Recycled micro-fines concrete and method for producing the same

Abstract

This application relates to the field of recycled concrete technology, and discloses a recycled micro-powder concrete and its preparation method. A recycled micro-powder concrete comprises the following raw materials in parts by weight: 210-310 parts natural aggregate, 550-810 parts recycled aggregate, 120-200 parts modified silica fume, 300-440 parts cement, 80-150 parts additives, 10-30 parts water-reducing agent, 580-700 parts sand, and 110-162 parts water; wherein the modified silica fume is prepared from a titanate coupling agent, sorbitol, and silica fume in a weight ratio of 1-5:2.2-6:89-97.8. This application uses specific raw materials and proportions to prepare recycled concrete with excellent comprehensive performance. By introducing modified silica fume, this application effectively strengthens the interface area between recycled concrete and natural concrete, significantly improving the crack resistance of the recycled concrete.

Description

Technical Field

[0001] This application relates to the field of recycled concrete technology, and in particular to a recycled micro-powder concrete and its preparation method. Background Technology

[0002] With the acceleration of urbanization, the treatment and resource utilization of construction waste has become increasingly important. The large-scale accumulation of construction waste not only occupies land and pollutes the environment, but may also negatively impact the city's image and residents' lives. At the same time, with the dwindling resources of natural aggregates, finding sustainable alternative materials is also crucial.

[0003] Recycled aggregates, as a sustainable alternative material, offer significant environmental and economic benefits. By processing waste concrete through crushing and screening, it can be transformed into recycled aggregates to replace natural aggregates in concrete. This not only reduces dependence on natural resources but also lowers the cost of construction waste disposal, achieving resource recycling.

[0004] The use of recycled aggregates not only reduces the environmental burden but also improves the performance of concrete. Studies have shown that concrete using recycled aggregates exhibits better compressive strength, durability, and workability. Furthermore, the use of recycled aggregates can promote the green transformation of the construction industry and drive the development of a circular economy.

[0005] However, recycled aggregates suffer internal damage and microcracks during the crushing process. Furthermore, the rough and porous nature of recycled aggregates results in weaker interfacial bonding with cement paste compared to natural aggregates. This weaker interfacial bonding creates an interfacial transition zone within the concrete, making it easier for stress to concentrate in these areas under load, leading to cracking. Additionally, the difference in water absorption rates between recycled and natural aggregates causes uneven moisture distribution within the concrete, resulting in uneven shrinkage during hardening and further cracking.

[0006] Therefore, there is an urgent need to provide a recycled concrete with high strength and excellent crack resistance. Summary of the Invention

[0007] In order to solve at least one of the above-mentioned technical problems and develop a recycled concrete with high strength and excellent crack resistance, this application provides a recycled micro-powder concrete and its preparation method.

[0008] On the one hand, the recycled micro-powder concrete provided in this application includes the following raw materials in parts by weight: 210-310 parts of natural aggregate, 550-810 parts of recycled aggregate, 120-200 parts of modified silica fume, 300-440 parts of cement, 80-150 parts of additives, 10-30 parts of water-reducing agent, 580-700 parts of sand, and 110-162 parts of water;

[0009] The modified silica fume is prepared by comprising a titanate coupling agent, sorbitol and silica fume in a weight ratio of 1-5:2.2-6:89-96.8.

[0010] By adopting the above technical solution, this application uses specific raw materials and proportions to prepare recycled concrete with excellent comprehensive performance and significantly improves the crack resistance of recycled concrete.

[0011] By introducing modified silica fume, this application effectively strengthens the interface area between recycled concrete and natural concrete, significantly improving the crack resistance of recycled concrete; at the same time, it not only enhances the interface properties of recycled concrete, but also has a positive impact on its overall strength and durability; and it makes full use of recycled aggregates in construction waste, realizing the effective recycling of resources, which meets the requirements of green building and sustainable development.

