A recycled aggregate synergistically enhanced by a two-step mineralization method and a particle shape optimization method and a preparation method thereof

Abstract

The invention discloses a recycled aggregate synergistically enhanced by a two-step mineralization method and a particle shape optimization method and a preparation method thereof, and relates to the technical field of recycled aggregates. The invention comprises the following steps: crushing and screening waste concrete to obtain recycled aggregate particles; soaking the recycled aggregate particles in a mixed solution of a nucleating agent and an organic substrate solution, and then transferring the recycled aggregate particles to a reactor; spraying a bacillus pasteurianus liquid on the recycled aggregate particles uniformly at one time, and then curing for 5 hours, stirring during the curing process, and simultaneously introducing carbon dioxide gas into the reactor, and adjusting the temperature and humidity to maintain the set environmental conditions, so as to enhance the mineralization of the recycled aggregate particles; pouring the mineralized and enhanced recycled aggregate particles and cement powder into a disc granulator for particle shape optimization, and finally obtaining the synergistically enhanced recycled aggregate with higher physical properties and self-strength.

Description

Technical Field

[0001] The invention relates to the technical field of recycled aggregates, and in particular to a recycled aggregate synergistically enhanced by a two-step mineralization method and a particle shape optimization method and a preparation method thereof. Background Art

[0002] With the rapid development of the construction industry, the recycling of waste concrete has become an important research direction. Traditional recycled aggregates are inferior to natural aggregates due to their loose internal structure, rough surface, poor particle shape and low crushing value. In order to improve the performance of recycled aggregates, special maintenance techniques are needed to optimize their performance.

[0003] In the prior art, the curing technologies that can be used include carbon dioxide mineralization curing and microbial mineralization curing. Among them, carbon dioxide mineralization curing of concrete is a technology that utilizes the mineralization reaction between carbon dioxide and the calcium and magnesium components in concrete to improve the strength and durability of aggregate or concrete. This technology can not only achieve long-term and stable storage of greenhouse gas carbon dioxide, but also has good economic and low-carbon benefits when a large amount of industrial solid waste is used as raw materials. The microbial mineralization curing method is to induce minerals to precipitate on the surface and inside of concrete aggregates through the metabolic activities of microorganisms, and generate calcium carbonate through mineralization inside the pores of aggregates, thereby reducing porosity and strengthening recycled aggregates.

[0004] However, mineralization maintenance is still in the technical development stage, and there are still problems such as incomplete mineralization and complicated mineralization process, which results in low mineralization efficiency and poor basic physical properties of the recycled aggregate, such as mechanical properties and durability. Summary of the invention

[0005] The purpose of the present invention is to provide a recycled aggregate synergistically enhanced by a two-step mineralization method and a particle shape optimization method and a preparation method thereof, so as to solve the following technical problems:

[0006] How to improve the mechanical properties and durability of recycled aggregates.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] In a first aspect, the present invention discloses a method for preparing recycled aggregate synergistically enhanced by a two-step mineralization method and a particle shape optimization method, comprising the following steps:

[0009] S1. Crushing and screening the waste concrete to retain recycled coarse aggregate particles with a particle size of 5-25 mm, and then washing to remove floating dust to obtain recycled aggregate particles;

[0010] S2, soaking the recycled aggregate particles in a mixed solution of a nucleating agent and an organic substrate solution for 2 hours, and then transferring the recycled aggregate particles to a reactor;

[0011] S3. In the reactor, the Bacillus pasteurianus liquid is evenly sprayed on the recycled aggregate particles at one time, and then cured for 5 hours. During the curing process, the mixture is stirred, and carbon dioxide gas is introduced into the reactor. The temperature and humidity are adjusted to maintain the set environmental conditions, so that the mineralization of the recycled aggregate particles is enhanced;

[0012] S4. Pour the mineralized and enhanced recycled aggregate particles and cement powder into the disc granulator. The disc lifts the recycled aggregate particles by rotating and tilting, and then sprays water evenly. The recycled aggregate particles adhere to the cement slurry and gradually form into spherical particles. After screening, the recycled aggregate particles of 5-25mm are retained. After hardening, they are cleaned and naturally dried to constant weight, and finally the synergistically enhanced recycled aggregate is obtained.

[0013] Furthermore, in step S2, the nucleating agent is a saturated calcium hydroxide solution.

