Preparation process and application of a kind of permeable brick made of recycled coarse aggregate from waste concrete

Abstract

The present invention relates to the technical field of cement-based permeable bricks, and specifically discloses a preparation process and application of permeable bricks made of waste concrete recycled coarse aggregate. The process includes the steps of: (1) adding an alkali solution dropwise to a solution containing calcium ions and magnesium ions under stirring conditions, adding nano-silica after complete precipitation, subjecting the obtained dispersion to hydrothermal reaction, separating the solid product and calcining it to obtain an interface strengthening agent. (2) Mixing the interface strengthening agent with water to form a slurry, mixing it with the concrete recycled coarse aggregate, and then drying the obtained recycled aggregate to obtain modified concrete recycled coarse aggregate. (3) Mixing Portland cement, silica fume, the modified concrete recycled coarse aggregate, rubber powder, dihydrogen phosphate, water reducer and mixing water to form a brick blank and then curing it, and a permeable brick is obtained after completion. The permeable brick of the present invention not only has good permeability, but also improves the mechanical properties of the cement-based permeable brick containing recycled aggregate.

Description

Technical Field

[0001] The present invention relates to the technical field of cement-based permeable bricks, and particularly to a preparation process and application of permeable bricks made of recycled coarse aggregate of waste concrete. Background Art

[0002] Disclosing the information of this background art section is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] The Urban Heat Island Effect refers to the phenomenon that the temperature in the urban center is higher than that in the surrounding suburbs, thus forming a phenomenon similar to a high-temperature isolated island. This is mainly caused by a large amount of artificial waste heat emissions, the large heat storage of buildings and roads in summer, and the reduction of green spaces, forests, and water bodies. The concept of sponge cities has a good effect on alleviating the urban heat island effect. For example, by using permeable concrete or permeable bricks instead of traditional concrete materials as pavement materials, rainwater can penetrate into the ground in time during rainfall for storage, preventing waterlogging. When the temperature rises, the stored water is "released" into the atmosphere, effectively promoting the water cycle, reducing the urban temperature, and alleviating the urban heat island effect.

[0004] Over time, a large number of buildings in the city need to be renovated, rebuilt, or demolished and rebuilt, and this process will generate a large amount of waste concrete. The resulting environmental and waste treatment problems have become issues that must be solved. Recycled aggregate of concrete is the particulate matter obtained from the above-mentioned waste concrete through processes such as crushing, screening, cleaning, and grading. The resource utilization of recycled aggregate not only helps to dispose of a large amount of waste concrete in our country, but also reduces the impact on the environment. However, the porosity of recycled aggregate of concrete is higher than that of natural aggregate, but the strength is lower, resulting in problems such as easy deterioration of mechanical strength, decline in bearing capacity and durability, etc. when using this recycled aggregate to prepare concrete materials, which limits the application of recycled coarse aggregate of concrete. Summary of the Invention

[0005] In view of the above problems, the present invention provides a preparation process and application of permeable bricks made of recycled coarse aggregate of waste concrete. Using the recycled coarse aggregate made of waste concrete as raw material, it not only makes the permeable bricks have good permeability, but also improves the bonding force between the recycled aggregate and the permeable brick matrix, and improves the mechanical properties of the permeable bricks. Specifically, the technical solution of the present invention is as follows.

[0006] First, the present invention provides a preparation process of permeable bricks made of recycled coarse aggregate of waste concrete, including the following steps:

[0007] (1) While stirring, add an alkali solution dropwise to a solution containing calcium ions and magnesium ions. After the precipitation is complete, add nano-silica, and then subject the resulting dispersion to a hydrothermal reaction. After completion, separate the solid product, calcine it, and then grind it to obtain an interface strengthening agent.

[0008] (2) Mix the interface strengthening agent with water to form a slurry, mix it evenly with recycled concrete coarse aggregate, and then dry the resulting recycled aggregate to obtain modified recycled concrete coarse aggregate.