[0012] Modifying silica fume with titanate coupling agents and sorbitol can effectively solve the interface problem between recycled and natural aggregates and improve the crack resistance of recycled concrete. Among them, titanate coupling agents have excellent coupling properties and can effectively improve the interfacial bonding performance between silica fume and cement paste. Sorbitol, as a polyhydroxy compound, can enhance the dispersibility and stability of silica fume, further improving its effect in concrete.

[0013] Optionally, the weight ratio of the modified silica fume to the sum of the weights of the natural aggregate and the recycled aggregate is 0.107-0.263.

[0014] Preferably, the weight ratio of the modified silica fume to the sum of the weights of the natural aggregate and the recycled aggregate is 0.157-0.210.

[0015] Preferably, the weight ratio of the modified silica fume to the sum of the weights of the natural aggregate and the recycled aggregate is 0.210.

[0016] By adopting the above technical solution, this application uses a specific ratio of the weight of modified silica fume to the sum of the weights of the natural aggregate and the recycled aggregate. The modified silica fume can effectively fill and strengthen the interface area between the recycled aggregate and the natural aggregate, improve the bond strength between the two, and at the same time, an appropriate amount of modified silica fume can also refine the pore structure of concrete, improve the density and durability of concrete.

[0017] Optionally, the weight ratio of the additive to the weight of the recycled aggregate is 0.098-0.272.

[0018] Preferably, the weight ratio of the additive to the weight of the recycled aggregate is 0.181.

[0019] By adopting the above technical solution, this application uses a specific ratio of additives to recycled aggregates, which can effectively modify recycled aggregates, optimize the interfacial properties between recycled aggregates and natural aggregates in recycled concrete, and significantly improve its crack resistance.

[0020] Optionally, the additive comprises the following raw materials in weight percentages: 8-15% aromatic oil, 3-10% sodium hydroxide, 20-35% rosin resin, 10-25% EDPC and 2-10% titanate coupling agent, with the balance being epichlorohydrin.

[0021] By adopting the above technical solutions, the titanate coupling agent in the additive has strong interfacial activity. It can form a thin film on the surface of recycled aggregate, enhancing the adhesion between recycled aggregate and cement paste. At the same time, the titanate coupling agent can also react chemically with components such as calcium hydroxide in cement paste to form a more stable interfacial layer. The added aromatic oil and rosin resin can improve the wettability of recycled aggregate, making it easier for it to be coated by cement paste. In addition, these components can also reduce friction and agglomeration between recycled aggregates and improve their dispersibility. The EDPC and epichlorohydrin in the additive have certain crack repair functions. When microcracks appear in recycled concrete, these components can penetrate into the cracks and react chemically to form new chemical bonds, thereby repairing the cracks and enhancing the crack resistance of recycled concrete.

[0022] Preferably, the rosin resin has a weight percentage of 25-30%, and the EDPC has a weight percentage of 15-20%.

[0023] By adopting the above technical solution, this application uses a specific ratio of rosin resin and EDPC to effectively enhance the interfacial bonding force between recycled aggregate and cement paste, improve the wettability and dispersibility of recycled aggregate, and enhance the crack resistance of recycled concrete.

[0024] Optionally, the recycled aggregate has an average particle size of 10-18 mm and an apparent density of 2652 kg / m³. 3 The bulk density is 1286 kg / m³. 3 The water absorption rate is 3.8%, and the crushing index is 16.3%.

[0025] Optionally, the water-reducing agent is a polycarboxylate water-reducing agent.

[0026] On the other hand, this application provides a method for preparing recycled micro-powder concrete, which includes the following steps:

[0027] S1. Take the additives and recycled aggregates, mix and stir them, then add the modified silica fume and continue mixing and stirring to prepare a recycled aggregate mixture;

[0028] S2. Take natural aggregate and the aforementioned recycled aggregate mixture, mix and stir, then add cement, water-reducing agent, sand and water and continue mixing and stirring to obtain the aforementioned recycled micro powder concrete.

