Process for the preparation of recycled aggregates from non-fluid silicate concrete waste

Abstract

The application relates to the technical field of concrete waste slurry application, and particularly discloses a process for preparing recycled aggregate from non-fluid silicate concrete waste. The process comprises the following steps: (1) after the non-fluid silicate concrete waste is finely ground, the non-fluid silicate concrete waste is uniformly mixed with a silicate cement, graphene, asbestos fiber, a ferrous sulfate or ferrous sulfate aqueous solution, and then granulated, the obtained granules are standard cured, and a pretreated body is obtained after completion; (2) the pretreated body is immersed in a calcium bicarbonate solution, after completion, the pretreated body is separated out and placed in an EDTA or EGTA-containing sodium carbonate solution for activation treatment. After completion, the obtained pretreated body is standard cured again, and recycled aggregate is obtained. The above process of the application utilizes the characteristics of the non-fluid silicate concrete waste to prepare high-strength recycled aggregate, not only realizes resource utilization of the non-fluid silicate concrete waste, but also makes the non-fluid silicate concrete waste better play its own advantages to obtain high-performance recycled aggregate products.

Description

Technical Field

[0001] This invention relates to the field of concrete waste slurry application technology, specifically to a process for preparing recycled aggregate from non-fluid silicate concrete waste. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Concrete mixing plants generate a significant amount of waste slurry during daily production, from cleaning mixers, transport vehicles, and the production site. Statistics show that a concrete mixing plant with an annual output of 400,000 cubic meters generates as much as 120 tons of waste slurry daily just from cleaning equipment within the production site. This large volume of waste slurry presents a difficult problem to handle: the first method is direct discharge, but this pollutes the environment and seriously violates environmental regulations. The second method is collection and transportation to designated locations, but this requires dehydration and drying before transport. A bigger problem is that this method not only occupies a large area and consumes substantial funds, resulting in a waste of manpower, material resources, and environmental pollution. Therefore, this waste slurry seriously hinders the operation of enterprises and has become a major problem that urgently needs to be solved by mixing plants.

[0004] Therefore, recycling and reusing waste slurry generated from concrete mixing plants not only helps save significant amounts of water and raw materials, protects the surrounding environment from pollution, and meets the requirements of sustainable development for enterprises, but also helps reduce production costs, resulting in significant economic, environmental, and social benefits. This invention has found that waste generated from concrete mixing plants can be broadly categorized into two types: fluid waste slurry and hardened, non-fluid solid waste that cannot be returned to a fluid state. However, current research on this type of waste mostly treats the waste slurry as a single type of paste and adds it to newly prepared concrete for utilization. This invention, however, finds that fluid waste slurry and non-fluid solid waste are two materials with significantly different properties. Adding them uniformly to newly prepared concrete affects the mechanical properties after hardening, increasing the difficulty and limitations of utilizing this type of waste. Therefore, this crude utilization method still has significant limitations. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a process for the refined utilization of concrete waste generated from concrete mixing plants after classification. This process utilizes the characteristics of non-fluid silicate concrete waste to prepare recycled aggregate, not only achieving resource utilization of non-fluid silicate concrete waste but also enabling this waste to better leverage its advantages and improve the performance of concrete prepared with this recycled aggregate. Specifically, the technical solution of this invention is as follows.

[0006] A process for preparing recycled aggregate from non-fluid silicate concrete waste includes the following steps:

[0007] (1) After grinding the non-fluid silicate concrete waste, it is mixed evenly with silicate cement, graphene, asbestos fiber, ferric sulfate or ferrous sulfate aqueous solution and then granulated. The resulting particles are cured according to standard, and a pretreated body is obtained after completion.

[0008] (2) The pretreated body is immersed in a calcium bicarbonate solution. After immersion, the pretreated body is separated and placed in a sodium carbonate solution containing EDTA or EGTA for activation treatment. After activation, the pretreated body is cured again according to standard conditions to obtain recycled aggregate.

[0009] Furthermore, in step (1), the particle size of the ground non-fluid silicate concrete waste is not less than 300 mesh. The non-fluid silicate concrete waste contains a large amount of hydration product calcium hydroxide, which can be more fully exposed and reacted after grinding.

