A pavement base cement-based solid waste composite material and a preparation method thereof

Abstract

This invention relates to the field of road material technology, specifically to a cement-based solid waste composite material for road base courses and its preparation method. The raw materials for preparing the cement-based solid waste composite material for road base courses include the following components in parts by weight: 400-600 parts of sulfoaluminate cement, 200-300 parts of calcined coal gangue powder, 150-250 parts of fly ash, 30-60 parts of desulfurized gypsum, 300-400 parts of river sand, 4-6 parts of modified carboxylic acid polymer, 8-12 parts of modified SiO2, 300-400 parts of water, and 20-25 parts of polyvinyl alcohol fiber. The cement-based solid waste composite material for road base courses obtained by this invention has good mechanical properties and durability.

Description

Technical Field

[0001] This invention relates to the field of road material technology, specifically to a cement-based solid waste composite material for road base and its preparation method. Background Technology

[0002] With the continuous increase in traffic load, higher requirements are placed on the strength, crack resistance, and durability of road base materials. At the same time, large quantities of industrial solid waste such as steel slag, coal gangue, construction waste, and desulfurization gypsum are stockpiled, not only occupying land resources but also easily causing environmental pollution. Although some solid waste has been applied in road engineering, the following problems are generally present: low activity of solid waste, slow early strength development; poor volume stability of steel slag, prone to expansion cracking; large drying shrinkage of base materials, prone to reflective cracking; low utilization rate of solid waste, insufficient resource utilization; and durability and frost resistance failing to meet the requirements of heavy traffic. Therefore, developing a cement-based solid waste composite material for road bases with high solid waste utilization rate, excellent mechanical properties, and good crack resistance and durability is of great significance. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a cement-based solid waste composite material for road base courses and its preparation method.

[0004] This invention is achieved through the following technical solution: A cement-based solid waste composite material for road base courses, the raw materials for which are prepared include the following components in parts by weight: 400-600 parts of sulfoaluminate cement, 200-300 parts of calcined coal gangue powder, 150-250 parts of fly ash, 30-60 parts of desulfurized gypsum, 300-400 parts of river sand, 4-6 parts of modified carboxylic acid polymer, 8-12 parts of modified SiO2, 300-400 parts of water, and 20-25 parts of polyvinyl alcohol fiber.

[0005] Furthermore, the particle size of the calcined coal gangue powder is 1000-1200 mesh.

[0006] Furthermore, the river sand has a particle size of 0.6-1 mm.

[0007] Furthermore, the polyvinyl alcohol fiber has a diameter of 15-20 μm and a length of 4-6 mm.

[0008] Furthermore, the preparation method of the modified carboxylic acid polymer includes the following steps: L1. Tung oil acid (TOA) and maleic anhydride (MA) were mixed and stirred at 140℃ for 3-4 h. After cooling, the product was washed with ethyl acetate and deionized water. A 50wt% NaOH aqueous solution was added dropwise to the washed organic phase and reacted at room temperature for 2 h. Hydrochloric acid was added dropwise to adjust the pH to 2-3. Ethyl acetate was added to extract the organic layer. The extract was washed with deionized water, dehydrated with anhydrous magnesium sulfate, and filtered. The filtrate was evaporated by rotary evaporation to remove ethyl acetate, yielding TOA-MA. L2. Take ethylene glycol monovinyl polyoxyethylene ether, TOA-MA obtained in step L1 and H2O2 and add them to deionized water and stir evenly to obtain a mixture. Take acrylic acid and add it to deionized water and mix to obtain solution A. Take 3-mercaptopropionic acid and ascorbic acid and add them to deionized water and mix to obtain solution B. L3. With stirring, add solution A obtained in step L2 dropwise to the mixture at a rate of 0.2-0.3 mL / min, and simultaneously add solution B obtained in step L2 dropwise at a rate of 0.2-0.3 mL / min. After the addition is complete, keep the mixture at 30℃ for 0.5-1 h, adjust the pH to 6-7 with 30wt% NaOH solution, and dialyze the mixture in deionized water using a 3500 Da dialysis bag for 7 days to obtain the modified carboxylic acid polymer.

[0009] Furthermore, in step L1, the mass ratio of tung oil acid to maleic anhydride is 12:5.

