl acrylate; Step A2: Disperse calcium sulfate whiskers evenly in a mixture of ethanol and water by ultrasonication, add silane modifier, heat to 55-65℃ and stir continuously for 5-8 hours, filter, wash and dry to obtain modified calcium sulfate whiskers. Furthermore, in step A2, the mass ratio of calcium sulfate whiskers to silane modifier is 1:0.05-0.3, and the volume ratio of ethanol to water in the ethanol-water mixture is 7-9:1-3. Step A3: Under nitrogen conditions, the modified calcium sulfate whiskers are added to methanol and stirred to disperse them. Then, ethylenediamine is added and stirred until homogeneous. The mixture is heated to 35°C and reacted for 8-12 hours. The mixture is then filtered, washed, and dried to collect the intermediate product. Under ice-water bath and nitrogen conditions, the intermediate product is dispersed in methanol, and methyl acrylate is slowly added dropwise. The mixture is then heated to 20-30°C and stirred for 12 hours. Diethylenetriamine is then added, and the mixture is heated to 45-55°C and stirred for 12-16 hours. The mixture is then distilled under reduced pressure to obtain hyperbranched modified calcium sulfate whiskers. Furthermore, in step A3, the ratio of modified calcium sulfate whiskers, methanol, and ethylenediamine in the intermediate product is 1g:50mL:1.2-1.6g; Further, in step A3, the ratio of intermediate product, methanol, methyl acrylate and diethylenetriamine in the hyperbranched modified calcium sulfate whiskers is 1g:50mL:3-6g:0.9-2g; Step A4: Disperse the hyperbranched modified calcium sulfate whiskers in ethanol and mix them evenly. Then adjust the pH of the system to 6.8-7.2, add hydroxylated nano-silica and stir for 12-18 hours. Filter, wash with water until neutral, and dry to obtain whisker reinforcing agent. Furthermore, in step A4, the ratio of hyperbranched modified calcium sulfate whiskers, ethanol, and hydroxylated nano-silica is 5g:200mL:0.5-1.5g. Further, the hydroxylated nano-silica described in step A4 is prepared by the following steps: L-arginine is mixed and stirred evenly in deionized water, tetraethyl silicate is added while maintaining stirring conditions, and then transferred to an oil bath and heated to 80°C for reflux reaction for 24 h. The mixture is concentrated to 50 mL by rotary evaporation, dialyzed for 24 h, and then rotary evaporated and dried to obtain hydroxylated nano-silica. Furthermore, the ratio of L-arginine, deionized water, and tetraethyl silicate in the above-mentioned hydroxylated nano silica is 0.15-0.18g:150-175g:16-20g.

[0006] A method for preparing an ultra-early strength composite mortar based on whisker toughening includes the following steps: Step S1: Weigh the raw materials according to the weight parts, mix the cement, fine aggregate, fly ash, whisker reinforcing agent and early strength agent evenly to obtain the premix; Step S2: Add water-reducing agent and 50% water to the premix and stir evenly. Then add the remaining water and stir thoroughly to obtain the ultra-early strength composite mortar based on whisker toughening.

[0007] The beneficial effects of this invention are: The composite mortar prepared by this invention is mainly made by thoroughly mixing and stirring cement, fine aggregate, fly ash, whisker reinforcing agent, early strength agent, water reducing agent and water. This composite mortar not only has the advantage of ultra-early strength, but also has excellent compressive strength and flexural strength.

[0008] This invention introduces a whisker reinforcing agent into the composite mortar for the first time. This whisker reinforcing agent uses calcium sulfate whiskers as a base, with hyperbranched polyamide modified on their surface. Utilizing the positively charged property of the hyperbranched polyamide in weak acids, negatively charged nano-silica is loaded through electrostatic interaction. The introduction of the whisker reinforcing agent not only improves the compressive and flexural strength of the matrix but also solves the problems of poor compatibility between traditional inorganic whiskers and the cement matrix, as well as the tendency of nanoparticles to agglomerate, thereby accelerating early hydration. The whisker reinforcing agent is uniformly dispersed in the matrix, allowing the nano-silica to react with the calcium hydroxide produced during cement hydration in the early stages, generating additional CSH gel to fill pores and impart early density. The hyperbranched polyamide structure is rich in amide and amine groups. These polar groups can capture calcium ions through hydrogen bonding or complexation, further promoting the precipitation of hydration products, transforming the whisker surface from "inert" to "active," and further enhancing the ultra-early strength performance of the matrix.