[0010] Further, in step (1), the weight ratio of the non-fluid silicate concrete waste, silicate cement, graphene, and fiber is 32–38: 20–25: 0.25–0.43: 1.5–2.5, respectively. Optionally, the ratio of the above solid raw materials to the ferric sulfate or ferrous sulfate aqueous solution is 1 g: 0.3–0.36 ml, wherein the mass fraction of the ferric sulfate or ferrous sulfate is 4.5–6%.

[0011] Furthermore, in step (1), the length of the asbestos fiber is 3-5 mm and the diameter is 20-50 μm. The asbestos fiber helps to enhance the crack resistance of the obtained recycled aggregate.

[0012] Furthermore, in step (1), the curing time is 10 to 20 hours, and while the mixture is hardening and forming, the non-fluid silicate concrete waste is modified by ferric sulfate or ferrous sulfate.

[0013] Further, in step (2), the ratio of the pretreated body to the calcium bicarbonate solution is 1g:25-40ml, and the immersion time is 30-50min. Optionally, the mass fraction of the calcium bicarbonate solution is 8-15%. This step utilizes the pores of the pretreated body to absorb calcium ions for further modification treatment of the pretreated body.

[0014] Further, in step (2), the ratio of the pretreated body to the sodium carbonate solution is 1g:18-30ml. Optionally, the mass fraction of the sodium carbonate solution is 7-10%. The sodium carbonate solution facilitates the dissolution of EDTA or EGTA and also forms a modified liquid to activate the pretreated body by adsorbing calcium ions, thereby improving the performance of the pretreated body.

[0015] Further, in step (2), the mass fraction of EDTA (ethylenediaminetetraacetic acid) or EGTA (ethylene glycol bis(2-aminoethyl ether)tetraacetic acid) in the sodium carbonate solution is 0.2% to 0.6%. The EDTA or EGTA can inhibit the transformation of highly reactive metastable calcium carbonate to less reactive stable calcium carbonate during the formation of calcium carbonate from calcium ions and carbonate ions in the pretreated body, thereby increasing the activity of the obtained recycled aggregate and improving the mechanical properties of the recycled aggregate and the concrete prepared from it.

[0016] Furthermore, in step (2), the activation treatment time is 50 to 72 hours. During this process, the sodium carbonate solution containing EDTA or EGTA forms highly reactive calcium carbonate in the pores of the pretreated body, while the pretreated body is immersed in water for curing, which helps to reduce the heat of hydration and reduce the generation of cracks in the pretreated body.

[0017] Furthermore, in step (2), the standard curing time is 14 to 28 days, so that the hydration reaction in the recycled aggregate can be carried out more fully.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention reveals that hardened, non-fluid solid waste from concrete mixing plants, having undergone hydration and hardening, cannot return to a fluid state. However, due to the lack of mold constraint during hydration, this type of non-fluid solid waste has low strength and is easily broken. Furthermore, its low reactivity means that when crushed into powder, it contributes little to the performance of the prepared concrete, resulting in low utilization value.

[0020] To this end, the present invention first grinds the non-fluid solid waste to fully expose the internal hydration products; then, the obtained waste powder is mixed with silicate cement, graphene, asbestos fiber, and an aqueous solution of ferric sulfate or ferrous sulfate, followed by curing. During this process, the cement hydration forms a cementitious component that binds the raw materials together to form the pretreated body. Simultaneously, the sulfate ions provided by the ferric sulfate or ferrous sulfate react with the silicon hydroxide hydration product provided by the waste powder to form calcium sulfate and ferric hydroxide / ferrous hydroxide. The calcium sulfate further reacts with the calcium aluminate provided by the silicate cement to form hydrated calcium sulfoaluminate (Ettringaite), which helps compensate for the porosity caused by volume shrinkage during the hydration stage of the pretreated body, improving its density and thus its early strength. At the same time, the ferric hydroxide or ferrous hydroxide also helps promote the hydration degree of the cement, reducing porosity and improving the strength and impermeability of the pretreated body. Furthermore, the structure formed by the interdoping of graphene and asbestos fibers with the cementing components can effectively improve the strength of the pretreated body, and the sheet-like graphene also helps to block the pores within the pretreated body, thereby improving its impermeability. It can be seen that this invention, by studying the characteristics of the non-fluid solid waste, transforms low-activity non-fluid solid waste into highly active raw materials, increasing the utilization value of non-fluid solid waste and contributing to the promotion of its recycling.