[0029] By adopting the above technical solution, the preparation method of recycled micro-powder concrete of this application is simple to operate and can be industrialized. At the same time, this application uses specific additives to modify recycled aggregates, and then adds specific modified silica fume to mix evenly with the modified recycled aggregates, which effectively enhances the interfacial adhesion between recycled aggregates and cement paste, improves the wettability and dispersibility of recycled aggregates, and repairs micro-cracks in recycled concrete, effectively solving the problem of easy cracking of recycled concrete.

[0030] Optionally, in S1, the method for preparing modified silica fume includes the following steps: after drying the silica fume, mixing and stirring it with a titanate coupling agent, then adding a sorbitol solution, mixing and stirring at a temperature of 55-60℃ for 1-2 hours, and then drying and sieving to obtain modified silica fume.

[0031] Optionally, in S1, the preparation method of the additive includes the following steps: taking aromatic oil, rosin resin and epichlorohydrin, mixing and stirring, then adding sodium hydroxide and mixing and stirring to prepare a mixed solution, taking EDPC and titanate coupling agent and adding them to the mixed solution in sequence, and continuing to mix and stir to obtain the modifier.

[0032] In summary, the present invention has at least one of the following beneficial technical effects:

[0033] 1. This application uses specific raw materials and proportions to prepare recycled concrete with excellent comprehensive performance, significantly improving the performance of recycled concrete;

[0034] 2. By introducing modified silica fume, this application effectively strengthens the interface area between recycled concrete and natural concrete, significantly improving the crack resistance of recycled concrete; at the same time, it not only enhances the interface properties of recycled concrete, but also has a positive impact on its overall strength, durability and deformation properties; and it makes full use of recycled aggregates in construction waste, realizing the effective recycling of resources, which meets the requirements of green building and sustainable development.

[0035] 3. Modifying silica fume with titanate coupling agents and sorbitol can effectively solve the interface problem between recycled aggregates and natural aggregates, and improve the crack resistance of recycled concrete. Among them, titanate coupling agents have excellent coupling properties, which can effectively improve the interfacial bonding performance between silica fume and cement paste; while sorbitol, as a polyhydroxy compound, can enhance the dispersibility and stability of silica fume, further improving its effect in concrete.

[0036] 4. The preparation method of recycled micro-powder concrete in this application is simple to operate and can be industrialized. At the same time, this application uses specific additives to modify recycled aggregates, and then adds specific modified silica fume to mix evenly with the modified recycled aggregates, which effectively enhances the interfacial adhesion between recycled aggregates and cement paste, improves the wettability and dispersibility of recycled aggregates, and repairs micro-cracks in recycled concrete, effectively solving the problem of easy cracking of recycled concrete. Detailed Implementation

[0037] The present application will be further described in detail below with reference to the embodiments.

[0038] This application designs a recycled micro-powder concrete, comprising the following raw materials in parts by weight: 210-310 parts of natural aggregate, 550-810 parts of recycled aggregate, 120-200 parts of modified silica fume, 300-440 parts of cement, 80-150 parts of additives, 10-30 parts of water-reducing agent, 580-700 parts of sand, and 110-162 parts of water.

[0039] The modified silica fume is prepared by comprising a titanate coupling agent, sorbitol and silica fume in a weight ratio of 1-5:2.2-6:89-97.8.

[0040] This application provides a method for preparing recycled micro-powder concrete, comprising the following steps:

[0041] S1. Take the additives and recycled aggregates, mix and stir them, then add the modified silica fume and continue mixing and stirring to prepare a recycled aggregate mixture;

[0042] S2. Take natural aggregate and the aforementioned recycled aggregate mixture, mix and stir, then add cement, water-reducing agent, sand and water and continue mixing and stirring to obtain the aforementioned recycled micro powder concrete. Specific Implementation

[0044] The raw materials used in this application are as follows. Unless otherwise specified, all raw materials used in this application are commercially available:

[0045] Sand: Fineness modulus is 2.3;

[0046] Water: Selected from tap water;

[0047] Natural aggregate: average particle size is 4-5cm;

[0048] Recycled aggregate: average particle size 10-18mm, apparent density 2652kg / m³ 3 The bulk density is 1286 kg / m³. 3 The water absorption rate is 3.8%, and the crushing index is 16.3%.