[0009] The improved toughness of the composite mortar is due to a multi-level energy dissipation mechanism within the matrix. When external forces are applied, the outermost layer of nano-silica in the whisker reinforcement detaches or is pulled out from the ends of the hyperbranched polyamide, consuming energy. The intermediate hyperbranched polyamide molecular chains extend and untangle during stretching, also consuming energy. Finally, the pull-out or breakage of the calcium sulfate whiskers themselves is the primary energy dissipation mechanism. The hyperbranched polyamide forms a flexible transition layer between the whiskers and the matrix. When the material is bent, tensile stress is generated, and this flexible transition layer ensures that the tensile stress is efficiently transferred from the matrix to the high-strength, high-modulus calcium sulfate whiskers, allowing the whiskers to truly become the load-bearing components, thereby improving the flexural strength of the matrix. Furthermore, the nano-silica at the ends of the whisker reinforcement can further fill the nanopores between the whiskers and cement hydration products. This "dual-doping" effect significantly reduces the porosity of the material and enhances the compressive strength of the matrix. Detailed Implementation

[0010] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] Example 1: Hydroxylated nano-silica was prepared by the following steps: 0.15g of L-arginine was mixed and stirred evenly in 150g of deionized water. While maintaining stirring, 16g of tetraethyl silicate was added. The mixture was then transferred to an oil bath and heated to 80℃ for reflux reaction for 24h. The mixture was concentrated to 50mL by rotary evaporation, dialyzed for 24h, and then rotary evaporated and dried to obtain hydroxylated nano-silica.

[0012] Whisker reinforcement is prepared by the following steps: Step A1: Under nitrogen atmosphere, add 1 mol of 3-isocyanopropyltrimethoxysilane and dibutyltin dilaurate to 200 mL of toluene and mix thoroughly. Then add 1 mol of hydroxypropyl acrylate and heat to 40 °C, mix and stir for 2 h. Remove the solvent by rotary evaporation to obtain the silane modifier. The amount of dibutyltin dilaurate used is 0.05% of the total mass of 3-isocyanopropyltrimethoxysilane and hydroxypropyl acrylate. Step A2: Disperse 1g of calcium sulfate whiskers evenly by ultrasonication in a mixture of 90mL ethanol and 10mL water, then add 0.05g of silane modifier, heat to 55℃ and stir continuously for 5h, filter, wash and dry to obtain modified calcium sulfate whiskers. Step A3: Under nitrogen conditions, 1g of modified calcium sulfate whiskers was added to 50mL of methanol and stirred to disperse. Then, 1.2g of ethylenediamine was added and stirred until homogeneous. The mixture was heated to 35℃ and reacted for 8 hours. The mixture was then filtered, washed, dried, and the intermediate product was collected. Under ice-water bath and nitrogen conditions, 1g of the intermediate product was dispersed in 50mL of methanol. 3g of methyl acrylate was slowly added dropwise. The mixture was then heated to 20℃ and stirred for 12 hours. Then, 0.9g of diethylenetriamine was added, and the mixture was heated to 45℃ and stirred for 12 hours. The mixture was then distilled under reduced pressure to obtain hyperbranched modified calcium sulfate whiskers. Step A4: Disperse 5g of hyperbranched modified calcium sulfate whiskers in 200mL of ethanol and mix thoroughly. Then adjust the pH of the system to 6.8, add 0.5g of hydroxylated nano-silica and stir for 12h. Filter, wash with water until neutral, and dry to obtain whisker reinforcing agent.

[0013] Example 2: Hydroxylated nano-silica was prepared by the following steps: 0.17g L-arginine was mixed and stirred evenly in 165g deionized water. While maintaining stirring, 18g tetraethyl silicate was added. The mixture was then transferred to an oil bath and heated to 80℃ for reflux reaction for 24h. The mixture was concentrated to 50mL by rotary evaporation, dialyzed for 24h, and then rotary evaporated and dried to obtain hydroxylated nano-silica.