[0014] Furthermore, in step S2, the organic substrate solution is a urea solution, and the concentration of the urea solution is 0.5-1 mol / L.

[0015] Furthermore, in step S2, the volume mass ratio of the nucleating agent to the organic substrate solution in the mixed solution is 1:(1-1.5).

[0016] Further, in step S3, the concentration of the Bacillus pasteurianus liquid is 10 6 -10 8 cells / mL, spraying amount = weight of recycled aggregate particles × water absorption rate of recycled aggregate particles × (105-108)%.

[0017] Furthermore, in step S3, the concentration of the carbon dioxide gas is 50-80% and the flow rate is 2-5 L / min.

[0018] Furthermore, in step S3, the stirring rate during the curing process is 40-100 r / min.

[0019] Furthermore, in step S3, during the curing process, the temperature is adjusted to 20-35° C. and the relative humidity is adjusted to 70-90%.

[0020] Furthermore, in step S4, the amount of cement powder used is 20-50% of the weight of the recycled aggregate particles, and the amount of water used is 5-20% of the weight of the recycled aggregate particles.

[0021] Furthermore, in step S4, the cement powder is a mixture of silicate cement and rapid hardening sulphoaluminate cement in a weight ratio of 9:1.

[0022] In a second aspect, the present invention further discloses a recycled aggregate synergistically enhanced by a two-step mineralization method and a particle shape optimization method, which is prepared by the method for preparing the recycled aggregate synergistically enhanced by a two-step mineralization method and a particle shape optimization method as described above.

[0023] Beneficial effects of the present invention:

[0024] 1. In the preparation method of recycled aggregate synergistically enhanced by two-step mineralization method and particle shape optimization method provided by the present invention, in the process of adopting microbial mineralization enhancement, carbon dioxide mineralization enhancement, and particle shape optimization synergistic enhancement, the nucleating agent provides an alkaline environment required for two mineralization reactions and cement hydration reaction. The alkaline environment can promote further hydration of cement, generate more hydration products, and improve the strength of recycled aggregate; at the same time, the alkaline environment is conducive to the subsequent microbial mineralization reaction, thereby improving the mineralization efficiency;

[0025] 2. The preparation method of recycled aggregate synergistically enhanced by two-step mineralization method and particle shape optimization method provided by the present invention adopts the process of microbial mineralization enhancement, carbon dioxide mineralization enhancement, and particle shape optimization synergistic enhancement, and the carbon dioxide produced by microbial mineralization reacts with calcium ions to generate calcium carbonate precipitate, and the calcium carbonate precipitate can react with calcium hydroxide in cement hydration products to generate more stable ettringite, which further fills the pores of the recycled aggregate and improves the density and strength of the aggregate;

[0026] 3. The preparation method of recycled aggregate synergistically enhanced by two-step mineralization method and particle shape optimization method provided by the present invention adopts a three-treatment method (microbial mineralization enhancement, carbon dioxide mineralization enhancement, particle shape optimization), adopts a reactor and stirs, so that the recycled aggregate is more fully in contact with carbon dioxide, and the mineralization efficiency is further improved; and after particle shape optimization, the recycled aggregate is round and regular, and the particle shape is good. After the prepared recycled aggregate is fully mixed into concrete, the working performance, mechanical properties and durability of the concrete can be significantly improved;

[0027] 4. The recycled aggregate prepared by the method of the present invention has higher physical properties and self-strength. Compared with other methods, this method has high mineralization efficiency, more significant improvement in the performance of recycled aggregate, convenient operation, high controllability, and batch processing of aggregates. It can not only effectively reduce the mining of natural sand and gravel and reduce resource consumption, but also solve the problem of stacking construction waste and reduce environmental pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below in conjunction with the accompanying drawings.

[0029] Figure 1 This is a morphological structure diagram of the recycled aggregate prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The experimental methods in the following examples, unless otherwise specified, are all conventional methods, and are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial channels.