[0009] (3) Mix Portland cement, silica fume, the modified recycled concrete coarse aggregate, rubber powder, dihydrogen phosphate, water reducer, and mixing water to form a brick blank and then cure it. After completion, a permeable brick is obtained.

[0010] Further, in step (1), the molar ratio of the calcium ions to the magnesium ions is 1.5 - 1.8:1. Optionally, the calcium ions are provided by at least one of calcium chloride, calcium nitrate, calcium acetate, etc. The magnesium ions are provided by at least one of magnesium chloride, magnesium sulfate, magnesium nitrate, etc.

[0011] Further, in step (1), the alkali solution includes at least one of sodium hydroxide solution, potassium hydroxide solution, and ammonia water. The concentration of the alkali solution is not specifically limited in the present invention.

[0012] Further, in step (1), the content of nano-silica in the dispersion is 1.8 - 2.5 g / L.

[0013] Further, in step (1), the temperature of the hydrothermal reaction is 160 - 220 °C, and the time is 7 - 9 hours.

[0014] Further, in step (1), the calcination temperature is 400 - 450 °C, and the time is 20 - 35 min. Optionally, the fineness of the interface strengthening agent is 350 - 500 mesh.

[0015] Further, in step (2), the solid content in the slurry is 45 - 58 wt.%.

[0016] Further, in step (2), the mass ratio of the recycled concrete coarse aggregate to the slurry is 10:1.3 - 2.

[0017] Further, in step (2), the drying temperature is 70 - 100 °C, and the time is 15 - 20 min.

[0018] Further, in step (3), the proportions of the components are as follows: 18-25 parts by weight of portland cement, 1.2-1.7 parts by weight of silica fume, 72-105 parts by weight of modified recycled coarse aggregate of concrete, 0.8-1.0 parts by weight of rubber powder, 0.55-0.7 parts by weight of dihydrogen phosphate, and 0.2-0.3 parts by weight of water reducing agent. The mixing water is taken according to a water-cement ratio of 0.28-0.35.

[0019] Further, in step (3), the water reducing agent includes at least one of polycarboxylate water reducing agent, naphthalene series water reducing agent, lignosulfonate water reducing agent, etc.

[0020] Further, in step (3), the dihydrogen phosphate includes at least one of ammonium dihydrogen phosphate, potassium dihydrogen phosphate, etc.

[0021] Further, in step (3), the fineness of the rubber powder is 80-150 mesh. Preferably, the rubber powder is made from waste rubber.

[0022] Secondly, the present invention provides the application of the permeable brick made of the recycled coarse aggregate of waste concrete obtained by the preparation process in the fields of construction engineering, municipal engineering, road engineering, etc.

[0023] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0024] (1) The permeable brick of the present invention uses recycled concrete particles as coarse aggregate, and uses portland cement and silica fume as cementitious components to fill the gaps between the coarse aggregates and bond the coarse aggregates together to form a permeable brick. Compared with the traditional permeable brick prepared with impermeable natural coarse aggregate and cement as raw materials, the permeable brick of the present invention realizes water permeability by using the recycled coarse aggregate to provide a water permeable channel. While the above traditional permeable brick uses the gaps between natural coarse aggregates as the water permeable channel. Therefore, the present invention utilizes the structural characteristics of the recycled coarse aggregate to convert it into the water permeable channel of the permeable brick, which not only realizes the good water permeability function of the brick body, but also avoids the problem of low proportion of cementitious components used to form water permeable pores between natural coarse aggregates, thereby resulting in insufficient mechanical strength and freeze-thaw resistance of the brick body. In addition, the rubber powder also helps to improve the freeze-thaw resistance of the permeable brick.

