High crack resistance and abrasion resistance low carbon concrete and preparation method thereof

Abstract

The application relates to the technical field of low-carbon concrete, in particular to high-anti-cracking water-abrasion-resistant low-carbon concrete and a preparation method thereof. The preparation method of the high-anti-cracking water-abrasion-resistant low-carbon concrete comprises the following steps: preparation of a high-water-absorption polymer, preparation of modified calcium-aluminum hydrotalcite, preparation of reinforcing fibers, and preparation of low-carbon concrete. The low-carbon concrete contains the high-water-absorption polymer, the modified calcium-aluminum hydrotalcite and the reinforcing fibers; the former is used for water retention by N-vinyl pyrrolidone, and shrinkage is reduced; the hydrotalcite is used for fixing chlorine ions and filling pores; the fibers are modified to resist cracking; the three components are synergized; the high-water-absorption polymer and the hydrotalcite help to be dense; the fibers are restrained to crack; and the concrete is improved in the anti-cracking, anti-permeability and water-abrasion resistance from multiple dimensions; and the low-carbon concrete is suitable for water conservancy and other scenes.

Description

Technical Field

[0001] This invention relates to the field of low-carbon concrete technology, specifically to a low-carbon concrete with high crack resistance and water erosion resistance, and its preparation method. Background Technology

[0002] As a key area for carbon emissions, the construction industry has made the low-carbon upgrading of concrete materials a core direction for its development. Low-carbon concrete typically replaces part of the cement by incorporating industrial solid waste mineral admixtures such as fly ash, slag powder, and silica fume. This not only reduces cement usage and related carbon emissions but also enables the resource utilization of industrial waste, aligning with the concept of green building materials. However, the large-scale introduction of mineral admixtures alters the hydration process of concrete, leading to an imbalance in the rate of free water consumption and making it highly susceptible to plastic shrinkage cracks and drying shrinkage cracks. Simultaneously, the delayed reaction of the pozzolanic material in the mineral admixtures slows down the early strength development of the concrete, resulting in a relatively loose structure in the interface transition zone. Under the abrasive action of high-speed water flow carrying silt, sand, and gravel, this can easily cause surface erosion, aggregate exposure, and other damage, severely shortening the service life of the concrete structure.

[0003] The crack resistance and water abrasion resistance of concrete are key indicators determining its service quality in special scenarios such as hydraulic engineering and high-speed water flow channels. To address the high carbon emissions and insufficient crack resistance of traditional concrete, existing technologies often use industrial solid wastes such as fly ash and slag powder as mineral admixtures to replace a portion of the cement, aiming to achieve low carbon emissions and improve the workability and volume stability of concrete. However, these mineral admixtures have relatively low activity; when the replacement amount is large, it can easily lead to slow early strength development in concrete and a decrease in surface erosion resistance under water abrasion. Furthermore, simply relying on mineral admixture modification cannot fundamentally solve the cracking problem caused by low tensile strength and insufficient toughness in concrete. To improve the water abrasion resistance of concrete, existing technologies often employ methods such as increasing concrete density or adding reinforcing phases like steel fibers and polypropylene fibers. Improving density usually relies on reducing the water-cement ratio or adding active admixtures such as silica fume. However, an excessively low water-cement ratio can lead to poor workability of concrete and increased construction difficulty. The high activity of silica fume can also exacerbate the problem of concentrated hydration heat. Although steel fibers can significantly improve the impact resistance and wear resistance of concrete, they have drawbacks such as easy corrosion, uneven distribution, and high cost. They can also increase the resistance of concrete mixing and pumping. The reinforcing effect of polypropylene fibers is limited. Under the action of high-speed water flow, interfacial peeling is likely to occur, and long-term wear resistance is difficult to guarantee.

[0004] Furthermore, in practical engineering applications, existing low-carbon concrete often faces the dilemma of balancing "low carbonization" and "high performance": if the amount of mineral admixtures is increased to reduce carbon emissions, the key properties of concrete, such as crack resistance and water erosion resistance, will be significantly reduced; if the focus is on improving performance by increasing the amount of cement or using high-cost reinforcing materials, it will violate the concept of low-carbon development and be less economical.

[0005] Therefore, developing a concrete material system that can synergistically achieve low cement consumption and low carbon emissions, while also possessing excellent crack resistance and strong resistance to water erosion, and optimizing its preparation process, are urgent technical challenges to be solved in the field of concrete materials. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a low-carbon concrete with high crack resistance and water erosion resistance, and a method for its preparation.

[0007] This invention provides a method for preparing low-carbon concrete with high crack resistance and water erosion resistance, comprising:

[0008] S1: Preparation of superabsorbent polymer;

[0009] 2-Acrylamide-2-methylpropanesulfonic acid, sodium hydroxide, acrylamide, N-vinylpyrrolidone, and N,N'-methylenebisacrylamide were added to deionized water to prepare a mixed monomer solution. Span80 and Tween-80 were added to cyclohexane, followed by the addition of gelatinized starch and potassium persulfate initiator solution. Finally, the mixed monomer solution was added, and the reaction was carried out to prepare a superabsorbent polymer.

[0010] S2: Preparation of modified calcium aluminum hydrotalcite;

[0011] Calcium and aluminum sources were added to deionized water to obtain mixture I. Sodium hydroxide and urea were added to deionized water and then frozen to -1 to -3°C. Microcrystalline cellulose was then added and stirred to obtain mixture II. Mixture I was added dropwise to mixture II at 1-2 mL / min and then reacted to prepare modified calcium aluminum hydrotalcite.

