A recycled aggregate strengthening method based on hydration process regulation of alkali-activated cementitious materials

Abstract

The application relates to a recycled aggregate strengthening method based on hydration process regulation of alkali-activated cementitious materials, and belongs to the technical field of building material preparation and solid waste resource utilization. Alkali-activated cementitious materials are mixed with water according to a water-cement ratio of 0.5-5.0:1 to prepare alkali-activated cementitious material solution; recycled aggregates are added into the alkali-activated cementitious material solution according to a mass ratio of recycled aggregates to alkali-activated cementitious materials of 1.1-2.5:1, and then the recycled aggregates are strengthened by the slurry wrapping method, and then dried and maintained, so that the recycled aggregates are obtained. In the application, nanoscale depolymerization monomers in the hydration process of alkali-activated cementitious materials are diffused into residual mortar pores and aggregate microcracks, and then the recycled aggregates are strengthened through the repolymerization process of the depolymerization monomers, so that the recycled aggregates are efficiently and low-costly strengthened, and the high-quality recycling of waste concrete is promoted.

Description

TECHNICAL FIELD

[0001] The application relates to a recycled aggregate strengthening method based on hydration process regulation of alkali-activated cementitious materials, and belongs to the technical field of building material preparation and solid waste resource utilization. BACKGROUND

[0002] The information disclosed in this BACKGROUND section is only for the purpose of increasing the understanding of the background of the application and should not be taken as an acknowledgement or any form of suggestion that this information forms prior art that is publicly known.

[0003] Recycled utilization of waste concrete can reduce the use amount of natural sand aggregate, and can also promote the solution of the environmental problems caused by waste concrete stockpiling. The recycled aggregate is covered with a considerable amount of old cement mortar, and the crushing process causes defects in the aggregate, which are manifested in small apparent density, large water absorption and high crushing value. After the recycled aggregate concrete is hardened, the internal pores increase, the mechanical strength decreases, and the durability deteriorates, which limits the large-scale utilization of the recycled aggregate. In order to improve the utilization rate and added value of waste concrete, the recycled aggregate prepared from the waste concrete needs to be strengthened.

[0004] According to the research of the inventors, the current recycled aggregate strengthening methods include mechanical grinding, acid treatment, heating grinding, carbonation modification, nano material modification and microbial modification. Among them, the nano material modification is a high-efficiency recycled aggregate strengthening method. However, the nano material modification has the following problems: 1. The nano material is easy to agglomerate, and has poor dispersion effect in residual mortar and microcracks, resulting in poor strengthening effect; 2. The cost of the nano material is high, so that the strengthened recycled aggregate is difficult to popularize and apply. Therefore, it is necessary to improve the existing nano material strengthening recycled aggregate technology and provide a new recycled aggregate strengthening method for improving the water absorption and crushing value of the recycled aggregate. SUMMARY

[0005] In order to solve the problems of the existing nano material strengthening aggregate technology, the application aims to provide a recycled aggregate strengthening method based on hydration process regulation of alkali-activated cementitious materials. Based on the depolymerization-repolymerization process of alkali-activated cementitious materials, the nano-level depolymerized monomers in the hydration process of alkali-activated cementitious materials are diffused into the residual mortar pores and the microcracks of the aggregate, and then the recycled aggregate is strengthened through the repolymerization process of the depolymerized monomers, so that the recycled aggregate is efficiently and low-costly strengthened, and the high-quality recycling of waste concrete is promoted.

[0006] In order to achieve the above-mentioned purpose, the application provides the following technical scheme:

[0007] The first aspect relates to a method for strengthening recycled aggregate based on hydration process regulation of alkali-activated cementitious material, wherein the alkali-activated cementitious material is mixed with water to form an alkali-activated cementitious material solution according to a water-cement ratio of 0.5-5:1; the recycled aggregate is added to the alkali-activated cementitious material solution according to a mass ratio of 1.1-2.5:1 of the recycled aggregate to the alkali-activated cementitious material, and then the recycled aggregate is strengthened by the slurry wrapping method, and then dried and cured to obtain the strengthened recycled aggregate.