[0032] Example 1

[0033] The synergistically reinforced recycled aggregate is prepared by using microbial mineralization method, carbon dioxide mineralization method and particle shape optimization method, as follows:

[0034] Step 1: crush and screen the waste concrete, retain the recycled coarse aggregate particles with a particle size of 5-25 mm, then wash with water to remove the floating dust, and wait for it to dry naturally to constant weight to obtain untreated recycled aggregate particles. The weight of the recycled aggregate particles at this time is measured to be 100 kg and the water absorption rate is 12%;

[0035] Step 2: Prepare 60L saturated calcium hydroxide solution as a nucleating agent and 72L 0.8mol / L urea solution as an organic substrate solution, mix the two evenly to form a mixed solution, soak the recycled aggregate particles in the mixed solution for 2h, so that the calcium hydroxide and urea can fully adhere to the surface of the recycled aggregate particles and penetrate into the pores of the recycled aggregate; then transfer the recycled aggregate particles to the reactor;

[0036] Step 3: In the reactor, add 12.72L of 10 7 The Bacillus pasteurianus liquid of 10 cells / mL was evenly sprayed on the recycled aggregate particles at one time, and then stirred at a speed of 80r / min. At the same time, a carbon dioxide gas with a concentration of 70% was introduced into the reactor at a flow rate of 3L / min. The temperature and humidity adjustment device was started to maintain the temperature at 30°C and the relative humidity at 80% for 5 hours to enhance the mineralization of the recycled aggregate particles.

[0037] Step 4: Evenly mix ordinary Portland cement and fast-hardening sulphoaluminate cement in a weight ratio of 9:1 to form cement powder, pour the mineralized and enhanced recycled aggregate particles and cement powder into a disc granulator, the mass of cement powder input is 30% of the mass of the recycled aggregate; start the disc granulator, the disc will bring up the recycled aggregate and cement powder by rotating and tilting, and then evenly spray water, the amount of water is 10% of the mass of the recycled aggregate, the recycled aggregate particles adhere to the cement slurry and gradually roll into spherical particles, continue granulation for 30 minutes, wait for the cement slurry to adhere to the recycled aggregate particles to harden, and screen them to retain the recycled aggregate particles of 5-25 mm, which is the synergistically enhanced recycled aggregate.

[0038] The synergistically reinforced recycled aggregate was cleaned and dried naturally to constant weight to obtain Figure 1 The synergistically reinforced recycled aggregate shown is then observed, and it can be seen that the obtained recycled aggregate has a good appearance and morphology.

[0039] Example 2

[0040] The synergistically reinforced recycled aggregate is prepared by using microbial mineralization method, carbon dioxide mineralization method and particle shape optimization method, as follows:

[0041] Step 1: crush and screen the waste concrete, retain the recycled coarse aggregate particles with a particle size of 5-25 mm, then wash with water to remove the floating dust, and wait for it to dry naturally to constant weight to obtain untreated recycled aggregate particles. The weight of the recycled aggregate particles at this time is measured to be 100 kg and the water absorption rate is 12%;

[0042] Step 2: Prepare 60L saturated calcium hydroxide solution as a nucleating agent and 60L 0.8mol / L urea solution as an organic substrate solution, mix the two evenly to form a mixed solution, soak the recycled aggregate particles in the mixed solution for 2h, so that the calcium hydroxide and urea can fully adhere to the surface of the recycled aggregate particles and penetrate into the pores of the recycled aggregate; then transfer the recycled aggregate particles to the reactor;

[0043] Step 3: In the reactor, add 12.6L of 10 7 The Bacillus pasteurianus liquid of 10 cells / mL was evenly sprayed on the recycled aggregate particles at one time, and then stirred at a speed of 80r / min. At the same time, a carbon dioxide gas with a concentration of 50% was introduced into the reactor at a flow rate of 5L / min. The temperature and humidity adjustment device was started to maintain the temperature at 30°C and the relative humidity at 80% for 5 hours to enhance the mineralization of the recycled aggregate particles.

[0044] Step 4: Evenly mix ordinary Portland cement and fast-hardening sulphoaluminate cement in a weight ratio of 9:1 to form cement powder, pour the mineralized and enhanced recycled aggregate particles and cement powder into a disc granulator, the mass of cement powder input is 20% of the mass of the recycled aggregate; start the disc granulator, the disc will bring up the recycled aggregate and cement powder by rotating and tilting, and then evenly spray water, the amount of water is 5% of the mass of the recycled aggregate, the recycled aggregate particles adhere to the cement slurry and gradually roll into spherical particles, continue granulation for 30 minutes, wait for the cement slurry to adhere to the recycled aggregate particles to harden, and screen them to retain the recycled aggregate particles of 5-25 mm, which is the synergistically enhanced recycled aggregate.