[0025] (2) Due to the relatively high water absorption rate of recycled concrete coarse aggregates, the bonding force between them and the permeable brick matrix is insufficient, which in turn affects the mechanical strength of the permeable bricks. This is because during the hydration process, the coarse aggregates gradually absorb the mixing water at the interface with the cementitious components. In addition, since the hydration reaction of the silica fume needs to rely on the hydration product calcium hydroxide of the portland cement, the hydration reaction of the silica fume starts relatively late. As a result, the hydration of the silica fume in the interface zone occurs in the later stage and there is insufficient mixing water for full hydration, resulting in a decrease in the content of the cementitious components formed, and a weak interface zone is formed between the permeable brick matrix and the coarse aggregates. Therefore, in the present invention, an interface strengthening agent is loaded on the surface of the recycled concrete coarse aggregates, and it acts together with the dihydrogen phosphate to effectively overcome the above problems. The reasons are as follows: First, a liquid phase system containing a composite precipitate of calcium hydroxide and magnesium hydroxide is prepared in the present invention, and then nano-silica is added and hydrothermal reaction is carried out. Calcium hydroxide in the composite precipitate reacts with silica to form calcium silicate hydrate. After further calcination, magnesium hydroxide is converted into magnesium oxide, thus forming an interface strengthening agent in which magnesium oxide and calcium silicate hydrate are mutually doped. When permeable bricks are prepared using recycled coarse aggregates with such an interface strengthening agent loaded on their surfaces, during the curing process, on the one hand, magnesium oxide in the strengthening agent reacts with dihydrogen phosphate to form hydration products with high strength and high bonding performance, which can effectively enhance the bonding force between the recycled coarse aggregates and the cementitious components and eliminate the weak interface zone. At the same time, the strengthening agent effectively avoids the problem that the reaction between magnesium oxide and dihydrogen phosphate during the mixing and casting of each raw material leads to a decrease in the fluidity of the slurry and is not easy to be cast into shape. On the other hand, calcium silicate hydrate in the interface strengthening agent acts as a nucleation inducer to promote the hydration reaction of silica fume, so that silica fume with a late-starting hydration reaction starts to react at an early stage when the mixing water is relatively sufficient, which not only avoids the problem that the hydration reaction of silica fume cannot be fully carried out due to insufficient mixing water in the later stage, but also increases the content of cementitious components at the interface, improves the bonding force between the recycled coarse aggregates and the cementitious components, and helps to further eliminate the weak interface zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention and do not constitute an improper limitation of the present invention. The following will describe the embodiments of the present invention in detail with reference to the drawings, where:

[0027] Figure 1 Figure showing the powder sample of the interface strengthening agent prepared in Example 1 below.

[0028] Figure 2 Figure showing the sample of the permeable brick prepared in Example 1 below.

[0029] Figure 3 Figure showing the test of the fluidity of the permeable brick slurry in Example 1 below.

[0030] Figure 4 Diagram of the permeable brick samples prepared for Example 2 below.

[0031] Figure 5 Diagram of the fluidity test of the permeable brick slurry for Example 2 below.

[0032] Figure 6 Diagram of the permeable brick samples prepared for Example 3 below.

[0033] Figure 7 Diagram of the fluidity test of the permeable brick slurry for Example 3 below.

[0034] Figure 8 Diagram of the fluidity test of the permeable brick slurry for Example 4 below. Detailed implementation manners

[0035] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions indicated in the following embodiments are generally carried out under conventional conditions or according to the conditions recommended by the manufacturers.

[0036] Unless otherwise defined, all professional and scientific terms used in the present invention have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be obtained through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in the conventional manner in the art or according to the product instructions. In addition, any methods and materials similar or equivalent to the described content can be applied to the method of the present invention. The technical solutions of the present invention will be further described below in conjunction with specific embodiments.

[0037] Example 1

[0038] A preparation process for permeable bricks made of recycled coarse aggregate from waste concrete includes the following steps:

[0039] (1) Under continuous stirring, an excessive amount of sodium hydroxide solution is added dropwise to a solution containing calcium nitrate and magnesium nitrate (the molar ratio of calcium and magnesium ions = 1.6:1). After the generated precipitate is complete, nano-silica is added to the system at a ratio of 1.8 g / L and ultrasonic dispersion is carried out for 5 min. Then the obtained dispersion is added to a reaction kettle and heated to 210 °C for heat preservation for 7.5 hours for hydrothermal reaction. After completion, the solid product is filtered out, heated to 430 °C for heat preservation for 30 min, and then ground and sieved to obtain an interface strengthening agent powder with a fineness of 500 meshes (as shown in Figure 1 ) for standby.