[0008] The strengthening procedure is as follows: the ultrasonic is turned on, and the ultrasonic-assisted strengthening is first performed at a temperature of 10-20 DEG C for 50-70 min, and then performed at a temperature of 20-30 DEG C for 50-70 min, and then the ultrasonic is turned off, and the strengthening is performed at a temperature of 60-70 DEG C for 500-600 min.

[0009] The alkali-activated cementitious material comprises, according to the mass fraction, 80-90 parts of a silico-alumina component, 9-15 parts of an alkali activator, and 1-5 parts of a setting time regulator; the alkali activator comprises, according to the mass fraction, 25-30 parts of sodium silicate, 15-20 parts of sodium carbonate, 4-9 parts of aluminum sulfate, and 0-8 parts of calcium sulfate; and the setting time regulator comprises, according to the mass fraction, 30-40 parts of glucose, 25-30 parts of sodium gluconate, and 30-45 parts of sodium hexametaphosphate.

[0010] The silico-alumina component is a substance containing aluminum and / or silicon as the main component, and can be industrial solid waste such as blast furnace slag, fly ash, steel slag, coal gangue, and red mud.

[0011] The second aspect relates to a strengthened recycled aggregate obtained by the above method.

[0012] The third aspect relates to the application of the strengthened recycled aggregate in concrete.

[0013] The application has the following advantages:

[0014] (1) The traditional method for strengthening nanomaterials is to directly add nanomaterials for strengthening and modification, and thus the nanomaterials are prone to agglomeration. The application provides a method for strengthening recycled aggregate based on the dissolution-diffusion-polymerization of alkali-activated cementitious material. The reaction principle of the alkali-activated cementitious material is that the silico-alumina component is depolymerized to generate nanoscale aluminum oxide tetrahedron and silicon oxide tetrahedron under the action of the alkali activator, and then the generated aluminum oxide tetrahedron and silicon oxide tetrahedron are polymerized to generate geopolymer gel with a three-dimensional network structure. The technical feature of the application is to generate nanoscale strengthening material in situ, and then to polymerize in situ, and finally to strengthen the aggregate, thereby solving the agglomeration problem caused in the traditional process for strengthening nanomaterials and improving the strengthening efficiency of the recycled aggregate.

[0015] (2) The traditional alkali-activated cementitious material strengthening recycled aggregate technology is mainly based on the principle of the slurry wrapping method, and there are problems such as uneven slurry thickness and large differences in strengthening effect. The present application adjusts the water-cement ratio in the alkali-activated cementitious material and adds a compounded setting time regulator to control the hydration process of the alkali-activated cementitious material, prolongs the existence time of aluminum oxide tetrahedron and silicon oxide tetrahedron, and improves the diffusion speed of aluminum oxide tetrahedron and silicon oxide tetrahedron through the improvement of ultrasonic mode, so that it can more efficiently enter the pores and cracks of the recycled aggregate, and then a new strengthening process technology based on nano material strengthening and supplemented by slurry strengthening is formed, and the strengthening effect of the recycled aggregate is improved.

[0016] (3) In the traditional alkali-activated cementitious material system, alkali activator is used, so that the recycled concrete prepared by the alkali-activated cementitious material is prone to alkali-aggregate reaction. The present application innovatively proposes the idea of alkali-salt synergistic activation, and uses an alkali-salt composite activator composed of sodium silicate, sodium carbonate, aluminum sulfate and calcium sulfate to greatly reduce the alkalinity of the recycled concrete system, thereby avoiding the alkali-aggregate reaction existing in the recycled concrete during the use of traditional single alkali activator such as sodium hydroxide and sodium silicate.

[0017] (4) The traditional nano material strengthened recycled aggregate has high cost, and the present application uses industrial solid waste as raw material, which has the advantages of low cost, solid waste disposal and significant ecological benefits. BRIEF DESCRIPTION OF DRAWINGS

[0018] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated herein for explanation.

[0019] Figure 1 It is a mechanism diagram of the present application based on the hydration process regulation of alkali-activated cementitious material for strengthening recycled aggregate. DETAILED DESCRIPTION

[0020] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0021] It should be noted that the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form, and in addition, it should be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, operation, device, component and / or combination thereof.

