Modified recycled coarse aggregate, preparation method and application thereof

Abstract

This invention provides a modified recycled coarse aggregate, its preparation method, and its application, belonging to the field of construction waste recycling. The invention involves adding an oil phase to an aqueous phase and stirring to obtain an O / W type emulsion; the oil phase includes a lipophilic emulsifier and a silane coupling agent; the aqueous phase includes an aqueous solution of a nonionic surfactant; and nano-SiO₂... 2 A composite emulsion is obtained by mixing the O / W type emulsion with the composite emulsion; the recycled coarse aggregate is then soaked in the composite emulsion to obtain modified recycled coarse aggregate. The composite emulsion obtained by this invention can form a dense hydrophobic network on the surface and inner capillary walls of the recycled aggregate and effectively fill the micropores, inhibiting the absorption of water by the recycled aggregate. Simultaneously, it improves the compatibility between nano-silica and the recycled coarse aggregate, thereby increasing the strength of the recycled coarse aggregate. Data from the examples show that the concrete prepared using the modified recycled coarse aggregate of this invention exhibits good waterproofing and compressive strength.

Description

A modified recycled coarse aggregate, its preparation method and application Technical Field

[0001] This invention belongs to the field of construction waste recycling technology, specifically relating to a modified recycled coarse aggregate, its preparation method, and its application. Background Technology

[0002] The vast majority of construction waste is not being utilized properly, and the rational resource integration and utilization of construction waste has become an urgent problem to be solved.

[0003] To improve the utilization rate of construction waste, existing technologies use recycled coarse aggregate from construction waste to replace part of the natural coarse aggregate in the preparation of concrete. However, compared with natural coarse aggregate, the internal structure of recycled coarse aggregate is changed, the porosity is significantly increased, the specific surface area is large, the surface activity is low, and the water absorption rate is significantly enhanced compared with natural aggregate. As a result, most of the concrete prepared by recycled coarse aggregate has a high water absorption rate and poor compressive strength. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a modified recycled coarse aggregate, its processing method, and its application. The modified recycled coarse aggregate provided by this invention has good waterproofing capabilities. When used in the preparation of concrete, it can prevent the concrete from absorbing excessive moisture during the mixing process, significantly improving the compressive strength of the recycled concrete.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing modified recycled coarse aggregate, comprising the following steps:

[0007] An oil phase is added to an aqueous phase and stirred to obtain an O / W type emulsion; the oil phase includes a lipophilic emulsifier and a silane coupling agent; the aqueous phase includes an aqueous solution of a nonionic surfactant.

[0008] A composite emulsion is obtained by mixing nano-SiO2 with the O / W type emulsion.

[0009] The recycled coarse aggregate is soaked in the composite emulsion to obtain modified recycled coarse aggregate.

[0010] Preferably, the lipophilic emulsifier includes Span;

[0011] The silane coupling agent includes 3-mercaptopropyltrimethoxysilane and / or isobutyltriethoxysilane;

[0012] The mass ratio of the lipophilic emulsifier to the silane coupling agent is 1:13-23.

[0013] Preferably, the nonionic surfactant includes Pingpingjia;

[0014] The mass ratio of the nonionic surfactant to water is 1:6 to 15.

[0015] Preferably, the volume ratio of the oil phase to the water phase is 1:0.8 to 1.4.

[0016] Preferably, the solid-liquid ratio of the nano-SiO2 to the O / W type emulsion is 3-6 g: 1 mL.

[0017] Preferably, the nano-SiO2 is further pretreated before being mixed with the O / W type emulsion;

[0018] The pretreatment includes: mixing nano-SiO2 with anhydrous ethanol and then drying it;

[0019] The solid-liquid ratio of the nano-SiO2 to anhydrous ethanol is 1g:2-5mL.

[0020] Preferably, the stirring speed is 1400-1600 r / min, the stirring time is 2-4 h, and the stirring temperature is 30-50 °C;

[0021] Preferably, the soaking time is 1 to 6 days.

[0022] The present invention also provides modified recycled coarse aggregate prepared by the preparation method described in the above technical solution.