[0012] S3: Preparation of reinforcing fibers;

[0013] First, TEOS was used to modify the sisal fiber, and then water-based polyurethane slurry was used for secondary modification to obtain reinforced fiber.

[0014] S4: Preparation of low-carbon concrete;

[0015] Prepare concrete raw materials by weight: 300-350 parts cement, 200-250 parts mineral admixtures, 650-750 parts fine aggregate, 1000-1100 parts coarse aggregate, 130-160 parts water, 3-5 parts water-reducing agent, 3-5 parts superabsorbent polymer, 8-10 parts modified calcium aluminum hydrotalcite, and 5-8 parts reinforcing fiber. Mix all raw materials to obtain low-carbon concrete.

[0016] As a preferred aspect, S1: the preparation of the superabsorbent polymer specifically includes the following steps:

[0017] S1.1: Add 2-3 parts by weight of potassium persulfate to 100-120 parts by weight of deionized water, stir and mix to obtain an initiator solution. Add 2-3 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 0.5-0.8 parts by weight of sodium hydroxide, 2-3 parts by weight of acrylamide, 2-3 parts by weight of N-vinylpyrrolidone and 0.05-0.06 parts by weight of N,N'-methylenebisacrylamide to 100-120 parts by weight of deionized water, stir and mix to dissolve to obtain a mixed monomer solution.

[0018] S1.2: Add 3-5 parts by weight of starch to 50-80 parts by weight of deionized water, and then stir and mix at 85-90℃ for 1-2 hours to obtain gelatinized starch. Add 1-2 parts by weight of Span80 and 1-2 parts by weight of Tween-80 to 92-95 parts by weight of cyclohexane, and stir at 28-30℃ for 20-30 minutes under nitrogen protection. Then add gelatinized starch and initiator solution, stir at 300-320 rpm for 1-2 minutes, and then add mixed monomer solution. React at 70-75℃ under nitrogen atmosphere for 2-3 hours to obtain reactant.

[0019] S1.3: Pour the reactants into anhydrous ethanol stirred at 1800-2000 rpm, filter to obtain a precipitate, wash the precipitate 3-5 times with anhydrous ethanol, and then dry it at 40-50℃ for 20-24 h to obtain a superabsorbent polymer.

[0020] As a preferred aspect, S2: the preparation of modified calcium aluminum hydrotalcite specifically includes the following steps:

[0021] S2.1: Add 4-6 parts by weight of calcium nitrate and 2-3 parts by weight of aluminum nitrate to 30-50 parts by weight of deionized water, and stir and mix at 300-400 rpm for 20-30 min to obtain mixture I;

[0022] S2.2: Add 7-8 parts by weight of sodium hydroxide and 12-15 parts by weight of urea to 100-120 parts by weight of deionized water, then freeze to -1 to -3°C, then add 0.5-0.8 parts by weight of microcrystalline cellulose, and stir and mix at 400-500 rpm for 20-30 min to obtain mixture II.

[0023] S2.3: Under stirring at 800-1000 rpm, add mixture I dropwise to mixture II at 1-2 mL / min to make the pH of the mixture 10-11. After the addition is complete, let it stand for 20-24 h, then add it to a high-pressure reactor lined with polytetrafluoroethylene and react in a homogeneous reactor at 80-90℃ for 24-26 h. After the reaction is complete, cool to room temperature, then centrifuge, wash with deionized water 2-4 times, and finally freeze dry to obtain modified calcium aluminum hydrotalcite.

[0024] As a preferred aspect, S3: the preparation of the reinforcing fiber specifically includes the following steps:

[0025] S3.1: Add 4-5 parts by weight of TEOS to 40-50 parts by weight of anhydrous ethanol, then add 20-30 parts by weight of sisal fiber, stir and mix to obtain a fiber mixture. Add 16-18 parts by weight of anhydrous ethanol and 4-5 parts by weight of deionized water to 10-12 parts by weight of ammonia solution with a concentration of 28-30wt%, stir and mix at 1000-1200 rpm for 1-3 min, then add the fiber mixture, stir and mix under closed conditions at 350-400 rpm for 2-3 h, then wash with deionized water 3-5 times, dry to obtain modified sisal fiber;

[0026] S3.2: Tighten the modified sisal fibers and keep them taut. Then immerse them in an aqueous polyurethane slurry containing 3-5% by mass for 15-20 minutes. After that, use a stick to squeeze out the excess liquid in one direction. Then dry them at 80-90℃ for 1-2 hours to obtain the reinforced fibers.

[0027] As a preferred aspect, S4: the preparation of low-carbon concrete specifically includes the following steps:

[0028] S4.1: Prepare concrete raw materials according to the following weight parts: 300-350 parts cement, 200-250 parts mineral admixtures, 650-750 parts fine aggregate, 1000-1100 parts coarse aggregate, 130-160 parts water, 3-5 parts water-reducing agent, 3-5 parts superabsorbent polymer, 8-10 parts modified calcium aluminum hydrotalcite, and 5-8 parts reinforcing fiber;

[0029] S4.2: Add the water-reducing agent to water and stir to obtain a water-reducing agent solution. Put the above-mentioned cement, mineral admixtures, fine aggregate, coarse aggregate, modified calcium aluminum hydrotalcite and superabsorbent polymer into a forced mixer and dry mix at a speed of 90-100 r / min for 60-90 s to obtain a mixture. Then add the water-reducing agent solution and reinforcing fibers and stir at a speed of 90-100 r / min for 10-12 min to obtain low-carbon concrete.

