Recycled aggregate self-compacting concrete with excellent impervious and waterproof effects

Abstract

The invention discloses recycled aggregate self-compacting concrete with excellent impervious and waterproof effects, and relates to the technical field of recycled aggregate concrete.The recycled aggregate self-compacting concrete is prepared from, by mass, 160-180 parts of aggregate particles, 280-300 parts of cement, 3-4 parts of water reducing agent, 1-3 parts of thickening agent, 2-11 parts of air entraining agent, 80-120 parts of mineral admixture, 100-200 parts of water and 7-9 parts of expanding agent. The recycled aggregate self-compacting concrete prepared by the invention is improved in strength, durability and impermeability and waterproofness, and the quality stability of the recycled aggregate is ensured, so that the quality and performance of the finally prepared recycled aggregate self-compacting concrete have consistency, and the recycled aggregate self-compacting concrete can be prepared according to a certain proportioning sequence and proportion. The water-cement ratio is reduced, and the compactness, durability and impermeability and waterproof performance of the concrete are improved at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of recycled aggregate concrete, and particularly to a recycled aggregate self-compacting concrete with excellent anti-seepage and waterproof effects. Background Art

[0002] Recycled aggregate self-compacting concrete is a concrete prepared by partially or fully replacing natural aggregates with recycled aggregates on the basis of self-compacting concrete. Self-compacting concrete has characteristics such as high fluidity, good segregation resistance, and filling performance. Recycled aggregates are aggregates obtained by processing waste concrete blocks, bricks, etc. through crushing, screening, etc. Recycled aggregate self-compacting concrete is widely used in construction projects, transportation infrastructure, water conservancy projects, urban infrastructure construction, etc. Existing self-compacting concrete is difficult to improve the performance of concrete while reducing the water-cement ratio.

[0003] The defects of existing recycled aggregate self-compacting concrete are as follows: Patent document CN115626796B discloses a recycled aggregate self-compacting concrete, which mainly considers how to improve the compressive strength and durability of recycled aggregate self-compacting concrete, and does not consider how to prepare concrete with improved density, durability, and anti-seepage and waterproof performance while reducing the water-cement ratio; Patent document CN114477873B discloses a recycled aggregate self-compacting concrete and its preparation method, which mainly considers how to improve the compressive strength, heat resistance, and anti-seepage of recycled aggregate self-compacting concrete, and does not consider how to ensure the stable performance of the aggregate while preventing excessive moisture from entering the recycled aggregate; Patent document CN114436601B discloses a recycled aggregate self-compacting concrete and its preparation method, which mainly considers how to improve the mechanical strength and frost resistance of recycled aggregate self-compacting concrete, and does not consider how to improve the quality and anti-seepage performance of the concrete; Patent document CN113773017B discloses a recycled aggregate self-compacting concrete and its preparation method, which mainly considers how to reasonably utilize waste building materials. The prepared recycled aggregates have excellent and stable performance, are high-strength and dense, and have significantly reduced water absorption. It does not consider enhancing the performance of the subsequent prepared concrete by improving the quality of the recycled aggregates and reducing the water absorption of the recycled aggregates. Summary of the Invention

[0004] The purpose of the present invention is to provide a recycled aggregate self-compacting concrete with excellent anti-seepage and waterproof effects to solve the problems raised in the above background art.

[0005] To achieve the above object, the present invention provides the following technical solutions: 1. A recycled aggregate self-compacting concrete with excellent impermeability and waterproofing effect, by mass parts: its raw materials include the following components: 160-180 parts of aggregate particles, 280-300 parts of cement, 3-4 parts of water reducer, 1-3 parts of thickening agent, 2-11 parts of air-entraining agent, 80-120 parts of mineral admixture, 100-200 parts of water, and 7-9 parts of expansive agent; The preparation method of recycled aggregate self-compacting concrete includes the following steps: Step S1: Solution preparation: Prepare nano-solution, coating modification solution and silane coupling agent solution; Step S2: Raw material pretreatment: Pretreat cement and recycled aggregate respectively; Step S3: Stirring and mixing: Add mineral admixture, water reducer, water, thickening agent, air-entraining agent, expansive agent, and the cement and aggregate particles pretreated in Step S2 into a mixer for stirring and mixing to obtain recycled aggregate self-compacting concrete; Step S4: Quality control: Detect the performance of the prepared recycled aggregate self-compacting concrete.