[0049] Cement: 42.5 Portland cement;

[0050] Titanate coupling agent: Wuhan Nengren Pharmaceutical Chemical Co., Ltd., CAS No. 109037-78-7;

[0051] Sorbitol: CAS No. 50-70-4;

[0052] Silica fume: Shandong Yonglida New Material Technology Co., Ltd., CAS No. 69012-64-2;

[0053] Aromatic oil: Shandong Yonglida New Material Technology Co., Ltd., aromatic content 75-80%, viscosity at 100℃ 20-50 mm. 2 / s; Sodium hydroxide: 99% purity;

[0054] Rosin resin: Hubei Xinkang Pharmaceutical Chemical Co., Ltd., CAS No. 85026-55-7;

[0055] EDPC (N-ethyl-2,3-dioxopiperazinylformyl chloride): Nanjing Bermuda Biotechnology Co., Ltd., purity 99%; Epichlorohydrin: CAS No. 106-89-8;

[0056] 3-Mercaptopropionic acid: CAS No. 107-96-0.

[0057] Testing items and methods:

[0058] Compressive strength: Refer to GB / T50081-2019 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete";

[0059] Crack resistance test: GB / T50082-2009 Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete.

[0060] Examples 1-8

[0061] The specific raw material weights for the recycled micro-powder concrete in Examples 1-8 are shown in Table 1.

[0062] Table 1

[0063]

[0064] The modified silica fume is prepared from titanate coupling agent, sorbitol and silica fume; the water-reducing agent is 3-mercaptopropionic acid.

[0065] The additives include the following raw materials: aromatic oil, sodium hydroxide, rosin resin, EDPC and titanate coupling agent, with the balance being epichlorohydrin. The specific weight percentages are shown in Table 2.

[0066] Table 2

[0067]

[0068] The additives in Examples 4-8 are the same as those in Example 2.

[0069] Example 1

[0070] A method for preparing recycled micro-powder concrete includes the following steps:

[0071] S1. Take the additives and recycled aggregates, mix and stir them, then add the modified silica fume and continue mixing and stirring to prepare a recycled aggregate mixture;

[0072] S2. Take natural aggregate and the aforementioned recycled aggregate mixture, mix and stir, then add cement, water-reducing agent, sand and water and continue mixing and stirring to obtain the aforementioned recycled micro powder concrete;

[0073] In S1, the method for preparing modified silica fume includes the following steps: after drying the silica fume, it is mixed and stirred with a titanate coupling agent, and then a 40wt% sorbitol solution is added. After mixing and stirring at a temperature of 55℃ for 2 hours, the mixture is dried and sieved to obtain modified silica fume; wherein, the weight ratio of titanate coupling agent, sorbitol and silica fume is 1:2.2:96.8.

[0074] The preparation method of the additive includes the following steps: after mixing and stirring aromatic oil, rosin resin and epichlorohydrin, sodium hydroxide is added and mixed and stirred to prepare a mixed solution. EDPC and titanate coupling agent are added to the mixed solution in sequence, and after continuing to mix and stir, the modifier is obtained.

[0075] Example 2

[0076] A method for preparing recycled micro-powder concrete includes the following steps:

[0077] S1. Take the additives and recycled aggregates, mix and stir them, then add the modified silica fume and continue mixing and stirring to prepare a recycled aggregate mixture;

[0078] S2. Take natural aggregate and the aforementioned recycled aggregate mixture, mix and stir, then add cement, water-reducing agent, sand and water and continue mixing and stirring to obtain the aforementioned recycled micro powder concrete;

[0079] In S1, the method for preparing modified silica fume includes the following steps: after drying the silica fume, it is mixed and stirred with a titanate coupling agent, and then a 40wt% sorbitol solution is added. After mixing and stirring at a temperature of 60℃ for 1 hour, the mixture is dried and sieved to obtain modified silica fume; wherein, the weight ratio of titanate coupling agent, sorbitol and silica fume is 1:2.2:96.8.

