阅读说明：本技术 采用膨胀土改性剂的再生混凝土 (Recycled concrete adopting expansive soil modifier ) 是由 赵旸 杨帆 于 2021-09-13 设计创作，主要内容包括：本申请涉及建筑材料领域,具体公开了一种采用膨胀土改性剂的再生混凝土。再生混凝土的原料包括以下质量份的组分：再生混凝土骨料150-400份,水泥120-200份,再生粉料50-100份,膨胀土10-20份,减水剂5-15份,缓凝剂20-40份,钛酸酯偶联剂5-10份,纤维素15-40份,水100-150份。本申请具有提高再生混凝土强度的效果。(The application relates to the field of building materials, and particularly discloses recycled concrete adopting an expansive soil modifier. The raw materials of the recycled concrete comprise the following components in parts by mass: the concrete mortar comprises, by weight, 150-400 parts of recycled concrete aggregate, 120-200 parts of cement, 50-100 parts of recycled powder, 10-20 parts of expansive soil, 5-15 parts of a water reducing agent, 20-40 parts of a retarder, 5-10 parts of a titanate coupling agent, 15-40 parts of cellulose and 150 parts of 100-containing water. This application has the effect that improves recycled concrete intensity.)

1. The recycled concrete adopting the expansive soil modifier is characterized in that: the raw materials of the recycled concrete comprise the following components in parts by mass: the concrete mortar comprises, by weight, 150-400 parts of recycled concrete aggregate, 120-200 parts of cement, 50-100 parts of recycled powder, 10-20 parts of expansive soil, 5-15 parts of a water reducing agent, 20-40 parts of a retarder, 5-10 parts of a titanate coupling agent, 15-40 parts of cellulose and 150 parts of 100-containing water.

2. The recycled concrete with expansive soil modifier of claim 1, wherein: the raw materials of the recycled concrete comprise the following components in parts by mass: 300 parts of recycled concrete aggregate, 150 parts of cement, 60-80 parts of recycled powder, 12-16 parts of expansive soil, 7-10 parts of water reducing agent, 20-30 parts of retarder, 7-10 parts of titanate coupling agent, 20-30 parts of cellulose and 130 parts of water.

3. The recycled concrete with expansive soil modifier of claim 1, wherein: the titanate coupling agent is one or more of a titanate coupling agent KR-TTS and a titanate coupling agent KR-41B.

4. The recycled concrete with expansive soil modifier of claim 1, wherein: the water reducing agent is one or more of a polycarboxylic acid water reducing agent and lignosulfonate.

5. The recycled concrete with expansive soil modifier of claim 1, wherein: the retarder is prepared from sodium pyrophosphate and methylcellulose in a mass ratio of (8-12): (14-20) mixing.

6. The recycled concrete with expansive soil modifier of claim 1, wherein: the recycled concrete also comprises the following components in parts by mass: 17-25 parts of external charging material, wherein the external charging material is prepared from fly ash and limestone powder according to the mass ratio (6-10): (14-18) mixing.

7. The recycled concrete with expansive soil modifier of claim 1, wherein: the cellulose is one or more of hydroxypropyl methyl cellulose and ethyl cellulose.

8. The recycled concrete with expansive soil modifier of claim 6, wherein: the particle size of the recycled concrete aggregate is 10-20 mm.

9. The recycled concrete with expansive soil modifier of claim 8, wherein: the preparation method of the recycled concrete aggregate comprises the following steps:

a1, crushing the waste concrete blocks, screening the concrete blocks with the particle size of 10-20mm, and collecting regenerated powder with the particle size of less than 5mm generated in the crushing process of the waste concrete blocks for later use;

a2, washing the screened concrete blocks with clear water;

and A3, soaking the washed concrete block in a phosphoric acid solution, and taking out to prepare the recycled concrete aggregate.

10. The recycled concrete with expansive soil modifier of claim 9, wherein: the preparation method of the recycled concrete comprises the following steps:

(1) premixing and stirring expansive soil and an external material to obtain a first mixture;

(2) adding recycled concrete aggregate, cement, recycled powder, external feed, a water reducing agent, cellulose, a retarder and a titanate coupling agent into the first mixture, and adding water while stirring to obtain recycled concrete.

Technical Field

The application relates to the field of building materials, in particular to recycled concrete adopting an expansive soil modifier.