[0023] The present invention also provides the application of the modified recycled coarse aggregate described above in concrete, wherein the modified recycled coarse aggregate replaces part of the coarse aggregate in the raw materials for concrete preparation, and the mass proportion of the modified recycled coarse aggregate in the coarse aggregate is 30-50%.

[0024] This invention provides a method for preparing modified recycled coarse aggregate, comprising the following steps: adding an oil phase to an aqueous phase and stirring to obtain an O / W type emulsion; the oil phase comprising a lipophilic emulsifier and a silane coupling agent; the aqueous phase comprising an aqueous solution of a nonionic surfactant; mixing nano-SiO2 with the O / W type emulsion to obtain a composite emulsion; and immersing the recycled coarse aggregate in the composite emulsion to obtain modified recycled coarse aggregate. This invention uses nano-silica as an inorganic sealing material, which is small in size and has high surface activity. By modifying the nano-silica through a reaction with a silane coupling agent, hydrophobic groups are grafted onto the surface of the nano-silica, reducing the number of hydroxyl groups and changing it from hydrophilic to hydrophobic. The resulting O / W emulsion effectively improves the compatibility between nano-silica and recycled coarse aggregate, enhancing the strength, hydrophobicity, abrasion resistance, and corrosion resistance of the recycled coarse aggregate. The composite emulsion obtained by mixing nano-silica and the O / W emulsion has good and stable waterproofing capabilities and a certain degree of permeability. It can form a dense hydrophobic network on the surface and inside the capillary walls of the recycled aggregate while effectively filling micropores, effectively inhibiting the absorption of water by the recycled aggregate and preventing excessive water absorption during concrete mixing, thereby significantly improving the workability of recycled concrete. The hydrophobic treatment significantly improves the workability of recycled coarse aggregate with high water absorption.

[0025] The test results from the examples show that the modified recycled coarse aggregate obtained by the method for modifying recycled coarse aggregate from construction waste provided by the present invention has good waterproof performance and strong mechanical properties. The capillary water absorption coefficient of concrete prepared using the modified recycled coarse aggregate is 186.86~254.64g / m³. 2 .h 0.5 The 28-day compressive strength is 37.2–42.7 MPa. Detailed Implementation

[0026] This invention provides a method for preparing modified recycled coarse aggregate, comprising the following steps:

[0027] An oil phase is added to an aqueous phase and stirred to obtain an O / W type emulsion; the oil phase includes a lipophilic emulsifier and a silane coupling agent; the aqueous phase includes an aqueous solution of a nonionic surfactant.

[0028] A composite emulsion is obtained by mixing nano-SiO2 with the O / W type emulsion.

[0029] The recycled coarse aggregate is soaked in the composite emulsion to obtain modified recycled coarse aggregate.

[0030] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0031] In this invention, an oil phase is added to an aqueous phase and stirred to obtain an O / W type emulsion; the oil phase includes a lipophilic emulsifier and a silane coupling agent; the aqueous phase includes an aqueous solution of a nonionic surfactant.

[0032] In this invention, the lipophilic emulsifier preferably includes Span, and the Span preferably includes Span 20, Span 40, Span 60, Span 80, or Span 85, more preferably Span 80 or Span 85. The silane coupling agent preferably includes 3-mercaptopropyltrimethoxysilane and / or isobutyltriethoxysilane, more preferably 3-mercaptopropyltrimethoxysilane. In this invention, the mass ratio of the lipophilic emulsifier to the silane coupling agent is preferably 1:13-23, more preferably 1:15-20, and even more preferably 1:16-18. This invention does not have special requirements for the mixing method; the raw materials can be directly mixed evenly. In the examples, a homogenizer is preferably used for uniform mixing through channels.

[0033] In this invention, the nonionic surfactant preferably includes a styrax, and the styrax preferably includes styrax O-15, styrax O-20, styrax O-25, or styrax O-30, more preferably styrax O-20 or styrax O-25. The mass ratio of the nonionic surfactant to water is preferably 1:6 to 15, more preferably 1:8 to 12, and even more preferably 1:10.

[0034] In this invention, the volume ratio of the oil phase to the water phase is preferably 1:0.8 to 1.4, more preferably 1:1.0 to 1.2, and even more preferably 1:1.1. In this invention, the oil phase is preferably added to the water phase dropwise. This invention does not have special requirements for the dropwise addition rate; dropwise addition is sufficient. The oil phase is added dropwise to the water phase and stirred to form a uniformly mixed oil-in-water structure.