[0045] The obtained synergistically reinforced recycled aggregate was cleaned and naturally dried to constant weight, and then observed, and it can be seen that the obtained recycled aggregate has a good appearance.

[0046] Example 3

[0047] The synergistically reinforced recycled aggregate is prepared by using microbial mineralization method, carbon dioxide mineralization method and particle shape optimization method, as follows:

[0048] Step 1: crush and screen the waste concrete, retain the recycled coarse aggregate particles with a particle size of 5-25 mm, then wash with water to remove the floating dust, and wait for it to dry naturally to constant weight to obtain untreated recycled aggregate particles. The weight of the recycled aggregate particles at this time is measured to be 100 kg and the water absorption rate is 12%;

[0049] Step 2: Prepare 60L saturated calcium hydroxide solution as a nucleating agent and 90L 0.8mol / L urea solution as an organic substrate solution, mix the two evenly to form a mixed solution, soak the recycled aggregate particles in the mixed solution for 2h, so that the calcium hydroxide and urea can fully adhere to the surface of the recycled aggregate particles and penetrate into the pores of the recycled aggregate; then transfer the recycled aggregate particles to the reactor;

[0050] Step 3: In the reactor, add 12.96L of 10 7 The Bacillus pasteurianus liquid of 10 cells / mL was evenly sprayed on the recycled aggregate particles at one time, and then stirred at a speed of 80r / min. At the same time, carbon dioxide gas with a concentration of 80% was introduced into the reactor at a flow rate of 2L / min. The temperature and humidity adjustment device was started to maintain the temperature at 30°C and the relative humidity at 80% for 5 hours to enhance the mineralization of the recycled aggregate particles.

[0051] Step 4: Evenly mix ordinary Portland cement and fast-hardening sulphoaluminate cement in a weight ratio of 9:1 to form cement powder, pour the mineralized and enhanced recycled aggregate particles and cement powder into a disc granulator, the mass of cement powder input is 50% of the mass of the recycled aggregate; start the disc granulator, the disc will bring up the recycled aggregate and cement powder by rotating and tilting, and then evenly spray water, the amount of water is 20% of the mass of the recycled aggregate, the recycled aggregate particles adhere to the cement slurry and gradually roll into spherical particles, continue granulation for 30 minutes, wait for the cement slurry to adhere to the recycled aggregate particles to harden, and screen them to retain the recycled aggregate particles of 5-25 mm, which is the synergistically enhanced recycled aggregate.

[0052] The obtained synergistically reinforced recycled aggregate was cleaned and naturally dried to constant weight, and then observed, and it can be seen that the obtained recycled aggregate has a good appearance.

[0053] Example 4

[0054] The synergistically reinforced recycled aggregate is prepared by using microbial mineralization method, carbon dioxide mineralization method and particle shape optimization method, as follows:

[0055] Step 1: crush and screen the waste concrete, retain the recycled coarse aggregate particles with a particle size of 5-25 mm, then wash with water to remove the floating dust, and wait for it to dry naturally to constant weight to obtain untreated recycled aggregate particles. The weight of the recycled aggregate particles at this time is measured to be 100 kg and the water absorption rate is 12%;

[0056] Step 2: Prepare 60L saturated calcium hydroxide solution as a nucleating agent and 72L 0.8mol / L urea solution as an organic substrate solution, mix the two evenly to form a mixed solution, soak the recycled aggregate particles in the mixed solution for 2h, so that the calcium hydroxide and urea can fully adhere to the surface of the recycled aggregate particles and penetrate into the pores of the recycled aggregate; then transfer the recycled aggregate particles to the reactor;

[0057] Step 3: In the reactor, add 12.72L of 10 6 cells / mL of Bacillus pasteurianus liquid was evenly sprayed on the recycled aggregate particles at one time, and then stirred at a speed of 40r / min. At the same time, a carbon dioxide gas with a concentration of 70% was introduced into the reactor at a flow rate of 3L / min. The temperature and humidity adjustment device was started to maintain the temperature at 20°C and the relative humidity at 90% for 5 hours to enhance the mineralization of the recycled aggregate particles.