[0040] (2) Mix the interface strengthening agent with water and stir evenly to form a slurry with a solid content of 55 wt.%. Then, mix the recycled coarse aggregate of concrete with a particle size distribution between 5 and 8 mm and the slurry at a mass ratio of 10:1.5 and stir evenly. Then, heat the obtained recycled aggregate to 80 °C and dry it for 20 min to obtain the modified recycled coarse aggregate of concrete, which is reserved for use.

[0041] (3) Take the following raw materials: 20 parts by weight of 42.5 ordinary Portland cement, 1.2 parts by weight of silica fume, 95 parts by weight of the modified recycled coarse aggregate of concrete in this example, 0.9 parts by weight of waste rubber powder with a fineness of 100 mesh, 0.6 parts by weight of potassium dihydrogen phosphate, and 0.22 parts by weight of polycarboxylate water reducer. After mixing the above raw materials evenly, add mixing water according to a water-cement ratio of 0.31 and stir evenly. Then, pour the obtained slurry into a mold. After hardening and forming, demold it. Place the obtained brick blank in a curing box and cure it for 28 days. Set the curing temperature to 20 °C. After completion, the permeable brick is obtained (as Figure 2 shown).

[0042] Performance test: 1. Test the compressive strength and water permeability coefficient of the permeable brick according to the Standard for Test Methods of Physical and Mechanical Properties of Concrete (GBT 50081-2019). 2. According to the Permeable Pavement Bricks and Pavement Panels (GB / T 25993-2010), freeze-thaw cycle the permeable brick 20 times at -15 °C, and then calculate the loss rate of compressive strength to measure the freeze-thaw resistance of the permeable brick. 3. Test the fluidity of the slurry prepared in step (3) of this example (as Figure 3 shown). The results are shown in the following table:

[0043] .

[0044] Example 2

[0045] A preparation process of a permeable brick made of recycled coarse aggregate of waste concrete includes the following steps:

[0046] (1) Dropwise add an excessive amount of sodium hydroxide solution to a solution containing calcium nitrate and magnesium sulfate (the molar ratio of calcium and magnesium ions = 1.5:1) under continuous stirring. After the generated precipitate is complete, add nano-silica to the system at a ratio of 2.1 g / L and ultrasonically disperse for 5 min. Then, add the obtained dispersion liquid to a reaction kettle, heat it to 160 °C, and keep it warm for 9 hours for hydrothermal reaction. After completion, filter out the solid product, heat it to 400 °C, and keep it warm for 35 min. After completion, grind and screen it to obtain an interface strengthening agent powder with a fineness of 400 mesh, which is reserved for use.

[0047] (2) Mix the interface strengthening agent with water and stir evenly to form a slurry with a solid content of 45 wt.%. Then, mix the recycled coarse concrete aggregates with a particle size distribution between 5 and 8 mm and the slurry at a mass ratio of 10:1.3 and stir evenly. Then, heat the obtained recycled aggregates to 70 °C and dry them for 20 min to obtain modified recycled coarse concrete aggregates for standby.

[0048] (3) Take the following raw materials: 25 parts by weight of 42.5 ordinary Portland cement, 1.5 parts by weight of silica fume, 105 parts by weight of the modified recycled coarse concrete aggregates of this example, 1.0 part by weight of waste rubber powder with a fineness of 80 mesh, 0.7 part by weight of potassium dihydrogen phosphate, and 0.3 part by weight of lignosulfonate water reducer. After mixing the above raw materials evenly, add mixing water according to a water-cement ratio of 0.35 and stir evenly. Then, pour the obtained slurry into a mold, demold after hardening and forming, and place the obtained brick blank in a curing box for curing for 28 days. The curing temperature is set at 25 °C. After completion, the permeable bricks are obtained (as Figure 4 shown).