[0030] As a preferred aspect, the water-reducing agent in step S4.1 is a polycarboxylate-based high-performance water-reducing agent.

[0031] As a preferred aspect, the fine aggregate in step S4.1 is one or both of natural river sand and manufactured sand.

[0032] As a preferred aspect, the mineral admixture in step S4.1 is prepared by mixing fly ash, slag powder and silica fume in a mass ratio of 1-2:1-2:1-2.

[0033] As a preferred aspect, the coarse aggregate in step S4.1 is continuously graded crushed stone with a particle size of 5-25 mm.

[0034] The present invention also provides a low-carbon concrete with high crack resistance and water erosion resistance, which is prepared by any of the methods for preparing a low-carbon concrete with high crack resistance and water erosion resistance as described in any one of the claims.

[0035] The present invention has the following advantages:

[0036] 1. This invention incorporates a superabsorbent polymer to prepare low-carbon concrete. This polymer absorbs free water generated during concrete mixing and releases it slowly in the later stages of hydration. This "internal reservoir" effect effectively compensates for water loss caused by hydration and evaporation, reducing plastic shrinkage and drying shrinkage of the concrete. Furthermore, the absorbed water expands and fills the capillary pores inside the concrete, increasing matrix density and enhancing impermeability and water erosion resistance. Additionally, N-vinylpyrrolidone is introduced into the superabsorbent polymer. N-vinylpyrrolidone is a strongly hydrophilic nonionic monomer, and its nonionic groups are insensitive to ion concentration in solution. In concrete, a high-carbon concrete... In alkaline ionic environments, the water absorption capacity of anionic polymers decreases significantly due to the "charge shielding effect." The introduction of N-vinylpyrrolidone can effectively counteract this negative impact, allowing the superabsorbent polymer to maintain a high water absorption rate and water retention capacity even in the harsh chemical environment of concrete pore solutions. This ensures the reliability of the internal curing effect. Furthermore, the carbonyl and amide groups in the N-vinylpyrrolidone molecule can interact with calcium ions or silanol groups on the surface of cement hydration products. This interaction can improve the bonding between the superabsorbent polymer and the cement paste interface, reduce interfacial gaps, and further enhance the crack resistance and water erosion resistance of concrete.

[0037] 2. The modified calcium-aluminum hydrotalcite added in this invention has a unique layered structure. Its layers carry a positive charge. When chloride ions penetrate concrete from the environment, they are captured and fixed between the layers by the hydrotalcite, thus delaying or even preventing chloride ions from reaching the surface of the reinforcing steel, effectively preventing steel corrosion. Furthermore, the dense layered structure of the hydrotalcite can fill the capillary pores inside the concrete, blocking the penetration channels of moisture and harmful ions, enhancing water erosion resistance and chemical corrosion resistance. Moreover, microcrystalline cellulose is introduced during the preparation of the modified calcium-aluminum hydrotalcite for modification; microcrystalline cellulose acts as a structural component... Crystal inhibitors can suppress the lateral growth of calcium aluminum hydrotalcite crystals, causing them to form smaller and thinner nanosheet structures. At the same time, microcrystalline cellulose can form hydrogen bonds with the OH⁻ of calcium aluminum hydrotalcite through hydroxyl groups, encapsulating the surface of calcium aluminum hydrotalcite, enhancing the electrostatic repulsion between modified calcium aluminum hydrotalcite and improving its dispersibility. In addition, smaller and thinner hydrotalcite particles can fill the capillary and gel pores of cement stone, making the microstructure of concrete more compact. This not only improves the compressive strength and toughness but also enhances the concrete's resistance to water erosion.

[0038] 3. This invention incorporates reinforcing fibers into the preparation of low-carbon concrete. These fibers can cross cracks, effectively transfer stress, and dissipate energy, thereby inhibiting crack initiation and preventing micro-cracks from expanding into macro-cracks. This improves the toughness and impact resistance of the concrete. The addition of fibers transforms the concrete from a brittle material into a more resilient composite material, better resisting the repeated action of dynamic water pressure and the cutting of silt particles, thus improving its resistance to water erosion. A dual modification process using TEOS modification and waterborne polyurethane coating overcomes the inherent defects of natural sisal fibers. The silica coating formed after TEOS hydrolysis coats the surface of the sisal fibers, not only improving their resistance to alkali corrosion but also preventing them from being eroded and degraded by the alkaline hydration environment of the concrete. The solution also increases the surface roughness of the fibers; the subsequent waterborne polyurethane coating further enhances the flexibility and tensile toughness of the fibers, reduces fiber breakage during concrete mixing, and ensures that the fibers can effectively play a mechanical reinforcing role in the matrix. The silanol groups introduced by TEOS modification can form chemical bonds with the cement hydration products and the hydroxyl groups of modified calcium aluminum hydrotalcite. The polar groups of waterborne polyurethane can also form hydrogen bonds with the amide groups of superabsorbent polymers and the active sites on the aggregate surface, reducing defects in the interface transition zone between the reinforcing fibers and the concrete matrix, and achieving a tight bond between the "fiber-matrix". This can reduce the cutting and erosion damage to the concrete surface caused by abrasives carried by water flow, enabling low-carbon concrete to have a longer service life in scenarios such as water conservancy projects and high-speed water flow channels.

