Preparation method of high-strength recycled concrete

Abstract

The application relates to the technical field of recycled concrete, in particular to high-strength recycled concrete and a preparation method thereof.In the concrete, a waste concrete block is crushed and sieved, and the surface of the recycled coarse aggregate obtained after surface strengthening treatment is mixed with cement, machine-made sand, fly ash, a water reducing agent, reinforcing fibers and the like, and a solidifying agent and a resin mixed solution are further introduced to improve the crosslinking of the concrete system, so that the comprehensive mechanical properties of the concrete are improved.The application discloses high-strength recycled concrete and a preparation method thereof, the preparation process of the recycled coarse aggregate is improved, and the proportioning components of the concrete are adjusted, so that the recycled coarse aggregate prepared has low water absorption and crushing indexes, and the mechanical strength of the concrete is improved, and the application has high practicability.

Description

Technical Field

[0001] This invention relates to the field of recycled concrete technology, specifically to a method for preparing high-strength recycled concrete. Background Technology

[0002] Recycled concrete refers to new concrete made by crushing, cleaning, and grading waste concrete blocks, mixing them with aggregates in a certain proportion, partially or completely replacing natural aggregates such as sand and gravel (mainly coarse aggregates), and then adding cement, water, etc. However, recycled aggregates generally have problems such as high water absorption and high crushing index, which will affect the overall performance of recycled concrete.

[0003] Existing companies typically use methods such as pickling and chemical surface treatment to strengthen the surface of recycled aggregates, but the overall performance of the resulting recycled aggregates still cannot meet actual needs, and processes such as pickling generate a large amount of strong acid waste liquid, which is not environmentally friendly.

[0004] Therefore, based on this situation, this application discloses a high-strength recycled concrete and its preparation method to solve this technical problem. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength recycled concrete and its preparation method to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] A method for preparing high-strength recycled concrete includes the following steps:

[0008] Step (1): Crush and screen the waste concrete blocks, heat treat them at 280~320℃ for 1~1.5h to obtain coarse aggregate; soak the coarse aggregate in acid solution, wash it with deionized water, and vacuum dry it to obtain recycled coarse aggregate;

[0009] Step (2): Take tannic acid, polyethylene glycol diglycidyl ether, deionized water and potassium hydroxide, stir until dissolved under nitrogen, heat to 90~100℃, keep warm for 20~24h, cool the product after the reaction, filter and wash to obtain tannic acid epoxy resin.

[0010] Step (3): Take epoxy resin and tannic acid epoxy resin, mix them, add diluent, stir evenly to obtain resin mixture; place the recycled coarse aggregate in the resin mixture and soak it under 0.3~0.5MPa pressure for 3~4h to obtain pretreated recycled coarse aggregate;

[0011] Step (4): Mix the pretreated recycled coarse aggregate, manufactured sand, cement, fly ash and reinforcing fiber, stir evenly to obtain component A;

[0012] Mix the water-reducing agent and water, stir evenly, add to component A, continue stirring for 20-30 minutes, then add the curing agent and the resin mixture prepared in step (3), stir evenly, and obtain concrete.

[0013] The optimized solution is as follows: Step (1) is: soak the coarse aggregate in acid solution A, take it out and wash it with deionized water, dry it, soak it in acid solution B, take it out and transfer it to acid solution C to continue soaking, wash it with deionized water, and vacuum dry it to obtain recycled coarse aggregate.

[0014] In a more optimized scheme, the acid solution A is a mixed solution of hydrochloric acid and sulfuric acid, wherein the mass concentration of the hydrochloric acid is 2-3%, the mass concentration of the sulfuric acid is 1-1.5%, and the soaking time of acid solution A is 25-35 minutes.

[0015] In a more optimized scheme, the acid solution B comprises the following components by mass fraction: 4-8 wt% tartaric acid, 15-25 wt% acetic acid, 5-10 wt% citric acid, with the balance being deionized water; the soaking time of acid solution B is 2-4 hours.