[0006] Preferably, in Step S1, the following steps are further included: Step S11: Nano-solution: First add nano-silica and nano-calcium carbonate into water, then add PEG and SDBS into the solution, and put the solution into a microwave reaction device, irradiate for 10-20 min at a microwave frequency of 600 mhz and a temperature of 120-140 °C to obtain nano-solution; Step S12: Coating modification solution: Add polyethylene glycol into water, stir at a stirring speed of 400-450 rpm for 20-30 min to form a uniform solution, then add the silane coupling agent into the solution at a speed of 2-3 drops / min, and continuously stir at 400-450 rpm for 10-15 min. Finally, add the polyacrylate emulsion into the mixed solution at a speed of 6-8 mL / min and stir at 270 rpm for 40-50 min to form a stable coating modification solution; Step S13: Silane coupling agent solution: Stir and dilute the silane coupling agent with 75% ethanol aqueous solution, where the mass ratio of the silane coupling agent to the ethanol aqueous solution is 1:(1-3), the stirring speed is 50-80 rpm, and the stirring time is 10-15 min to prepare the silane coupling agent solution.

[0007] Preferably, in Step S2, the following steps are further included: Step S21: Cement pretreatment: Place the cement in an environment of 60 - 90°C and heat it for 2 - 6 min, with a stirring speed of 160 - 200 rpm. Then use a ball mill to grind the cement, where the rotational speed of the ball mill is 30 - 40 rpm and the grinding time is 20 - 90 min. Then add a silane coupling agent solution to the ground cement and stir it at a speed of 120 - 160 rpm for 0.5 - 3 h at room temperature; Step S22: Aggregate pretreatment: Conduct primary crushing using a jaw crusher to obtain aggregate blocks. Then use a counter - impact crusher for secondary crushing to obtain aggregate slag. Then use an impact crusher for tertiary crushing to obtain aggregate particles. The eccentric shaft rotational speed of the jaw crusher is 160 - 220 rpm and the crushing time is 1 - 2 h. The rotor rotational speed of the counter - impact crusher is 420 - 500 rpm and the crushing time is 1 - 2 h. The impeller rotational speed of the impact crusher is 1200 - 1600 rpm and the crushing time is 0.5 - 2 h. Then use a ball mill to grind the aggregate particles, where the rotational speed of the ball mill is 40 - 60 rpm and the grinding time is 0.5 - 3 h. Then use a vibrating screen to finely screen the obtained aggregate particles, where the vibration frequency is 900 - 1000 times per minute, the amplitude is 4 - 5 mm, the aperture of the sieve mesh is 10 mm, and the particle size of the screened aggregate particles is 5 - 10 mm. Subsequently, use a 6% hydrochloric acid solution to chemically clean the screened aggregate particles; Step S23: Nano - treatment: Immerse the pretreated aggregate particles in a nano - solution. After soaking for 2 - 4 h, take out the aggregate particles and put them into an oven for drying. The temperature of the oven is 75°C and the drying time is 0.5 - 1.5 h; Step S24: Pre - wetting treatment: Add water to a concrete pool and place the nano - treated aggregate particles in it so that the aggregate particles are completely immersed in water. After soaking for 0.5 - 2 h, take out the aggregate particles and dry them at 60 - 90°C for 15 - 30 min; Step S25: Coating modification solution combined with ultrasonic vibration: Add the aggregate particles treated in Step S24 to the coating modification solution and soak them at a pressure of 4 MPa for 30 - 90 min. Then conduct ultrasonic vibration treatment, where the ultrasonic power is 280 - 300 W, the frequency is 40 kHz, and the treatment time is 20 - 40 min.

[0008] Preferably, in Step S3, the following steps are further included: Step S31: First, place the pretreated cement, aggregate particles, and mineral admixture into a mixer and dry - mix them for 1 - 2 min, with a stirring speed of 30 - 50 rpm; Step S32: Then mix the water reducer, water and thickening agent and add them to the mixer, and continue to stir at a speed of 30 - 50 rpm for 1 - 2 min; Step S33: Finally, add the air-entraining agent and expansive agent to the concrete mixture, and stir at a speed of 30 - 40 rpm for 1 - 2 min to obtain recycled aggregate self-compacting concrete.