[0039] 4. In this invention, the superabsorbent polymer, modified calcium aluminum hydrotalcite, and reinforcing fibers can form a synergistically reinforcing composite system within the concrete. The internal curing effect of the superabsorbent polymer promotes the full hydration of cement, and together with the pore-filling effect of the modified calcium aluminum hydrotalcite, it contributes to the micro-densification of the matrix. The uniformly dispersed reinforcing fibers constrain the shrinkage and cracking of the matrix on a macroscopic scale. Meanwhile, the modified calcium aluminum hydrotalcite, while increasing density, provides additional protection for the reinforcing steel through its chloride ion curing function. These three components each play their respective roles while complementing each other, jointly improving the crack resistance, impermeability, and water erosion resistance of low-carbon concrete from multiple dimensions, including physical filling, chemical curing, and mechanical reinforcement. Attached Figure Description

[0040] Figure 1 This invention relates to a method for preparing low-carbon concrete with high crack resistance and water erosion resistance, as used in an embodiment of the invention. Detailed Implementation

[0041] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0042] Example 1: A method for preparing low-carbon concrete with high crack resistance and water erosion resistance, referring to... Figure 1 ,include:

[0043] S1: Preparation of superabsorbent polymer;

[0044] S1.1: Add 2 parts by weight of potassium persulfate to 100 parts by weight of deionized water, stir and mix to obtain an initiator solution. Add 2 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 0.5 parts by weight of sodium hydroxide, 2 parts by weight of acrylamide, 2 parts by weight of N-vinylpyrrolidone and 0.05 parts by weight of N,N'-methylenebisacrylamide to 100 parts by weight of deionized water, stir and mix to dissolve to obtain a mixed monomer solution.

[0045] S1.2: Add 3 parts by weight of starch to 50 parts by weight of deionized water, and then stir and mix at 85°C for 1 hour to obtain gelatinized starch. Add 1 part by weight of Span80 and 1 part by weight of Tween-80 to 92 parts by weight of cyclohexane, and stir at 28°C for 20 minutes under nitrogen protection. Then add gelatinized starch and initiator solution, stir at 300 rpm for 1 minute, and then add mixed monomer solution. React at 70°C for 2 hours under nitrogen atmosphere to obtain reactant.

[0046] S1.3: The reactants were poured into anhydrous ethanol stirred at 1800 rpm, filtered to obtain a precipitate, washed three times with anhydrous ethanol, and then dried at 40°C for 20 h to obtain a superabsorbent polymer.

[0047] S2: Preparation of modified calcium aluminum hydrotalcite;

[0048] S2.1: Add 4 parts by weight of calcium nitrate and 2 parts by weight of aluminum nitrate to 30 parts by weight of deionized water, and stir at 300 rpm for 20 min to obtain mixture I;

[0049] S2.2: Add 7 parts by weight of sodium hydroxide and 12 parts by weight of urea to 100 parts by weight of deionized water, then freeze to -1°C, then add 0.5 parts by weight of microcrystalline cellulose, and stir at 400 rpm for 20 min to obtain mixture II.

[0050] S2.3: Under stirring at 800 rpm, mixture I was added dropwise to mixture II at 1 mL / min to make the pH of the mixture 10. After the addition was complete, the mixture was allowed to stand for 20 h, and then added to a high-pressure reactor lined with polytetrafluoroethylene. The mixture was reacted at 80 °C for 24 h in a homogeneous reactor. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, washed twice with deionized water, and finally freeze-dried to obtain modified calcium aluminum hydrotalcite.

[0051] S3: Preparation of reinforcing fibers;

[0052] S3.1: Add 4 parts by weight of TEOS to 40 parts by weight of anhydrous ethanol, then add 20 parts by weight of sisal fiber, stir and mix to obtain a fiber mixture. Add 16 parts by weight of anhydrous ethanol and 4 parts by weight of deionized water to 10 parts by weight of ammonia solution with a concentration of 28wt%, stir and mix at 1000 rpm for 1 min, then add the fiber mixture, stir and mix under a closed system at 350 rpm for 2 h, then wash with deionized water 3 times, dry to obtain modified sisal fiber.

[0053] S3.2: Tighten the modified sisal fiber and keep it taut. Then immerse it in a water-based polyurethane slurry containing 3% by mass for 15 minutes. After that, use a stick to squeeze out the excess liquid in one direction. Then dry it at 80°C for 1 hour to obtain the reinforced fiber.

[0054] S4: Preparation of low-carbon concrete;

[0055] S4.1: Prepare concrete raw materials according to the following parts by weight: 300 parts cement, 200 parts mineral admixtures, 650 parts fine aggregate, 1000 parts coarse aggregate, 130 parts water, 3 parts water-reducing agent, 3 parts superabsorbent polymer, 8 parts modified calcium aluminum hydrotalcite and 5 parts reinforcing fiber.

[0056] Among them, the mineral admixture is made by mixing fly ash, slag powder and silica fume in a mass ratio of 1:1:1, and the fine aggregate is made by mixing natural river sand and manufactured sand in a mass ratio of 1:1.

[0057] S4.2: Add the water-reducing agent to water and stir to obtain a water-reducing agent solution. Put the above-mentioned cement, mineral admixtures, fine aggregate, coarse aggregate, modified calcium aluminum hydrotalcite and superabsorbent polymer into a forced mixer and dry mix at 90 r / min for 60 s to obtain a mixture. Then add the water-reducing agent solution and reinforcing fibers and stir at 90 r / min for 10 s to obtain low-carbon concrete.