[0049] Performance test: Use the same method as in Example 1 above to test the compressive strength, water permeability coefficient, freeze-thaw resistance of the permeable bricks prepared in this example, and the fluidity of the slurry prepared in step (3) of this example (as Figure 5 shown), and the results are shown in the following table:

[0050] .

[0051] Example 3

[0052] A preparation process for permeable bricks made of waste concrete recycled coarse aggregates, comprising the following steps:

[0053] (1) Dropwise add an excessive amount of potassium hydroxide solution to a solution containing calcium chloride and magnesium chloride (the molar ratio of calcium and magnesium ions = 1.8:1) under continuous stirring. After the generated precipitate is complete, add nano-silica to the system at a ratio of 2.5 g / L and ultrasonically disperse for 5 min. Then, add the obtained dispersion liquid to a reaction kettle, heat it to 220 °C, and keep it warm for 7 hours for hydrothermal reaction. After completion, filter out the solid product, heat it to 450 °C, and keep it warm for 20 min. After completion, grind and screen to obtain an interface strengthening agent powder with a fineness of 350 mesh for standby.

[0054] (2) Mix the interface strengthening agent with water and stir evenly to form a slurry with a solid content of 58 wt.%. Then, mix the recycled coarse concrete aggregates with a particle size distribution between 5 and 8 mm and the slurry at a mass ratio of 10:2 and stir evenly. Then, heat the obtained recycled aggregates to 100 °C and dry them for 15 min to obtain modified recycled coarse concrete aggregates for standby.

[0055] (3) Take the following raw materials: 18 parts by weight of 42.5 ordinary Portland cement, 1.7 parts by weight of silica fume, 72 parts by weight of the modified concrete recycled coarse aggregate of this example, 0.8 parts by weight of waste rubber powder with a fineness of 150 mesh, 0.55 parts by weight of ammonium dihydrogen phosphate, and 0.2 parts by weight of naphthalene-based water reducer. After mixing the above raw materials evenly, add mixing water according to a water-cement ratio of 0.28 and stir evenly. Then pour the obtained slurry into a mold, demold after hardening and forming, and place the obtained brick blank in a curing box for 28 days. Set the curing temperature at 25 °C, and then the permeable brick is obtained (as Figure 6 shown).

[0056] Performance test: Use the same method as in Example 1 above to test the compressive strength, water permeability coefficient, freeze-thaw resistance of the permeable brick prepared in this example, and the fluidity of the slurry prepared in step (3) of this example (as Figure 7 shown), and the results are shown in the following table:

[0057] .

[0058] Example 4

[0059] A preparation process of a permeable brick made of waste concrete recycled coarse aggregate, comprising the following steps:

[0060] (1) Mix magnesium oxide powder with a fineness of 400 mesh and water evenly to form a slurry with a solid content of 45 wt.%. Then mix the concrete recycled coarse aggregate with a particle size distribution between 5 and 8 mm and the slurry at a mass ratio of 10:1.3 and stir evenly. Then heat the obtained recycled aggregate to 70 °C and dry it for 20 min to obtain the modified concrete recycled coarse aggregate.

[0061] (2) Take the following raw materials: 25 parts by weight of 42.5 ordinary Portland cement, 1.5 parts by weight of silica fume, 105 parts by weight of the modified concrete recycled coarse aggregate of this example, 1.0 parts by weight of waste rubber powder with a fineness of 80 mesh, 0.7 parts by weight of potassium dihydrogen phosphate, and 0.3 parts by weight of lignosulfonate water reducer. After mixing the above raw materials evenly, add mixing water according to a water-cement ratio of 0.35 and stir evenly to obtain a slurry. Then use the same method as in Example 1 above to test the fluidity of the slurry prepared in this example (as Figure 8 shown), and the result is 151 mm.