Background

The recycled concrete is new concrete formed by crushing, cleaning and screening waste concrete blocks, adding a mixture of cement, water and the like and stirring. With the rapid development of economy and the common phenomenon of urbanization migration of population in China, the building of houses in cities and towns gradually becomes the rigid demand of social development. Because the available new housing land area in the city is limited, the existing old building needs to be dismantled and rebuilt, a large amount of waste concrete is generated in the dismantling process, the post-treatment cost of the waste concrete is high, the environmental pollution is large, the construction cost is saved by the application of the recycled concrete, and the environmental pollution is reduced.

The related technology discloses recycled concrete which mainly comprises the following raw materials in parts by weight: 350 parts of recycled concrete aggregate, 400 parts of cement, 300 parts of sand, 150 parts of water, 10-20 parts of thickening agent and 8-15 parts of water reducing agent.

In view of the above-mentioned related technologies, the inventors believe that recycled concrete aggregate is mainly prepared by mechanical crushing, cracks are easily generated in waste concrete blocks during crushing, the effect of repairing cracks is limited only by a cementing material formed by adding cement, and many pores are easily generated in the recycled concrete prepared in a later stage, thereby affecting the strength of the recycled concrete.

Disclosure of Invention

In order to improve the strength of the recycled concrete, the application provides the recycled concrete adopting the expansive soil modifier.

The application provides an adopt recycled concrete of inflation soil modifier adopts following technical scheme:

the raw materials of the recycled concrete comprise the following components in parts by mass: the concrete mortar comprises, by weight, 150-400 parts of recycled concrete aggregate, 120-200 parts of cement, 50-100 parts of recycled powder, 10-20 parts of expansive soil, 5-15 parts of a water reducing agent, 20-40 parts of a retarder, 5-10 parts of a titanate coupling agent, 15-40 parts of cellulose and 150 parts of 100-containing water.

By adopting the technical scheme, the recycled concrete contains a large amount of silicate, the Y group in the titanate coupling agent structure is combined with the hydroxyl in the cellulose, so that the cellulose is grafted on the titanate coupling agent, the X group in the titanate coupling agent structure is combined with the silicate, and the titanate coupling agent is used as a molecular bridge between the silicate and the cellulose to form a cross-linked network structure, so that the strength of the recycled concrete is improved; meanwhile, the waste concrete contains more calcium carbonate, and (R1-O) m at one end of the titanate coupling agent structure reacts with surface water and free proton hydrogen of the calcium carbonate to form a monomolecular layer surrounding the calcium carbonate, so that the recycled concrete has better toughness and impact strength; titanium ions in the titanate coupling agent are in a free state after coupling, can be combined with free silicate, carbonate and the like in the slurry to form colloid, and fills gaps in the recycled concrete aggregate, so that the strength of the recycled concrete is improved.

The recycled concrete aggregate is used as a coarse aggregate to replace stones, the recycled powder is produced by crushing waste concrete, the recycled powder is used for replacing river sand, and the main raw materials are obtained by recycling waste resources, so that the cost is greatly saved, and the recycled concrete aggregate is green and environment-friendly. The cement slurry generated by adding water into the cement can have a certain filling effect on the pores in the recycled concrete aggregate; the expansive soil has better viscosity and has a thickening effect on cement slurry, so that the recycled concrete aggregate is bonded more firmly, and the strength of the recycled concrete is improved; the water reducing agent is matched for use, so that the water content in the slurry can be controlled, and the slurry has good slump; the retarder can prolong the hydration hardening time of cement, so that the reaction of each component in the recycled concrete is sufficient, the recycled concrete keeps plasticity for a long time, and the setting time of the recycled concrete is adjusted according to actual conditions.

Preferably, the raw materials of the recycled concrete comprise the following components in parts by mass: 300 parts of recycled concrete aggregate, 150 parts of cement, 60-80 parts of recycled powder, 12-16 parts of expansive soil, 7-10 parts of water reducing agent, 20-30 parts of retarder, 7-10 parts of titanate coupling agent, 20-30 parts of cellulose and 130 parts of water.

By adopting the technical scheme, the mass parts of the raw materials of the recycled concrete are optimized, and the strength of the recycled concrete is further improved.

Preferably, the titanate coupling agent is one or more of a titanate coupling agent KR-TTS and a titanate coupling agent KR-41B.