[0058] Example 2: A method for preparing low-carbon concrete with high crack resistance and water erosion resistance, see [link to example]. Figure 1 ,include:

[0059] S1: Preparation of superabsorbent polymer;

[0060] S1.1: Add 3 parts by weight of potassium persulfate to 120 parts by weight of deionized water, stir and mix to obtain an initiator solution. Add 3 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 0.8 parts by weight of sodium hydroxide, 3 parts by weight of acrylamide, 3 parts by weight of N-vinylpyrrolidone and 0.06 parts by weight of N,N'-methylenebisacrylamide to 120 parts by weight of deionized water, stir and mix to dissolve to obtain a mixed monomer solution.

[0061] S1.2: Add 5 parts by weight of starch to 80 parts by weight of deionized water, and then stir and mix at 90°C for 2 hours to obtain gelatinized starch. Add 2 parts by weight of Span80 and 2 parts by weight of Tween-80 to 95 parts by weight of cyclohexane, and stir at 30°C for 30 minutes under nitrogen protection. Then add gelatinized starch and initiator solution, stir at 320 rpm for 2 minutes, and then add mixed monomer solution. React at 75°C for 3 hours under nitrogen atmosphere to obtain reactant.

[0062] S1.3: The reactants were poured into anhydrous ethanol stirred at 2000 rpm, filtered to obtain a precipitate, washed 5 times with anhydrous ethanol, and then dried at 50°C for 24 h to obtain a superabsorbent polymer.

[0063] S2: Preparation of modified calcium aluminum hydrotalcite;

[0064] S2.1: Add 6 parts by weight of calcium nitrate and 3 parts by weight of aluminum nitrate to 50 parts by weight of deionized water, and stir at 400 rpm for 30 min to obtain mixture I;

[0065] S2.2: Add 8 parts by weight of sodium hydroxide and 15 parts by weight of urea to 120 parts by weight of deionized water, then freeze to -3°C, then add 0.8 parts by weight of microcrystalline cellulose, and stir at 500 rpm for 30 min to obtain mixture II;

[0066] S2.3: Under stirring at 1000 rpm, mixture I was added dropwise to mixture II at 2 mL / min to make the pH of the mixture 11. After the addition was complete, the mixture was allowed to stand for 24 h, and then added to a high-pressure reactor lined with polytetrafluoroethylene. The mixture was reacted at 90 °C for 26 h in a homogeneous reactor. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, washed 4 times with deionized water, and finally freeze-dried to obtain modified calcium aluminum hydrotalcite.

[0067] S3: Preparation of reinforcing fibers;

[0068] S3.1: Add 5 parts by weight of TEOS to 50 parts by weight of anhydrous ethanol, then add 30 parts by weight of sisal fiber, stir and mix to obtain a fiber mixture. Add 18 parts by weight of anhydrous ethanol and 5 parts by weight of deionized water to 12 parts by weight of a 30 wt% ammonia solution, stir and mix at 1200 rpm for 3 min, then add the fiber mixture, stir and mix under closed conditions at 400 rpm for 3 h, then wash with deionized water 5 times, dry to obtain modified sisal fiber.

[0069] S3.2: Tighten the modified sisal fiber and keep it taut. Then immerse it in a water-based polyurethane slurry containing 5% by mass for 20 minutes. After that, use a stick to squeeze out the excess liquid in one direction. Then dry it at 90°C for 2 hours to obtain the reinforced fiber.

[0070] S4: Preparation of low-carbon concrete;

[0071] S4.1: Prepare concrete raw materials according to the following parts by weight: 350 parts cement, 250 parts mineral admixtures, 750 parts fine aggregate, 1100 parts coarse aggregate, 160 parts water, 5 parts water-reducing agent, 5 parts superabsorbent polymer, 10 parts modified calcium aluminum hydrotalcite and 8 parts reinforcing fiber.

[0072] Among them, the mineral admixture is prepared by mixing fly ash, slag powder and silica fume in a mass ratio of 2:2:1, and the fine aggregate is prepared by mixing natural river sand and manufactured sand in a mass ratio of 1:2.

[0073] S4.2: Add the water-reducing agent to water and stir to obtain a water-reducing agent solution. Put the above-mentioned cement, mineral admixtures, fine aggregate, coarse aggregate, modified calcium aluminum hydrotalcite and superabsorbent polymer into a forced mixer and dry mix at 100 r / min for 90 s to obtain a mixture. Then add the water-reducing agent solution and reinforcing fibers and stir at 100 r / min for 12 min to obtain low-carbon concrete.

[0074] Example 3: A method for preparing low-carbon concrete with high crack resistance and water erosion resistance, see [link to example]. Figure 1 ,include:

[0075] S1: Preparation of superabsorbent polymer;

[0076] S1.1: Add 2.5 parts by weight of potassium persulfate to 110 parts by weight of deionized water, stir and mix to obtain an initiator solution. Add 2.5 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 0.65 parts by weight of sodium hydroxide, 2.5 parts by weight of acrylamide, 2.5 parts by weight of N-vinylpyrrolidone and 0.055 parts by weight of N,N'-methylenebisacrylamide to 110 parts by weight of deionized water, stir and mix to dissolve, and obtain a mixed monomer solution.