[0021] Furthermore, the present invention further treats the pretreated body with a calcium bicarbonate solution and a sodium carbonate solution containing EDTA or EGTA, respectively. The modified solution formed by the sodium carbonate solution and EDTA or EGTA activates the pretreated body that has adsorbed calcium ions, thereby improving the performance of the pretreated body. In this process, the pretreated body first absorbs calcium ions through its pores, and then reacts with the carbonate ions to form calcium carbonate solid, which refills the pores in the pretreated body, increasing the density of the pretreated body and thus improving its strength and impermeability. Simultaneously, during the formation of calcium carbonate, since the outermost shell of the calcium ion lacks electrons, the resulting empty orbitals require coordination. The oxygen and nitrogen elements on EDTA or EGTA possess lone pairs of electrons, which can form coordination bonds with these empty orbitals. This allows EDTA or EGTA to form a complex with the calcium ion. When reacting with the carbonate ion to form calcium carbonate, this complex inhibits the transformation of highly reactive metastable calcium carbonate into less reactive stable calcium carbonate. Consequently, the calcium carbonate particles filling the pores and surface of the pretreated aggregate exhibit high reactivity. When the resulting recycled aggregate enters the concrete, this highly reactive calcium carbonate can dissolve and recrystallize, bonding with the cementitious components produced by hydration in the concrete. This not only further improves the density and strength of the recycled aggregate but also strengthens the bond between the recycled aggregate and the concrete matrix, enhancing the concrete's strength. Furthermore, the water-curing process in the pretreated aggregate also helps reduce the heat of hydration, decreases cracks in the recycled aggregate, and improves its performance. Attached Figure Description

[0022] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings, wherein:

[0023] Figure 1 The following is an illustration of the effect of using non-fluid solid waste in the following embodiments.

[0024] Figure 2 The image shows the XRD pattern of the recycled aggregate prepared in Example 1 below. Detailed Implementation

[0025] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. The present invention will now be further described with reference to specific embodiments.

[0026] Example 1

[0027] A process for preparing recycled aggregate from non-fluid silicate concrete waste includes the following steps:

[0028] (1) Dry non-flowing silicate concrete waste blocks (such as...) Figure 1 (As shown) is placed in a crusher for crushing, then ground and passed through a 350-mesh sieve to obtain non-fluid silicate concrete waste powder for later use.

[0029] (2) The fluidized silicate concrete waste powder, 42.5 silicate cement, graphene, and asbestos fiber were added to a mixer in a weight ratio of 35:22:0.4:1.8 and stirred for 5 minutes. The length of the asbestos fiber was mainly distributed between 3 and 5 mm, and the diameter was mainly distributed between 20 and 50 μm. Then, a 5% ferric sulfate aqueous solution was added to the obtained mixed powder at a ratio of 1 g:0.35 ml and mixed evenly. The mixture was then granulated using a granulator. The resulting particles were cured for 12 hours (temperature 20±3℃, relative humidity 92%). After completion, a pretreated body was obtained for later use.

[0030] (3) The pretreated body was immersed in a 12% calcium bicarbonate solution at a ratio of 1g:30ml for 40 minutes. After immersion, the pretreated body was removed and activated in a sodium carbonate solution containing EDTA at a ratio of 1g:20ml for 60 hours. The sodium carbonate solution had a mass fraction of 8%, and the EDTA had a mass fraction of 0.5%. After activation, the pretreated body was removed and cured under standard conditions for 20 days (temperature 20±3℃, relative humidity 92%). Then, particles with a particle size between 15 and 30 mm were sieved to obtain recycled coarse aggregate. The XRD test results are as follows: Figure 2 As shown.

[0031] Strength performance test: The recycled coarse aggregate prepared in this embodiment was configured into concrete slurry to make standard test blocks (wherein the recycled coarse aggregate replaced 35% of the natural aggregate). Then, the compressive strength of the test blocks at 28 days was measured to be 47.16 Ma according to the "Standard for Test Method of Mechanical Properties of Ordinary Concrete" (GB / T50081-2016).