[0010] Furthermore, in step L1, the ratio of tung oil acid to NaOH aqueous solution is 4 g: 5 mL.

[0011] Furthermore, in step L2, the molecular weight of the ethylene glycol monovinyl polyoxyethylene ether is preferably 3000.

[0012] Further, in step L2, the ratio of the amount of ethylene glycol monovinyl polyoxyethylene ether, TOA-MA, H2O2 and deionized water is 36 g:0.9 g:0.25 g:15 mL.

[0013] Further, in step L2, the mass ratio of acrylic acid to ethylene glycol monovinyl polyoxyethylene ether is 1:10.

[0014] Furthermore, in step L2, the ratio of acrylic acid to deionized water is 3.6 g: 16 mL.

[0015] Furthermore, in step L2, the ratio of 3-mercaptopropionic acid, ascorbic acid, and deionized water is 0.25 g:0.035 g:20 mL.

[0016] Further, in step L2, the mass ratio of 3-mercaptopropionic acid to ethylene glycol monovinyl polyoxyethylene ether is 0.25:36.

[0017] Furthermore, the method for preparing the modified SiO2 includes the following steps: V1. Take nano-SiO2 and add it to anhydrous ethanol, disperse it by ultrasonication, adjust the pH value to 4 with hydrochloric acid solution, add 3-chloropropyltrimethoxysilane, stir and disperse, stir and react at 80℃ for 3-4 h, centrifuge at 8000 rpm for 15-20 min, wash the precipitate with anhydrous ethanol, and dry it under vacuum to obtain SiO2 chloride. V2. Take the SiO2 chloride obtained in step V1 and add it to DMF for ultrasonic dispersion. Add tannic acid and potassium carbonate, stir and react at 60-70℃ for 8-12 h, centrifuge at 8000 rpm for 15-20 min, wash the precipitate with ethanol and deionized water, and vacuum dry to obtain modified SiO2.

[0018] Furthermore, in step V1, the particle size of the nano-SiO2 is preferably 40-50 nm.

[0019] Furthermore, in step V1, the mass concentration of the nano-SiO2 in anhydrous ethanol is 15-20 mg / mL.

[0020] Furthermore, in step V1, the ratio of 3-chloropropyltrimethoxysilane to nano-SiO2 is 1-1.5 mL: 1 g.

[0021] Further, in step V2, the mass concentration of SiO2 chloride in DMF is 10-20 mg / mL.

[0022] Furthermore, in step V2, the mass ratio of tannic acid to SiO2 chloride is 1:1-2.

[0023] Furthermore, in step V2, the amount of potassium carbonate used is 6-10 wt% of the mass of tannic acid.

[0024] Furthermore, the present invention also provides a method for preparing the cement-based solid waste composite material for road base courses, comprising the following steps: mixing sulfoaluminate cement, calcined coal gangue powder, fly ash, desulfurized gypsum, and river sand, stirring at 150 rpm for 1-2 min, adding modified carboxylic acid polymer, modified SiO2, and water, stirring at 300 rpm for 3-5 min, adding polyvinyl alcohol fiber, and stirring at 300 rpm for 2-3 min to obtain the cement-based solid waste composite material for road base courses.