[0014] Whisker reinforcement is prepared by the following steps: Step A1: Under nitrogen atmosphere, 1 mol of 3-isocyanopropyltrimethoxysilane and dibutyltin dilaurate were added to 200 mL of toluene and stirred until homogeneous. Then, 1.03 mol of hydroxypropyl acrylate was added, and the mixture was heated to 45 °C and stirred for 2.5 h. The solvent was removed by rotary evaporation to obtain the silane modifier. The amount of dibutyltin dilaurate used was 0.08% of the total mass of 3-isocyanopropyltrimethoxysilane and hydroxypropyl acrylate. Step A2: Disperse 1g of calcium sulfate whiskers evenly in a mixture of 80mL ethanol and 20mL water by ultrasonication, then add 0.15g of silane modifier, heat to 60℃ and stir continuously for 6.5h, filter, wash and dry to obtain modified calcium sulfate whiskers. Step A3: Under nitrogen conditions, 1g of modified calcium sulfate whiskers was added to 50mL of methanol and stirred to disperse. Then, 1.4g of ethylenediamine was added and stirred until homogeneous. The mixture was heated to 35℃ and reacted for 10h. The mixture was then filtered, washed, dried, and the intermediate product was collected. Under ice-water bath and nitrogen conditions, 1g of the intermediate product was dispersed in 50mL of methanol. 4.5g of methyl acrylate was slowly added dropwise. The mixture was then heated to 25℃ and stirred to react for 12h. Then, 1.5g of diethylenetriamine was added, and the mixture was heated to 50℃ and stirred to react for 14h. The mixture was then distilled under reduced pressure to obtain hyperbranched modified calcium sulfate whiskers. Step A4: Disperse 5g of hyperbranched modified calcium sulfate whiskers in 200mL of ethanol and mix thoroughly. Then adjust the pH of the system to 7, add 1g of hydroxylated nano silica and stir for 14h. Filter, wash with water until neutral, and dry to obtain whisker reinforcing agent.

[0015] Example 3: Hydroxylated nano-silica was prepared by the following steps: 0.18 g of L-arginine was mixed and stirred evenly in 175 g of deionized water. While maintaining stirring, 20 g of tetraethyl silicate was added. The mixture was then transferred to an oil bath and heated to 80 °C for reflux reaction for 24 h. The mixture was concentrated to 50 mL by rotary evaporation, dialyzed for 24 h, and then rotary evaporated and dried to obtain hydroxylated nano-silica.

[0016] Whisker reinforcement is prepared by the following steps: Step A1: Under nitrogen atmosphere, add 1 mol of 3-isocyanopropyltrimethoxysilane and dibutyltin dilaurate to 200 mL of toluene and mix thoroughly. Then add 1.05 mol of hydroxypropyl acrylate and heat to 50 °C, mix and stir for 3 h. Remove the solvent by rotary evaporation to obtain the silane modifier. The amount of dibutyltin dilaurate used is 0.1% of the total mass of 3-isocyanopropyltrimethoxysilane and hydroxypropyl acrylate. Step A2: Disperse 1g of calcium sulfate whiskers evenly in a mixture of 70mL ethanol and 30mL water by ultrasonication, then add 0.3g of silane modifier, heat to 65℃ and stir continuously for 8h, filter, wash and dry to obtain modified calcium sulfate whiskers. Step A3: Under nitrogen conditions, 1g of modified calcium sulfate whiskers was added to 50mL of methanol and stirred to disperse. Then, 1.6g of ethylenediamine was added and stirred until homogeneous. The mixture was heated to 35℃ and reacted for 12h. The mixture was then filtered, washed, dried, and the intermediate product was collected. Under ice-water bath and nitrogen conditions, 1g of the intermediate product was dispersed in 50mL of methanol. 6g of methyl acrylate was slowly added dropwise. The mixture was then heated to 30℃ and stirred for 12h. Then, 2g of diethylenetriamine was added and the mixture was heated to 55℃ and stirred for 16h. The mixture was then distilled under reduced pressure to obtain hyperbranched modified calcium sulfate whiskers. Step A4: Disperse 5g of hyperbranched modified calcium sulfate whiskers in 200mL of ethanol and mix thoroughly. Then adjust the pH of the system to 7.2, add 1.5g of hydroxylated nano-silica and stir for 18h. Filter, wash with water until neutral, and dry to obtain whisker reinforcing agent.

[0017] Example 4: A method for preparing an ultra-early strength composite putty based on whisker toughening includes the following steps: 200 parts of ordinary silicate cement, 250 parts of fine aggregate (quartz sand with a particle size of 0.1-0.4 mm), 80 parts of fly ash, 25 parts of whisker reinforcing agent prepared in Example 1, 120 parts of water, 1 part of polyether-type polycarboxylate superplasticizer, and 2 parts of sodium carbonate. Step S1: Weigh the raw materials according to the weight parts, and mix and stir the ordinary silicate cement, quartz sand, fly ash, whisker reinforcing agent prepared in Example 1 and sodium carbonate evenly to obtain the premix. Step S2: Add polyether-type polycarboxylate superplasticizer and 50% water to the premix and stir evenly. Then add the remaining water and stir thoroughly to obtain the ultra-early strength composite mortar based on whisker toughening.