[0022] The recycled aggregate has a large water absorption rate and a high crushing value, and the existing nano-modified reinforced recycled aggregate has an unsatisfactory reinforcing effect and still has a large difference with the performance of the natural aggregate, mainly because the nano material has a small particle size and is prone to agglomeration, which leads to poor dispersion effect in residual mortar and micro-cracks, which is not conducive to the reinforcement of the recycled aggregate, and the application provides a recycled aggregate reinforcement method based on hydration process regulation of alkali-activated cementitious materials.

[0023] In a typical embodiment of the application, a recycled aggregate reinforcement method based on hydration process regulation of alkali-activated cementitious materials is provided, wherein alkali-activated cementitious materials are mixed with water according to a water-cement ratio of 0.5-5:1 to prepare an alkali-activated cementitious material solution; the recycled aggregate is added to the alkali-activated cementitious material solution according to a mass ratio of recycled aggregate to alkali-activated cementitious material of 1.1-2.5:1 for reinforcement, and then dried and cured to obtain the product.

[0024] The reinforcement procedure is as follows: open the ultrasonic, first ultrasonic-assisted reinforcement at a temperature of 10-20 DEG C for 50-70 min, then ultrasonic-assisted reinforcement at a temperature of 20-30 DEG C for 50-70 min, then close the ultrasonic, and reinforcement at a temperature of 60-70 DEG C for 500-600 min.

[0025] The alkali-activated cementitious material comprises, in terms of mass fraction, 80-90 parts of a silico-alumina component, 9-15 parts of an alkali activator, and 1-5 parts of a setting time regulator; the alkali salt composite activator comprises, in terms of mass fraction, 25-30 parts of sodium silicate, 15-20 parts of sodium carbonate, 4-9 parts of aluminum sulfate, and 0-8 parts of calcium sulfate; and the setting time regulator comprises, in terms of mass fraction, 30-40 parts of glucose, 25-30 parts of sodium gluconate, and 30-45 parts of sodium hexametaphosphate.

[0026] In some embodiments, the alkali-activated cementitious material has an atomic ratio of Si / Al of 1-2:1 and an atomic ratio of Si / Ca of 0.2-1.5:1, so as to ensure that the alkali-activated cementitious material has high mechanical strength.

[0027] In some embodiments, the silico-alumina component is one or more of blast furnace slag, fly ash, steel slag, coal gangue, and red mud.

[0028] In some embodiments, the specific surface area of the silico-alumina component is 600-1000 m 2 / kg, and the water content is less than 2%.

[0029] In some embodiments, the alkali-activated cementitious material has an initial setting time of 300-480 min and a final setting time of 500-600 min. The alkali-activated cementitious material has the advantages of long initial setting time and short final setting time, ensuring better diffusion of the depolymerized monomers into the pores and cracks of the recycled aggregate.

[0030] The recycled aggregate is obtained by crushing and screening waste concrete. In some embodiments, the recycled aggregate is classified into 0-4.75 mm, 4.75-9.5 mm, 9.5-19 mm, and 19-31.5 mm fractions for strengthening.

[0031] In another embodiment of the present application, a strengthened recycled aggregate is provided, which is obtained by the above-mentioned method for strengthening recycled aggregate.

[0032] In some embodiments, the strengthened recycled aggregate has a water absorption rate of 0.96-1.26% and a crushing value of 8.82-10.52%.

[0033] In a third embodiment of the present application, a use of the strengthened recycled aggregate in concrete is provided.

[0034] In some embodiments, the concrete is ultra-high performance concrete.

[0035] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below with specific examples and comparative examples.

[0036] Example 1:

[0037] (1) The waste concrete was screened and impurities were removed, and then crushed by a jaw crusher. The recycled aggregate with particle sizes of 0-4.75 mm, 4.75-9.5 mm, 9.5-19 mm, and 19-31.5 mm was obtained by screening. The recycled aggregate was rinsed and air-dried to constant weight for standby use.

[0038] (2) A composite of blast furnace slag powder and fly ash with Si / Al of 1 and Si / Ca of 0.2 was prepared as the silico-alumina component raw material, and was ground to a specific surface area of 600 m 2 / kg for standby use.

[0039] (3) Sodium silicate 30 parts, sodium carbonate 20 parts, aluminum sulfate 9 parts, and calcium sulfate 8 parts were weighed and mixed uniformly to prepare an alkali-salt composite activator for standby use.