[0062] Example 5

[0063] A preparation process of permeable bricks made of recycled coarse aggregate from waste concrete is the same as that in Example 3 above, except that in this example, the interface strengthening agent is prepared by the following method: Under continuous stirring conditions, an excessive amount of potassium hydroxide solution is added dropwise to a solution containing calcium chloride and magnesium chloride (the molar ratio of calcium ions to magnesium ions = 1.8:1). After the generated precipitate is complete, nano-silica is added to the system at a ratio of 2.5 g / L and ultrasonic dispersion is carried out for 5 minutes. Then, the obtained dispersion liquid is added to a reaction kettle and heated to 220 °C and kept warm for 7 hours for hydrothermal reaction. After completion, the solid product is filtered out, dried to remove moisture, ground, and sieved to obtain an interface strengthening agent powder with a fineness of 350 mesh.

[0064] Performance test: The same method as in Example 1 above is used to test the compressive strength, water permeability coefficient, freeze-thaw resistance of the permeable bricks prepared in this example, and the fluidity of the slurry prepared in step (3) of this example. The results are shown in the following table:

[0065] 。

[0066] Example 6

[0067] A preparation process of permeable bricks made of recycled coarse aggregate from waste concrete is the same as that in Example 2 above, except that in this example, the interface strengthening agent is prepared by the following method: Under continuous stirring conditions, an excessive amount of sodium hydroxide solution is added dropwise to a solution containing calcium nitrate and magnesium sulfate (the molar ratio of calcium ions to magnesium ions = 1.5:1). After the generated precipitate is complete, the obtained reaction system is added to a reaction kettle and heated to 160 °C and kept warm for 9 hours for hydrothermal reaction. After completion, the solid product is filtered out, heated to 400 °C and kept warm for 35 minutes. After completion, it is ground and sieved to obtain an interface strengthening agent powder with a fineness of 400 mesh.

[0068] Performance test: The same method as in Example 1 above is used to test the compressive strength, water permeability coefficient, freeze-thaw resistance of the permeable bricks prepared in this example, and the fluidity of the slurry prepared in step (3) of this example. The results are shown in the following table:

[0069] 。

[0070] Example 7

[0071] A preparation process of permeable bricks made of recycled coarse aggregate from waste concrete includes the following steps:

[0072] Take the following raw materials: 20 parts by weight of 42.5 ordinary Portland cement, 1.2 parts by weight of silica fume, 95 parts by weight of the modified concrete recycled coarse aggregate of the above-mentioned Example 1, 0.6 parts by weight of potassium dihydrogen phosphate, and 0.22 parts by weight of polycarboxylate water reducer. After mixing the above raw materials evenly, add mixing water according to a water-cement ratio of 0.31 and stir evenly. Then pour the obtained slurry into a mold, demold after hardening and forming, place the obtained brick blank in a curing box for 28 days, and set the curing temperature to 20°C. After completion, the permeable brick is obtained.

[0073] Performance test: Use the same method as in Example 1 above to test the compressive strength, water permeability coefficient, freeze-thaw resistance of the permeable brick prepared in this example, and the fluidity of the slurry prepared in step (3) of this example. The results are shown in the following table:

[0074] 。

[0075] Example 8

[0076] A preparation process for permeable bricks made of waste concrete recycled coarse aggregate includes the following steps:

[0077] Take the following raw materials: 20 parts by weight of 42.5 ordinary Portland cement, 1.2 parts by weight of silica fume, 95 parts by weight of concrete recycled coarse aggregate with a particle size distribution between 5 and 8 mm, 0.9 parts by weight of waste rubber powder with a fineness of 100 mesh, 0.6 parts by weight of potassium dihydrogen phosphate, and 0.22 parts by weight of polycarboxylate water reducer. After mixing the above raw materials evenly, add mixing water according to a water-cement ratio of 0.31 and stir evenly. Then pour the obtained slurry into a mold, demold after hardening and forming, place the obtained brick blank in a curing box for 28 days, and set the curing temperature to 20°C. After completion, the permeable brick is obtained.