[0058] Step 4: Evenly mix ordinary Portland cement and fast-hardening sulphoaluminate cement in a weight ratio of 9:1 to form cement powder, pour the mineralized and enhanced recycled aggregate particles and cement powder into a disc granulator, the mass of cement powder input is 20% of the mass of the recycled aggregate; start the disc granulator, the disc will bring up the recycled aggregate and cement powder by rotating and tilting, and then evenly spray water, the amount of water is 10% of the mass of the recycled aggregate, the recycled aggregate particles adhere to the cement slurry and gradually roll into spherical particles, continue granulation for 30 minutes, wait for the cement slurry to adhere to the recycled aggregate particles to harden, and screen them to retain the recycled aggregate particles of 5-25 mm, which is the synergistically enhanced recycled aggregate.

[0059] The obtained synergistically reinforced recycled aggregate was cleaned and naturally dried to constant weight, and then observed, and it can be seen that the obtained recycled aggregate has a good appearance.

[0060] Example 5

[0061] The synergistically reinforced recycled aggregate is prepared by using microbial mineralization method, carbon dioxide mineralization method and particle shape optimization method, as follows:

[0062] Step 1: crush and screen the waste concrete, retain the recycled coarse aggregate particles with a particle size of 5-25 mm, then wash with water to remove the floating dust, and wait for it to dry naturally to constant weight to obtain untreated recycled aggregate particles. The weight of the recycled aggregate particles at this time is measured to be 100 kg and the water absorption rate is 12%;

[0063] Step 2: Prepare 60L saturated calcium hydroxide solution as a nucleating agent and 72L 0.8mol / L urea solution as an organic substrate solution, mix the two evenly to form a mixed solution, soak the recycled aggregate particles in the mixed solution for 2h, so that the calcium hydroxide and urea can fully adhere to the surface of the recycled aggregate particles and penetrate into the pores of the recycled aggregate; then transfer the recycled aggregate particles to the reactor;

[0064] Step 3: In the reactor, add 12.72L of 10 8 The Bacillus pasteurianus liquid of 10 cells / mL was evenly sprayed on the recycled aggregate particles at one time, and then stirred at a speed of 100 r / min. At the same time, a carbon dioxide gas with a concentration of 70% was introduced into the reactor at a flow rate of 3 L / min. The temperature and humidity adjustment device was started to maintain the temperature at 35°C and the relative humidity at 70% for 5 hours to enhance the mineralization of the recycled aggregate particles.

[0065] Step 4: Evenly mix ordinary Portland cement and fast-hardening sulphoaluminate cement in a weight ratio of 9:1 to form cement powder, pour the mineralized and enhanced recycled aggregate particles and cement powder into a disc granulator, the mass of cement powder input is 30% of the mass of the recycled aggregate; start the disc granulator, the disc will bring up the recycled aggregate and cement powder by rotating and tilting, and then evenly spray water, the amount of water is 10% of the mass of the recycled aggregate, the recycled aggregate particles adhere to the cement slurry and gradually roll into spherical particles, continue granulation for 30 minutes, wait for the cement slurry to adhere to the recycled aggregate particles to harden, and screen them to retain the recycled aggregate particles of 5-25 mm, which is the synergistically enhanced recycled aggregate.

[0066] The obtained synergistically reinforced recycled aggregate was cleaned and naturally dried to constant weight, and then observed, and it can be seen that the obtained recycled aggregate has a good appearance.

[0067] Comparative Example 1

[0068] The recycled aggregate is prepared by screening method as follows:

[0069] The waste concrete is crushed and sieved to retain recycled coarse aggregate particles with a particle size of 5-25 mm, which are then washed with water to remove floating dust and dried naturally to constant weight to obtain recycled aggregate particles.