[0009] Preferably, in step S4, the following steps are further included: Step S41: Test the workability and mechanical properties of the recycled aggregate self-compacting concrete according to the standard of JGJ / T283 "Technical Specification for Application of Self-Compacting Concrete"; Step S42: Determine the impermeability and frost resistance of the recycled aggregate self-compacting concrete according to JGJ / T193 "Standard for Inspection and Evaluation of Concrete Durability", and comprehensively evaluate the durability of the concrete.

[0010] Preferably, the mass ratio of the nano-silica, nano-calcium carbonate, water, PEG and SDBS is (1 - 4):(0.2 - 1.5):100:0.05:(0.1 - 1).

[0011] Preferably, the particle size of the nano-calcium carbonate is 30 - 40 nm, and the particle size of the nano-silica is 20 - 40 nm.

[0012] Preferably, the particle size of the cement is 10 - 20 μm.

[0013] Preferably, the mass ratio of the polyacrylate emulsion, silane coupling agent, polyethylene glycol and water is (64 - 75):(2 - 4):(6 - 10):(11 - 28).

[0014] Preferably, the mineral admixture is composed of fly ash, natural volcanic ash and silica fume mixed in a mass ratio of (2 - 3):1:1, and the particle size of the mineral admixture is 0.1 - 0.3 μm.

[0015] Compared with the prior art, the beneficial effects of the present invention are: The recycled aggregate self-compacting concrete prepared by the present invention has improved strength, durability and impermeability and waterproof performance, and ensures the quality stability of the recycled aggregate, so that the quality and performance of the finally prepared recycled aggregate self-compacting concrete are consistent. According to a certain mixing ratio sequence and proportion, while reducing the water-cement ratio, the compactness, durability and impermeability and waterproof performance of the concrete are improved.

[0016] 2. The present invention first treats the pretreated recycled aggregate with a nano-solution, enabling the nano-materials to be evenly distributed on the surface and in the pores of the recycled aggregate and forming a protective film on the surface of the recycled aggregate. This helps to improve the bonding property between the recycled aggregate and other raw materials during the subsequent preparation process, further enhancing the antioxidant strength and durability of the final product. Then, pre-wetting treatment is carried out to adjust the water absorption rate of the recycled aggregate. By adopting the method of first performing nano-treatment and then pre-wetting treatment, it can prevent excessive water from entering the interior of the recycled aggregate to a certain extent, further ensuring the stability of the properties of the recycled aggregate.

[0017] 3. After the pre-wetting treatment, the present invention treats the recycled aggregate with a coating modification solution and uses ultrasonic vibration treatment, which helps the coating modification solution to better adhere to the surface of the recycled aggregate. It can inhibit the expansion of cracks to a certain extent. The ultrasonic vibration generates high-frequency vibration waves, making the coating modification solution more evenly dispersed and filled in the pores and on the surface of the recycled aggregate, further improving the bonding property between the recycled aggregate and cement paste, etc., and thus enhancing the strength and durability of the final product. The ultrasonic vibration can also help to remove the bubbles in the coating modification solution, avoiding the formation of pores and defects by the bubbles in the concrete, and further improving the quality and impermeability of the concrete.

[0018] 4. The present invention strictly controls the source and quality of the recycled aggregate, and uses mechanical grinding and chemical cleaning methods to thoroughly remove the old cement mortar attached to the surface of the recycled aggregate, improving the quality and performance of the recycled aggregate, which is beneficial to improving the mechanical strength of the recycled aggregate self-compacting concrete prepared subsequently. Further pretreatment is carried out on the selected recycled aggregate to ensure a reasonable particle size distribution and good particle shape of the recycled aggregate, so as to improve the compactness and strength of the concrete, and thus enhance the durability. And the mechanical grinding is carried out between multi-stage crushing and fine screening to smooth the surface of the uneven recycled aggregate particles after crushing, which helps to reduce the water absorption rate of the recycled aggregate and enhance the bonding force with cement, etc. in the subsequent preparation process. Specific embodiments