[0016] In a more optimized scheme, the acid solution C comprises the following components by mass fraction: tartaric acid 3-5 wt%, acetic acid 8-10 wt%, citric acid 4-7 wt%, tannic acid 1-1.5 wt%, with the balance being deionized water; the soaking time of acid solution C is 1-2 hours.

[0017] In a more optimized scheme, the amount of each component in step (4) is as follows: by mass, 12-15 parts of resin mixture, 120-140 parts of pretreated recycled coarse aggregate, 100-120 parts of manufactured sand, 75-85 parts of cement, 15-25 parts of fly ash, 3-5 parts of water-reducing agent, 20-25 parts of water, 2-3 parts of curing agent, and 10-14 parts of reinforcing fiber.

[0018] In a more optimized scheme, in step (2), the mass ratio of tannic acid to polyethylene glycol diglycidyl ether is 1:(23~24); the amount of potassium hydroxide used is 0.5~0.8wt% of polyethylene glycol diglycidyl ether.

[0019] In a more optimized scheme, in step (3), the amount of tannic acid epoxy resin is 2~3wt% of the epoxy resin; the diluent is N-butyl glycidyl ether, and the amount is 20~25wt% of the epoxy resin; the solid-liquid ratio of the recycled coarse aggregate and resin mixture is 1.5:1.

[0020] A more optimized solution is high-strength recycled concrete prepared according to any one of the above-described methods.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0022] This invention discloses a high-strength recycled concrete and its preparation method. In this concrete, the waste concrete blocks are crushed, screened, and then surface-strengthened to obtain pretreated recycled coarse aggregate. This pretreated aggregate is then mixed with cement, and components such as manufactured sand, fly ash, water-reducing agent, and reinforcing fiber are added. At the same time, a curing agent and resin mixture are also introduced to improve the cross-linking of the concrete system and thus improve the comprehensive mechanical properties of the concrete.

[0023] In this application, the method uses C30 waste concrete blocks as raw materials, crushes and removes impurities such as wood, plastic, and bricks contained therein to form aggregates, and then heat-treats the aggregates at 280~320℃ for 1~1.5h. Since the linear expansion coefficients of natural aggregates and the hardened mortar on their surface are different, pre-heat treatment is performed to facilitate subsequent acid washing to remove the hardened mortar.

[0024] The solution then places the aggregate in an acid solution for pickling. This process involves a triple pickling process. First, the coarse aggregate is placed in acid solution A, which is a mixture of hydrochloric acid and sulfuric acid. The soaking time is limited to 25-35 minutes. This short-time, high-concentration strong acid solution can quickly remove the hardened mortar adhering to the surface of the coarse aggregate. The short time limit can prevent the strong acid from corroding the aggregate and causing the water absorption rate to increase.

[0025] Next, the coarse aggregate is placed in acid solution B and acid solution C in sequence. Both acid solutions B and C are compounded with tartaric acid, acetic acid, citric acid and deionized water. On the one hand, weak acid is more environmentally friendly than strong acid such as hydrochloric acid and sulfuric acid, and is green and environmentally friendly. On the other hand, strong acid is used first to quickly remove the hardened mortar attached to the surface of the aggregate, and then weak acid is used for a long time to further remove the residual hardened mortar and avoid the erosion of the internal aggregate. Moreover, acid solution C is the third acid washing, in which the concentration of each acid solution is reduced and tannic acid is introduced. Tannic acid can not only remove loose particles on the surface of the aggregate, but also react with the aggregate to produce particles to fill and strengthen its surface, thereby improving the comprehensive mechanical properties of the recycled aggregate and significantly reducing the water absorption rate of the aggregate.

[0026] Simultaneously, after triple pickling, the recycled coarse aggregate is further strengthened in epoxy resin. This epoxy resin incorporates tannic acid, which not only reinforces the system to enhance the surface strengthening effect of the recycled coarse aggregate, but also, due to the introduction of tannic acid, combined with the triple pickling of the natural coarse aggregate, especially the component blending of acid C, the compatibility between the two is superior. This improves the compatibility between the pretreated recycled coarse aggregate and the concrete system. Furthermore, the epoxy resin system is also incorporated into the concrete, further enhancing its mechanical properties.