[0035] In this invention, the stirring speed is preferably 1400-1600 r / min, more preferably 1500 r / min, the stirring time is preferably 2-4 h, more preferably 3 h, and the stirring temperature is preferably 30-50 °C, more preferably 40 °C.

[0036] After obtaining the O / W type emulsion, the present invention mixes nano-SiO2 with the O / W type emulsion to obtain a composite emulsion.

[0037] In this invention, the nano-SiO2 is preferably pretreated before being mixed with the O / W emulsion; the pretreatment preferably includes mixing the nano-SiO2 with anhydrous ethanol and then drying it. In this invention, the solid-liquid ratio of nano-SiO2 to anhydrous ethanol is preferably 1g:2-5mL, more preferably 1g:3mL. In this invention, the mixing of nano-SiO2 and anhydrous ethanol is preferably carried out under stirring conditions, more preferably magnetic stirring, with a stirring speed preferably of 500-800 r / min, more preferably 650-750 r / min, and a stirring time preferably of 40-50 min, more preferably 45 min. This invention does not have special requirements for the drying process; operations well known in the art can be used. This invention, through pretreatment, makes the nano-SiO2 particle size more uniformly dispersed, improves the composite effect of nano-SiO2 and silane coupling agent, and thus improves the modification and regeneration effect on coarse aggregate.

[0038] In this invention, the solid-liquid ratio of the nano-SiO2 to the O / W type emulsion is preferably 1g:100-120mL, more preferably 1g:105-115mL, and even more preferably 1g:110-112mL.

[0039] In this invention, the mixing of nano-SiO2 and the O / W emulsion is preferably carried out under stirring conditions. The stirring speed is preferably 1400-1600 r / min, more preferably 1500 r / min, the stirring time is preferably 2-4 h, more preferably 3 h, and the stirring temperature is preferably 30-50 °C, more preferably 40 °C. The nano-silica reacts with a silane coupling agent to graft hydrophobic groups onto the surface of the nano-silica, reducing the number of hydroxyl groups on the surface of the nano-silica and changing it from hydrophilic to hydrophobic.

[0040] After obtaining the composite emulsion, the present invention soaks the recycled coarse aggregate in the composite emulsion to obtain modified recycled coarse aggregate.

[0041] In this invention, the soaking time is preferably 1 to 6 days, more preferably 3 to 5 days. This invention does not have special requirements on the amount of the composite emulsion used, as long as the recycled coarse aggregate is completely soaked. This invention ensures optimal hydrophobicity of the recycled coarse aggregate through thorough soaking.

[0042] After soaking, the present invention preferably dries the obtained recycled coarse aggregate to obtain modified recycled coarse aggregate. The present invention does not have any special requirements for the drying method; any drying method well known in the art can be used. In the embodiments of the present invention, natural air drying is specifically employed.

[0043] The present invention also provides modified recycled coarse aggregate prepared by the preparation method described in the above technical solution.

[0044] This invention modifies nano-silica by grafting hydrophobic groups onto its surface, reducing the number of hydroxyl groups and changing it from hydrophilic to hydrophobic. The resulting composite emulsion, when mixed with a prepared O / W emulsion, exhibits good and stable waterproof and permeability capabilities. It can form a dense hydrophobic network on the surface and inside the capillary walls of recycled coarse aggregate while effectively filling micropores, thus effectively inhibiting the absorption of water by the recycled coarse aggregate. The composite emulsion effectively improves the compatibility between nano-silica and recycled coarse aggregate, resulting in good hydrophobicity and compressive strength in the modified recycled coarse aggregate.

[0045] The present invention also provides the application of the modified recycled coarse aggregate described above in concrete, wherein the modified recycled coarse aggregate replaces part of the coarse aggregate in the raw materials for concrete preparation, and the mass proportion of the modified recycled coarse aggregate in the coarse aggregate is 30-50%, preferably 35-45%, and more preferably 40%.

[0046] This invention uses modified recycled coarse aggregate in concrete, which can significantly reduce the water absorption rate of recycled coarse aggregate from construction waste, improve the strength of recycled aggregate and recycled aggregate concrete, and greatly improve the utilization rate of recycled aggregate in high-performance concrete.