By adopting the technical scheme, the titanate coupling agent KR-TTS is a monoalkoxy coupling agent, and the main component is triisostearoyl isopropyl titanate; the titanate coupling agent KR-41B is a coordination type coupling agent, and the main component is di (dioctyl phosphite) tetraisopropyl titanate. Both can effectively combine silicate and cellulose to form under the prerequisite of crosslinked network structure, have fine affinity to calcium carbonate simultaneously, wrap up calcium carbonate easily, form the monomolecular layer to improve recycled concrete's intensity.

Preferably, the water reducing agent is one or more of a polycarboxylic acid water reducing agent and lignosulfonate.

By adopting the technical scheme, the polycarboxylate superplasticizer molecules can be adsorbed on the surfaces of cement particles, so that the surfaces of the cement particles are charged, and the cement particles are mutually dispersed due to the electrostatic repulsion effect to release water wrapped among the particles, so that the fluidity of slurry is improved; lignosulfonates are anionic surface active substances that can adsorb and disperse cement, thereby improving the workability of recycled concrete.

Preferably, the retarder is prepared from sodium pyrophosphate and methylcellulose according to the mass ratio of (8-12): (14-20) mixing.

By adopting the technical scheme, sodium pyrophosphate can ionize charged ions in an aqueous solution to generate a film layer in the setting and hardening process of cement, so that the precipitation nucleation of calcium hydroxide and C-S-H and the formation process of C-A-S-H are delayed, the setting and hardening of recycled concrete are delayed, and a delayed setting effect is generated; the methyl cellulose has good water retention performance, can delay the coagulation and hardening of the recycled concrete and generate a delayed coagulation effect; meanwhile, the methyl cellulose can be matched with cellulose to be used as a titanate coupling agent crosslinking material, so that the strength of the recycled concrete is improved.

Preferably, the recycled concrete further comprises the following components in parts by mass: 17-25 parts of external charging material, wherein the external charging material is prepared from fly ash and limestone powder according to the mass ratio (6-10): (14-18) mixing.

By adopting the technical scheme, the addition of the fly ash can convert calcium hydroxide into C-S-H gel, so that the strength of the recycled concrete is improved; the particle size of the fly ash is smaller than that of the cement, so that the water consumption of the recycled concrete is reduced, the workability of the recycled concrete is improved, the recycled concrete is uniform and dense, and the strength and the durability of the recycled concrete are improved; the particle size of siliceous and calcareous particles in the limestone powder is small, so that the pores of the recycled concrete can be filled, and the strength of the recycled concrete is improved. Meanwhile, the fly ash and the limestone powder can be mixed and stirred with the expansive soil in advance, the fly ash and the limestone powder can perform ion exchange with the expansive soil, the plasticity index and the activity index of the expansive soil are reduced, and a hard setting reaction is generated to form calcium silicate hydrate and calcium aluminate hydrate gel, so that the strength of the expansive soil can be effectively improved, and the deformation of the expansive soil can be inhibited.

Preferably, the cellulose is one or more of hydroxypropyl methylcellulose and ethylcellulose.

By adopting the technical scheme, the hydroxypropyl methyl cellulose and the ethyl cellulose both belong to hydroxyl-containing macromolecules, have certain viscosity, can be used as coupling objects of titanate coupling agents, and improve the strength of the recycled concrete.

Preferably, the particle size of the recycled concrete aggregate is 10-20 mm.

By adopting the technical scheme, the excessive grain size of the recycled concrete aggregate is not beneficial to uniform stirring, the bonding effect is poor, and the strength of the recycled concrete is influenced; the strength of the recycled concrete is affected by the undersize particle size of the recycled concrete aggregate, and the manufacturing cost is high. The recycled concrete aggregate with the grain diameter of 10-20mm has good stirring and mixing effects, and the prepared recycled concrete has high strength.

Preferably, the preparation method of the recycled concrete aggregate comprises the following steps:

a1, crushing the waste concrete blocks, screening the concrete blocks with the particle size of 10-20mm, and collecting regenerated powder with the particle size of less than 5mm generated in the crushing process of the waste concrete blocks for later use;

a2, washing the screened concrete blocks with clear water;

and A3, soaking the washed concrete block in a phosphoric acid solution, and taking out to prepare the recycled concrete aggregate.