[0025] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a cement-based solid waste composite material for road base courses and its preparation method. Through the synergistic effect of modified carboxylic acid polymers and tannic acid-grafted modified SiO2, the compressive and flexural strengths of the composite material are significantly improved. The modified carboxylic acid polymer consists of tung oil acid-maleic anhydride (TOA-MA) copolymer segments, long polyoxyethylene ether side chains, and carboxyl groups. The polyether side chains provide steric hindrance and dispersion, resulting in a uniform and dense cement paste. The aliphatic long carbon chains and carboxyl groups in TOA-MA effectively dissipate stress at the microcrack tips, thus providing toughening. A large amount of tannic acid is covalently grafted onto the surface of the modified SiO2. The catechol groups of the tannic acid can react with Ca in the cement hydration products. 2+ The formation of stable coordination bonds not only ensures high dispersion of nano-SiO2 in the matrix but also strengthens the interfacial transition zone between nanoparticles and the cement matrix, effectively transferring loads and inhibiting crack propagation. Combined with the bridging effect of an appropriate amount of polyvinyl alcohol fiber, both compressive and flexural strengths are significantly improved. The polyether long side chains of the modified carboxylic acid polymer in this invention exhibit a water-storage-release effect, slowly releasing moisture as the internal humidity of the matrix decreases, compensating for shrinkage stress caused by capillary water loss. The tannic acid-grafted modified SiO2 particles fill micropores, refining the pore structure, and form a cross-linked network with the cement matrix through polyphenolic hydroxyl groups, further constraining the volume deformation of the slurry. The combined effect of these two factors significantly reduces the drying shrinkage coefficient, effectively minimizing reflective cracks in the pavement base course caused by drying shrinkage and improving structural durability. This invention utilizes a large amount of industrial solid waste such as calcined coal gangue powder, fly ash, and desulfurized gypsum in its matrix material. While ensuring excellent mechanical properties and volume stability, it significantly improves the resource utilization rate of solid waste, reduces land occupation and environmental pollution caused by industrial solid waste stockpiling, and aligns with the requirements of green and low-carbon development. The modified carboxylic acid polymer introduces polycarboxyl groups and flexible segments through the reaction of tung oil acid conjugated double bonds with maleic anhydride, followed by copolymerization with polyether macromonomers, resulting in strong structural tunability. Modified SiO2 is bridged with silane coupling agents and grafted with natural polyphenolic tannins under mild reaction conditions. The entire composite material preparation process is simple and easy to scale up for application. Attached Figure Description

[0026] Figure 1 The compressive strength of the composite materials described in Examples 1-3 and Comparative Examples 1-4 of this invention; Figure 2 The flexural strength of the composite materials described in Examples 1-3 and Comparative Examples 1-4 of this invention; Figure 3 The drying shrinkage coefficient is the coefficient of the composite material described in Examples 1-3 and Comparative Examples 1-4 of this invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. However, this invention is not limited to the following embodiments. It should be noted that, unless otherwise specified, all chemical reagents involved in this invention are purchased through commercial channels.

[0028] Example 1: A cement-based solid waste composite material for road base course, the raw materials for preparation include the following components in parts by weight: 600 parts of sulfoaluminate cement, 300 parts of calcined coal gangue powder, 250 parts of fly ash, 60 parts of desulfurized gypsum, 400 parts of river sand, 6 parts of modified carboxylic acid polymer, 12 parts of modified SiO2, 400 parts of water, and 25 parts of polyvinyl alcohol fiber.

[0029] The particle size of the calcined coal gangue powder is 1200 mesh, the particle size of the river sand is 1 mm, and the diameter of the polyvinyl alcohol fiber is 20 μm and the length is 6 mm.

[0030] A method for preparing modified carboxylic acid polymers includes the following steps: L1. Tung oil acid (TOA) and maleic anhydride (MA) were mixed and reacted at 140℃ for 4 h with stirring. After cooling, the product was washed with ethyl acetate and deionized water. A 50wt% NaOH aqueous solution was added dropwise to the washed organic phase, and the reaction was carried out at room temperature for 2 h. Hydrochloric acid was added dropwise to adjust the pH to 3. Ethyl acetate was added to extract the organic layer, and the extract was washed with deionized water. After dehydration with anhydrous magnesium sulfate, the extract was filtered, and the filtrate was evaporated by rotary evaporation to remove ethyl acetate, yielding TOA-MA. The mass ratio of tung oil acid to maleic anhydride was 12:5, and the volume ratio of tung oil acid to NaOH aqueous solution was 4 g:5 mL. L2. Ethylene glycol monovinyl polyoxyethylene ether, TOA-MA obtained in step L1, and H2O2 were added to deionized water and stirred until homogeneous to obtain a mixture. Acrylic acid was added to deionized water and mixed to obtain solution A. 3-mercaptopropionic acid and ascorbic acid were added to deionized water and mixed to obtain solution B. The molecular weight of ethylene glycol monovinyl polyoxyethylene ether was 3000. The ratio of ethylene glycol monovinyl polyoxyethylene ether, TOA-MA, H2O2, and deionized water was 36 g:0.9 g:0.25 g:15 mL. The mass ratio of acrylic acid to ethylene glycol monovinyl polyoxyethylene ether was 1:10. The ratio of acrylic acid to deionized water was 3.6 g:16 mL. The ratio of 3-mercaptopropionic acid, ascorbic acid, and deionized water was 0.25 g:0.035 g:20 mL. The mass ratio of 3-mercaptopropionic acid to ethylene glycol monovinyl polyoxyethylene ether was 0.25:36. L3. With stirring, add solution A obtained in step L2 dropwise to the mixture at a rate of 0.3 mL / min, and simultaneously add solution B obtained in step L2 dropwise at a rate of 0.3 mL / min. After the addition is complete, keep the mixture at 30°C for 1 h. Adjust the pH to 7 with 30 wt% NaOH solution, and dialyze the mixture in deionized water using a 3500 Da dialysis bag for 7 days to obtain the modified carboxylic acid polymer.