[0040] (4) Glucose 30 parts, sodium gluconate 25 parts, and sodium hexametaphosphate 45 parts were weighed and mixed uniformly to prepare a setting time regulator for standby use.

[0041] (5) According to 80 parts of silico-alumina component, 15 parts of alkali-salt composite activator and 5 parts of setting time regulator, an alkali-activated cementitious material is prepared for standby.

[0042] (6) An alkali-activated cementitious material slurry solution is prepared according to a water-cement ratio of 0.5.

[0043] (7) According to a mass ratio of recycled aggregate to alkali-activated cementitious material of 1.5:1, the recycled aggregate is added to the cementitious material solution, and at the same time, an ultrasonic system is started, the slurry temperature is 10℃ for 0-60min; the temperature is 20℃ for 60-120min; after 120min, the ultrasonic system is closed, the temperature is 60℃, and the strengthening is continued for 500min.

[0044] (8) The strengthened recycled aggregate is cured under standard conditions (temperature 20±3℃, relative humidity maintained above 90%) for 7 days, hot air is blown to dry, and it can be used.

[0045] Example 2:

[0046] (1) The waste concrete is screened, impurities are removed, and is processed and crushed by a jaw crusher, and is sieved to obtain recycled aggregate with particle sizes of 0-4.75mm, 4.75-9.5mm, 9.5-19mm and 19-31.5mm, is washed clean and air-dried to constant weight for standby.

[0047] (2) A composite of blast furnace slag powder and fly ash with Si / Al of 1 and Si / Ca of 0.2 is prepared as a silico-alumina component raw material, and is ground to a specific surface area of 600m 2 / kg for standby.

[0048] (3) 30 parts of sodium silicate, 20 parts of sodium carbonate, 9 parts of aluminum sulfate and 8 parts of calcium sulfate are weighed and uniformly mixed to prepare an alkali-salt composite activator for standby.

[0049] (4) 35 parts of glucose, 27 parts of sodium gluconate and 30 parts of sodium hexametaphosphate are mixed uniformly to prepare a setting time regulator for standby.

[0050] (5) An alkali-activated cementitious material is prepared according to 90 parts of silico-alumina component, 9 parts of alkali-salt composite activator and 1 part of setting time regulator for standby.

[0051] (6) An alkali-activated cementitious material slurry solution is prepared according to a water-cement ratio of 0.5.

[0052] (7) According to a mass ratio of recycled aggregate to alkali-activated cementitious material of 1.5:1, the recycled aggregate is added to the cementitious material solution, and at the same time, an ultrasonic system is started, the slurry temperature is 10℃ for 0-60min; the temperature is 20℃ for 60-120min; after 120min, the ultrasonic system is closed, the temperature is 60℃, and the strengthening is continued for 500min.

[0053] (8) The reinforced recycled aggregate is cured under standard conditions (temperature 20±3℃, relative humidity maintained above 90%) for 7 days, hot air dried, and ready for use.

[0054] Example 3:

[0055] (1) The waste concrete is screened, impurities are removed, and is processed and crushed by a jaw crusher. Recycled aggregates with particle sizes of 0-4.75 mm, 4.75-9.5 mm, 9.5-19 mm, and 19-31.5 mm are obtained by screening. The recycled aggregates are washed clean and air-dried to constant weight for standby use.

[0056] (2) A red mud and coal gangue composite with a Si / Al ratio of 1 and a Si / Ca ratio of 0.2 is configured as a silico-alumina component raw material, and is ground to a specific surface area of 600 m 2 / kg for standby use.

[0057] (3) 30 parts of sodium silicate, 20 parts of sodium carbonate, 9 parts of aluminum sulfate, and 8 parts of calcium sulfate are weighed and uniformly mixed to configure an alkali-salt composite activator for standby use.

[0058] (4) 30 parts of glucose, 25 parts of sodium gluconate, and 45 parts of sodium hexametaphosphate are mixed uniformly to configure a setting time regulator for standby use.

[0059] (5) An alkali-activated cementitious material is configured according to 89 parts of silico-alumina components, 9 parts of alkali-salt composite activator, and 2 parts of setting time regulator for standby use.