By adopting the technical scheme, the waste concrete blocks are crushed and screened, so that the particle size of the recycled concrete aggregate is appropriate, and the prepared recycled concrete has better strength; meanwhile, the concrete blocks are soaked by phosphoric acid, so that calcium hydroxide coated on the concrete blocks is eliminated, the rough apparent structure of the concrete blocks is improved, the slurry can be favorably permeated into the pores of the recycled concrete aggregate, and the strength of the recycled concrete is improved; meanwhile, a certain amount of free phosphate radicals are attached to the surface of the recycled concrete aggregate soaked by phosphoric acid and can be combined with free titanium ions in the slurry after coupling with the titanate coupling agent to form a colloid, and the colloid fills gaps in the recycled concrete aggregate, so that the strength of the recycled concrete is improved.

Preferably, the preparation method of the recycled concrete comprises the following steps:

(1) premixing and stirring expansive soil and an external material to obtain a first mixture;

(2) adding recycled concrete aggregate, cement, recycled powder, external feed, a water reducing agent, cellulose, a retarder and a titanate coupling agent into the first mixture, and adding water while stirring to obtain recycled concrete.

By adopting the technical scheme, the expansive soil is stirred and mixed in advance and part of the external charging material is added, so that the expansive soil is improved, and the performance of the expansive soil is improved; and the raw materials are added in batches and stirred, so that the raw materials are uniformly and fully mixed, the interaction effect among the raw materials is improved, and the strength of the recycled concrete is further improved.

In summary, the present application has the following beneficial effects:

1. according to the preparation method, the titanate coupling agent is used for crosslinking the cellulose and the silicate in the recycled concrete, the three are crosslinked to form a net structure, and the (R1-O) m group in the titanate coupling agent acts on the surface water and the free proton hydrogen of the calcium carbonate to form a monomolecular layer surrounding the calcium carbonate, so that the strength of the recycled concrete is effectively improved.

2. This application improves the bentonite through adding fly ash and lime stone, when the bentonite improves recycled concrete intensity, reduces the bentonite because of the nature of water absorption expansion loss of water shrinkage to recycled concrete's negative effect.

3. According to the method for soaking the recycled concrete aggregate prepared by crushing and screening in the phosphoric acid, the calcium hydroxide on the surface layer of the recycled concrete aggregate is reduced, the rough apparent structure of the concrete block is improved, the slurry can permeate into the pores of the recycled concrete aggregate, and the strength of the recycled concrete is improved.

Detailed Description

The present application will be described in further detail with reference to examples.

In the embodiment, except that the recycled concrete aggregate and the recycled powder are prepared by crushing and screening waste concrete blocks, other raw materials can be obtained by marketing, wherein the titanate coupling agent KR-TTS is produced from Nanjing Quanxi chemical industry Co., Ltd, and the product number is 105; the titanate coupling agent KR-41B is produced by Nanjing Quanxi chemical Co., Ltd, and has the product number of QX-401;

the silane coupling agent is produced by Nanjing Doxi New Material science and technology Limited, and has a product number of 151;

the cement is produced from West lake sea snail cement company Limited, and the product number is P.I 62.5;

sodium lignosulfonate made by Jinan Hai Wei chemical Co., Ltd, with a product number of HW-01;

sodium pyrophosphate is produced by the wave chemical limited of Suzhou city with a product number of 234163;

methylcellulose is produced by sigma aldrich (shanghai) trade, ltd, under the designation V900506-250G;

the fly ash is produced from Shijiazhuang Daheng mineral products processing Co., Ltd, and the product number is FMH-325;

limestone powder is produced from a processing plant of a constantly aggregated mineral product in Lingshou county, and the product number is 3120;

hydroxypropyl methylcellulose is produced by Shandong de-sourced New chemical materials, Inc., Cat # 009;

phosphoric acid is produced by Jining chemical Limited, GYLS 0012;

diethanolamine is produced from Jiangyin silver Lin chemical company Limited, with the product number of 1801;

the shell powder is produced from Lingshou county Ruixin mineral powder plant, and the cargo number is 011;

the carboxymethyl cellulose is produced by Hebei Kaixing chemical Co., Ltd, and has a product number of 006;

the sodium naphthanate water reducing agent is produced by novel building materials of Shandong Jingfeng, Inc., product number 1001;

the polycarboxylate superplasticizer is produced from the novel building materials of Shandong Jingfeng, Inc., product number 1001.

Examples

Examples 1 to 22

Examples 1 to 5 are described below as examples.