[0032] Impermeability test: The recycled coarse aggregate prepared in this embodiment was configured into concrete slurry and made into test blocks. Then, the Cl was tested according to the "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete" (GB / T50082-2009). - Ion mobility coefficient, measured Cl - The ion permeability coefficient is 11.2 × 10⁻⁶. -10 .

[0033] Example 2

[0034] A process for preparing recycled aggregate from non-fluid silicate concrete waste includes the following steps:

[0035] (1) Place the dry non-fluid silicate concrete waste block in a crusher to crush it, then grind it and pass it through a 300-mesh sieve to obtain non-fluid silicate concrete waste powder for later use.

[0036] (2) The fluidized silicate concrete waste powder, 42.5 silicate cement, graphene, and asbestos fiber were added to a mixer in a weight ratio of 32:20:0.25:1.5 and stirred for 8 minutes. The length of the asbestos fiber was mainly distributed between 3 and 5 mm, and the diameter was mainly distributed between 20 and 50 μm. Then, a 4.5% ferric sulfate aqueous solution was added to the obtained mixed powder at a ratio of 1 g:0.3 ml and mixed evenly. The mixture was then granulated using a granulator. The resulting particles were cured for 10 hours (temperature 20±3℃, relative humidity 92%). After completion, a pretreated body was obtained for later use.

[0037] (3) The pretreated body was immersed in a 15% calcium bicarbonate solution at a ratio of 1g:40ml for 30 minutes. After immersion, the pretreated body was removed and activated in a sodium carbonate solution containing EGTA at a ratio of 1g:18ml for 50 hours. The sodium carbonate solution had a mass fraction of 7%, and the EGTA had a mass fraction of 0.2%. After activation, the pretreated body was removed and cured for 28 days (temperature 20±3℃, relative humidity 92%). Then, particles with a particle size between 20 and 30 mm were sieved to obtain recycled coarse aggregate.

[0038] The compressive strength and Cl of the concrete specimens prepared from the recycled coarse aggregate described in this embodiment were tested at a curing age of 28 days using the same method as in Example 1 above. - The ion permeability coefficients were 43.73 MPa and 13.7 × 10⁻⁶, respectively. -10 .

[0039] Example 3

[0040] A process for preparing recycled aggregate from non-fluid silicate concrete waste includes the following steps:

[0041] (1) Place the dry non-fluid silicate concrete waste block in a crusher to crush it, then grind it and pass it through a 400-mesh sieve to obtain non-fluid silicate concrete waste powder for later use.

[0042] (2) The fluidized silicate concrete waste powder, 42.5 silicate cement, graphene, and asbestos fiber were added to a mixer in a weight ratio of 38:25:0.43:2.5 and stirred for 10 minutes. The length of the asbestos fiber was mainly distributed between 3 and 5 mm, and the diameter was mainly distributed between 20 and 50 μm. Then, a 6% ferrous sulfate aqueous solution was added to the obtained mixed powder at a ratio of 1 g:0.36 ml and mixed evenly. The mixture was then granulated using a granulator. The resulting particles were cured under standard conditions for 20 hours (temperature 20±3℃, relative humidity 92%). After completion, a pretreated body was obtained for later use.

[0043] (3) The pretreated body was immersed in an 8% calcium bicarbonate solution at a ratio of 1g:25ml for 50 minutes. After immersion, the pretreated body was removed and activated in a sodium carbonate solution containing EGTA at a ratio of 1g:30ml for 72 hours. The sodium carbonate solution had a mass fraction of 10%, and the EGTA had a mass fraction of 0.6%. After activation, the pretreated body was removed and cured for 14 days (temperature 20±3℃, relative humidity 92%). Then, particles with a particle size between 10 and 20 mm were sieved to obtain recycled coarse aggregate.

[0044] The compressive strength and Cl of the concrete specimens prepared from the recycled coarse aggregate described in this embodiment were tested at a curing age of 28 days using the same method as in Example 1 above. - The ion permeability coefficients were 44.57 MPa and 14.6 × 10⁻⁶, respectively. -10 .

[0045] Example 4

[0046] A process for preparing recycled aggregate from non-fluid silicate concrete waste includes the following steps:

[0047] (1) Place the dry non-fluid silicate concrete waste block in a crusher to crush it, then grind it and pass it through a 350-mesh sieve to obtain non-fluid silicate concrete waste powder for later use.