[0027] This invention discloses a high-strength recycled concrete and its preparation method. The method improves the preparation process of recycled coarse aggregate and adjusts the mix proportions of the concrete. The recycled coarse aggregate prepared has a low water absorption rate and crushing index, and the mechanical strength of the concrete is also improved, making it highly practical. Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In this embodiment, the performance parameters of aggregates with a particle size of 5~20mm are shown in Table 1 below; the Mn of polyethylene glycol diglycidyl ether is 1000; the epoxy resin is E51; the curing agent is polyamide curing agent D230; the fineness modulus of the manufactured sand is 2.55, and the specification is medium sand; the cement is silicate cement (PO42.5R), provided by Chongqing Tianzhu Cement Co., Ltd.; the fly ash is Class F II fly ash provided by Guangxi Nanning Power Plant; the reinforcing fiber is basalt fiber, provided by Haining Anjie Composite Fiber Co., Ltd., with a diameter of 15μm and a length of 3mm; the water-reducing agent is Jiangsu Subote PCA-I type polycarboxylate water-reducing agent, with a solid content of 13.4% and a water reduction rate of 23.7%.

[0030] Table 1

[0031]

[0032] Example 1: A method for preparing high-strength recycled concrete, comprising the following steps:

[0033] Step (1): Crush and screen C30 waste concrete blocks to obtain continuously graded aggregate with a particle size of 5~20mm. Heat treat at 280℃ for 1.5h to obtain coarse aggregate. Immerse the coarse aggregate in acid solution A, remove it, wash it with deionized water, dry it, then immerse it in acid solution B, remove it, transfer it to acid solution C for further immersion, wash it with deionized water, and vacuum dry it to obtain recycled coarse aggregate. The aggregate is submerged in acid solution during immersion.

[0034] The acid solution A is a mixed solution of hydrochloric acid and sulfuric acid, with a mass concentration of 2% for hydrochloric acid and a mass concentration of 1% for sulfuric acid. The soaking time for acid solution A is 25 minutes.

[0035] The acid solution B comprises the following components by mass fraction: 6 wt% tartaric acid, 20 wt% acetic acid, 8 wt% citric acid, with the balance being deionized water; the soaking time for acid solution B is 4 hours.

[0036] The acid solution C comprises the following components by mass fraction: 4 wt% tartaric acid, 10 wt% acetic acid, 5 wt% citric acid, 1.5 wt% tannic acid, with the balance being deionized water; the soaking time for acid solution C is 1.5 h.

[0037] Step (2): Take 4g tannic acid, 92g polyethylene glycol diglycidyl ether, 250mL deionized water and 0.46g potassium hydroxide, stir until dissolved under nitrogen atmosphere, heat to 90℃, keep warm for 24h, cool the product after the reaction is completed, filter and wash to obtain tannic acid epoxy resin.

[0038] Step (3): Take epoxy resin and tannic acid epoxy resin, mix them, add diluent, stir evenly to obtain resin mixture; the amount of tannic acid epoxy resin is 3wt% of epoxy resin; the diluent is N-butyl glycidyl ether, and the amount is 25wt% of epoxy resin.

[0039] Recycled coarse aggregate was placed in a resin mixture and soaked for 3.5 hours under a pressure of 0.5 MPa to obtain pretreated recycled coarse aggregate; the solid-liquid ratio of the recycled coarse aggregate and the resin mixture was 1.5:1.

[0040] Step (4): By weight, mix 125 parts of pretreated recycled coarse aggregate, 100 parts of manufactured sand, 85 parts of cement, 20 parts of fly ash and 12 parts of reinforcing fiber, stir evenly to obtain component A;

[0041] Mix 5 parts of water-reducing agent and 25 parts of water, stir evenly, add to component A, continue stirring for 20 minutes, then add 2.5 parts of curing agent and 12 parts of resin mixture prepared in step (3), stir evenly, and obtain concrete.