The raw materials of the recycled concrete comprise the following components in parts by mass: the concrete mortar comprises, by weight, 150-400 parts of recycled concrete aggregate, 120-200 parts of cement, 50-100 parts of recycled powder, 10-20 parts of expansive soil, 5-15 parts of a water reducing agent, 20-40 parts of a retarder, 5-10 parts of a titanate coupling agent, 15-40 parts of cellulose and 150 parts of 100-containing water.

Wherein the titanate coupling agent is a titanate coupling agent KR-TTS;

the water reducing agent is sodium lignosulphonate;

the retarder is prepared from sodium pyrophosphate and methylcellulose according to a mass ratio of 4:7, mixing;

the cellulose is hydroxypropyl methylcellulose;

the preparation method of the recycled concrete aggregate comprises the following steps:

a1, crushing the waste concrete blocks, screening the concrete blocks with the particle size of 10-20mm, and collecting regenerated powder with the particle size of less than 5mm generated in the crushing process of the waste concrete blocks for later use;

a2, washing the screened concrete blocks with clear water;

a3, diluting the phosphoric acid solution to 10 Wt%, soaking the washed concrete block in the 10 Wt% phosphoric acid solution, and taking out the concrete block after 20h to obtain the recycled concrete aggregate.

The preparation method of the recycled concrete comprises the following steps:

s1, mixing the recycled aggregate, the cement and the recycled powder, adding water while stirring, wherein the stirring speed is 600r/min, and stirring for 5min to obtain a mixture a;

s2, adding expansive soil and a water reducing agent into the mixture a, continuously stirring, adjusting the stirring speed to 400r/min, and stirring for 10min to obtain a mixture b;

s3, adding cellulose and a retarder into the mixture b, continuously stirring, adjusting the stirring speed to 250r/min, and stirring for 10min to obtain a mixture c;

and S4, adding the titanate coupling agent into the mixture c, continuously stirring, adjusting the stirring speed to 200r/min, taking out after stirring for 15min, and standing for 5min to obtain the recycled concrete.

As shown in Table 1, examples 1 to 5 are different in the amount of each raw material for recycled concrete.

TABLE 1 recycled concrete raw material composition Table

Example 6

The difference between the present example and example 3 is that the mass ratio of sodium pyrophosphate to methylcellulose in the retarder is 1:1.25, and the mass of the retarder is 11 kg.

Example 7

The difference between the present example and example 3 is that the mass ratio of sodium pyrophosphate to methylcellulose in the retarder is 1:2.5, and the mass of the retarder is 11 kg.

Example 8

This example differs from example 3 in that the titanate coupling agent KR-TTS had a mass of 4kg and the hydroxypropylmethylcellulose had a mass of 7.5 kg.

Example 9

This example differs from example 3 in that the titanate coupling agent KR-TTS had a mass of 4kg and the hydroxypropylmethylcellulose had a mass of 20 kg.

Example 10

This example differs from example 3 in that the mass of the titanate coupling agent KR-TTS was 4kg and the mass of the hydroxypropylmethylcellulose was 11 kg.

Example 11

This example differs from example 3 in that the titanate coupling agent KR-TTS is replaced by the same amount of titanate coupling agent KR-41B.

Example 12

The difference between this example and example 3 is that the recycled concrete further comprises 12kg of external charge, which is a mixture of 4kg of fly ash and 8kg of limestone powder.

This example differs from the preparation of examples 1-5 in that: mixing and stirring the expansive soil and 6kg of external materials for 30min at the stirring speed of 300r/min to obtain a mixture; the resulting mixture was added to S2 and stirred, and 6kg of additional ingredients were added to S3 and stirred.

Example 13

This example differs from example 12 in that the external charge was a mixture of 3kg fly ash and 9kg limestone powder.

Example 14

This example differs from example 12 in that the external charge is a mixture of 5kg fly ash and 7kg limestone powder.

Example 15

The difference between the embodiment and the embodiment 12 is that the addition amount of the external feeding is 8.5kg, and the mass ratio of the fly ash to the limestone powder is 1:2.

example 16

The difference between the embodiment and the embodiment 12 is that the external charging is 10kg, and the mass ratio of the fly ash to the limestone powder is 1:2.

example 17

This example differs from example 3 in that the sodium lignosulfonate was replaced with an equal amount of polycarboxylic acid water reducing agent.

Example 18

The difference between the embodiment and the embodiment 3 is that the water reducing agent is a mixture of a polycarboxylic acid water reducing agent and sodium lignosulfonate with a ratio of 1:1, and the addition amount of the water reducing agent is unchanged.