[0031] The preparation method of modified SiO2 includes the following steps: V1. Nano-SiO2 was added to anhydrous ethanol and ultrasonically dispersed. The pH was adjusted to 4 with hydrochloric acid solution. 3-Chloropropyltrimethoxysilane was added and stirred to disperse. The mixture was stirred at 80℃ for 4 h and centrifuged at 8000 rpm for 20 min. The precipitate was washed with anhydrous ethanol and vacuum dried to obtain chloride-containing SiO2. The particle size of nano-SiO2 was 50 nm. The mass concentration of nano-SiO2 in anhydrous ethanol was 20 mg / mL. The ratio of 3-chloropropyltrimethoxysilane to nano-SiO2 was 1.5 mL:1 g. V2. The SiO2 chloride obtained in step V1 was added to DMF and ultrasonically dispersed. Tannic acid and potassium carbonate were added, and the mixture was stirred at 70°C for 12 h. After centrifugation at 8000 rpm for 20 min, the precipitate was washed with ethanol and deionized water and dried under vacuum to obtain modified SiO2. The mass concentration of SiO2 chloride in DMF was 20 mg / mL. The mass ratio of tannic acid to SiO2 chloride was 1:2. The amount of potassium carbonate used was 10 wt% of the mass of tannic acid.

[0032] This embodiment also provides a method for preparing the cement-based solid waste composite material for road base, including the following steps: mixing sulfoaluminate cement, calcined coal gangue powder, fly ash, desulfurized gypsum, and river sand, stirring at 150 rpm for 2 min, adding modified carboxylic acid polymer, modified SiO2, and water, stirring at 300 rpm for 5 min, adding polyvinyl alcohol fiber, and stirring at 300 rpm for 3 min to obtain the cement-based solid waste composite material for road base.

[0033] Example 2: A cement-based solid waste composite material for road base course, the raw materials for preparation include the following components in parts by weight: 400 parts of sulfoaluminate cement, 200 parts of calcined coal gangue powder, 150 parts of fly ash, 30 parts of desulfurized gypsum, 300 parts of river sand, 4 parts of modified carboxylic acid polymer, 8 parts of modified SiO2, 300 parts of water, and 20 parts of polyvinyl alcohol fiber.

[0034] The calcined coal gangue powder has a particle size of 1000 mesh, the river sand has a particle size of 0.6 mm, and the polyvinyl alcohol fiber has a diameter of 15 μm and a length of 4 mm.