[0048] (2) The fluidized silicate concrete waste powder, 42.5 silicate cement, graphene, and asbestos fiber were added to a mixer in a weight ratio of 35:22:0.4:1.8 and stirred for 5 minutes. The length of the asbestos fiber was mainly distributed between 3 and 5 mm, and the diameter was mainly distributed between 20 and 50 μm. Then, water was added to the obtained mixed powder in a ratio of 1 g:0.35 ml and mixed evenly. The mixture was then granulated using a granulator. The resulting particles were cured for 12 hours (temperature 20±3℃, relative humidity 92%). After completion, a pretreated body was obtained for later use.

[0049] (3) The pretreated body was immersed in a 12% calcium bicarbonate solution at a ratio of 1g:30ml for 40 minutes. After immersion, the pretreated body was removed and activated in a sodium carbonate solution containing EDTA at a ratio of 1g:20ml for 60 hours. The sodium carbonate solution had a mass fraction of 8%, and the EDTA had a mass fraction of 0.5%. After activation, the pretreated body was removed and cured under standard conditions for 20 days (temperature 20±3℃, relative humidity 92%). Then, particles with a particle size between 15 and 30 mm were sieved to obtain recycled coarse aggregate.

[0050] The compressive strength and Cl of the concrete specimens prepared from the recycled coarse aggregate described in this embodiment were tested at a curing age of 28 days using the same method as in Example 1 above. - The ion permeability coefficients were 32.24 MPa and 26.8 × 10⁻⁶, respectively. -10 .

[0051] Example 5

[0052] A process for preparing recycled aggregate from non-fluid silicate concrete waste includes the following steps:

[0053] (1) Place the dry non-fluid silicate concrete waste block in a crusher to crush it, then grind it and pass it through a 350-mesh sieve to obtain non-fluid silicate concrete waste powder for later use.

[0054] (2) The fluidized silicate concrete waste powder, 42.5 silicate cement, graphene, and asbestos fiber were added to a mixer in a weight ratio of 35:22:0.4:1.8 and stirred for 5 minutes. The length of the asbestos fiber was mainly distributed between 3 and 5 mm, and the diameter was mainly distributed between 20 and 50 μm. Then, a 5% ferric chloride aqueous solution was added to the obtained mixed powder at a ratio of 1 g:0.35 ml and mixed evenly. The mixture was then granulated using a granulator. The resulting particles were cured for 12 hours (temperature 20±3℃, relative humidity 92%). After completion, a pretreated body was obtained for later use.

[0055] (3) The pretreated body was immersed in a 12% calcium bicarbonate solution at a ratio of 1g:30ml for 40 minutes. After immersion, the pretreated body was removed and activated in a sodium carbonate solution containing EDTA at a ratio of 1g:20ml for 60 hours. The sodium carbonate solution had a mass fraction of 8%, and the EDTA had a mass fraction of 0.5%. After activation, the pretreated body was removed and cured under standard conditions for 20 days (temperature 20±3℃, relative humidity 92%). Then, particles with a particle size between 15 and 30 mm were sieved to obtain recycled coarse aggregate.

[0056] The compressive strength and Cl of the concrete specimens prepared from the recycled coarse aggregate described in this embodiment were tested at a curing age of 28 days using the same method as in Example 1 above. - The ion permeability coefficients were 33.62 MPa and 25.1 × 10⁻⁶, respectively. -10 .

[0057] Example 6

[0058] A process for preparing recycled aggregate from non-fluid silicate concrete waste includes the following steps:

[0059] (1) Place the dry non-fluid silicate concrete waste block in a crusher to crush it, then grind it and pass it through a 300-mesh sieve to obtain non-fluid silicate concrete waste powder for later use.

[0060] (2) The fluidized silicate concrete waste powder and 42.5 silicate cement were added to a mixer at a weight ratio of 32:20 and stirred for 8 minutes. Then, a 4.5% ferric sulfate aqueous solution was added to the resulting mixed powder at a ratio of 1g:0.3ml and mixed evenly. The mixture was then granulated using a granulator. The resulting granules were cured under standard conditions for 10 hours (temperature 20±3℃, relative humidity 92%). The pretreated body was then obtained and ready for use.