[0077] S1.2: Add 4 parts by weight of starch to 65 parts by weight of deionized water, and then stir and mix at 86.5℃ for 1.5h to obtain gelatinized starch. Add 1.5 parts by weight of Span80 and 1.5 parts by weight of Tween-80 to 93.5 parts by weight of cyclohexane, and stir at 29℃ for 25min under nitrogen protection. Then add gelatinized starch and initiator solution, stir at 310rpm for 1.5min, and then add mixed monomer solution. React at 72.5℃ for 2.5h under nitrogen atmosphere to obtain reactant.

[0078] S1.3: The reactants were poured into anhydrous ethanol stirred at 1900 rpm, filtered to obtain a precipitate, washed 4 times with anhydrous ethanol, and then dried at 45°C for 22 h to obtain a superabsorbent polymer.

[0079] S2: Preparation of modified calcium aluminum hydrotalcite;

[0080] S2.1: Add 5 parts by weight of calcium nitrate and 2.5 parts by weight of aluminum nitrate to 40 parts by weight of deionized water, and stir at 350 rpm for 25 min to obtain mixture I;

[0081] S2.2: Add 7.5 parts by weight of sodium hydroxide and 13.5 parts by weight of urea to 110 parts by weight of deionized water, then freeze to -2°C, then add 0.65 parts by weight of microcrystalline cellulose, and stir at 450 rpm for 25 min to obtain mixture II.

[0082] S2.3: Under stirring at 900 rpm, mixture I was added dropwise to mixture II at 1.5 mL / min to make the pH of the mixture 10.5. After the addition was complete, the mixture was allowed to stand for 22 h, and then added to a high-pressure reactor lined with polytetrafluoroethylene. The mixture was reacted at 85 °C for 25 h in a homogeneous reactor. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, washed three times with deionized water, and finally freeze-dried to obtain modified calcium aluminum hydrotalcite.

[0083] S3: Preparation of reinforcing fibers;

[0084] S3.1: Add 4.5 parts by weight of TEOS to 45 parts by weight of anhydrous ethanol, then add 25 parts by weight of sisal fiber, stir and mix to obtain a fiber mixture. Add 17 parts by weight of anhydrous ethanol and 4.5 parts by weight of deionized water to 11 parts by weight of ammonia solution with a concentration of 29 wt%, stir and mix at 1100 rpm for 2 min, then add the fiber mixture, stir and mix under closed conditions at 375 rpm for 2-3 h, then wash with deionized water 4 times, dry to obtain modified sisal fiber;

[0085] S3.2: Tighten the modified sisal fiber and keep it taut. Then immerse it in an aqueous polyurethane slurry containing 4% by mass for 17.5 minutes. After that, use a stick to squeeze out the excess liquid in one direction. Then dry it at 85°C for 1.5 hours to obtain the reinforced fiber.

[0086] S4: Preparation of low-carbon concrete;

[0087] S4.1: Prepare concrete raw materials according to the following parts by weight: 325 parts cement, 225 parts mineral admixtures, 700 parts fine aggregate, 1050 parts coarse aggregate, 145 parts water, 4 parts water-reducing agent, 4 parts superabsorbent polymer, 9 parts modified calcium aluminum hydrotalcite and 6.5 parts reinforcing fiber.

[0088] Among them, the mineral admixture is prepared by mixing fly ash, slag powder and silica fume in a mass ratio of 1:1:2, and the fine aggregate is prepared by mixing natural river sand and manufactured sand in a mass ratio of 2:1.

[0089] S4.2: Add the water-reducing agent to water and stir to obtain a water-reducing agent solution. Put the above-mentioned cement, mineral admixtures, fine aggregate, coarse aggregate, modified calcium aluminum hydrotalcite and superabsorbent polymer into a forced mixer and dry mix at a speed of 95 r / min for 75 s to obtain a mixture. Then add the water-reducing agent solution and reinforcing fibers and stir at a speed of 95 r / min for 11 min to obtain low-carbon concrete.

[0090] Comparative Example 1 differs from Example 1 in that the superabsorbent polymer, modified calcium aluminum hydrotalcite and reinforcing fiber in steps S1-S3 and S4.1 are removed, while the remaining steps remain unchanged to prepare low-carbon concrete. This is referred to as Comparative Example 1.

[0091] Comparative Example 2 differs from Example 1 in that step S1 is removed, and the superabsorbent polymer in step S4.1 is replaced with an equal amount of polyacrylic acid, while the remaining steps remain unchanged to prepare low-carbon concrete. This is referred to as Comparative Example 2.

[0092] Comparative Example 3 differs from Example 1 in that N-vinylpyrrolidone in step S1.1 is removed, while the remaining steps remain unchanged in preparing low-carbon concrete. This example is referred to as Comparative Example 3.

[0093] Comparative Example 4 differs from Example 1 in that it involves removing microcrystalline cellulose in step S2.2 while keeping the other steps unchanged in preparing low-carbon concrete.

[0094] Comparative Example 5 differs from Example 1 in that step S3 is removed, and the reinforcing fiber in step S4.1 is replaced with an equal amount of sisal fiber, while the remaining steps remain unchanged in preparing low-carbon concrete. This is referred to as Comparative Example 5.

[0095] The low-carbon concrete prepared in Examples 1-3 and Comparative Examples 1-5 was poured and cured for 28 days according to standard concrete specimens to obtain each concrete specimen.