[0035] A method for preparing modified carboxylic acid polymers includes the following steps: L1. Tung oil acid (TOA) and maleic anhydride (MA) were mixed and reacted at 140℃ for 3 h with stirring. After cooling, the product was washed with ethyl acetate and deionized water. A 50wt% NaOH aqueous solution was added dropwise to the washed organic phase, and the reaction was carried out at room temperature for 2 h. Hydrochloric acid was added dropwise to adjust the pH to 2, and ethyl acetate was added to extract the organic layer. The extract was washed with deionized water, dehydrated with anhydrous magnesium sulfate, filtered, and the filtrate was evaporated by rotary evaporation to remove ethyl acetate, yielding TOA-MA. The mass ratio of tung oil acid to maleic anhydride was 12:5; the volume ratio of tung oil acid to NaOH aqueous solution was 4 g:5 mL. L2. Ethylene glycol monovinyl polyoxyethylene ether, TOA-MA obtained in step L1, and H2O2 were added to deionized water and stirred until homogeneous to obtain a mixture. Acrylic acid was added to deionized water and mixed to obtain solution A. 3-mercaptopropionic acid and ascorbic acid were added to deionized water and mixed to obtain solution B. The molecular weight of ethylene glycol monovinyl polyoxyethylene ether was 3000. The ratio of ethylene glycol monovinyl polyoxyethylene ether, TOA-MA, H2O2, and deionized water was 36 g:0.9 g:0.25 g:15 mL. The mass ratio of acrylic acid to ethylene glycol monovinyl polyoxyethylene ether was 1:10. The ratio of acrylic acid to deionized water was 3.6 g:16 mL. The ratio of 3-mercaptopropionic acid, ascorbic acid, and deionized water was 0.25 g:0.035 g:20 mL. The mass ratio of 3-mercaptopropionic acid to ethylene glycol monovinyl polyoxyethylene ether was 0.25:36. L3. Under stirring, solution A obtained in step L2 was added dropwise to the mixture at a rate of 0.2 mL / min, while solution B obtained in step L2 was added dropwise at a rate of 0.2 mL / min. After the addition was complete, the mixture was kept at 30°C for 0.5 h. The pH was adjusted to 6 with 30 wt% NaOH solution, and the mixture was dialyzed in deionized water using a 3500 Da dialysis bag for 7 days to obtain the modified carboxylic acid polymer.

[0036] The preparation method of modified SiO2 includes the following steps: V1. Nano-SiO2 was added to anhydrous ethanol and ultrasonically dispersed. The pH was adjusted to 4 with hydrochloric acid solution. 3-Chloropropyltrimethoxysilane was added and stirred to disperse. The mixture was stirred at 80℃ for 3 h and centrifuged at 8000 rpm for 15 min. The precipitate was washed with anhydrous ethanol and vacuum dried to obtain chloride-containing SiO2. The particle size of nano-SiO2 was 40-50 nm. The mass concentration of nano-SiO2 in anhydrous ethanol was 15 mg / mL. The ratio of 3-chloropropyltrimethoxysilane to nano-SiO2 was 1 mL:1 g. V2. The SiO2 chloride obtained in step V1 was added to DMF and ultrasonically dispersed. Tannic acid and potassium carbonate were added, and the mixture was stirred at 60°C for 8 h. After centrifugation at 8000 rpm for 15 min, the precipitate was washed with ethanol and deionized water and dried under vacuum to obtain modified SiO2. The mass concentration of SiO2 chloride in DMF was 10 mg / mL. The mass ratio of tannic acid to SiO2 chloride was 1:1. The amount of potassium carbonate used was 6 wt% of the mass of tannic acid.

[0037] This embodiment also provides a method for preparing the cement-based solid waste composite material for road base, including the following steps: mixing sulfoaluminate cement, calcined coal gangue powder, fly ash, desulfurized gypsum, and river sand, stirring at 150 rpm for 1 min, adding modified carboxylic acid polymer, modified SiO2, and water, stirring at 300 rpm for 3 min, adding polyvinyl alcohol fiber, and stirring at 300 rpm for 2 min to obtain the cement-based solid waste composite material for road base.

[0038] Example 3: A cement-based solid waste composite material for road base course, the raw materials for preparation include the following components in parts by weight: 500 parts of sulfoaluminate cement, 250 parts of calcined coal gangue powder, 200 parts of fly ash, 50 parts of desulfurized gypsum, 350 parts of river sand, 5 parts of modified carboxylic acid polymer, 10 parts of modified SiO2, 350 parts of water, and 22 parts of polyvinyl alcohol fiber.

[0039] The particle size of the calcined coal gangue powder is 1100 mesh, the particle size of the river sand is 0.8 mm, and the diameter of the polyvinyl alcohol fiber is 18 μm and the length is 5 mm.