[0018] Example 5: A method for preparing an ultra-early strength composite putty based on whisker toughening includes the following steps: 250 parts of ordinary silicate cement, 320 parts of fine aggregate (quartz sand with a particle size of 0.1-0.4 mm), 120 parts of fly ash, 35 parts of whisker reinforcing agent prepared in Example 2, 145 parts of water, 1.5 parts of polyether-type polycarboxylate superplasticizer, and 5 parts of sodium chloride. Step S1: Weigh the raw materials according to the weight parts, and mix and stir the ordinary silicate cement, quartz sand, fly ash, whisker reinforcing agent prepared in Example 2 and sodium chloride evenly to obtain the premix. Step S2: Add polyether-type polycarboxylate superplasticizer and 50% water to the premix and stir evenly. Then add the remaining water and stir thoroughly to obtain the ultra-early strength composite mortar based on whisker toughening.

[0019] Example 6: A method for preparing an ultra-early strength composite putty based on whisker toughening includes the following steps: 300 parts of ordinary silicate cement, 400 parts of fine aggregate (quartz sand with a particle size of 0.1-0.4 mm), 150 parts of fly ash, 45 parts of whisker reinforcing agent prepared in Example 3, 170 parts of water, 2 parts of polyether-type polycarboxylate superplasticizer, and 3.5 parts of sodium carbonate. Step S1: Weigh the raw materials according to the weight parts, and mix and stir the ordinary silicate cement, quartz sand, fly ash, whisker reinforcing agent prepared in Example 3 and sodium carbonate evenly to obtain the premix. Step S2: Add polyether-type polycarboxylate superplasticizer and 50% water to the premix and stir evenly. Then add the remaining water and stir thoroughly to obtain the ultra-early strength composite mortar based on whisker toughening.

[0020] Comparative Example 1: This comparative example is an ultra-early strength composite mortar. The difference between this example and Example 6 is that calcium sulfate whiskers are used instead of the whisker reinforcing agent prepared in Example 3. All other aspects are the same.

[0021] Comparative Example 2: This comparative example is an ultra-early strength composite mortar. The difference between this example and Example 6 is that the hyperbranched modified calcium sulfate whiskers prepared in Example 3 are used instead of the whisker reinforcing agent prepared in Example 3. All other aspects are the same.

[0022] Comparative Example 3: This comparative example is an ultra-early strength composite putty. The difference between it and Example 6 is that the hydroxylated nano-silica prepared in Example 3 is used instead of the whisker reinforcing agent prepared in Example 3.

[0023] The performance of the ultra-early strength composite mortars prepared in Examples 4-6 and Comparative Examples 1-3 was tested: (1) According to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", test blocks with a size of 100mm×100mm×400mm were prepared, and the compressive strength of the composite mortar was measured; (2) The 28-day flexural strength was tested according to GB / T 50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete"; the test results are shown in Table 1: Table 1: Performance Test Results As can be seen from Table 1, the ultra-early strength composite mortar prepared by the present invention has a high compressive strength at 2h, ranging from 45.8 to 47.2 (MPa), demonstrating the advantage of ultra-early strength. In the examples, the flexural strength ranges from 38.6 to 41.3 (MPa). Compared with the comparative example, the addition of whisker reinforcing agent in the composite mortar significantly improves the toughness of the mortar, which is reflected in the flexural strength.

[0024] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A super-early-strength composite mortar based on whisker-reinforced toughening, characterized in that, The raw materials include the following parts by weight: 200-300 parts cement, 250-400 parts fine aggregate, 80-150 parts fly ash, 25-45 parts whisker reinforcing agent, 120-170 parts water, 1-2 parts water-reducing agent, and 2-5 parts early strength agent. The whisker reinforcing agent is prepared by electrostatic interaction of negatively charged hydroxylated nano-silica and hyperbranched modified calcium sulfate whiskers at pH 6.8-7.2; the hyperbranched modified calcium sulfate whiskers are prepared by grafting ethylenediamine onto modified calcium sulfate whiskers to obtain an intermediate product, and then reacting it with methyl acrylate and diethylenetriamine; the modified calcium sulfate whiskers are prepared by modifying calcium sulfate whiskers with a silane modifier; the silane modifier is prepared by reacting 3-isocyanatopropyltrimethoxysilane and hydroxypropyl acrylate.