[0042] Example 2: A method for preparing high-strength recycled concrete, comprising the following steps:

[0043] Step (1): Crush and screen C30 waste concrete blocks to obtain continuously graded aggregate with a particle size of 5~20mm. Heat treat at 300℃ for 1 hour to obtain coarse aggregate. Immerse the coarse aggregate in acid solution A, remove it, wash it with deionized water, dry it, then immerse it in acid solution B, remove it, transfer it to acid solution C for further immersion, wash it with deionized water, and vacuum dry it to obtain recycled coarse aggregate. The aggregate is submerged in acid solution during immersion.

[0044] The acid solution A is a mixed solution of hydrochloric acid and sulfuric acid, with a mass concentration of 2% for hydrochloric acid and a mass concentration of 1% for sulfuric acid. The soaking time for acid solution A is 30 minutes.

[0045] The acid solution B comprises the following components by mass fraction: 6 wt% tartaric acid, 20 wt% acetic acid, 8 wt% citric acid, with the balance being deionized water; the soaking time for acid solution B is 4 hours.

[0046] The acid solution C comprises the following components by mass fraction: 4 wt% tartaric acid, 10 wt% acetic acid, 5 wt% citric acid, 1.5 wt% tannic acid, with the balance being deionized water; the soaking time for acid solution C is 1.5 h.

[0047] Step (2): Take 4g tannic acid, 92g polyethylene glycol diglycidyl ether, 250mL deionized water and 0.46g potassium hydroxide, stir until dissolved under nitrogen atmosphere, heat to 95℃, keep warm for 22h, cool the product after the reaction is completed, filter and wash to obtain tannic acid epoxy resin.

[0048] Step (3): Take epoxy resin and tannic acid epoxy resin, mix them, add diluent, stir evenly to obtain resin mixture; the amount of tannic acid epoxy resin is 3wt% of epoxy resin; the diluent is N-butyl glycidyl ether, and the amount is 25wt% of epoxy resin.

[0049] Recycled coarse aggregate was placed in a resin mixture and soaked for 3.5 hours under a pressure of 0.5 MPa to obtain pretreated recycled coarse aggregate; the solid-liquid ratio of the recycled coarse aggregate and the resin mixture was 1.5:1.

[0050] Step (4): By weight, mix 125 parts of pretreated recycled coarse aggregate, 100 parts of manufactured sand, 85 parts of cement, 20 parts of fly ash and 12 parts of reinforcing fiber, stir evenly to obtain component A;

[0051] Mix 5 parts of water-reducing agent and 25 parts of water, stir evenly, add to component A, continue stirring for 25 minutes, then add 2.5 parts of curing agent and 12 parts of resin mixture prepared in step (3), stir evenly, and obtain concrete.

[0052] Example 3: A method for preparing high-strength recycled concrete, comprising the following steps:

[0053] Step (1): Crush and screen C30 waste concrete blocks to obtain continuously graded aggregate with a particle size of 5~20mm. Heat treat at 320℃ for 1 hour to obtain coarse aggregate. Immerse the coarse aggregate in acid solution A, remove it, wash it with deionized water, dry it, then immerse it in acid solution B, remove it, transfer it to acid solution C for further immersion, wash it with deionized water, and vacuum dry it to obtain recycled coarse aggregate. The aggregate is submerged in acid solution during immersion.

[0054] The acid solution A is a mixed solution of hydrochloric acid and sulfuric acid, with a mass concentration of 2% for hydrochloric acid and a mass concentration of 1% for sulfuric acid. The soaking time for acid solution A is 35 minutes.

[0055] The acid solution B comprises the following components by mass fraction: 6 wt% tartaric acid, 20 wt% acetic acid, 8 wt% citric acid, with the balance being deionized water; the soaking time for acid solution B is 4 hours.