[0019] The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] The present invention provides a recycled aggregate self-compacting concrete with excellent impermeability and waterproofing effect. The preparation method of the recycled aggregate self-compacting concrete is as follows: Step S1: Solution preparation: First, add nano-silica and nano-calcium carbonate into water, then add PEG and SDBS into the solution, and place the solution into a microwave reaction device. Irradiate it for 10 min at a microwave frequency of 600 mhz and a temperature of 140 °C to obtain a nano-solution. The mass ratio of nano-silica, nano-calcium carbonate, water, PEG, and SDBS is 3:1:100:0.05:0.4. The particle size of nano-calcium carbonate is 30 nm, and the particle size of nano-silica is 20 nm. Then add polyethylene glycol into water and stir for 20 min at a stirring speed of 420 rpm to form a uniform solution. Then add the silane coupling agent into the solution at a speed of 2 drops / min while continuously stirring at 420 rpm for 15 min. Finally, add the polyacrylate emulsion into the mixed solution at a speed of 6 mL / min and stir at 270 rpm for 45 min to form a stable coated and modified solution. Dilute the silane coupling agent with a 75% ethanol aqueous solution by stirring. The mass ratio of the silane coupling agent to the ethanol aqueous solution is 1:2, the stirring speed is 60 rpm, and the stirring time is 15 min to prepare a silane coupling agent solution. The mass ratio of the polyacrylate emulsion, silane coupling agent, polyethylene glycol, and water is 66:3:7:16; Step S2: Raw material pretreatment: First, pretreat the cement by heating it in an environment of 70°C for 4 minutes with a stirring speed of 480 rpm. Then, grind the cement using a ball mill with a rotation speed of 30 rpm for 40 minutes. Next, add a silane coupling agent solution to the ground cement and stir it at a speed of 130 rpm for 1.5 hours at room temperature. Then, pretreat the aggregate. First, perform primary crushing using a jaw crusher to obtain aggregate blocks. Then, use a counterattack crusher for secondary crushing to obtain aggregate slag. Then, use an impact crusher for tertiary crushing to obtain aggregate particles. The eccentric shaft rotation speed of the jaw crusher is 200 rpm, and the crushing time is 1.5 hours. The rotor rotation speed of the counterattack crusher is 450 rpm, and the crushing time is 1.5 hours. The impeller rotation speed of the impact crusher is 1500 rpm, and the crushing time is 1.5 hours. Then, grind the aggregate particles using a ball mill with a rotation speed of 50 rpm for 2 hours. Then, use a vibrating screen to finely screen the obtained aggregate particles. The vibration frequency is 900 times per minute, the amplitude is 5 mm, the aperture of the sieve mesh is 10 mm, and the particle size of the screened aggregate particles is 6 mm. Subsequently, chemically clean the screened aggregate particles with a 6% hydrochloric acid solution. Then, immerse the pretreated aggregate particles in a nano-solution. After soaking for 3 hours, take out the aggregate particles and put them into an oven for drying. The temperature of the oven is 75°C, and the drying time is 1 hour. Then, add water to the concrete pool and place the nano-treated aggregate particles in it to completely immerse the aggregate particles in water. After soaking for 1.5 hours, take out the aggregate particles and dry them at 80°C for 20 minutes. Then, add the pre-wet treated aggregate particles to the coating modification solution and soak them at a pressure of 4 MPa for 45 minutes. Then, perform ultrasonic vibration treatment with an ultrasonic power of 290 W, a frequency of 40 kHz, and a treatment time of 30 minutes; Step S3: Stirring and mixing: First, place the pretreated cement, aggregate particles, and mineral admixture into a mixer and dry mix for 1 - 2 minutes at a stirring speed of 30 - 50 rpm. Then, mix the water reducer, water, and thickener evenly and add them to the mixer, and continue to stir at a speed of 30 - 50 rpm for 1 - 2 minutes. Finally, add the air-entraining agent and expansion agent to the concrete mixture and stir at a speed of 30 - 40 rpm for 1 - 2 minutes to obtain recycled aggregate self-compacting concrete. The mineral admixture is composed of fly ash, natural pozzolan, and silica fume mixed in a mass ratio of 3:1:1. The particle size of the mineral admixture is 0.2 μm, and the particle size of the cement is 15 μm. The mass ratio of the aggregate particles, cement, water reducer, thickener, air-entraining agent, mineral admixture, water, and expansion agent is (160 - 180):(280 - 300):3:1:(2 - 11):(80 - 120):(100 - 200):7.