[0040] A method for preparing modified carboxylic acid polymers includes the following steps: L1. Tung oil acid (TOA) and maleic anhydride (MA) were mixed and reacted at 140℃ for 3.5 h with stirring. After cooling, the product was washed with ethyl acetate and deionized water. A 50wt% NaOH aqueous solution was added dropwise to the washed organic phase, and the reaction was carried out at room temperature for 2 h. Hydrochloric acid was added dropwise to adjust the pH to 2.5. Ethyl acetate was added to extract the organic layer, and the extract was washed with deionized water. After dehydration with anhydrous magnesium sulfate, the mixture was filtered, and the filtrate was evaporated by rotary evaporation to remove ethyl acetate, yielding TOA-MA. The mass ratio of tung oil acid to maleic anhydride was 12:5, and the volume ratio of tung oil acid to NaOH aqueous solution was 4 g:5 mL. L2. Ethylene glycol monovinyl polyoxyethylene ether, TOA-MA obtained in step L1, and H2O2 were added to deionized water and stirred until homogeneous to obtain a mixture. Acrylic acid was added to deionized water and mixed to obtain solution A. 3-mercaptopropionic acid and ascorbic acid were added to deionized water and mixed to obtain solution B. The molecular weight of ethylene glycol monovinyl polyoxyethylene ether was 3000. The ratio of ethylene glycol monovinyl polyoxyethylene ether, TOA-MA, H2O2, and deionized water was 36 g:0.9 g:0.25 g:15 mL. The mass ratio of acrylic acid to ethylene glycol monovinyl polyoxyethylene ether was 1:10. The ratio of acrylic acid to deionized water was 3.6 g:16 mL. The ratio of 3-mercaptopropionic acid, ascorbic acid, and deionized water was 0.25 g:0.035 g:20 mL. The mass ratio of 3-mercaptopropionic acid to ethylene glycol monovinyl polyoxyethylene ether was 0.25:36. L3. Under stirring, solution A obtained in step L2 was added dropwise to the mixture at a rate of 0.25 mL / min, while solution B obtained in step L2 was added dropwise at a rate of 0.25 mL / min. After the addition was complete, the mixture was kept at 30°C for 0.8 h. The pH was adjusted to 6.5 with 30 wt% NaOH solution, and the mixture was dialyzed in deionized water using a 3500 Da dialysis bag for 7 days to obtain the modified carboxylic acid polymer.

[0041] The preparation method of modified SiO2 includes the following steps: V1. Nano-SiO2 was added to anhydrous ethanol and ultrasonically dispersed. The pH was adjusted to 4 with hydrochloric acid solution. 3-Chloropropyltrimethoxysilane was added and stirred to disperse. The mixture was stirred at 80℃ for 3.5 h and centrifuged at 8000 rpm for 18 min. The precipitate was washed with anhydrous ethanol and vacuum dried to obtain chloride SiO2. The particle size of nano-SiO2 was 45 nm. The mass concentration of nano-SiO2 in anhydrous ethanol was 18 mg / mL. The ratio of 3-chloropropyltrimethoxysilane to nano-SiO2 was 1.2 mL:1 g. V2. The SiO2 chloride obtained in step V1 was added to DMF and ultrasonically dispersed. Tannic acid and potassium carbonate were added, and the mixture was stirred at 65°C for 10 h. After centrifugation at 8000 rpm for 18 min, the precipitate was washed with ethanol and deionized water and dried under vacuum to obtain modified SiO2. The mass concentration of SiO2 chloride in DMF was 15 mg / mL. The mass ratio of tannic acid to SiO2 chloride was 1:1.5. The amount of potassium carbonate used was 8 wt% of the mass of tannic acid.

[0042] This embodiment also provides a method for preparing the cement-based solid waste composite material for road base, including the following steps: mixing sulfoaluminate cement, calcined coal gangue powder, fly ash, desulfurized gypsum, and river sand, stirring at 150 rpm for 1.5 min, adding modified carboxylic acid polymer, modified SiO2, and water, stirring at 300 rpm for 4 min, adding polyvinyl alcohol fiber, and stirring at 300 rpm for 2.5 min to obtain the cement-based solid waste composite material for road base.

[0043] The only difference between Comparative Example 1 and Example 1 is that step L1 is not performed and TOA-MA is not added in step L2.

[0044] The only difference between Comparative Example 2 and Example 1 is that step L1 is omitted and TOA-MA in step L2 is replaced with tung oil acid.