[0070] Comparative Example 2

[0071] The microbial mineralization method is used to prepare recycled aggregates, as follows:

[0072] Step 1: crush and screen the waste concrete, retain the recycled coarse aggregate particles with a particle size of 5-25 mm, then wash with water to remove the floating dust, and wait for it to dry naturally to constant weight to obtain untreated recycled aggregate particles. The weight of the recycled aggregate particles at this time is measured to be 100 kg and the water absorption rate is 12%;

[0073] Step 2: Prepare 60L saturated calcium hydroxide solution as a nucleating agent and 72L 0.8mol / L urea solution as an organic substrate solution, mix the two evenly to form a mixed solution, soak the recycled aggregate particles in the mixed solution for 2h, so that the calcium hydroxide and urea can fully adhere to the surface of the recycled aggregate particles and penetrate into the pores of the recycled aggregate; then transfer the recycled aggregate particles to the reactor;

[0074] Step 3: In the reactor, add 12.72L of 10 7 cells / mL of Bacillus pasteurianus liquid was evenly sprayed on the recycled aggregate particles at one time, and then stirred at a speed of 80r / min for 5 hours to enhance the mineralization of the recycled aggregate particles;

[0075] Step 4: Screen the recycled aggregate particles after mineralization and enhancement, retain the recycled aggregate particles of 5-25 mm, clean them and dry them naturally to constant weight, which is the recycled aggregate.

[0076] Comparative Example 3

[0077] The recycled aggregate is prepared by the carbon dioxide mineralization method as follows:

[0078] Step 1: crush and screen the waste concrete, retain recycled coarse aggregate particles with a particle size of 5-25 mm, then wash with water to remove floating dust, and allow it to dry naturally to constant weight to obtain untreated recycled aggregate particles;

[0079] Step 2: Prepare 60L saturated calcium hydroxide solution as a nucleating agent and 72L 0.8mol / L urea solution as an organic substrate solution, mix the two evenly to form a mixed solution, soak the recycled aggregate particles in the mixed solution for 2h, so that the calcium hydroxide and urea can fully adhere to the surface of the recycled aggregate particles and penetrate into the pores of the recycled aggregate; then transfer the recycled aggregate particles to the reactor;

[0080] Step 3: introduce 70% carbon dioxide gas into the reactor at a flow rate of 3L / min, start the temperature and humidity adjustment device, maintain the temperature at 30°C and the relative humidity at 80% for 5 hours to enhance the mineralization of the recycled aggregate particles;

[0081] Step 4: Screen the recycled aggregate particles after mineralization and enhancement, retain the recycled aggregate particles of 5-25 mm, clean them and dry them naturally to constant weight, which is the recycled aggregate.

[0082] Comparative Example 4

[0083] The particle shape optimization method is used to prepare recycled aggregate, as follows:

[0084] Step 1: crush and screen the waste concrete, retain recycled coarse aggregate particles with a particle size of 5-25 mm, then wash with water to remove floating dust, and allow it to dry naturally to constant weight to obtain untreated recycled aggregate particles;

[0085] Step 2: Evenly mix ordinary Portland cement and fast-hardening sulphoaluminate cement in a weight ratio of 9:1 to form cement powder, pour the recycled aggregate particles and cement powder into a disc granulator, the mass of cement powder input is 30% of the mass of the recycled aggregate; start the disc granulator, the disc will bring up the recycled aggregate and cement powder by rotating and tilting, and then evenly spray water, the amount of water is 10% of the mass of the recycled aggregate, the recycled aggregate particles adhere to the cement slurry and gradually roll into spherical particles, continue granulation for 30 minutes, wait for the cement slurry to adhere to the recycled aggregate particles to harden, screen, retain 5-25mm recycled aggregate particles, clean them and dry them naturally to constant weight, which is the recycled aggregate.

[0086] Comparative Example 5

[0087] The recycled aggregate is prepared by microbial mineralization method and particle shape optimization method, as follows:

[0088] Step 1: crush and screen the waste concrete, retain the recycled coarse aggregate particles with a particle size of 5-25 mm, then wash with water to remove the floating dust, and wait for it to dry naturally to constant weight to obtain untreated recycled aggregate particles. The weight of the recycled aggregate particles at this time is measured to be 100 kg and the water absorption rate is 12%;

[0089] Step 2: Prepare 60L saturated calcium hydroxide solution as a nucleating agent and 72L 0.8mol / L urea solution as an organic substrate solution, mix the two evenly to form a mixed solution, soak the recycled aggregate particles in the mixed solution for 2h, so that the calcium hydroxide and urea can fully adhere to the surface of the recycled aggregate particles and penetrate into the pores of the recycled aggregate; then transfer the recycled aggregate particles to the reactor;

[0090] Step 3: In the reactor, add 12.72L of 10 7 cells / mL of Bacillus pasteurianus liquid was evenly sprayed on the recycled aggregate particles at one time, and then stirred at a speed of 80r / min for 5 hours to enhance the mineralization of the recycled aggregate particles;