[0080] The preparation method of the additive includes the following steps: after mixing and stirring aromatic oil, rosin resin and epichlorohydrin, sodium hydroxide is added and mixed and stirred to prepare a mixed solution. EDPC and titanate coupling agent are added to the mixed solution in sequence, and after continuing to mix and stir, the modifier is obtained.

[0081] Example 3

[0082] A method for preparing recycled micro-powder concrete includes the following steps:

[0083] S1. Take the additives and recycled aggregates, mix and stir them, then add the modified silica fume and continue mixing and stirring to prepare a recycled aggregate mixture;

[0084] S2. Take natural aggregate and the aforementioned recycled aggregate mixture, mix and stir, then add cement, water-reducing agent, sand and water and continue mixing and stirring to obtain the aforementioned recycled micro powder concrete;

[0085] In S1, the preparation method of modified silica fume includes the following steps: after drying the silica fume, it is mixed and stirred with a titanate coupling agent, and then a 40wt% sorbitol solution is added. After mixing and stirring at a temperature of 58℃ for 1.5h, it is dried and sieved to obtain modified silica fume; wherein, the weight ratio of titanate coupling agent, sorbitol and silica fume is 1:2.2:96.8.

[0086] The preparation method of the additive includes the following steps: after mixing and stirring aromatic oil, rosin resin and epichlorohydrin, sodium hydroxide is added and mixed and stirred to prepare a mixed solution. EDPC and titanate coupling agent are added to the mixed solution in sequence, and after continuing to mix and stir, the modifier is obtained.

[0087] Examples 4-8 show a method for preparing recycled micro-powder concrete that is consistent with the method in Example 2.

[0088] Comparative Example 1

[0089] Based on Example 2, except that an equal amount of silica fume was used to replace the modified silica fume, the other components and preparation methods were the same as in Example 2.

[0090] Comparative Example 2

[0091] Based on Example 2, except that an equal amount of titanate coupling agent is used to replace sorbitol, the other components and preparation methods are the same as in Example 2.

[0092] Comparative Example 3

[0093] Based on Example 2, except that an equal amount of sorbitol was used to replace the titanate coupling agent, the other components and preparation methods were the same as in Example 2.

[0094] Comparative Example 4

[0095] Based on Example 2, except that an equal amount of rosin resin was used to replace EDPC, the other components and preparation methods were the same as in Example 2.

[0096] Comparative Example 5

[0097] Based on Example 2, except that an equal amount of EDPC was used to replace rosin resin, the other components and preparation methods were the same as in Example 2.

[0098] The performance of the recycled concrete prepared in Examples 1-8 and Comparative Examples 1-5 was tested, and the test results are shown in Table 3.

[0099] Table 3

[0100]

[0101] As shown in Table 3 of Examples 1-8 and Comparative Examples 1-5, the recycled concrete prepared by this application using specific raw materials and proportions exhibits excellent comprehensive performance and significantly improves the crack resistance of recycled concrete. By introducing modified silica fume, the interface area between recycled concrete and natural concrete can be effectively strengthened, significantly improving the crack resistance of recycled concrete. Furthermore, it not only enhances the interface properties of recycled concrete but also positively impacts its overall strength, durability, and deformation properties. The inventors discovered that modifying silica fume with titanate coupling agents and sorbitol can effectively solve the interface problem between recycled aggregates and natural aggregates, improving the crack resistance of recycled concrete. Among these, titanate coupling agents have excellent coupling properties, effectively improving the interfacial bonding performance between silica fume and cement paste. Sorbitol, as a polyhydroxy compound, can enhance the dispersibility and stability of silica fume, further improving its effect in concrete.

[0102] Examples 9-10

[0103] Based on Example 7, except for the raw materials of modified silica fume, the weight ratio of titanate coupling agent, sorbitol and silica fume are different, the other components and preparation methods are the same as in Example 7.