[0056] The acid solution C comprises the following components by mass fraction: 4 wt% tartaric acid, 10 wt% acetic acid, 5 wt% citric acid, 1.5 wt% tannic acid, with the balance being deionized water; the soaking time for acid solution C is 1.5 h.

[0057] Step (2): Take 4g tannic acid, 92g polyethylene glycol diglycidyl ether, 250mL deionized water and 0.46g potassium hydroxide, stir until dissolved under nitrogen atmosphere, heat to 100℃, keep warm for 20h, cool the product after the reaction is completed, filter and wash to obtain tannic acid epoxy resin.

[0058] Step (3): Take epoxy resin and tannic acid epoxy resin, mix them, add diluent, stir evenly to obtain resin mixture; the amount of tannic acid epoxy resin is 3wt% of epoxy resin; the diluent is N-butyl glycidyl ether, and the amount is 25wt% of epoxy resin.

[0059] Recycled coarse aggregate was placed in a resin mixture and soaked for 4 hours under a pressure of 0.5 MPa to obtain pretreated recycled coarse aggregate; the solid-liquid ratio of recycled coarse aggregate to resin mixture was 1.5:1.

[0060] Step (4): By weight, mix 125 parts of pretreated recycled coarse aggregate, 100 parts of manufactured sand, 85 parts of cement, 20 parts of fly ash and 12 parts of reinforcing fiber, stir evenly to obtain component A;

[0061] Mix 5 parts of water-reducing agent and 25 parts of water, stir evenly, add to component A, continue stirring for 30 minutes, then add 2.5 parts of curing agent and 12 parts of resin mixture prepared in step (3), stir evenly, and obtain concrete.

[0062] Comparative Example 1: With Example 2 as the control group, no resin mixture was added to the concrete in Comparative Example 1, and the other steps remained unchanged.

[0063] A method for preparing high-strength recycled concrete includes the following steps:

[0064] Step (1): Crush and screen C30 waste concrete blocks to obtain continuously graded aggregate with a particle size of 5~20mm. Heat treat at 300℃ for 1 hour to obtain coarse aggregate. Immerse the coarse aggregate in acid solution A, remove it, wash it with deionized water, dry it, then immerse it in acid solution B, remove it, transfer it to acid solution C for further immersion, wash it with deionized water, and vacuum dry it to obtain recycled coarse aggregate. The aggregate is submerged in acid solution during immersion.

[0065] The acid solution A is a mixed solution of hydrochloric acid and sulfuric acid, with a mass concentration of 2% for hydrochloric acid and a mass concentration of 1% for sulfuric acid. The soaking time for acid solution A is 30 minutes.

[0066] The acid solution B comprises the following components by mass fraction: 6 wt% tartaric acid, 20 wt% acetic acid, 8 wt% citric acid, with the balance being deionized water; the soaking time for acid solution B is 4 hours.

[0067] The acid solution C comprises the following components by mass fraction: 4 wt% tartaric acid, 10 wt% acetic acid, 5 wt% citric acid, 1.5 wt% tannic acid, with the balance being deionized water; the soaking time for acid solution C is 1.5 h.

[0068] Step (2): Take 4g tannic acid, 92g polyethylene glycol diglycidyl ether, 250mL deionized water and 0.46g potassium hydroxide, stir until dissolved under nitrogen atmosphere, heat to 95℃, keep warm for 22h, cool the product after the reaction is completed, filter and wash to obtain tannic acid epoxy resin.

[0069] Step (3): Take epoxy resin and tannic acid epoxy resin, mix them, add diluent, stir evenly to obtain resin mixture; the amount of tannic acid epoxy resin is 3wt% of epoxy resin; the diluent is N-butyl glycidyl ether, and the amount is 25wt% of epoxy resin.

[0070] Recycled coarse aggregate was placed in a resin mixture and soaked for 3.5 hours under a pressure of 0.5 MPa to obtain pretreated recycled coarse aggregate; the solid-liquid ratio of the recycled coarse aggregate and the resin mixture was 1.5:1.