[0060] (6) An alkali-activated cementitious material slurry solution is prepared according to a water-cement ratio of 0.5.

[0061] (7) According to a recycled aggregate to alkali-activated cementitious material mass ratio of 1.5:1, the recycled aggregate is added to the cementitious material solution, and an ultrasonic system is started. The slurry temperature is 10℃ for 0-60 min, 20℃ for 60-120 min, and 60℃ after 120 min. The ultrasonic system is turned off, and the strengthening is performed for 500 min.

[0062] (8) The reinforced recycled aggregate is cured under standard conditions (temperature 20±3℃, relative humidity maintained above 90%) for 7 days, hot air dried, and ready for use.

[0063] Example 4:

[0064] (1) The waste concrete is screened, impurities are removed, and is processed and crushed by a jaw crusher. Recycled aggregates with particle sizes of 0-4.75 mm, 4.75-9.5 mm, 9.5-19 mm, and 19-31.5 mm are obtained by screening. The recycled aggregates are washed clean and air-dried to constant weight for standby use.

[0065] (2) The blast furnace slag powder and fly ash complex with Si / Al of 2 and Si / Ca of 1.5 is configured as the silico-alumina component raw material, and is ground to a specific surface area of 600 m 2 / kg, for standby.

[0066] (3) 25 parts of sodium silicate, 15 parts of sodium carbonate and 4 parts of aluminum sulfate are weighed and uniformly mixed to configure an alkali-salt composite activator for standby.

[0067] (4) 30 parts of glucose, 25 parts of sodium gluconate and 45 parts of sodium hexametaphosphate are weighed and uniformly mixed to configure a setting time regulator for standby.

[0068] (5) The alkali-activated cementitious material is configured according to 90 parts of the silico-alumina component, 9 parts of the alkali-salt composite activator and 1 part of the setting time regulator for standby.

[0069] (6) The alkali-activated cementitious material slurry solution is prepared according to a water-cement ratio of 0.5.

[0070] (7) The recycled aggregate is added to the cementitious material solution according to a recycled aggregate to alkali-activated cementitious material mass ratio of 1.5:1, and the ultrasonic system is started. The slurry temperature is 10℃ for 0-60 min, 20℃ for 60-120 min, and 60℃ after 120 min. The ultrasonic system is turned off, and the strengthening is continued for 500 min.

[0071] (8) The strengthened recycled aggregate is cured under standard conditions (temperature 20±3℃, relative humidity maintained above 90%) for 7 days, and can be used.

[0072] Example 5:

[0073] (1) The waste concrete is screened and impurities are removed, and is processed and crushed by a jaw crusher. Recycled aggregates with particle sizes of 0-4.75 mm, 4.75-9.5 mm, 9.5-19 mm and 19-31.5 mm are obtained by screening, are washed clean and air-dried to constant weight for standby.

[0074] (2) The blast furnace slag powder and fly ash complex with Si / Al of 1 and Si / Ca of 0.2 is configured as the silico-alumina component raw material, and is ground to a specific surface area of 600 m 2 / kg, for standby.

[0075] (3) 30 parts of sodium silicate, 20 parts of sodium carbonate, 9 parts of aluminum sulfate and 2 parts of calcium sulfate are weighed and uniformly mixed to configure an alkali-salt composite activator for standby.

[0076] (4) 30 parts of glucose, 25 parts of sodium gluconate and 45 parts of sodium hexametaphosphate are weighed and uniformly mixed to configure a setting time regulator for standby.

[0077] (5) According to 90 parts of silico-alumina component, 9 parts of alkali-salt composite activator and 1 part of setting time regulator, an alkali-activated cementitious material is prepared for standby.

[0078] (6) An alkali-activated cementitious material slurry solution is prepared according to a water-cement ratio of 0.5.

[0079] (7) According to a mass ratio of recycled aggregate to alkali-activated cementitious material of 1.5:1, the recycled aggregate is added to the cementitious material solution, and at the same time, an ultrasonic system is started, the slurry temperature is 10°C for 0-60 min; the temperature is 20°C for 60-120 min; after 120 min, the ultrasonic system is closed, the temperature is 60°C, and the strengthening is continued for 500 min.