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. The described embodiments are only some embodiments of the present invention, and not all embodiments. Any modifications, equivalent substitutions, improvements, etc., made to the embodiments of the present invention based on the technical essence and general principles of the present invention without creative effort should be within the protection scope of the present invention.

[0048] Example 1

[0049] Preparation of 3-mercaptopropyltrimethoxysilane (MPTS)-nano SiO2 composite emulsion

[0050] Weigh 1g of 20-60nm nano-SiO2, measure 30mL of anhydrous ethanol using a graduated cylinder, mix the two and add the mixture to a three-necked flask. Stir at room temperature to disperse the nano-SiO2 evenly in the anhydrous ethanol, obtaining a uniform dispersion of nano-SiO2. Dry the uniform dispersion of nano-SiO2 at 90℃ to obtain nano-SiO2 powder.

[0051] 6g of Span80 and 60g of 3-mercaptopropyltrimethoxysilane (MPTS) were uniformly mixed through a channel and homogenized at 2800 rpm to form an oil phase. 6g of PPG O and 50g of distilled water were mixed uniformly to form an aqueous phase. 56g of the aqueous phase was poured into a three-necked flask and placed in a 40℃ constant-temperature oil bath. The oil phase was added dropwise to the aqueous phase at 75 drops / min, and the mixture was stirred at 1400 rpm to form a homogeneous oil-in-water structure. The mixture was rapidly stirred at 3200 rpm for 2 hours at 40℃. Then, 1g of nano-SiO2 powder was added to the three-necked flask, and the mixture was stirred at 3200 rpm for 3 hours to obtain the MPTS-nano-SiO2 composite emulsion.

[0052] Preparation of modified recycled coarse aggregate

[0053] Modified recycled coarse aggregate can be obtained by soaking 1 kg of recycled coarse aggregate in MPTS-nano SiO2 composite emulsion at room temperature for 4 days and then air-drying it naturally.

[0054] Application Example 1

[0055] Preparation of recycled concrete

[0056] 342g of modified recycled coarse aggregate from Example 1, 798g of natural coarse aggregate, 450g of cement, 660g of natural fine aggregate, and 150g of water were mixed to prepare recycled concrete. The modified recycled coarse aggregate was added internally at a mass ratio of 30% of the coarse aggregate. Capillary water absorption tests were conducted according to the test methods specified in UNIEN 1015-18:2004. The 28-day compressive strength of the recycled concrete with 30% modified recycled coarse aggregate from construction waste was determined according to the test methods in the "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" (GB / T50081).

[0057] Application Example 2

[0058] The preparation method of MPTS-nano SiO2 composite emulsion and modified recycled coarse aggregate is the same as in Example 1. The difference is that 456g of modified recycled coarse aggregate, 684g of natural coarse aggregate, 450g of cement, 660g of natural fine aggregate and 150g of water are mixed to prepare recycled concrete. The modified recycled coarse aggregate is added internally at a mass ratio of 40% of the coarse aggregate.

[0059] Application Example 3

[0060] The preparation method of MPTS-nano SiO2 composite emulsion and modified recycled coarse aggregate is the same as in Example 1. The difference is that 570g of modified recycled coarse aggregate, 570g of natural coarse aggregate, 450g of cement, 660g of natural fine aggregate and 150g of water are mixed to prepare recycled concrete. The modified recycled coarse aggregate is added internally at a mass ratio of 50% of the coarse aggregate.

[0061] Example 2

[0062] The recycled coarse aggregate was soaked in MPTS-nano SiO2 composite emulsion for 5 days, and the rest of the method was the same as in Example 1.

[0063] Application Example 4

[0064] Recycled concrete was prepared using the modified recycled coarse aggregate prepared in Example 2, with the other components and their mass ratios being the same as in Application Example 2.