[0071] Step (4): By weight, mix 125 parts of pretreated recycled coarse aggregate, 100 parts of manufactured sand, 85 parts of cement, 20 parts of fly ash and 12 parts of reinforcing fiber, stir evenly to obtain component A;

[0072] Mix 5 parts water-reducing agent and 25 parts water, stir well, add to component A, and continue stirring for 25 minutes to obtain concrete.

[0073] Comparative Example 2: Compared with Example 2, no resin mixture was added to the concrete in Comparative Example 2, and the surface of the recycled coarse aggregate was not pretreated. The other steps remained unchanged.

[0074] A method for preparing high-strength recycled concrete includes the following steps:

[0075] Step (1): Crush and screen C30 waste concrete blocks to obtain continuously graded aggregate with a particle size of 5~20mm. Heat treat at 300℃ for 1 hour to obtain coarse aggregate. Immerse the coarse aggregate in acid solution A, remove it, wash it with deionized water, dry it, then immerse it in acid solution B, remove it, transfer it to acid solution C for further immersion, wash it with deionized water, and vacuum dry it to obtain recycled coarse aggregate. The aggregate is submerged in acid solution during immersion.

[0076] The acid solution A is a mixed solution of hydrochloric acid and sulfuric acid, with a mass concentration of 2% for hydrochloric acid and a mass concentration of 1% for sulfuric acid. The soaking time for acid solution A is 30 minutes.

[0077] The acid solution B comprises the following components by mass fraction: 6 wt% tartaric acid, 20 wt% acetic acid, 8 wt% citric acid, with the balance being deionized water; the soaking time for acid solution B is 4 hours.

[0078] The acid solution C comprises the following components by mass fraction: 4 wt% tartaric acid, 10 wt% acetic acid, 5 wt% citric acid, 1.5 wt% tannic acid, with the balance being deionized water; the soaking time for acid solution C is 1.5 h.

[0079] Step (3): By weight, mix 125 parts of recycled coarse aggregate, 100 parts of manufactured sand, 85 parts of cement, 20 parts of fly ash and 12 parts of reinforcing fiber, stir evenly to obtain component A;

[0080] Mix 5 parts water-reducing agent and 25 parts water, stir well, add to component A, and continue stirring for 25 minutes to obtain concrete.

[0081] Comparative Example 3: With Example 2 as the control group, the soaking in acid solution C was not adjusted in Comparative Example 3, and the other steps remained unchanged.

[0082] A method for preparing high-strength recycled concrete includes the following steps:

[0083] Step (1): Crush and screen the C30 waste concrete blocks to obtain continuously graded aggregate with a particle size of 5~20mm. Heat treat the aggregate at 300℃ for 1 hour to obtain coarse aggregate. Soak the coarse aggregate in acid solution A, remove it, wash it with deionized water, dry it, soak it in acid solution B, wash it with deionized water, and vacuum dry it to obtain recycled coarse aggregate. The aggregate is immersed in acid solution during soaking.

[0084] The acid solution A is a mixed solution of hydrochloric acid and sulfuric acid, with a mass concentration of 2% for hydrochloric acid and a mass concentration of 1% for sulfuric acid. The soaking time for acid solution A is 30 minutes.

[0085] The acid solution B comprises the following components by mass fraction: 6 wt% tartaric acid, 20 wt% acetic acid, 8 wt% citric acid, with the balance being deionized water; the soaking time for acid solution B is 5.5 h.

[0086] Step (2): Take 4g tannic acid, 92g polyethylene glycol diglycidyl ether, 250mL deionized water and 0.46g potassium hydroxide, stir until dissolved under nitrogen atmosphere, heat to 95℃, keep warm for 22h, cool the product after the reaction is completed, filter and wash to obtain tannic acid epoxy resin.

[0087] Step (3): Take epoxy resin and tannic acid epoxy resin, mix them, add diluent, stir evenly to obtain resin mixture; the amount of tannic acid epoxy resin is 3wt% of epoxy resin; the diluent is N-butyl glycidyl ether, and the amount is 25wt% of epoxy resin.