[0096] Compressive strength test: The compressive strength of concrete specimens was tested using a pressure testing machine in accordance with the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081-2002).

[0097] Crack resistance test: The square and round crack resistance test was adopted. The low carbon concrete prepared in Examples 1-3 and Comparative Examples 1-5 were poured according to the standard concrete specimens and cured for 3 days. Then, they were transferred to the oven and forced to crack at 120°C for 28 days. The total area of ​​cracks in the concrete specimens was measured.

[0098] Water abrasion resistance test: Refer to the "Test Procedure for Hydraulic Concrete" (DL / T5150-2001), abrasion tester is used to abrade the concrete specimens for 72 hours at a water flow rate of 12 m / s, and the mass loss rate of the concrete specimens is calculated.

[0099] The performance of concrete specimens prepared in Examples 1-3 and Comparative Examples 1-5 was measured three times, and the average value was taken. The results are shown in Table 1.

[0100] Table 1. Performance test results of Examples 1-3 and Comparative Examples 1-5

[0101]

[0102] As can be seen from the data in Table 1, the data in Comparative Example 1 is worse than that in the Example 1, indicating that the addition of superabsorbent polymer, modified calcium aluminum hydrotalcite, and reinforcing fibers in this invention collectively improves the crack resistance and water abrasion resistance of low-carbon concrete. The data from Comparative Examples 2-3 show that the novel superabsorbent polymer prepared in this invention exhibits better "internal curing" effect, crack resistance, and water abrasion resistance in concrete under high-alkali conditions than traditional polyacrylic acid, and the addition of N-vinylpyrrolidone further enhances crack resistance and abrasion resistance. The data from Comparative Example 4 shows that the hydrotalcite without microcrystalline cellulose modification has poor crack resistance and abrasion resistance because its dispersibility is poor, resulting in unsatisfactory reinforcement, crack resistance, and abrasion resistance. This indicates that the introduction of microcrystalline cellulose effectively inhibits crystal growth and improves dispersion, thus effectively improving crack resistance and water abrasion resistance. The data from Comparative Example 5 shows that the modified sisal fiber can significantly improve the crack resistance, water abrasion resistance, and compressive strength of concrete.

[0103] The concrete specimens prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to drying shrinkage tests in accordance with GB / T50082-2009. The tests were performed three times, and the average value was taken. The test results are shown in Table 2.

[0104] Table 2. Results of drying shrinkage performance tests for Examples 1-3 and Comparative Examples 1-3

[0105]

[0106] As can be seen from the data in Table 2, the drying shrinkage values ​​of Examples 1-3 are significantly lower than those of Comparative Example 1, indicating that the synergistic system of superabsorbent polymer, modified calcium aluminum hydrotalcite and reinforcing fiber introduced in this invention has an extremely significant effect on inhibiting concrete drying shrinkage and preventing cracking. As can be seen from the data in Comparative Example 2, the superabsorbent polymer prepared in this invention has a better "internal curing" effect than the traditional ordinary polyacrylic acid superabsorbent polymer. As can be seen from the data in Comparative Example 3, the introduction of N-vinylpyrrolidone can further improve the "internal curing" effect and reduce concrete drying shrinkage.

[0107] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for preparing low-carbon concrete with high crack resistance and water erosion resistance, characterized in that, include: S1: Preparation of superabsorbent polymer; 2-Acrylamide-2-methylpropanesulfonic acid, sodium hydroxide, acrylamide, N-vinylpyrrolidone, and N,N'-methylenebisacrylamide were added to deionized water to prepare a mixed monomer solution. Span80 and Tween-80 were added to cyclohexane, followed by the addition of gelatinized starch and potassium persulfate initiator solution. Finally, the mixed monomer solution was added, and the reaction was carried out to prepare a superabsorbent polymer. S2: Preparation of modified calcium aluminum hydrotalcite; Calcium and aluminum sources were added to deionized water to obtain mixture I. Sodium hydroxide and urea were added to deionized water and then frozen to -1 to -3°C. Microcrystalline cellulose was then added and stirred to obtain mixture II. Mixture I was added dropwise to mixture II at 1-2 mL / min and then reacted to prepare modified calcium aluminum hydrotalcite. S3: Preparation of reinforcing fibers; First, TEOS was used to modify the sisal fiber, and then water-based polyurethane slurry was used for secondary modification to obtain reinforced fiber. S4: Preparation of low-carbon concrete; Prepare concrete raw materials by weight: 300-350 parts cement, 200-250 parts mineral admixtures, 650-750 parts fine aggregate, 1000-1100 parts coarse aggregate, 130-160 parts water, 3-5 parts water-reducing agent, 3-5 parts superabsorbent polymer, 8-10 parts modified calcium aluminum hydrotalcite, and 5-8 parts reinforcing fiber. Mix all raw materials to obtain low-carbon concrete.