[0065] Example 3

[0066] 6g of Span80 and 60g of isobutyltriethoxysilane were uniformly mixed through a channel and homogenized at 2800 rpm using a homogenizer to form an oil phase. 6g of PPG O and 50g of distilled water were mixed uniformly to form an aqueous phase. 56g of the aqueous phase was poured into a three-necked flask and placed in a 40℃ constant-temperature oil bath. The oil phase was added dropwise to the aqueous phase at 75 drops / min, and the mixture was stirred at 1400 rpm to form a uniformly mixed oil-in-water structure. The mixture was rapidly stirred at 3200 rpm for 2 hours at 40℃. Then, 1g of nano-SiO2 powder was added to the three-necked flask, and the mixture was stirred at 3200 rpm for 3 hours to obtain an isobutyltriethoxysilane monomer-nano-SiO2 composite emulsion.

[0067] Modified recycled coarse aggregate can be obtained by soaking 1 kg of recycled coarse aggregate in isobutyltriethoxysilane-nano SiO2 composite emulsion for 4 days and then air-drying it naturally.

[0068] Application Example 5

[0069] Recycled concrete was prepared using the modified recycled coarse aggregate prepared in Example 3, with the other components and their mass ratios being the same as in Application Example 2.

[0070] Comparative Example 1

[0071] 6g of Span80 and 60g of MPTS were uniformly mixed through a channel and homogenized at 2800r / min to obtain an MPTS emulsion. 1kg of recycled coarse aggregate was soaked in the MPTS emulsion for 4 days and then air-dried to obtain modified recycled coarse aggregate.

[0072] Comparative Application Example 1

[0073] Recycled concrete was prepared using unmodified recycled coarse aggregate, with the same types and mass ratios of other components as in Application Example 2.

[0074] Comparative Application Example 2

[0075] Recycled concrete was prepared using the modified recycled coarse aggregate prepared in Comparative Example 1, with the same types and mass ratios of other components as in Application Example 2.

[0076] Table 1. Water absorption rate of recycled coarse aggregate from construction waste before and after modification in Example 1.

[0077] Saturated surface-dry water absorption rate (%) Unmodified recycled coarse aggregate 13.8 Example 1 Modified recycled coarse aggregate 7.2 Example 2 Modified recycled coarse aggregate 7.15 Example 3 Modified recycled coarse aggregate 7.3 surface

[0078] As shown in Table 1, the saturated surface-dry water absorption rate of the modified recycled coarse aggregate is lower than that of the unmodified recycled coarse aggregate. This indicates that the MPTS-nano SiO2 composite emulsion forms a dense hydrophobic network on the surface and inside the capillary walls of the recycled aggregate, effectively filling the micropores and inhibiting the absorption of water by the recycled coarse aggregate.

[0079] Following the test methods specified in UNIEN 1015-18:2004, capillary water absorption tests were conducted to determine the capillary water absorption coefficients of recycled concrete with different volume ratios of recycled coarse aggregate before and after modification. The test results are shown in Table 2.

[0080] Table 2. Capillary water absorption coefficient and compressive strength of recycled concrete with different volume ratios of modified recycled fine aggregate.

[0081] Capillary water absorption coefficient / g / (m 2 .h 0.5 Comparison of 28-day compressive strength / MPa and doping ratio: Application Example 1: 271.63%, 43.34%; Application Example 2: 254.64%, 42.73%; Application Example 3: 243.85%, 41.94%; Application Example 4: 186.63%, 37.25% surface

[0082] As shown in Table 2, in recycled concrete, the capillary water absorption coefficient gradually decreases as the proportion of modified recycled coarse aggregate gradually increases. The modified recycled coarse aggregate can produce a dense, hydrophobic protective layer inside the recycled concrete, filling the internal capillary pores, effectively improving the density and reducing porosity of the recycled concrete, thereby enhancing its waterproof performance. In Application Example 3, compared to Application Examples 1 and 2, although the water absorption rate of the recycled coarse aggregate was significantly reduced due to the 50% admixture ratio, the 28-day compressive strength was relatively low. Application Example 2 not only significantly reduced the water absorption rate of the recycled coarse aggregate but also significantly improved the strength of the recycled aggregate concrete, resulting in a substantial improvement in the workability, mechanical properties, and durability of the recycled aggregate, greatly increasing the utilization rate of recycled aggregate in high-performance concrete.

[0083] Table 3. Capillary water absorption coefficient of recycled concrete with the same volume ratio of modified recycled fine aggregate and different soaking times.