[0088] Recycled coarse aggregate was placed in a resin mixture and soaked for 3.5 hours under a pressure of 0.5 MPa to obtain pretreated recycled coarse aggregate; the solid-liquid ratio of the recycled coarse aggregate and the resin mixture was 1.5:1.

[0089] Step (4): By weight, mix 125 parts of pretreated recycled coarse aggregate, 100 parts of manufactured sand, 85 parts of cement, 20 parts of fly ash and 12 parts of reinforcing fiber, stir evenly to obtain component A;

[0090] Mix 5 parts of water-reducing agent and 25 parts of water, stir evenly, add to component A, continue stirring for 25 minutes, then add 2.5 parts of curing agent and 12 parts of resin mixture prepared in step (3), stir evenly, and obtain concrete.

[0091] Comparative Example 4: With Example 2 as the control group, Comparative Example 4 only involved strong acid washing, with the other steps remaining unchanged.

[0092] A method for preparing high-strength recycled concrete includes the following steps:

[0093] Step (1): Crush and screen the C30 waste concrete blocks to obtain continuously graded aggregate with a particle size of 5~20mm. Heat treat the aggregate at 300℃ for 1 hour to obtain coarse aggregate. Soak the coarse aggregate in acid solution A, remove it, wash it with deionized water, and dry it to obtain recycled coarse aggregate. The aggregate is immersed in acid solution during soaking.

[0094] The acid solution A is a mixed solution of hydrochloric acid and sulfuric acid, with a mass concentration of 2% for hydrochloric acid and a mass concentration of 1% for sulfuric acid. The soaking time for acid solution A is 70 minutes.

[0095] Step (2): Take 4g tannic acid, 92g polyethylene glycol diglycidyl ether, 250mL deionized water and 0.46g potassium hydroxide, stir until dissolved under nitrogen atmosphere, heat to 95℃, keep warm for 22h, cool the product after the reaction is completed, filter and wash to obtain tannic acid epoxy resin.

[0096] Step (3): By weight, mix 125 parts of recycled coarse aggregate, 100 parts of manufactured sand, 85 parts of cement, 20 parts of fly ash and 12 parts of reinforcing fiber, stir evenly to obtain component A;

[0097] Mix 5 parts of water-reducing agent and 25 parts of water, stir evenly, add to component A, continue stirring for 25 minutes, then add 2.5 parts of curing agent and 12 parts of resin mixture prepared in step (3), stir evenly, and obtain concrete.

[0098] Testing experiment:

[0099] 1. Recycled coarse aggregates were tested according to the methods disclosed in Examples 1-3 and Comparative Examples 2-4; wherein A1-A3 were pretreated recycled coarse aggregates prepared in Examples 1-3, which were reinforced by triple pickling and resin mixture; A4 was recycled coarse aggregates prepared in Comparative Example 2, which were only subjected to triple pickling; A5 and A6 were pretreated recycled coarse aggregates prepared in Comparative Examples 3 and 4, respectively, with the pickling process adjusted.

[0100] The water absorption rate and crushing index of samples A1 to A6 were tested. The water absorption rate test method was as follows: 4 kg of sample was placed in water, with the water level approximately 5 mm above the sample, and soaked at 25℃ for 24 hours. After removal, the surface moisture was wiped off, and the sample was weighed. It was then dried to constant weight, weighed again, and the water absorption rate was calculated. The test was repeated 3-5 times, and the average value was taken. The crushing index test method followed JGJ52-2006, with a load of 200 kN and a stabilization time of 5 seconds. The crushing index was tested and recorded. The data are shown in Table 2.

[0101] Table 2

[0102]

[0103] 2. Concrete was tested according to the methods disclosed in Examples 1-3 and Comparative Examples 1-3. Concrete samples were prepared, cured for 28 days, and their compressive strength was tested. The specimen size was 150mm x 150mm x 150mm. The splitting tensile strength was tested by continuously and uniformly loading at a rate of 0.08MPa / s until the specimen failed. The test method was in accordance with GB / T50081-2019, and the specific test data are shown in Table 3.