[0091] Step 4. Evenly mix ordinary Portland cement and fast-hardening sulphoaluminate cement in a weight ratio of 9:1 to form cement powder, pour the mineralized enhanced recycled aggregate particles and cement powder into the disc granulator, the mass of cement powder input is 30% of the mass of the recycled aggregate; start the disc granulator, the disc will bring up the recycled aggregate and cement powder by rotating and tilting, and then evenly spray water, the water amount is 10% of the mass of the recycled aggregate, the recycled aggregate particles adhere to the cement slurry and gradually roll into spherical particles, continue granulation for 30 minutes, wait for the cement slurry to adhere to the recycled aggregate particles to harden, screen, retain 5-25mm recycled aggregate particles, clean them and dry them naturally to constant weight, which is the recycled aggregate.

[0092] Comparative Example 6

[0093] The recycled aggregate is prepared by using the carbon dioxide mineralization method and the particle shape optimization method, as follows:

[0094] Step 1: crush and screen the waste concrete, retain recycled coarse aggregate particles with a particle size of 5-25 mm, then wash with water to remove floating dust, and allow it to dry naturally to constant weight to obtain untreated recycled aggregate particles;

[0095] Step 2: Prepare 60L saturated calcium hydroxide solution as a nucleating agent and 72L 0.8mol / L urea solution as an organic substrate solution, mix the two evenly to form a mixed solution, soak the recycled aggregate particles in the mixed solution for 2h, so that the calcium hydroxide and urea can fully adhere to the surface of the recycled aggregate particles and penetrate into the pores of the recycled aggregate; then transfer the recycled aggregate particles to the reactor;

[0096] Step 3: introduce 70% carbon dioxide gas into the reactor at a flow rate of 3L / min, start the temperature and humidity adjustment device, maintain the temperature at 30°C and the relative humidity at 80% for 5 hours to enhance the mineralization of the recycled aggregate particles;

[0097] Step 4. Evenly mix ordinary Portland cement and fast-hardening sulphoaluminate cement in a weight ratio of 9:1 to form cement powder, pour the mineralized enhanced recycled aggregate particles and cement powder into the disc granulator, the mass of cement powder input is 30% of the mass of the recycled aggregate; start the disc granulator, the disc will bring up the recycled aggregate and cement powder by rotating and tilting, and then evenly spray water, the water amount is 10% of the mass of the recycled aggregate, the recycled aggregate particles adhere to the cement slurry and gradually roll into spherical particles, continue granulation for 30 minutes, wait for the cement slurry to adhere to the recycled aggregate particles to harden, screen, retain 5-25mm recycled aggregate particles, clean them and dry them naturally to constant weight, which is the recycled aggregate.

[0098] Comparative Example 7

[0099] The recycled aggregate is prepared by microbial mineralization and carbon dioxide mineralization, as follows:

[0100] Step 1: crush and screen the waste concrete, retain the recycled coarse aggregate particles with a particle size of 5-25 mm, then wash with water to remove the floating dust, and wait for it to dry naturally to constant weight to obtain untreated recycled aggregate particles. The weight of the recycled aggregate particles at this time is measured to be 100 kg and the water absorption rate is 12%;

[0101] Step 2: Prepare 60L saturated calcium hydroxide solution as a nucleating agent and 72L 0.8mol / L urea solution as an organic substrate solution, mix the two evenly to form a mixed solution, soak the recycled aggregate particles in the mixed solution for 2h, so that the calcium hydroxide and urea can fully adhere to the surface of the recycled aggregate particles and penetrate into the pores of the recycled aggregate; then transfer the recycled aggregate particles to the reactor;

[0102] Step 3: In the reactor, add 12.72L of 10 7 The Bacillus pasteurianus liquid of 10 cells / mL was evenly sprayed on the recycled aggregate particles at one time, and then stirred at a speed of 80r / min. At the same time, a carbon dioxide gas with a concentration of 70% was introduced into the reactor at a flow rate of 3L / min. The temperature and humidity adjustment device was started to maintain the temperature at 30°C and the relative humidity at 80% for 5 hours to enhance the mineralization of the recycled aggregate particles.