[0045] The only difference between Comparative Example 3 and Example 1 is that step V2 is omitted and modified SiO2 is replaced with chlorinated SiO2.

[0046] The only difference between Comparative Example 4 and Example 1 is that no modified SiO2 is added.

[0047] Experimental Example 1: The composite materials prepared in Examples 1-3 and Comparative Examples 1-4 were cast into cubic specimens of 100mm × 100mm × 100mm, respectively. The specimens were cured under standard curing conditions (temperature 20±2℃, relative humidity ≥95%) for 7 days and 28 days, and then their compressive strength was tested. The results are as follows: Figure 1 As shown.

[0048] Figure 1 The results showed that the 7-day and 28-day compressive strengths of Examples 1-3 were significantly higher than those of Comparative Examples 1-4. In Comparative Example 1, the lack of TOA-MA introduction reduced the water-reducing, dispersing, and toughening effects of the modified carboxylic acid polymer, leading to decreased matrix density and limited strength development. Comparative Example 2, using unmodified tung oil acid directly, failed to form an effective cross-linked copolymer network, resulting in poor strength improvement. Comparative Example 3, using chlorinated SiO2 instead of modified SiO2, lacked the chemical anchoring function of tannic acid on the nanoparticle surface, resulting in insufficient dispersibility and interfacial bonding, and a smaller strength increase. Comparative Example 4, completely removing modified SiO2, exhibited the lowest strength. The results indicate that the modified carboxylic acid polymer and modified SiO2 synergistically refined the pore structure and strengthened the connections between hydration products, endowing the composite material with excellent compressive strength.

[0049] Experimental Example 2: A 100mm×100mm×400mm prism specimen was used and cured under standard conditions for 28 days. The flexural strength was tested using the three-point bending method. The results are as follows: Figure 2 As shown.

[0050] Figure 2 The results showed that the flexural strength of Examples 1-3 was significantly better than that of Comparative Examples 1-4. The modified carboxylic acid polymer molecular chain contains tung oil acid-maleic anhydride copolymer segments, which can efficiently dissipate stress at the microcrack tips; combined with an appropriate amount of fiber, it effectively inhibits crack initiation and propagation. The tannic acid-grafted modified SiO2 forms strong coordination bonds with cement hydration products through polyphenolic hydroxyl groups, which not only improves the dispersion uniformity of nanoparticles but also strengthens the interfacial bonding between the polymer and the cement matrix. Comparative Examples 1 and 2 showed poor toughening effects due to missing or incomplete polymer functional side chains; Comparative Examples 3 and 4 showed a significant decrease in flexural strength due to defects at the nano-reinforcing phase interface or the absence of nano-phases. This experiment fully demonstrates that the functional additive combination of the present invention can significantly improve the flexural strength of road base materials.

[0051] Experimental Example 3: The composite material was molded into 100mm×100mm×400mm specimens. After standard curing for 7 days, the specimens were moved to a drying shrinkage chamber (temperature 20±2℃, relative humidity 60±5%). The length change of the specimens was monitored using a drying shrinkage meter, and the 28-day drying shrinkage value was calculated. The results are shown below. Figure 3 .

[0052] Figure 3 The results showed that the 28-day shrinkage coefficients of Examples 1-3 were significantly lower than those of Comparative Examples 1-4. The modified carboxylic acid polymer, through the water-storage and water-release effect of its hydrophilic polyether long side chains, effectively compensated for the shrinkage stress caused by capillary water loss. Simultaneously, the filling of micropores by the modified SiO2 particles and the chemical bonding between tannic acid and the cement matrix further constrained the volume deformation of the slurry. Comparative Examples 1 and 2, due to their imperfect polymer structures, exhibited limited shrinkage reduction effects; Comparative Examples 3 and 4, lacking nanofillers or interfacial reinforcement, had high matrix porosity, resulting in severe water migration and significantly increased shrinkage. These results indicate that the composite material of this invention possesses outstanding volume stability, which is beneficial for reducing the generation of reflective cracks in the substrate.