[0084] Capillary water absorption coefficient / g / (m 2 .h0.5 Soaking time / day comparison: Application Example 1: 271.63 / Application Example 2: 243.854 / Application Example 4: 243.905 surface

[0085] As shown in Table 3, compared to Application Example 2, Application Example 4 extended the soaking time of the recycled coarse aggregate, yet the capillary coefficient of the recycled concrete remained essentially the same as that after soaking for 4 days. This indicates that extending the soaking time does not significantly reduce the capillary water absorption effect of the recycled concrete.

[0086] Table 4. Capillary water absorption coefficient and compressive strength of recycled concrete with the same volume ratio of recycled fine aggregate under different surface treatment methods.

[0087] Capillary water absorption coefficient / g / (m 2 .h 0.5 28-day compressive strength / MPa Application Example 2: 243.8 541.2 Application Example 5: 249.9 440.8 surface

[0088] As shown in Table 4, compared to Application Example 2, the capillary coefficient of the recycled concrete soaked in MPTS-nano SiO2 composite emulsion was lower in Application Example 5 than that soaked in isobutyltriethoxysilane-nano SiO2 composite emulsion. Furthermore, the compressive strength of the recycled concrete soaked in MPTS-nano SiO2 composite emulsion was higher than that soaked in isobutyltriethoxysilane-nano SiO2 composite emulsion, indicating that MPTS-nano SiO2 composite emulsion has a more effective modification effect on recycled coarse aggregate.

[0089] Table 5. Capillary water absorption coefficient and compressive strength of recycled concrete with different modified recycled fine aggregates at the same volume ratio.

[0090]

[0091]

[0092] As shown in Table 5, compared to Application Example 2, the capillary coefficient of the recycled concrete soaked only with MPTS emulsion was higher than that of the MPTS-nano SiO2 composite emulsion soaked in the same solution, indicating that the MPTS-nano SiO2 composite emulsion had a greater modification effect on the recycled coarse aggregate. Furthermore, the recycled concrete soaked only with MPTS emulsion had lower strength than the recycled concrete soaked in the MPTS-nano SiO2 composite emulsion, indicating that the MPTS-nano SiO2 composite emulsion had a greater strength improvement effect on the recycled coarse aggregate.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing modified recycled coarse aggregate, characterized in that, Includes the following steps: An oil phase is added to an aqueous phase and stirred to obtain an O / W type emulsion; the oil phase includes a lipophilic emulsifier and a silane coupling agent; the aqueous phase includes an aqueous solution of a nonionic surfactant; the mass ratio of the nonionic surfactant to water is 1:6~15; nano-SiO2 is mixed with the O / W type emulsion to obtain a composite emulsion; recycled coarse aggregate is soaked in the composite emulsion to obtain modified recycled coarse aggregate; the lipophilic emulsifier includes Span; the nonionic surfactant includes Pintodione; the mass ratio of the lipophilic emulsifier to the silane coupling agent is 1:13~23; the volume ratio of the oil phase to the aqueous phase is 1:0.8~1.4; the solid-liquid ratio of the nano-SiO2 to the O / W type emulsion is 3~6 g:1 mL.

2. The preparation method according to claim 1, characterized in that, The silane coupling agent includes 3-mercaptopropyltrimethoxysilane and / or isobutyltriethoxysilane.

3. The preparation method according to claim 1, characterized in that, The nano-SiO2 is further pretreated before being mixed with the O / W type emulsion; the pretreatment includes: mixing nano-SiO2 with anhydrous ethanol and then drying; the solid-liquid ratio of nano-SiO2 to anhydrous ethanol is 1g:2~5mL.

4. The preparation method according to claim 1, characterized in that, The stirring speed is 1400~1600 r / min, the stirring time is 2~4 h, and the stirring temperature is 30~50℃.

5. The preparation method according to claim 1, characterized in that, The soaking time is 1 to 6 days.

6. Modified recycled coarse aggregate prepared by the preparation method according to any one of claims 1 to 5.

7. The application of the modified recycled coarse aggregate according to claim 6 in concrete, characterized in that, The modified recycled coarse aggregate replaces part of the coarse aggregate in the concrete preparation raw materials, and the mass ratio of the modified recycled coarse aggregate in the coarse aggregate is 30-50%.

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