[0061] (3) The pretreated body was immersed in a 15% calcium bicarbonate solution at a ratio of 1g:40ml for 30 minutes. After immersion, the pretreated body was removed and activated in a sodium carbonate solution containing EGTA at a ratio of 1g:18ml for 50 hours. The sodium carbonate solution had a mass fraction of 7%, and the EGTA had a mass fraction of 0.2%. After activation, the pretreated body was removed and cured for 28 days (temperature 20±3℃, relative humidity 92%). Then, particles with a particle size between 20 and 30 mm were sieved to obtain recycled coarse aggregate.

[0062] The compressive strength and Cl of the concrete specimens prepared from the recycled coarse aggregate described in this embodiment were tested at a curing age of 28 days using the same method as in Example 1 above. - The ion permeability coefficients were 38.08 MPa and 20.3 × 10⁻⁶ MPa, respectively. -10 .

[0063] Example 7

[0064] A process for preparing recycled aggregate from non-fluid silicate concrete waste includes the following steps:

[0065] (1) Place the dry non-fluid silicate concrete waste block in a crusher to crush it, then grind it and pass it through a 300-mesh sieve to obtain non-fluid silicate concrete waste powder for later use.

[0066] (2) The fluidized silicate concrete waste powder, 42.5 silicate cement, graphene, and asbestos fiber were added to a mixer in a weight ratio of 32:20:0.25:1.5 and stirred for 8 minutes. The length of the asbestos fiber was mainly distributed between 3 and 5 mm, and the diameter was mainly distributed between 20 and 50 μm. Then, a 4.5% ferric sulfate aqueous solution was added to the obtained mixed powder at a ratio of 1 g:0.3 ml and mixed evenly. The mixture was then granulated using a granulator. The resulting particles were cured for 10 hours (temperature 20±3℃, relative humidity 92%). After completion, a pretreated body was obtained for later use.

[0067] (3) The pretreated material was immersed in a 15% calcium bicarbonate solution at a ratio of 1g:40ml for 30 minutes. After immersion, the pretreated material was removed and activated in a 7% sodium carbonate solution at a ratio of 1g:18ml for 50 hours. After activation, the pretreated material was removed and cured under standard conditions for 28 days (temperature 20±3℃, relative humidity 92%). Then, particles with a particle size between 20 and 30 mm were sieved to obtain recycled coarse aggregate.

[0068] The compressive strength and Cl of the concrete specimens prepared from the recycled coarse aggregate described in this embodiment were tested at a curing age of 28 days using the same method as in Example 1 above. - The ion permeability coefficients were 34.75 MPa and 17.4 × 10⁻⁶, respectively. -10 .

[0069] Example 8

[0070] A process for preparing recycled aggregate from non-fluid silicate concrete waste includes the following steps:

[0071] (1) Place the dry non-fluid silicate concrete waste block in a crusher to crush it, then grind it and pass it through a 400-mesh sieve to obtain non-fluid silicate concrete waste powder for later use.

[0072] (2) The fluidized silicate concrete waste powder, 42.5 silicate cement, graphene, and asbestos fiber were added to a mixer in a weight ratio of 38:25:0.43:2.5 and stirred for 10 minutes. The length of the asbestos fiber was mainly distributed between 3 and 5 mm, and the diameter was mainly distributed between 20 and 50 μm. Then, a 6% ferrous sulfate aqueous solution was added to the obtained mixed powder at a ratio of 1 g:0.36 ml and mixed evenly. The mixture was then granulated using a granulator. The resulting particles were cured under standard conditions for 20 hours (temperature 20±3℃, relative humidity 92%). After completion, a pretreated body was obtained for later use.

[0073] (3) The pretreated body was immersed in an 8% calcium bicarbonate solution at a ratio of 1g:25ml for 50 minutes. After immersion, the pretreated body was removed and placed in clean water at a ratio of 1g:30ml for 72 hours. After immersion, the pretreated body was removed and cured for 14 days (temperature 20±3℃, relative humidity 92%). Then, particles with a particle size between 10 and 20 mm were sieved to obtain recycled coarse aggregate.

[0074] The compressive strength and Cl of the concrete specimens prepared from the recycled coarse aggregate described in this embodiment were tested at a curing age of 28 days using the same method as in Example 1 above. - The ion permeability coefficients were 37.11 MPa and 18.6 × 10⁻⁶, respectively. -10 .