[0104] Table 3

[0105]

[0106] Conclusion: This invention discloses a high-strength recycled concrete and its preparation method. This method improves the preparation process of recycled coarse aggregate and adjusts the concrete mix proportions. The prepared recycled coarse aggregate has a low water absorption rate and crushing index, and the mechanical strength of the concrete is also improved, making it highly practical.

[0107] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of producing high strength recycled concrete, characterized by: The method comprises the following steps: Step (1): crushing and screening the waste concrete blocks, and heat treating the waste concrete blocks at 280-320 DEG C for 1-1.5 h to obtain coarse aggregates; soaking the coarse aggregates in an acid solution, washing with deionized water, and vacuum drying to obtain recycled coarse aggregates; Step (2): taking tannic acid, polyethylene glycol diglycidyl ether, deionized water and potassium hydroxide, stirring to dissolve under a nitrogen environment, heating to 90-100 DEG C, and keeping the temperature for 20-24 h; after the reaction is completed, the product is cooled, filtered and washed to obtain tannic acid epoxy resin; Step (3): mixing the epoxy resin and the tannic acid epoxy resin, adding a diluent, and stirring uniformly to obtain a resin mixture; soaking the recycled coarse aggregates in the resin mixture under a pressure of 0.3-0.5 MPa for 3-4 h to obtain pretreated recycled coarse aggregates; the amount of the tannic acid epoxy resin is 2-3 wt% of the epoxy resin; Step (4): mixing the pretreated recycled coarse aggregates, machine-made sand, cement, fly ash and reinforcing fibers, and stirring uniformly to obtain component A; mixing the water reducing agent and water, stirring uniformly, adding to component A, continuing to stir for 20-30 min, and then adding the curing agent and the resin mixture prepared in step (3) and stirring uniformly to obtain concrete; Step (1) specifically comprises: soaking the coarse aggregates in acid solution A, washing with deionized water after taking out, drying, soaking in acid solution B again, transferring to acid solution C for continuous soaking after taking out, washing with deionized water, and vacuum drying to obtain recycled coarse aggregates; The acid solution C comprises the following components: 3-5 wt% tartaric acid, 8-10 wt% acetic acid, 4-7 wt% citric acid, 1-1.5 wt% tannic acid, and the balance being deionized water; the soaking time of the acid solution C is 1-2 h; In step (4), the amounts of the components are as follows: 12-15 parts of the resin mixture, 120-140 parts of the pretreated recycled coarse aggregates, 100-120 parts of the machine-made sand, 75-85 parts of the cement, 15-25 parts of the fly ash, 3-5 parts of the water reducing agent, 20-25 parts of the water, 2-3 parts of the curing agent, and 10-14 parts of the reinforcing fibers; The acid solution A is a mixed solution of hydrochloric acid and sulfuric acid, the mass concentration of the hydrochloric acid is 2-3%, the mass concentration of the sulfuric acid is 1-1.5%, the soaking time of the acid solution A is 25-35 min; the acid solution B comprises the following components: 4-8 wt% tartaric acid, 15-25 wt% acetic acid, 5-10 wt% citric acid, and the balance being deionized water; the soaking time of the acid solution B is 2-4 h.

2. A method of producing high strength recycled concrete according to claim 1, characterized in that: In step (2), the mass ratio of the tannic acid to the polyethylene glycol diglycidyl ether is 1:(23-24); the amount of the potassium hydroxide is 0.5-0.8 wt% of the polyethylene glycol diglycidyl ether.

3. A method of producing high strength recycled concrete according to claim 1, characterized in that: In step (3), the diluent is N-butyl glycidyl ether, and the amount is 20-25 wt% of the epoxy resin; the solid-liquid ratio of the recycled coarse aggregates to the resin mixture is 1.5:

1.

4. High-strength recycled concrete prepared by the method of any one of claims 1-3.

Images