Solid waste-based recycled aggregate concrete and method of making the same

Abstract

The present application relates to cement-based building material technical field, especially to a kind of solid waste-based recycled aggregate concrete and preparation method thereof, the present application is specifically adjusted the composition of cementitious material for recycled aggregate, and modified SAP particle is prepared from the molecular design angle, reduce the mechanical property loss of solid waste-based recycled aggregate concrete caused by water-absorbing resin, high-strength solid waste-based recycled aggregate concrete is prepared, and environmental protection is realized.

Description

Technical Field

[0001] This invention relates to the field of cement-based building materials technology, and in particular to a solid waste-based recycled aggregate concrete and its preparation method. Background Technology

[0002] Solid waste-based recycled aggregate concrete is a new type of low-carbon building material. It is produced by the reaction of recycled aggregate, active silica-alumina materials and activators. It has a three-dimensional network structure with amorphous and quasi-crystalline states. The performance of solid waste-based recycled aggregate concrete is affected by a variety of factors, including the choice of activator, the activity of cementitious materials, and the type of admixtures.

[0003] Superabsorbent polymer (SAP) is an effective internal curing agent that significantly impacts the strength of concrete pore walls and its self-healing properties. SAP improves the internal moisture and pore structure of concrete through its water absorption and release characteristics, thereby enhancing concrete durability and strength. The addition of SAP affects the compressive strength of concrete, and the water absorption and release behavior of SAP has a significant impact on the autogenous shrinkage and early hydration process of concrete. Low molecular weight SAP, while exhibiting better shrinkage reduction effects, better controls the heat release during hydration and strength loss, making it more suitable as an internal curing material than high molecular weight SAP. However, in solid waste-based recycled aggregate concrete, the release of water from SAP leads to increased porosity and decreased density of the SAP pore walls.

[0004] Reference 1 (Lao Jiarong, Huang Zhongcai, Guo Yinchuan, Chen Lin, Shen Aiqin, Yang Jingyu. Study on shrinkage and mechanical properties of SAP-cured pavement concrete [J]. Bulletin of the Chinese Ceramic Society, 2021, 40(2): 676-682.) reported that the addition of SAP can significantly reduce the van der Waals forces between capillary pores in concrete, inhibit the shrinkage strain of concrete; and can timely compensate for the moisture content of concrete when the internal humidity decreases, so that the relative humidity can be maintained above 90% within 28 days; the incorporation of SAP can improve the degree of cement hydration, generate more hydration products, improve the internal structure of concrete, enhance its density, and reduce the length and width of microcracks inside concrete, thereby increasing the relative humidity inside concrete to a certain extent, thus improving the mechanical strength of concrete and reducing its shrinkage deformation.

[0005] Reference 2 (Chen Huaxin, Zheng Suining, He Rui, et al. Review on the water absorption and release behavior of SAP and its influence mechanism on concrete performance [J]. China Journal of Highway and Transport, 2024, 37(1):1-19.DOI:10.19721 / j.cnki.1001-7372.2024.01.001.) published the ion network theory, solution thermodynamics theory and gel phase transition theory, which can well explain the water absorption and release behavior of SAP in different solutions. The content of adsorbed water and capillary water inside SAP is the key factor affecting the water release cycle of SAP. The water absorption and release characteristics of SAP determine the distribution of water inside concrete. The microstructure and macro properties of SAP-cured concrete are comprehensively affected by parameters such as SAP dosage, particle size and additional water absorption. Appropriate parameters can make the hydration products fill the pores generated by SAP water release, refine the pore structure of concrete, improve density, improve mechanical properties and enhance durability. SAP can also improve the self-healing ability of concrete, enhance its resistance to spalling, and enable algae colonization on concrete.

[0006] The shortcomings of the above technologies are:

[0007] (1) The study in Reference 1 shows that the incorporation of SAP can improve the degree of cement hydration, generate more hydration products, improve the internal structure of concrete, and enhance its density. However, the traces left in the concrete after SAP release may increase the porosity. These pores may reduce the density of the concrete, thereby affecting its durability and mechanical properties. Furthermore, although the dosage and particle size of SAP have a significant impact on the mechanical properties of concrete, excessively high SAP dosage may lead to a decrease in concrete strength.