[0075] Example 9

[0076] A process for preparing recycled aggregate from non-fluid silicate concrete waste includes the following steps:

[0077] (1) Place the dry non-fluid silicate concrete waste block in a crusher to crush it, then grind it and pass it through a 400-mesh sieve to obtain non-fluid silicate concrete waste powder for later use.

[0078] (2) The fluidized silicate concrete waste powder, 42.5 silicate cement, graphene, and asbestos fiber were added to a mixer in a weight ratio of 38:25:0.43:2.5 and stirred for 10 minutes. The length of the asbestos fiber was mainly distributed between 3 and 5 mm, and the diameter was mainly distributed between 20 and 50 μm. Then, a 6% ferrous sulfate aqueous solution was added to the obtained mixed powder at a ratio of 1 g:0.36 ml and mixed evenly. The mixture was then granulated using a granulator. The resulting particles were cured under standard conditions for 20 hours (temperature 20±3℃, relative humidity 92%). After completion, a pretreated body was obtained for later use.

[0079] (3) The pretreated body was immersed in an 8% calcium bicarbonate solution at a ratio of 1g:25ml for 50 minutes. After immersion, the pretreated body was removed and activated in a sodium carbonate solution containing EGTA at a ratio of 1g:30ml for 1 hour. The sodium carbonate solution had a mass fraction of 10%, and the EGTA had a mass fraction of 0.6%. After activation, the pretreated body was removed and cured for 17 days (temperature 20±3℃, relative humidity 92%). Then, particles with a particle size between 10 and 20 mm were sieved to obtain recycled coarse aggregate.

[0080] The compressive strength and Cl of the concrete specimens prepared from the recycled coarse aggregate described in this embodiment were tested at a curing age of 28 days using the same method as in Example 1 above. - The ion permeability coefficients were 41.36 MPa and 16.9 × 10⁻⁶ MPa, respectively. -10 .

[0081] The above description is merely a preferred embodiment of the present invention and is 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 process for preparing recycled aggregate from non-fluid silicate concrete waste, characterized in that, Includes the following steps: (1) The non-fluid silicate concrete waste is ground finely and then mixed evenly with silicate cement, graphene, asbestos fiber and sulfate aqueous solution, and then granulated. The resulting granules are cured according to standard, and a pretreated body is obtained after completion; the sulfate is selected from ferric sulfate or ferrous sulfate. (2) The pretreated body is immersed in calcium bicarbonate solution. After the pretreated body is completed, it is separated and placed in sodium carbonate solution containing EDTA or EGTA for activation treatment. After the pretreated body is completed, it is cured again according to standard to obtain recycled aggregate.

2. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, In step (1), the particle size of the ground non-fluid silicate concrete waste is not less than 300 mesh.

3. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, In step (1), the weight ratio of the non-fluid silicate concrete waste, silicate cement, graphene, and asbestos fiber is 32~38: 20~25: 0.25~0.43: 1.5~2.5 respectively.

4. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, The ratio of solid raw material to the sulfate aqueous solution is 1g:0.3~0.36ml, wherein the mass fraction of the sulfate aqueous solution is 4.5~6%; the solid raw material is the non-fluid silicate concrete waste, silicate cement, graphene and asbestos fiber.

5. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, In step (1), the length of the asbestos fiber is 3~5mm and the diameter is 20~50μm.

6. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, In step (1), the maintenance time is 10 to 20 hours.

7. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, In step (2), the ratio of the pretreated body to the calcium bicarbonate solution is 1g: 25~40ml.

8. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, In step (2), the soaking time is 30~50 minutes.

9. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, In step (2), the mass fraction of the calcium bicarbonate solution is 8-15%.

10. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, In step (2), the ratio of the pretreated body to the sodium carbonate solution is 1g: 18~30ml.

11. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, In step (2), the sodium carbonate solution has a mass fraction of 7-10%.

12. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, In step (2), the mass fraction of EDTA or EGTA in the sodium carbonate solution is 0.2~0.6%.

13. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to claim 1, characterized in that, In step (2), the activation treatment time is 50 to 72 hours.

14. The process for preparing recycled aggregate from non-fluid silicate concrete waste according to any one of claims 1-13, characterized in that, In step (2), the standard curing time is 14 to 28 days to allow the hydration reaction in the recycled aggregate to proceed more fully.

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