[0021] Furthermore, change the value of step S3, and perform step S1-2. Conduct performance tests on the prepared recycled aggregate self-compacting concrete. Fill the slump cone with the concrete in three layers, and insert the tamper 25 times for each layer. After filling and leveling, vertically lift the slump cone, measure the height of the concrete slump to obtain the slump. Based on the slump test, observe the spread diameter of the concrete on the horizontal plane to obtain the slump flow. At the same time, measure the time required for the concrete to spread to a diameter of 500 mm starting from when the slump cone is lifted to obtain the T500 time. Use the prepared concrete to make multiple 150 mm×150 mm×150 mm concrete cube specimens. After curing the specimens for 28 days under the conditions of a temperature of 20°C and a relative humidity of 95%, place the concrete cube specimens in a compression testing machine and apply axial pressure at a loading rate of 0.4 MPa / s until the specimens are damaged, measure the compressive strength, and conduct tests in accordance with GBT50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" to obtain the elastic modulus of the recycled aggregate self-compacting concrete. Place the concrete cube specimens in an impermeability tester, start from 0.1 MPa, gradually increase the water pressure, and maintain each water pressure level for 8 h until water seepage occurs in the specimens, and calculate the impermeability grade according to the formula P = 10H - 1, where P is the impermeability grade and H is the maximum water pressure that the specimens can withstand. Place the concrete cube specimens in a freeze-thaw test chamber, freeze at -18°C for 4 h, and then thaw at +5°C for 4 h. Take this as one cycle, repeat this cycle 300 times, and then conduct compressive and splitting tests on the specimens to evaluate the frost resistance of the concrete and comprehensively evaluate the durability of the concrete. Example 1

[0022] Step S3: Mixing: First, place the pretreated cement, aggregate particles, and mineral admixture into a mixer and dry mix for 1 min at a mixing speed of 40 rpm. Then, mix the water reducer, water, and thickening agent evenly and add them to the mixer, and continue to mix at a speed of 40 rpm for 1 min. Finally, add the air-entraining agent and expansion agent to the concrete mixture and mix at a speed of 30 rpm for 1 min to obtain the recycled aggregate self-compacting concrete. The mineral admixture is composed of fly ash, natural pozzolan, and silica fume mixed in a mass ratio of 3:1:1, the particle size of the mineral admixture is 0.2 μm, the particle size of the cement is 15 μm, and the mass ratio of the aggregate particles, cement, water reducer, thickening agent, air-entraining agent, mineral admixture, water, and expansion agent is 160:300:3:1:5:110:120:7.

[0023] Furthermore, the slump of the recycled aggregate self-compacting concrete was measured to be 267 mm, the slump flow was 686 mm, the T500 time was 2.43 s, the compressive strength was 86.7 MPa, the elastic modulus was 56.1 GPa, the impermeability grade was P10, the reduction rate of compressive strength after 300 freeze-thaw cycles was 6.13%, and the reduction rate of splitting strength after 300 freeze-thaw cycles was 4.21%. Example 2

[0024] Step S3: Stir and mix: First, place the pretreated cement, aggregate particles, and mineral admixture into a mixer and dry mix for 1 min at a stirring speed of 40 rpm. Then, mix the water reducer, water, and thickener evenly and add them to the mixer, and continue to stir at a speed of 40 rpm for 1 min. Finally, add the air-entraining agent and expansive agent to the concrete mixture and stir at a speed of 30 rpm for 1 min to obtain the recycled aggregate self-compacting concrete. The mineral admixture is composed of fly ash, natural pozzolan, and silica fume mixed in a mass ratio of 3:1:1. The particle size of the mineral admixture is 0.2 μm, the particle size of the cement is 15 μm, and the mass ratio of the aggregate particles, cement, water reducer, thickener, air-entraining agent, mineral admixture, water, and expansive agent is 160:290:3:1:6:110:140:7.