Example 19

This example differs from example 3 in that the hydroxypropyl methylcellulose is replaced by an equal amount of ethylcellulose.

Example 20

The difference between this example and example 3 is that the cellulose is a mixture of hydroxypropyl methylcellulose and ethyl cellulose in a ratio of 1:1, and the amount of cellulose added is not changed.

Example 21

This example differs from example 3 in that the prepared recycled concrete aggregate was not soaked with phosphoric acid.

Example 22

This example differs from example 3 in that the recycled concrete aggregate is soaked with an equal amount of hydrochloric acid of the same percentage concentration.

Comparative example

Comparative example 1

This comparative example differs from example 3 in that the titanate coupling agent is replaced with an equal amount of silane coupling agent.

Comparative example 2

This comparative example differs from example 3 in that no titanate coupling agent is added.

Comparative example 3

This comparative example differs from example 12 in that fly ash and limestone powder are replaced with equal amounts of shell powder.

Comparative example 4

The difference between the comparative example and the example 12 is that the ratio of the fly ash to the limestone powder in the external addition material is 1:5, and the addition amount of the external addition material is unchanged.

Comparative example 5

The difference between the comparative example and the example 12 is that the ratio of the fly ash to the limestone powder in the external material is 2:1, and the addition amount of the external material is unchanged.

Comparative example 6

This comparative example differs from example 3 in that the hydroxypropyl methylcellulose is replaced by an equal amount of carboxymethyl cellulose.

Comparative example 7

This comparative example differs from example 3 in that no cellulose was added.

Comparative example 8

The recycled concrete in the related art comprises the following raw materials by mass: 150kg of recycled concrete aggregate, 130kg of cement, 80kg of sand, 80kg of water, 10kg of thickening agent and 7kg of water reducing agent.

Wherein the thickening agent is polyvinyl alcohol;

the water reducing agent is melamine water reducing agent.

The preparation method of the recycled concrete in the comparative example comprises the following steps:

mixing the recycled aggregate, the cement and the sand, adding water while stirring at the speed of 500r/min, adding the water reducing agent and the thickening agent after stirring for 5min, and continuously stirring for 5min to obtain the recycled concrete.

Performance detection test method

And (3) testing the compressive strength and the flexural strength:

(1) according to GB/T50081-2019 'Standard test method for mechanical properties of common concrete', a recycled concrete product is made into a plurality of cubic standard blocks with the side length of 150mm, a sample can be prepared by curing at room temperature for 14 days, and the compressive strength and the flexural strength of the sample are respectively tested after 3 days, 7 days and 28 days.

TABLE 2 detection data table for flexural strength and compressive strength of recycled concrete

As can be seen from Table 2, the recycled concrete of the present application has excellent compressive strength and flexural strength by combining the test results of examples 1 to 5 and comparative example 8. Among them, example 3 is the most preferable example, and the strength of the recycled concrete is the best.

According to the detection results of the embodiment 3, the embodiment 8-10, the comparative example 1-2 and the comparative example 6-7, the titanate coupling agent and the cellulose have a synergistic effect, so that the strength of the recycled concrete can be obviously improved, the effect of the titanate coupling agent KR-TTS on improving the strength of the recycled concrete is far better than that of a silane coupling agent, and the effect of the titanate coupling agent KR-TTS is better than that of the titanate coupling agent KR-41B.

Combining the test results of example 3 and examples 6-7, it is known that the addition of sodium pyrophosphate and methylcellulose effectively improves the strength of recycled concrete, and the effect is best when the ratio of sodium pyrophosphate to methylcellulose is 4: 7.

By combining the detection results of the examples 3, 12-16 and the comparative examples 3-5, the addition of the fly ash and the limestone powder can effectively improve the strength of the recycled concrete, and the effect is best when the ratio of the fly ash to the limestone powder is 1:2.

Combining the test results of example 3 and example 12, it is found that the addition of expansive soil can improve the strength of recycled concrete, and the influence of expansive soil on the strength of recycled concrete can be reduced by improving expansive soil by stirring and mixing fly ash, limestone powder and expansive soil in advance.

According to the detection results of the embodiment 3 and the embodiments 21 to 22, the strength of the recycled concrete can be effectively improved by soaking the recycled concrete aggregate prepared by crushing and screening in phosphoric acid, and the effect of the phosphoric acid is better than that of hydrochloric acid.

The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.