[0078] Performance test: Use the same method as in Example 1 above to test the compressive strength, water permeability coefficient, freeze-thaw resistance of the permeable brick prepared in this example, and the fluidity of the slurry prepared in step (3) of this example. The results are shown in the following table:

[0079] 。

[0080] The above are only the preferred embodiments of the present invention and are not used 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 recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation process for waste concrete recycled coarse aggregate permeable bricks, characterized in that: The steps include: (1) adding alkali solution dropwise to a solution containing calcium ions and magnesium ions under stirring conditions, adding nano-silicon dioxide after precipitation is complete, and then subjecting the obtained dispersion to a hydrothermal reaction, separating a solid product after completion, calcining it, and then grinding it to obtain an interface strengthener; wherein: the molar ratio of the calcium ions to the magnesium ions is 1.5-1.8:1; the content of nano-silicon dioxide in the dispersion is 1.8-2.5 g / L; the calcination temperature is 400-450°C, and the time is 20-35 min; (2) mixing the interface strengthener with water to form a slurry, mixing the slurry with the recycled coarse aggregate for concrete, and then drying the recycled aggregate to obtain the modified recycled coarse aggregate for concrete; (3) Mixing silicate cement, silica fume, the modified concrete recycled coarse aggregate, rubber powder, dihydrogen phosphate, water reducer and mixing water to form a brick blank, and then curing to obtain a permeable brick.

2. The preparation process of waste concrete recycled coarse aggregate permeable brick according to claim 1, characterized in that: In step (1), the calcium ions are provided by at least one of calcium chloride, calcium nitrate and calcium acetate; Alternatively, in step (1), the magnesium ions are provided by at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate.

3. The preparation process of waste concrete recycled coarse aggregate permeable brick according to claim 1, characterized in that: In step (1), the alkaline solution includes at least one of sodium hydroxide solution, potassium hydroxide solution and ammonia water.

4. The preparation process of waste concrete recycled coarse aggregate permeable brick according to claim 1, characterized in that: In step (1), the temperature of the hydrothermal reaction is 160-220° C. and the time is 7-9 hours; Alternatively, in step (1), the fineness of the interface strengthener is 350-500 mesh.

5. The process for preparing waste concrete recycled coarse aggregate permeable bricks according to claim 1, characterized in that: In step (2), the solid content of the slurry is 45-58 wt.%.

6. The process for preparing waste concrete recycled coarse aggregate permeable bricks according to claim 1, characterized in that: In step (2), the mass ratio of the recycled coarse aggregate to the slurry in the concrete is 10:1.3-2; Alternatively, in step (2), the drying temperature is 70-100° C. and the drying time is 15-20 min.

7. The process for preparing waste concrete recycled coarse aggregate permeable bricks according to claim 1, characterized in that: In step (3), the proportions of the components are: 18-25 parts by weight of silicate cement, 1.2-1.7 parts by weight of silica fume, 72-105 parts by weight of modified concrete recycled coarse aggregate, 0.8-1.0 parts by weight of rubber powder, 0.55-0.7 parts by weight of dihydrogen phosphate, and 0.2-0.3 parts by weight of water reducer, and the mixing water is taken at a water-cement ratio of 0.28-0.

35.

8. The process for preparing permeable bricks made of recycled coarse aggregate from waste concrete according to any one of claims 1 to 7, characterized in that: In step (3), the water reducer includes: at least one of a polycarboxylate water reducer, a naphthalene-based water reducer, and a lignin sulfonate water reducer; Alternatively, in step (3), the dihydrogen phosphate includes at least one of ammonium dihydrogen phosphate and potassium dihydrogen phosphate.

9. The process for preparing waste concrete recycled coarse aggregate permeable bricks according to any one of claims 1 to 7, characterized in that: In step (3), the fineness of the rubber powder is 80-150 mesh.

10. Use of waste concrete recycled coarse aggregate permeable bricks obtained by the preparation process according to any one of claims 1 to 9 in construction engineering, municipal engineering or road engineering.

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