[0080] (8) The strengthened recycled aggregate is cured under standard conditions (temperature 20±3°C, relative humidity maintained above 90%) for 7 days, hot air is blown to dry, and it can be used.

[0081] Example 6:

[0082] (1) The waste concrete is screened, impurities are removed, and is processed and crushed by a jaw crusher, and is sieved to obtain recycled aggregate with particle sizes of 0-4.75 mm, 4.75-9.5 mm, 9.5-19 mm and 19-31.5 mm, is washed clean and air-dried to constant weight for standby.

[0083] (2) A composite of blast furnace slag powder and fly ash with Si / Al of 1 and Si / Ca of 0.2 is prepared as a silico-alumina component raw material, and is ground to a specific surface area of 600 m 2 / kg for standby.

[0084] (3) 25 parts of sodium silicate, 20 parts of sodium carbonate, 9 parts of aluminum sulfate and 8 parts of calcium sulfate are weighed and uniformly mixed to prepare an alkali-salt composite activator for standby.

[0085] (4) 40 parts of glucose, 30 parts of sodium gluconate and 30 parts of sodium hexametaphosphate are mixed uniformly to prepare a setting time regulator for standby.

[0086] (5) An alkali-activated cementitious material is prepared according to 90 parts of silico-alumina component, 9 parts of alkali-salt composite activator and 1 part of setting time regulator for standby.

[0087] (6) An alkali-activated cementitious material slurry solution is prepared according to a water-cement ratio of 0.5.

[0088] (7) According to a mass ratio of recycled aggregate to alkali-activated cementitious material of 1.5:1, the recycled aggregate is added to the cementitious material solution, and at the same time, an ultrasonic system is started, the slurry temperature is 10°C for 0-60 min; the temperature is 20°C for 60-120 min; after 120 min, the ultrasonic system is closed, the temperature is 60°C, and the strengthening is continued for 500 min.

[0089] (8) The reinforced recycled aggregate is cured under standard conditions (temperature 20±3℃, relative humidity maintained above 90%) for 7 days, hot air dried, and ready for use.

[0090] Example 7:

[0091] (1) The waste concrete is screened, impurities are removed, and is processed and crushed by a jaw crusher. Recycled aggregates with particle sizes of 0-4.75 mm, 4.75-9.5 mm, 9.5-19 mm, and 19-31.5 mm are obtained by screening. The recycled aggregates are washed clean and air-dried to constant weight for standby use.

[0092] (2) A composite of blast furnace slag powder and fly ash with Si / Al of 1 and Si / Ca of 0.2 is configured as a silico-alumina component raw material, and is ground to a specific surface area of 600 m 2 / kg for standby use.

[0093] (3) 27 parts of sodium silicate, 15 parts of sodium carbonate, 9 parts of aluminum sulfate, and 8 parts of calcium sulfate are weighed and uniformly mixed to configure an alkali-salt composite activator for standby use.

[0094] (4) 30 parts of glucose, 25 parts of sodium gluconate, and 45 parts of sodium hexametaphosphate are mixed uniformly to configure a setting time regulator for standby use.

[0095] (5) An alkali-activated cementitious material is configured with 90 parts of the silico-alumina component, 9 parts of the alkali-salt composite activator, and 1 part of the setting time regulator for standby use.

[0096] (6) An alkali-activated cementitious material slurry solution is prepared with a water-cement ratio of 1.0.

[0097] (7) The recycled aggregate and the alkali-activated cementitious material are added to the cementitious material solution at a mass ratio of 1.5:1, and the ultrasonic system is started. The slurry temperature is 10℃ for 0-60 min, 20℃ for 60-120 min, and 60℃ after 120 min. The ultrasonic system is turned off, and the strengthening is performed for 500 min.

[0098] (8) The reinforced recycled aggregate is cured under standard conditions (temperature 20±3℃, relative humidity maintained above 90%) for 7 days, hot air dried, and ready for use.

[0099] Example 8:

[0100] (1) The waste concrete is screened, impurities are removed, and is processed and crushed by a jaw crusher. Recycled aggregates with particle sizes of 0-4.75 mm, 4.75-9.5 mm, 9.5-19 mm, and 19-31.5 mm are obtained by screening. The recycled aggregates are washed clean and air-dried to constant weight for standby use.