[0025] Furthermore, the slump of the recycled aggregate self-compacting concrete was measured to be 271 mm, the slump flow was 694 mm, the T500 time was 2.11 s, the compressive strength was 88.3 MPa, the elastic modulus was 57.9 GPa, the impermeability grade was P10, the reduction rate of compressive strength after 300 freeze-thaw cycles was 6.02%, and the reduction rate of splitting strength after 300 freeze-thaw cycles was 4.07%. Example 3

[0026] Step S3: Stir and mix: First, place the pretreated cement, aggregate particles, and mineral admixture into a mixer and dry mix for 2 min at a stirring speed of 40 rpm. Then, mix the water reducer, water, and thickener evenly and add them to the mixer, and continue to stir at a speed of 40 rpm for 2 min. Finally, add the air-entraining agent and expansive agent to the concrete mixture and stir at a speed of 30 rpm for 1 min to obtain the recycled aggregate self-compacting concrete. The mineral admixture is composed of fly ash, natural pozzolan, and silica fume mixed in a mass ratio of 3:1:1. The particle size of the mineral admixture is 0.2 μm, the particle size of the cement is 15 μm, and the mass ratio of the aggregate particles, cement, water reducer, thickener, air-entraining agent, mineral admixture, water, and expansive agent is 170:290:3:1:6:100:120:7.

[0027] Furthermore, the slump of the recycled aggregate self-compacting concrete was measured to be 287 mm, the slump flow was 711 mm, the T500 time was 1.96 s, the compressive strength was 89.7 MPa, the elastic modulus was 59.7 GPa, the impermeability grade was P12, the reduction rate of compressive strength after 300 freeze-thaw cycles was 5.91%, and the reduction rate of splitting strength after 300 freeze-thaw cycles was 3.94%. Example 4

[0028] Step S3: Stir and mix: First, place the pretreated cement, aggregate particles, and mineral admixture into a mixer and dry mix for 2 min at a stirring speed of 40 rpm. Then, mix the water reducer, water, and thickener evenly and add them to the mixer, and continue to stir at a speed of 40 rpm for 2 min. Finally, add the air-entraining agent and expansive agent to the concrete mixture and stir at a speed of 30 rpm for 1 min to obtain recycled aggregate self-compacting concrete. The mineral admixture is composed of fly ash, natural volcanic ash, and silica fume mixed in a mass ratio of 3:1:1, the particle size of the mineral admixture is 0.2 μm, the particle size of the cement is 15 μm, and the mass ratio of the aggregate particles, cement, water reducer, thickener, air-entraining agent, mineral admixture, water, and expansive agent is 170:280:3:1:6:100:120:7.

[0029] Furthermore, the slump of the recycled aggregate self-compacting concrete was measured to be 281 mm, the slump flow was 703 mm, the T500 time was 2.04 s, the compressive strength was 89.1 MPa, the elastic modulus was 58.3 GPa, the impermeability grade was P10, the reduction rate of compressive strength after 300 freeze-thaw cycles was 5.98%, and the reduction rate of splitting strength after 300 freeze-thaw cycles was 4.01%. Example 5

[0030] Step S3: Stir and mix: First, place the pretreated cement, aggregate particles, and mineral admixture into a mixer and dry mix for 2 min at a stirring speed of 40 rpm. Then, mix the water reducer, water, and thickener evenly and add them to the mixer, and continue to stir at a speed of 40 rpm for 2 min. Finally, add the air-entraining agent and expansive agent to the concrete mixture and stir at a speed of 30 rpm for 2 min to obtain recycled aggregate self-compacting concrete. The mineral admixture is composed of fly ash, natural volcanic ash, and silica fume mixed in a mass ratio of 3:1:1, the particle size of the mineral admixture is 0.2 μm, the particle size of the cement is 15 μm, and the mass ratio of the aggregate particles, cement, water reducer, thickener, air-entraining agent, mineral admixture, water, and expansive agent is 160:280:3:1:7:100:100:7.

[0031] Furthermore, the slump of the recycled aggregate self-compacting concrete was measured to be 274 mm, the slump flow was 697 mm, the T500 time was 2.1 s, the compressive strength was 88.1 MPa, the elastic modulus was 57.8 GPa, the impermeability grade was P10, the reduction rate of the compressive strength after 300 freeze-thaw cycles was 6.04%, and the reduction rate of the splitting strength after 300 freeze-thaw cycles was 4.1%.