2. The ultra-early strength composite mortar based on whisker toughening according to claim 1, characterized in that, The whisker reinforcing agent is prepared by the following steps: Step A1: Under nitrogen atmosphere, 3-isocyanate-propyltrimethoxysilane and dibutyltin dilaurate are added to toluene and mixed evenly. Then, hydroxypropyl acrylate is added and the mixture is heated to 40-50℃ and stirred for 2-3 hours. The solvent is removed by rotary evaporation to obtain the silane modifier. Step A2: Disperse calcium sulfate whiskers evenly in a mixture of ethanol and water by ultrasonication, add silane modifier, heat to 55-65℃ and stir continuously for 5-8 hours, filter, wash and dry to obtain modified calcium sulfate whiskers. Step A3: Under nitrogen conditions, the modified calcium sulfate whiskers are added to methanol and stirred to disperse them. Then, ethylenediamine is added and stirred until homogeneous. The mixture is heated to 35°C and reacted for 8-12 hours. The mixture is then filtered, washed, and dried to collect the intermediate product. Under ice-water bath and nitrogen conditions, the intermediate product is dispersed in methanol, and methyl acrylate is slowly added dropwise. The mixture is then heated to 20-30°C and stirred for 12 hours. Diethylenetriamine is then added, and the mixture is heated to 45-55°C and stirred for 12-16 hours. The mixture is then distilled under reduced pressure to obtain hyperbranched modified calcium sulfate whiskers. Step A4: Disperse the hyperbranched modified calcium sulfate whiskers in ethanol and mix thoroughly. Then adjust the pH of the system to 6.8-7.2, add hydroxylated nano-silica and stir for 12-18 hours. Filter, wash with water until neutral, and dry to obtain the whisker reinforcing agent.

3. The ultra-early strength composite mortar based on whisker toughening according to claim 2, characterized in that, In step A1, the molar ratio of 3-isocyanate-propyltrimethoxysilane to hydroxypropyl acrylate is 1:1-1.05, and the amount of dibutyltin dilaurate is 0.05%-0.1% of the total mass of 3-isocyanate-propyltrimethoxysilane and hydroxypropyl acrylate.

4. The ultra-early strength composite mortar based on whisker toughening according to claim 2, characterized in that, In step A2, the mass ratio of calcium sulfate whiskers to silane modifier is 1:0.05-0.3, and the volume ratio of ethanol to water in the ethanol-water mixture is 7-9:1-3.

5. The ultra-early strength composite mortar based on whisker toughening according to claim 2, characterized in that, In step A3, the ratio of modified calcium sulfate whiskers, methanol, and ethylenediamine in the intermediate product is 1g:50mL:1.2-1.6g, and the ratio of intermediate product, methanol, methyl acrylate, and diethylenetriamine in the hyperbranched modified calcium sulfate whiskers is 1g:50mL:3-6g:0.9-2g.

6. The ultra-early strength composite mortar based on whisker toughening according to claim 2, characterized in that, In step A4, the ratio of hyperbranched modified calcium sulfate whiskers, ethanol, and hydroxylated nano-silica is 5g:200mL:0.5-1.5g.

7. The ultra-early strength composite mortar based on whisker toughening according to claim 2, characterized in that, The hydroxylated nano-silica described in step A4 is prepared by the following steps: L-arginine is mixed and stirred evenly in deionized water, tetraethyl silicate is added while maintaining stirring conditions, and then transferred to an oil bath and heated to 80°C for reflux reaction for 24 h. The mixture is concentrated to 50 mL by rotary evaporation, dialyzed for 24 h, and then dried by rotary evaporation to obtain hydroxylated nano-silica.

8. The ultra-early strength composite mortar based on whisker toughening according to claim 7, characterized in that, The ratio of L-arginine, deionized water, and tetraethyl silicate in the hydroxylated nano-silica is 0.15-0.18g:150-175g:16-20g.

9. The ultra-early strength composite mortar based on whisker toughening according to claim 1, characterized in that, The cement is ordinary Portland cement, the fine aggregate is quartz sand with a particle size of 0.1-0.4mm, the water-reducing agent is polyether-type polycarboxylate water-reducing agent, and the early strength agent is one of sodium carbonate and sodium chloride.

10. A method for preparing the ultra-early strength composite mortar based on whisker toughening as described in any one of claims 1-9, characterized in that, Includes the following steps: Step S1: Weigh the raw materials according to the weight parts, mix the cement, fine aggregate, fly ash, whisker reinforcing agent and early strength agent evenly to obtain the premix; Step S2: Add water-reducing agent and 50% water to the premix and stir evenly. Then add the remaining water and stir thoroughly to obtain the ultra-early strength composite mortar based on whisker toughening.

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