[0101] (2) Configuration of blast furnace slag powder and fly ash complex with Si / Al of 1 and Si / Ca of 0.2 as silico-alumina component raw material, grinding to specific surface area of 600m 2 / kg, standby.

[0102] (3) Take sodium silicate 27 parts, sodium carbonate 15 parts, aluminum sulfate 4 parts, calcium sulfate 8 parts, mix evenly, and configure into alkali-salt composite activator, standby.

[0103] (4) Take glucose 30 parts, sodium gluconate 25 parts, sodium hexametaphosphate 45 parts, mix evenly, and configure into setting time regulator, standby.

[0104] (5) Configuration of alkali-activated cementitious material according to silico-alumina component 90 parts, alkali-salt composite activator 9 parts, and setting time regulator 1 part, standby.

[0105] (6) Preparation of alkali-activated cementitious material slurry solution according to water-cement ratio of 0.5.

[0106] (7) According to the mass ratio of recycled aggregate to alkali-activated cementitious material of 3:1, add recycled aggregate to the cementitious material solution, and start the ultrasonic system at the same time. The slurry temperature is 10℃ for 0-60min; the temperature is 20℃ for 60-120min; after 120min, the ultrasonic system is turned off, and the temperature is 60℃, and the strengthening is 500min.

[0107] (8) The strengthened recycled aggregate is cured under standard conditions (temperature 20±3℃, relative humidity maintained above 90%) for 7 days, hot air dried, and ready for use.

[0108] Example 9:

[0109] (1) The waste concrete is screened, impurities are removed, and is processed and crushed by a jaw crusher. Recycled aggregates with particle sizes of 0-4.75mm, 4.75-9.5mm, 9.5-19mm, and 19-31.5mm are obtained by screening, washed clean and air dried to constant weight, standby.

[0110] (2) Configuration of blast furnace slag powder and fly ash complex with Si / Al of 1 and Si / Ca of 0.2 as silico-alumina component raw material, grinding to specific surface area of 600m 2 / kg, standby.

[0111] (3) Take sodium silicate 25 parts, sodium carbonate 18 parts, aluminum sulfate 4 parts, calcium sulfate 5 parts, mix evenly, and configure into alkali-salt composite activator, standby.

[0112] (4) Take glucose 30 parts, sodium gluconate 25 parts, sodium hexametaphosphate 45 parts, mix evenly, and configure into setting time regulator, standby.

[0113] (5) Prepare the alkali-activated cementitious material with 90 parts of silico-aluminate component, 9 parts of alkali-salt composite activator and 1 part of setting time regulator.

[0114] (6) Prepare the alkali-activated cementitious material slurry solution with water-cement ratio of 0.5.

[0115] (7) Add the recycled aggregate to the cementitious material solution with recycled aggregate to alkali-activated cementitious material mass ratio of 1.5:1, and start the ultrasonic system. The slurry temperature is 20℃ for 0-60min, 30℃ for 60-120min, and 70℃ after 120min. The ultrasonic system is turned off after 500min of strengthening.

[0116] (8) Cure the strengthened recycled aggregate under standard conditions (temperature 20±3℃, relative humidity maintained above 90%) for 7 days, and dry with hot air. The strengthened recycled aggregate is ready for use.

[0117] The strengthening mechanism of examples 1-9 is shown in Figure 1 .

[0118] Comparative Example 1:

[0119] Compared with Example 1, the activator is traditional sodium silicate activation, and no alkali-salt composite activator is used.

[0120] Comparative Example 2:

[0121] Compared with Example 1, no setting time regulator is added.

[0122] Comparative Example 3:

[0123] Compared with Example 1, the temperature during the strengthening process is always 20℃.

[0124] According to the relevant test methods in "Recycled Coarse Aggregate for Concrete" GB / T 25177-2010, the crushing value and water absorption of natural aggregate, un-strengthened recycled aggregate, and recycled aggregate treated according to the above strengthening method are tested.

[0125] The test results are shown in Table 1

[0126] The main physical properties of untreated recycled aggregate are: water absorption 10.25%, crushing value 28.0%. The main physical properties of natural aggregate are: water absorption 0.88%, crushing value 8.66%.