[0103] Step 4: Screen the recycled aggregate particles after mineralization and enhancement, and retain the recycled aggregate particles of 5-25 mm, which are the recycled aggregate.

[0104] The basic physical properties of the recycled aggregates obtained in Examples 1-5 and Comparative Examples 1-7 were tested. The testing method was based on the test method of JGJ52-2006 "Standard for Quality and Inspection Methods of Sand and Stone for Ordinary Concrete". The test items included bulk density, porosity, needle-like particle content and crushing value. The test results are listed in Table 1. Table 1 is as follows:

[0105] Table 1

[0106]

[0107] By analyzing the data in Table 1, it can be found that compared with Comparative Examples 1-7, the packing density of the synergistically reinforced recycled aggregate prepared in Examples 1-5 is significantly higher, and the porosity, needle-like particle content and crushing value are significantly lower, which shows that the recycled aggregate prepared by the preparation method of the present invention using microbial mineralization method, carbon dioxide mineralization method and particle shape optimization method to synergistically enhance the recycled aggregate has stronger basic physical properties.

[0108] The above describes some embodiments of the present invention in detail, but the contents are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preparing recycled aggregate synergistically enhanced by a two-step mineralization method and a particle shape optimization method, characterized in that: The steps include: S1. Crushing and screening the waste concrete to retain recycled coarse aggregate particles with a particle size of 5-25 mm, and then washing to remove floating dust to obtain recycled aggregate particles; S2, soaking the recycled aggregate particles in a mixed solution of a nucleating agent and an organic substrate solution, and after soaking for 2 hours, transferring the recycled aggregate particles to a reactor; the nucleating agent is a saturated calcium hydroxide solution; the organic substrate solution is a urea solution; S3. In the reactor, the Bacillus pasteurianus liquid is evenly sprayed on the recycled aggregate particles at one time, and then cured for 5 hours. During the curing process, the mixture is stirred, and carbon dioxide gas is introduced into the reactor. The temperature and humidity are adjusted to maintain the set environmental conditions to enhance the mineralization of the recycled aggregate particles. The concentration of the Bacillus pasteurianus liquid is 10 6 -10 8 cells / mL; the spraying amount of the Bacillus pasteurianus liquid = the weight of the recycled aggregate particles × the water absorption rate of the recycled aggregate particles × (105-108)%; the concentration of the carbon dioxide gas is 50-80% and the flow rate is 2-5L / min; the stirring rate during the curing process is 40-100r / min; the temperature during the curing process is adjusted to 20-35℃ and the relative humidity is adjusted to 70-90%; S4. Pour the mineralized and enhanced recycled aggregate particles and cement powder into the disc granulator. The disc lifts the recycled aggregate particles by rotating and tilting, and then sprays water evenly. The recycled aggregate particles adhere to the cement slurry and gradually form into spherical particles. After screening, the recycled aggregate particles of 5-25mm are retained. After hardening, they are cleaned and naturally dried to constant weight, and finally the synergistically enhanced recycled aggregate is obtained.

2. The method for preparing recycled aggregate synergistically enhanced by two-step mineralization method and particle shape optimization method according to claim 1, characterized in that: In step S2, the concentration of the urea solution is 0.5-1 mol / L.

3. The method for preparing recycled aggregate synergistically enhanced by two-step mineralization method and particle shape optimization method according to claim 1, characterized in that: In step S2, the volume ratio of the nucleating agent to the organic substrate solution in the mixed solution is 1:(1-1.5).

4. The method for preparing recycled aggregate synergistically enhanced by two-step mineralization method and particle shape optimization method according to claim 1, characterized in that: In step S4, the amount of cement powder used is 20-50% of the weight of the recycled aggregate particles, and the amount of water used is 5-20% of the weight of the recycled aggregate particles.

5. The method for preparing recycled aggregate synergistically enhanced by two-step mineralization method and particle shape optimization method according to claim 1, characterized in that: In step S4, the cement powder is a mixture of silicate cement and rapid hardening sulphoaluminate cement in a weight ratio of 9:

1.

6. A recycled aggregate synergistically enhanced by a two-step mineralization method and a particle shape optimization method, characterized in that: The invention discloses a method for preparing recycled aggregate synergistically enhanced by a two-step mineralization method and a particle shape optimization method as described in any one of claims 1 to 5.

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