[0053] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A cement-based solid waste composite material for road base courses, characterized in that, The raw materials for preparation include the following components in parts by weight: 400-600 parts of sulfoaluminate cement, 200-300 parts of calcined coal gangue powder, 150-250 parts of fly ash, 30-60 parts of desulfurized gypsum, 300-400 parts of river sand, 4-6 parts of modified carboxylic acid polymer, 8-12 parts of modified SiO2, 300-400 parts of water, and 20-25 parts of polyvinyl alcohol fiber; The preparation method of the modified carboxylic acid polymer includes the following steps: L1. Tung oil acid and maleic anhydride were mixed and stirred at 140°C. After cooling, the mixture was washed with ethyl acetate and deionized water. A 50wt% NaOH aqueous solution was added dropwise to the washed organic phase. The reaction was carried out at room temperature. The pH was adjusted to 2-3. Ethyl acetate was added to extract the organic layer. The extract was washed with deionized water and water was removed. The filtrate was evaporated by rotary evaporation to obtain TOA-MA. L2. Take ethylene glycol monovinyl polyoxyethylene ether, TOA-MA obtained in step L1 and H2O2 and add them to deionized water and stir evenly to obtain a mixture. Take acrylic acid and add it to deionized water and mix to obtain solution A. Take 3-mercaptopropionic acid and ascorbic acid and add them to deionized water and mix to obtain solution B. L3. While stirring, add solution A obtained in step L2 dropwise to the mixture, and simultaneously add solution B obtained in step L2 dropwise. After the addition is complete, keep the reaction at the temperature, adjust the pH to 6-7 with NaOH solution, dialyze, and obtain the modified carboxylic acid polymer. The method for preparing the modified SiO2 includes the following steps: V1. Add nano-SiO2 to anhydrous ethanol, disperse, adjust the pH to 4, add 3-chloropropyltrimethoxysilane, stir and disperse, react, centrifuge, wash, and dry to obtain chloride SiO2; V2. Take the SiO2 chloride obtained in step V1 and disperse it in DMF. Add tannic acid and potassium carbonate, stir to react, centrifuge, wash, and dry to obtain modified SiO2.

2. The cement-based solid waste composite material for road base courses according to claim 1, characterized in that, In step L1, the mass ratio of tung oil acid to maleic anhydride is 12:5; the volume ratio of tung oil acid to NaOH aqueous solution is 4 g:5 mL.

3. The cement-based solid waste composite material for road base courses according to claim 2, characterized in that, In step L2, the ratio of ethylene glycol monovinyl polyoxyethylene ether, TOA-MA, H2O2 and deionized water is 36 g:0.9 g:0.25 g:15 mL.

4. The cement-based solid waste composite material for road base courses according to claim 3, characterized in that, In step L2, the mass ratio of acrylic acid to ethylene glycol monovinyl polyoxyethylene ether is 1:

10.

5. The cement-based solid waste composite material for road base courses according to claim 4, characterized in that, In step L2, the ratio of acrylic acid to deionized water is 3.6 g: 16 mL.

6. The cement-based solid waste composite material for road base courses according to claim 5, characterized in that, In step L2, the ratio of 3-mercaptopropionic acid, ascorbic acid, and deionized water is 0.25 g:0.035 g:20 mL.

7. The cement-based solid waste composite material for road base courses according to claim 6, characterized in that, In step L2, the mass ratio of 3-mercaptopropionic acid to ethylene glycol monovinyl polyoxyethylene ether is 0.25:

36.

8. The cement-based solid waste composite material for road base courses according to claim 7, characterized in that, In step V1, the ratio of 3-chloropropyltrimethoxysilane to nano-SiO2 is 1-1.5 mL:1 g.

9. The cement-based solid waste composite material for road base courses according to claim 8, characterized in that, In step V2, the mass ratio of tannic acid to SiO2 chloride is 1:1-2; the amount of potassium carbonate used is 6-10 wt% of the mass of tannic acid.

10. A method for preparing a cement-based solid waste composite material for road base courses as described in any one of claims 1-9, characterized in that, The process includes the following steps: mixing sulfoaluminate cement, calcined coal gangue powder, fly ash, desulfurized gypsum, and river sand, stirring, adding modified carboxylic acid polymer, modified SiO2, and water, stirring, adding polyvinyl alcohol fiber, and stirring to obtain a cement-based solid waste composite material for road base.

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