[0127] Table 1 Basic physical properties of different recycled aggregates

[0128]

[0129]

[0130] From Table 1, it can be seen that the recycled aggregate strengthening method based on the setting time regulation of alkali-activated cementitious materials in Examples 1-9 can significantly reduce the water absorption and crushing value of the strengthened recycled aggregate. Compared with the un-strengthened aggregate, the minimum water absorption is 0.96%, and the minimum crushing value is 8.82%, reaching the I-class aggregate standard. The quality of the recycled aggregate is significantly improved, and it can completely replace natural aggregate to be applied to ultra-high performance concrete, thereby realizing large-scale application of waste concrete.

[0131] The above-mentioned recycled aggregate strengthened by Example 6 and natural aggregate were used to prepare ultra-high performance concrete according to Table 2, and the test results are shown in Table 3.

[0132] Table 2: Mix proportion of ultra-high performance concrete

[0133]

[0134] Table 3: Strength test results of ultra-high performance concrete

[0135]

[0136] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for strengthening recycled aggregate based on the regulation of the hydration process of alkali-activated cementitious materials, characterized in that: Alkali-activated cementitious material is mixed with water at a water-cement ratio of 0.5 to 5.0:1 to prepare an alkali-activated cementitious material solution; recycled aggregate is added to the alkali-activated cementitious material solution at a mass ratio of recycled aggregate to alkali-activated cementitious material of 1.1 to 2.5:1, and reinforced by a slurry coating method, followed by drying and curing to obtain the product; The strengthening procedure is as follows: turn on ultrasound, first strengthen at a temperature of 10-20°C for 50-70 minutes, then strengthen at a temperature of 20-30°C for 50-70 minutes, then turn off ultrasound, and strengthen at a temperature of 60-70°C for 500-600 minutes; The raw materials of the alkali-activated gelling material include, by weight, 80-90 parts of a silicoaluminous component, 9-15 parts of an alkali salt composite activator, and 1-5 parts of a setting time regulator; the raw materials of the alkali salt composite activator include, by weight, 25-30 parts of sodium silicate, 15-20 parts of sodium carbonate, 4-9 parts of aluminum sulfate, and 0-8 parts of calcium sulfate; the raw materials of the setting time regulator include, by weight, 30-40 parts of glucose, 25-30 parts of sodium gluconate, and 30-45 parts of sodium hexametaphosphate.

2. The recycled aggregate strengthening method based on the regulation of the hydration process of alkali-activated cementitious materials according to claim 1 is characterized in that: In the alkali-activated gelling material, the Si / Al atomic ratio is 1-2:1, and the Si / Ca atomic ratio is 0.2-1.5:

1.

3. The recycled aggregate strengthening method based on the regulation of the hydration process of alkali-activated cementitious materials according to claim 1 is characterized in that: The siliceous and aluminous components are one or more of blast furnace slag, fly ash, steel slag, coal gangue, and red mud.

4. The recycled aggregate strengthening method based on the regulation of the hydration process of alkali-activated cementitious materials according to claim 1 is characterized in that: The specific surface area of ​​the silicon-aluminum component is 600-1000 m 2 / kg, moisture content is less than 2%.

5. The recycled aggregate strengthening method based on the regulation of the hydration process of alkali-activated cementitious materials according to claim 1 is characterized in that: The initial setting time of the alkali-activated gelling material is 300-480 minutes, and the final setting time is 500-600 minutes.

6. The recycled aggregate strengthening method based on the regulation of the hydration process of alkali-activated cementitious materials according to claim 1 is characterized in that: The particle size of recycled aggregate shall not exceed 31.5 mm.

7. A reinforced recycled aggregate, characterized in that: Obtained by the recycled aggregate strengthening method according to any one of claims 1 to 6.

8. The reinforced recycled aggregate according to claim 7, characterized in that: The water absorption rate of the reinforced recycled aggregate is 0.96-1.26%, and the crushing value is 8.82-10.52%.

9. Use of the reinforced recycled aggregate according to claim 7 or 8 in concrete.

10. The use according to claim 9, characterized in that: The concrete is ultra-high performance concrete.

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