[0032] The performance test results of the recycled aggregate self-compacting concrete are as follows: Example One Two Three Four Five Slump (mm) 267 271 287 281 274 Slump flow (mm) 686 694 711 703 697 T500 (s) 2.43 2.11 1.96 2.04 2.1 Compressive strength (MPa) 86.7 88.3 89.7 89.1 88.1 Elastic modulus (GPa) 56.1 57.9 59.7 58.3 57.8 Impermeability grade P10 P10 P12 P10 P10 Reduction rate of compressive strength after 300 freeze-thaw cycles (%) 6.13 6.02 5.91 5.98 6.04 Reduction rate of splitting strength after 300 freeze-thaw cycles (%) 4.21 4.07 3.94 4.01 4.1 For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

Claims

1. A recycled aggregate self-compacting concrete with excellent impermeability and waterproofing effect, characterized in that: By mass fraction: Its raw materials include the following components: 160 - 180 parts of aggregate particles, 280 - 300 parts of cement, 3 - 4 parts of water reducing agent, 1 - 3 parts of thickening agent, 2 - 11 parts of air entraining agent, 80 - 120 parts of mineral admixture, 100 - 200 parts of water, and 7 - 9 parts of expansive agent; The preparation method of recycled aggregate self - compacting concrete includes the following steps: Step S1: Solution preparation: Prepare nano - solution, coating modification solution, and silane coupling agent solution; Step S2: Raw material pretreatment: Pretreat cement and recycled aggregate respectively; Step S3: Stirring and mixing: Add mineral admixture, water reducing agent, water, thickening agent, air entraining agent, expansive agent, and the cement and aggregate particles pretreated in Step S2 into a mixer for stirring and mixing to obtain recycled aggregate self - compacting concrete; Step S4: Quality control: Conduct performance testing on the prepared recycled aggregate self - compacting concrete.

2. The self-compacting recycled aggregate concrete with excellent impermeability and waterproofing effect according to claim 1, characterized in that: In Step S1, it also includes the following steps: Step S11: Nano - solution: First, add nano - silica and nano - calcium carbonate into water, then add PEG and SDBS into the solution, and put the solution into a microwave reaction device. Radiate it at a microwave frequency of 600 mhz for 10 - 20 min, and the temperature is 120 - 140 °C to obtain nano - solution; Step S12: Coating modification solution: Add polyethylene glycol into water, stir at a stirring speed of 400 - 450 rpm for 20 - 30 min to form a uniform solution. Then add the silane coupling agent into the solution at a speed of 2 - 3 drops / min, and continuously stir at 400 - 450 rpm for 10 - 15 min. Finally, add the polyacrylate emulsion into the mixed solution at a speed of 6 - 8 mL / min and stir at 270 rpm for 40 - 50 min to form a stable coating modification solution; Step S13: Silane coupling agent solution: Stir and dilute the silane coupling agent with 75% ethanol aqueous solution, where the mass ratio of the silane coupling agent to the ethanol aqueous solution is 1:(1 - 3), the stirring speed is 50 - 80 rpm, and the stirring time is 10 - 15 min to prepare the silane coupling agent solution.