[0104] Example 9

[0105] The weight ratio of titanate coupling agent, sorbitol and silica fume is 3:5:92.

[0106] Example 10

[0107] The weight ratio of titanate coupling agent, sorbitol and silica fume is 5:6:89.

[0108] Examples 11-14

[0109] Based on Example 9, except for the weight percentage of rosin resin and EDPC in the additives, the other components and preparation methods are the same as in Example 9.

[0110] Example 11

[0111] Rosin resin 25%, EDPC 20%.

[0112] Example 12

[0113] Rosin resin 28%, EDPC 17%.

[0114] Example 13

[0115] Rosin resin 30%, EDPC 15%.

[0116] Example 14

[0117] Rosin resin 35%, EDPC 10%.

[0118] The recycled concrete prepared in Examples 9-14 was subjected to performance testing, and the test results are shown in Table 4.

[0119] Table 4

[0120]

[0121] As can be seen from Examples 9-10, 7 and Table 4, the recycled concrete prepared by the present application using modified silica fume with a better proportion has superior comprehensive performance.

[0122] As can be seen from Examples 11-14, 9 and Table 4, the present application uses a better ratio of rosin resin and EDPC, which can effectively enhance the interfacial bonding between recycled aggregate and cement paste, improve the wettability and dispersibility of recycled aggregate, and improve the crack resistance of recycled concrete.

[0123] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the principles of this application should be covered within the scope of protection of this application.

Claims

1. A type of recycled micro-powder concrete, characterized in that, The raw materials include the following parts by weight: 210-310 parts natural aggregate, 550-810 parts recycled aggregate, 120-200 parts modified silica fume, 300-440 parts cement, 80-150 parts additives, 10-30 parts water-reducing agent, 580-700 parts sand, and 110-162 parts water. The modified silica fume is prepared by comprising a titanate coupling agent, sorbitol, and silica fume in a weight ratio of 1-5:2.2-6:89-96.8; the preparation method of the modified silica fume includes the following steps: after drying the silica fume, it is mixed and stirred with the titanate coupling agent, then a sorbitol solution is added, and the mixture is stirred at a temperature of 55-60℃ for 1-2 hours, then dried and sieved to obtain the modified silica fume; The additive comprises the following raw materials by weight percentage: 8-15% aromatic oil, 3-10% sodium hydroxide, 20-35% rosin resin, 10-25% EDPC, and 2-10% titanate coupling agent, with the balance being epichlorohydrin; the preparation method of the additive includes the following steps: mixing and stirring aromatic oil, rosin resin, and epichlorohydrin, then adding sodium hydroxide and mixing and stirring to prepare a mixed solution; adding EDPC and titanate coupling agent sequentially to the mixed solution, and continuing to mix and stir to obtain the additive.

2. The recycled micro-powder concrete according to claim 1, characterized in that, The weight ratio of the modified silica fume to the sum of the weights of the natural aggregate and the recycled aggregate is 0.107-0.

263.

3. The recycled micro-powder concrete according to claim 1, characterized in that, The weight ratio of the additive to the recycled aggregate is 0.098-0.

272.

4. The recycled micro-powder concrete according to claim 1, characterized in that, The rosin resin has a weight percentage of 25-30%, and the EDPC has a weight percentage of 15-20%.

5. The recycled micro-powder concrete according to claim 1, characterized in that, The recycled aggregate has an average particle size of 15-25 mm and an apparent density of 2652 kg / m³. 3 The bulk density is 1286 kg / m³. 3 The water absorption rate is 3.8%, and the crushing index is 16.3%.

6. The recycled micro-powder concrete according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent.

7. A method for preparing recycled micro-powder concrete according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Take the additives and recycled aggregates, mix and stir them, then add the modified silica fume and continue mixing and stirring to prepare a recycled aggregate mixture; S2. Take natural aggregate and the aforementioned recycled aggregate mixture, mix and stir, then add cement, water-reducing agent, sand and water and continue mixing and stirring to obtain the aforementioned recycled micro powder concrete.

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