[0008] (2) Reference 2 shows that appropriate parameters can allow hydration products to fill the pores created by SAP water release, refine the concrete pore structure, improve density, enhance mechanical properties, and increase durability. However, excessive water release may create larger pores inside the concrete, thereby reducing its density. This may affect the long-term performance of the concrete, especially under load or harsh environmental conditions. Although SAP can reduce the drying shrinkage of concrete, the pores remaining after water release may affect the long-term stability and durability of the concrete. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a solid waste-based recycled aggregate concrete. Specifically, this invention specifically adjusts the composition of the cementitious material for the recycled aggregate and prepares modified SAP particles from a molecular design perspective to reduce the mechanical property loss of solid waste-based recycled aggregate concrete caused by water-absorbing resin, thereby preparing high-strength solid waste-based recycled aggregate concrete and achieving environmental protection and waste utilization.

[0010] Specifically, the solid waste-based recycled aggregate concrete of the present invention is composed of the following raw materials in parts by weight: 300-350 parts mineral powder, 100-120 parts fly ash, 80-100 parts industrial by-product gypsum, 20-30 parts desulfurization slag powder from molten iron, 700-800 parts recycled fine aggregate, 1000-1050 parts recycled coarse aggregate, 5-8 parts water-reducing agent, 3-6 parts modified SAP particles, 1-5 parts retarder, and 150-160 parts water.

[0011] Preferably, the modified SAP particles are obtained by crosslinking and polymerization of 90-100 parts acrylic acid, 10-15 parts acrylamide, and 2-4 parts triphenylacetic acid-2-butenyl ester with 3-5 parts crosslinking agent.

[0012] Recycled aggregate particles are not rounded, have many sharp edges, and are adhered to the surface by hydrated cement paste, exhibiting a certain degree of water absorption. This invention, starting from both the cementitious material system and the molecular design of modified SAP particles, has undergone extensive experiments. Specifically, mineral powder and fly ash are used as the main silica-alumina active raw materials, and industrial by-product gypsum and molten iron desulfurization slag powder are used as activators. The activation process is mainly sulfate activation, supplemented by molten iron desulfurization slag powder. Experimental results show that molten iron desulfurization slag powder has high alkalinity and contains sulfate. The sulfate activation composite part is high-calcium-alkali activation, which is more suitable for improving the mechanical properties of recycled aggregate concrete with internal curing effect. In the preparation process of modified SAP particles, the molecular structure is optimized by using part of triphenylacetic acid-2-butenyl ester on the acrylic acid-acrylamide main structure, which has a water absorption-release effect suitable for recycled aggregate. Combined with the sulfate-high-calcium-alkali activator of this invention, it can effectively inhibit the decline in mechanical properties of recycled aggregate concrete caused by water-absorbing resin.

[0013] Preferably, the mineral powder is at least one of S95 grade and S105 grade.

[0014] Preferably, the fly ash is at least one of Grade I or Grade II fly ash.

[0015] Preferably, the industrial by-product gypsum is at least one of desulfurized gypsum, phosphogypsum, and fluorogypsum.

[0016] Preferably, the particle size of the desulfurization slag powder from molten iron is 5-20 μm.

[0017] Preferably, the recycled fine aggregate and recycled coarse aggregate are obtained by crushing and screening construction waste.

[0018] Preferably, the fineness modulus of the recycled fine aggregate is 2.0-2.6.

[0019] Preferably, the recycled coarse aggregate has a particle size of 5-20 mm.

[0020] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent.

[0021] Preferably, the modified SAP preparation process is as follows:

[0022] 1) Mix 0.6-1 parts of the initiator with 49-60 parts of water until homogeneous to obtain an initiator solution; mix 1.5-2 parts of the reducing agent with 40-50 parts of water until homogeneous to obtain a reducing agent solution.

[0023] 2) Mix 90-100 parts of acrylic acid, 10-15 parts of acrylamide, 2-4 parts of triphenylacetic acid-2-butenyl ester, and 240-260 parts of water evenly, adjust the pH value to 6-7, add 3-5 parts of crosslinking agent, stir evenly, add initiator solution and reducing agent solution dropwise to carry out polymerization reaction, obtain gel, wash the gel, and pulverize it to 20-40μm to obtain the final product.

[0024] Preferably, the crosslinking agent is N,N'-methylenebisacrylamide.

[0025] Preferably, the initiator is ammonium persulfate and the reducing agent is sodium sulfite.

[0026] Preferably, the gel is cleaned with deionized water.

[0027] Preferably, the retarder is at least one of tartaric acid, sodium gluconate, and boric acid.

[0028] This invention also relates to a method for preparing the aforementioned solid waste-based recycled aggregate concrete, specifically comprising the following steps: weighing each raw material according to its weight proportions, and mixing the raw materials evenly to obtain the final product. This invention does not limit the mixing order of the raw materials; commonly used step-by-step concrete mixing processes in the art are all within the protection scope of this invention's preparation method, as long as the raw materials can be mixed evenly and the concrete has good workability.