2. The method for preparing a low-carbon concrete with high crack resistance and water erosion resistance according to claim 1, characterized in that, S1: The preparation of the superabsorbent polymer includes the following steps: S1.1: Add 2-3 parts by weight of potassium persulfate to 100-120 parts by weight of deionized water, stir and mix to obtain an initiator solution. Add 2-3 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 0.5-0.8 parts by weight of sodium hydroxide, 2-3 parts by weight of acrylamide, 2-3 parts by weight of N-vinylpyrrolidone and 0.05-0.06 parts by weight of N,N'-methylenebisacrylamide to 100-120 parts by weight of deionized water, stir and mix to dissolve to obtain a mixed monomer solution. S1.2: Add 3-5 parts by weight of starch to 50-80 parts by weight of deionized water, and then stir and mix at 85-90℃ for 1-2 hours to obtain gelatinized starch. Add 1-2 parts by weight of Span80 and 1-2 parts by weight of Tween-80 to 92-95 parts by weight of cyclohexane, and stir at 28-30℃ for 20-30 minutes under nitrogen protection. Then add gelatinized starch and initiator solution, stir at 300-320 rpm for 1-2 minutes, and then add mixed monomer solution. React at 70-75℃ under nitrogen atmosphere for 2-3 hours to obtain reactant. S1.3: Pour the reactants into anhydrous ethanol stirred at 1800-2000 rpm, filter to obtain a precipitate, wash the precipitate 3-5 times with anhydrous ethanol, and then dry it at 40-50℃ for 20-24 h to obtain a superabsorbent polymer.

3. The method for preparing low-carbon concrete with high crack resistance and water erosion resistance according to claim 2, characterized in that, S2: The preparation of modified calcium aluminum hydrotalcite includes the following steps: S2.1: Add 4-6 parts by weight of calcium nitrate and 2-3 parts by weight of aluminum nitrate to 30-50 parts by weight of deionized water, and stir and mix at 300-400 rpm for 20-30 min to obtain mixture I; S2.2: Add 7-8 parts by weight of sodium hydroxide and 12-15 parts by weight of urea to 100-120 parts by weight of deionized water, then freeze to -1 to -3°C, then add 0.5-0.8 parts by weight of microcrystalline cellulose, and stir and mix at 400-500 rpm for 20-30 min to obtain mixture II. S2.3: Under stirring at 800-1000 rpm, add mixture I dropwise to mixture II at 1-2 mL / min to make the pH of the mixture 10-11. After the addition is complete, let it stand for 20-24 h, then add it to a high-pressure reactor lined with polytetrafluoroethylene and react in a homogeneous reactor at 80-90℃ for 24-26 h. After the reaction is complete, cool to room temperature, then centrifuge, wash with deionized water 2-4 times, and finally freeze dry to obtain modified calcium aluminum hydrotalcite.

4. The method for preparing a low-carbon concrete with high crack resistance and water erosion resistance according to claim 3, characterized in that, S3: Preparation of reinforcing fibers, specifically including the following steps: S3.1: Add 4-5 parts by weight of TEOS to 40-50 parts by weight of anhydrous ethanol, then add 20-30 parts by weight of sisal fiber, stir and mix to obtain a fiber mixture. Add 16-18 parts by weight of anhydrous ethanol and 4-5 parts by weight of deionized water to 10-12 parts by weight of ammonia solution with a concentration of 28-30wt%, stir and mix at 1000-1200 rpm for 1-3 min, then add the fiber mixture, stir and mix under closed conditions at 350-400 rpm for 2-3 h, then wash with deionized water 3-5 times, dry to obtain modified sisal fiber; S3.2: Tighten the modified sisal fibers and keep them taut. Then immerse them in an aqueous polyurethane slurry containing 3-5% by mass for 15-20 minutes. After that, use a stick to squeeze out the excess liquid in one direction. Then dry them at 80-90℃ for 1-2 hours to obtain the reinforced fibers.

5. The method for preparing a low-carbon concrete with high crack resistance and water erosion resistance according to claim 4, characterized in that, S4: The preparation of low-carbon concrete includes the following steps: S4.1: Prepare concrete raw materials according to the following parts by weight: 300-350 parts cement, 200-250 parts mineral admixtures, 650-750 parts fine aggregate, 1000-1100 parts coarse aggregate, 130-160 parts water, 3-5 parts water-reducing agent, 3-5 parts superabsorbent polymer, 8-10 parts modified calcium aluminum hydrotalcite, and 5-8 parts reinforcing fiber; S4.2: Add the water-reducing agent to water and stir to obtain a water-reducing agent solution. Put the above-mentioned cement, mineral admixtures, fine aggregate, coarse aggregate, modified calcium aluminum hydrotalcite and superabsorbent polymer into a forced mixer and dry mix at a speed of 90-100 r / min for 60-90 s to obtain a mixture. Then add the water-reducing agent solution and reinforcing fibers and stir at a speed of 90-100 r / min for 10-12 min to obtain low-carbon concrete.

6. The method for preparing a low-carbon concrete with high crack resistance and water erosion resistance according to claim 5, characterized in that, The water-reducing agent in step S4.1 is a polycarboxylate-based high-performance water-reducing agent.

7. The method for preparing a low-carbon concrete with high crack resistance and water erosion resistance according to claim 5, characterized in that, The fine aggregate in step S4.1 is one or both of natural river sand and manufactured sand.

8. The method for preparing a low-carbon concrete with high crack resistance and water erosion resistance according to claim 5, characterized in that, The mineral admixture in step S4.1 is prepared by mixing fly ash, slag powder and silica fume in a mass ratio of 1-2:1-2:1-2.

9. The method for preparing a low-carbon concrete with high crack resistance and water erosion resistance according to claim 5, characterized in that, The coarse aggregate in step S4.1 is continuously graded crushed stone with a particle size of 5-25mm.

10. A low-carbon concrete with high crack resistance and resistance to water erosion, characterized in that, It is prepared by the method for preparing a low-carbon concrete with high crack resistance and water erosion resistance as described in any one of claims 1-9.

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