3. An anti-permeation and waterproofing regenerated aggregate self-compacting concrete according to claim 1, characterized in that: In Step S2, it also includes the following steps: Step S21: Cement pretreatment: Place the cement in an environment of 60 - 90 °C and heat it for 2 - 6 min, where the stirring speed is 160 - 200 rpm. Then use a ball mill to grind the cement, where the rotation speed of the ball mill is 30 - 40 rpm and the grinding time is 20 - 90 min. Then add the silane coupling agent solution to the ground cement and stir at a speed of 120 - 160 rpm in a normal temperature environment for 0.5 - 3 h; Step S22: Aggregate pretreatment: Primary crushing is carried out using a jaw crusher to obtain aggregate blocks. Then, a counterattack crusher is used for secondary crushing to obtain aggregate slag. Subsequently, an impact crusher is used for tertiary crushing to obtain aggregate particles. The eccentric shaft speed of the jaw crusher is 160 - 220 rpm, and the crushing time is 1 - 2 h. The rotor speed of the counterattack crusher is 420 - 500 rpm, and the crushing time is 1 - 2 h. The impeller speed of the impact crusher is 1200 - 1600 rpm, and the crushing time is 0.5 - 2 h. Then, a ball mill is used to grind the aggregate particles. The speed of the ball mill is 40 - 60 rpm, and the grinding time is 0.5 - 3 h. Then, a vibrating screen is used to finely screen the obtained aggregate particles. The vibration frequency is 900 - 1000 times per minute, the amplitude is 4 - 5 mm, the aperture of the sieve mesh is 10 mm, and the particle size of the screened aggregate particles is 5 - 10 mm. Subsequently, the screened aggregate particles are chemically cleaned with a 6% hydrochloric acid solution; Step S23: Nano-treatment: The pretreated aggregate particles are immersed in a nano-solution. After 2 - 4 h of immersion, the aggregate particles are taken out and placed in an oven for drying. The temperature of the oven is 75 °C, and the drying time is 0.5 - 1.5 h; Step S24: Pre-wetting treatment: Water is added to a concrete pool, and the nano-treated aggregate particles are placed therein so that the aggregate particles are completely immersed in water. After 0.5 - 2 h of immersion, the aggregate particles are taken out and dried at 60 - 90 °C for 15 - 30 min; Step S25: Coating modification solution combined with ultrasonic vibration: The aggregate particles treated in Step S24 are added to the coating modification solution and immersed for 30 - 90 min under a pressure of 4 MPa. Then, ultrasonic vibration treatment is carried out. The ultrasonic power is 280 - 300 W, the frequency is 40 kHz, and the treatment time is 20 - 40 min.

4. An anti-permeability and waterproofing effect excellent recycled aggregate self-compacting concrete according to claim 1, characterized in that: In Step S3, the following steps are also included: Step S31: First, the pretreated cement, aggregate particles, and mineral admixtures are placed in a mixer and dry-mixed for 1 - 2 min at a stirring speed of 30 - 50 rpm; Step S32: Then, the water reducer, water, and thickener are mixed evenly and added to the mixer, and stirring continues at a speed of 30 - 50 rpm for 1 - 2 min; Step S33: Finally, the air-entraining agent and expansive agent are added to the concrete mixture, and stirring is carried out at a speed of 30 - 40 rpm for 1 - 2 min to obtain recycled aggregate self-compacting concrete.

5. An anti-permeation and waterproofing regenerated aggregate self-compacting concrete according to claim 1, characterized in that: In Step S4, the following steps are also included: Step S41: According to the standard of JGJ / T283 "Technical Specification for Application of Self-Compacting Concrete", the workability and mechanical properties of the recycled aggregate self-compacting concrete are tested; Step S42: According to JGJ / T193 "Standard for Inspection and Evaluation of Durability of Concrete", the impermeability and frost resistance of the recycled aggregate self-compacting concrete are determined to comprehensively evaluate the durability of the concrete.

6. The self-compacting recycled aggregate concrete with excellent anti-seepage and waterproofing effects according to claim 2, characterized in that: The mass ratio of the nano-silica, nano-calcium carbonate, water, PEG, and SDBS is (1 - 4):(0.2 - 1.5):100:0.05:(0.1 - 1).

7. An improved recycled aggregate self-compacting concrete with excellent impermeability and waterproofing effect, characterized in that: The particle size of the nano-calcium carbonate is 30 - 40 nm, and the particle size of the nano-silica is 20 - 40 nm.

8. An improved recycled aggregate self-compacting concrete with excellent impermeability and waterproofing effect, characterized in that: The particle size of the cement is 10 - 20 μm.

9. The self-compacting recycled aggregate concrete with excellent anti-seepage and waterproofing effects according to claim 2, characterized in that: The mass ratio of the polyacrylate emulsion, silane coupling agent, polyethylene glycol, and water is (64 - 75):(2 - 4):(6 - 10):(11 - 28).

10. An excellently impermeable and waterproof recycled aggregate self-compacting concrete according to claim 1, characterized in that: The mineral admixture is composed of fly ash, natural pozzolan, and silica fume mixed in a mass ratio of (2 - 3):1:1, and the particle size of the mineral admixture is 0.1 - 0.3 μm.