[0029] This invention has the following technical advantages:

[0030] 1. This invention uses mineral powder and fly ash as active silica-alumina raw materials, and utilizes industrial by-product gypsum and desulfurization slag powder from molten iron for activation, combined with modified SAP particles, to enhance the mechanical properties of solid waste-based recycled aggregate concrete.

[0031] 2. This invention utilizes a large amount of industrial solid waste, which is environmentally friendly and has good economic value and environmental benefits.

[0032] 3. The preparation process of this invention is simple and easy to promote in engineering. Detailed Implementation

[0033] To characterize the technical effects of this invention, solid waste-based recycled aggregate concrete was prepared, concrete specimens were prepared, and performance tests were conducted after standard curing for 28 days. During the experiment, S95 grade mineral powder was used, Grade II fly ash was used, the particle size of desulfurized slag powder from molten iron was 5-20 μm, the fineness modulus of recycled fine aggregate was 2.5, the particle size of recycled coarse aggregate was 5-20 mm in continuous gradation, polycarboxylate superplasticizer was used, and the modified SAP particles were prepared using the process of this invention. Triphenylacetic acid-2-butenyl ester was obtained by esterification of 2-buten-1-ol and triphenylacetic acid. In the following examples and comparative examples, only simplified formulations are used.

[0034] Example 1

[0035] Solid waste-based recycled aggregate concrete is composed of the following raw materials in parts by weight: 320 parts mineral powder, 120 parts fly ash, 90 parts desulfurized gypsum, 25 parts desulfurized slag powder from molten iron, 780 parts recycled fine aggregate, 1020 parts recycled coarse aggregate, 8 parts water-reducing agent, 5 parts modified SAP particles, 3 parts sodium gluconate, and 156 parts water. The modified SAP particles are obtained by crosslinking and polymerizing 100 parts acrylic acid, 11 parts acrylamide, and 3 parts triphenylacetic acid-2-butenyl ester with 5 parts N,N'-methylenebisacrylamide.

[0036] The concrete was tested and found to have a 28-day compressive strength of 58.2 MPa, a 28-day flexural strength of 5.7 MPa, and a shrinkage rate of 0.017%.

[0037] Example 2

[0038] Solid waste-based recycled aggregate concrete is composed of the following raw materials in parts by weight: 340 parts mineral powder, 100 parts fly ash, 100 parts desulfurized gypsum, 20 parts desulfurized slag powder from molten iron, 780 parts recycled fine aggregate, 1020 parts recycled coarse aggregate, 8 parts water-reducing agent, 6 parts modified SAP particles, 4 parts sodium gluconate, and 156 parts water. The modified SAP particles are obtained by crosslinking and polymerization of 95 parts acrylic acid, 13 parts acrylamide, and 3 parts triphenylacetic acid-2-butenyl ester with 4 parts N,N'-methylenebisacrylamide.

[0039] The concrete was tested and found to have a 28-day compressive strength of 59.6 MPa, a 28-day flexural strength of 5.9 MPa, and a shrinkage rate of 0.015%.

[0040] Comparative Example 1

[0041] Solid waste-based recycled aggregate concrete is composed of the following raw materials in parts by weight: 340 parts mineral powder, 100 parts fly ash, 100 parts desulfurized gypsum, 20 parts desulfurized slag powder from molten iron, 780 parts recycled fine aggregate, 1020 parts recycled coarse aggregate, 8 parts water-reducing agent, 4 parts sodium gluconate, and 156 parts water.

[0042] The concrete was tested and found to have a 28-day compressive strength of 47.5 MPa, a 28-day flexural strength of 4.6 MPa, and a shrinkage rate of 0.045%.

[0043] Comparative Example 2

[0044] Solid waste-based recycled aggregate concrete is composed of the following raw materials in parts by weight: 340 parts mineral powder, 100 parts fly ash, 100 parts desulfurized gypsum, 20 parts desulfurized slag powder from molten iron, 780 parts recycled fine aggregate, 1020 parts recycled coarse aggregate, 8 parts water-reducing agent, 6 parts acrylic-acrylamide type SAP particles, 4 parts sodium gluconate, and 156 parts water.

[0045] The concrete was tested and found to have a 28-day compressive strength of 42.4 MPa, a 28-day flexural strength of 4.3 MPa, and a shrinkage rate of 0.022%.

[0046] Comparative Example 3

[0047] Solid waste-based recycled aggregate concrete is composed of the following raw materials in parts by weight: 340 parts fly ash, 100 parts mineral powder, 100 parts desulfurized gypsum, 20 parts desulfurized slag powder from molten iron, 780 parts recycled fine aggregate, 1020 parts recycled coarse aggregate, 8 parts water-reducing agent, 6 parts modified SAP particles, 4 parts sodium gluconate, and 156 parts water. The modified SAP particles are obtained by crosslinking and polymerization of 95 parts acrylic acid, 13 parts acrylamide, and 3 parts triphenylacetic acid-2-butenyl ester with 4 parts N,N'-methylenebisacrylamide.

[0048] The concrete was tested and found to have a 28-day compressive strength of 52.3 MPa, a 28-day flexural strength of 5.1 MPa, and a shrinkage rate of 0.020%.

[0049] Comparative Example 4

[0050] Solid waste-based recycled aggregate concrete is composed of the following raw materials in parts by weight: 340 parts mineral powder, 100 parts fly ash, 100 parts desulfurized gypsum, 20 parts carbide slag, 780 parts recycled fine aggregate, 1020 parts recycled coarse aggregate, 8 parts water-reducing agent, 6 parts modified SAP particles, 4 parts sodium gluconate, and 156 parts water. The modified SAP particles are obtained by crosslinking and polymerization of 95 parts acrylic acid, 13 parts acrylamide, and 3 parts triphenylacetic acid-2-butenyl ester with 4 parts N,N'-methylenebisacrylamide.

[0051] The concrete was tested and found to have a 28-day compressive strength of 50.7 MPa, a 28-day flexural strength of 4.9 MPa, and a shrinkage rate of 0.024%.

[0052] Comparative Example 5

[0053] Solid waste-based recycled aggregate concrete is composed of the following raw materials in parts by weight: 340 parts mineral powder, 100 parts fly ash, 100 parts carbide slag, 20 parts water glass, 780 parts recycled fine aggregate, 1020 parts recycled coarse aggregate, 8 parts water-reducing agent, 6 parts modified SAP particles, 4 parts sodium gluconate, and 156 parts water. The modified SAP particles are obtained by crosslinking and polymerization of 95 parts acrylic acid, 13 parts acrylamide, and 3 parts triphenylacetic acid-2-butenyl ester with 4 parts N,N'-methylenebisacrylamide.

[0054] The concrete was tested and found to have a 28-day compressive strength of 46.6 MPa, a 28-day flexural strength of 4.5 MPa, and a shrinkage rate of 0.029%.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A solid waste based recycled aggregate concrete, characterized in that The modified SAP granules are prepared by the following process: 1) 0.6-1 parts of initiator is mixed with 49-60 parts of water to obtain an initiator solution, and 1.5-2 parts of reducing agent is mixed with 40-50 parts of water to obtain a reducing agent solution, 2) 90-100 parts of acrylic acid, 10-15 parts of acrylamide, 2-4 parts of triphenyl acetic acid-2-butene ester and 240-260 parts of water are mixed uniformly, the pH value is adjusted to 6-7, 3-5 parts of crosslinking agent is added and stirred uniformly, the initiator solution and the reducing agent solution are added dropwise for polymerization, the gel is cleaned and crushed to 20-40 microns to obtain the modified SAP granules. The mineral powder is at least one of S95 grade and S105 grade.

2. The solid waste based recycled aggregate concrete as claimed in claim 1, wherein, The fly ash is at least one of grade I and grade II fly ash.

3. The solid waste based recycled aggregate concrete as claimed in claim 1, wherein, The industrial by-product gypsum is at least one of desulfurization gypsum, phosphogypsum and fluorogypsum.

4. The solid waste based recycled aggregate concrete as claimed in claim 1, wherein, The particle size of the hot metal desulfurization slag powder is 5-20 microns.

5. The solid waste based recycled aggregate concrete as claimed in claim 1, wherein, The fineness modulus of the recycled fine aggregate is 2.0-2.6, and the particle size of the recycled coarse aggregate is 5-20 mm.

6. The solid waste based recycled aggregate concrete as claimed in claim 1, wherein, The water reducing agent is polycarboxylic acid water reducing agent.

7. The solid waste based recycled aggregate concrete as claimed in claim 1, wherein, The retarder is at least one of tartaric acid, sodium gluconate and boric acid.

8. The solid waste based recycled aggregate concrete as claimed in claim 1, wherein, The process comprises the following steps: each raw material is weighed by weight parts, and each raw material is mixed uniformly to obtain the product.

9. The method of producing solid waste based recycled aggregate concrete as claimed in any one of claims 1 to 8, wherein, ​