WO2022253355A1

WO2022253355A1 - Strengthening method for recycled aggregate using biological deposition

Info

Publication number: WO2022253355A1
Application number: PCT/CN2022/099669
Authority: WO
Inventors: 冯春花; 朱建平; 崔卜文; 杜明星; 张文艳; 郭晖; 宗旭东
Original assignee: 河南理工大学
Priority date: 2022-01-20
Filing date: 2022-06-20
Publication date: 2022-12-08
Also published as: CN114591016B; SE2251564A1; CN114591016A

Abstract

The present invention relates to a strengthening method for a recycled aggregate using biological deposition, comprising the following steps: (1) filling and soaking: in a vacuum environment, soaking a recycled aggregate in a bacterial solution, then taking out the recycled aggregate from the bacterial solution, soaking in a mineralized culture solution, taking out the recycled aggregate after the soaking is finished, and cleaning and drying; (2) repairing and soaking: taking out the recycled aggregate treated in step (1), cleaning and drying, then soaking in a mixed culture solution of the bacterial solution and the mineralized culture solution; wherein the bacterial solution contains bacillus. In the present invention, the strengthening method for a recycled aggregate using biological deposition can better target areas needing to be repaired of the recycled aggregate, thereby obtaining a better repairing effect, and a bacterial powder produced by industrial production is used to greatly reduce process costs, so that the microbial mineralization deposition (MICP) technology has a wider application range.

Description

A Renewable Aggregate Strengthening Method Utilizing Biodeposition

technical field

The invention belongs to the technical field of building materials, and in particular relates to a method for strengthening recycled aggregates using biological deposition.

Background technique

According to statistics, as of 2019, construction waste in China accounted for four tenths of urban waste. As far as the sustainable development of the construction industry is concerned, it is of great significance to recycle construction materials from construction waste to alleviate the shortage of natural construction materials and the shortage of land resources for landfill construction waste. However, the performance of recycled aggregate itself is significantly inferior to that of natural aggregate. The reason for the poor performance of recycled aggregates is that a large amount of old mortar is attached to the surface and microcracks generated during the crushing process, which cause recycled aggregates to have much higher water absorption and crushing values than natural aggregates. The strengthening technology of recycled aggregate is usually based on reducing the water absorption and crushing index of recycled aggregate, and increasing the apparent density and hardness of recycled aggregate. On the one hand, the reduction of water absorption and the increase of apparent density are based on the reduction of the porosity of recycled aggregates. The improvement of aggregate pore structure can further improve the working performance of recycled concrete. In addition, the reduction of porosity also improves the performance of recycled concrete. Excessive water absorption will make the interface transition zone of recycled concrete rich in water, which will affect the mechanical properties and durability of the specimen; on the other hand, the crushing value of recycled aggregate is much higher than that of natural aggregate, while The hardness of recycled aggregate directly affects the mechanical properties of recycled concrete. Based on the above two points, the present invention focuses on improving the water absorption and crushing index of the recycled aggregate.

At present, some progress has been made in the research field of strengthening recycled aggregate in our country. The invention patent with the application number CN113683330A provides a preparation method and system for strengthening recycled aggregates, and the application number CN111153618A discloses a preparation device and method for strengthening recycled aggregates through microbial mineralization. The above methods can strengthen regeneration Aggregate, but the existing methods are mostly limited to the use of spraying means, it is difficult for organisms to completely enter all the holes and survive effectively, thereby effectively improving the pore structure of recycled aggregates, and in addition, complex devices cause high reinforcement costs for recycled aggregates , which violates the purpose of strengthening recycled aggregates.

Contents of the invention

The purpose of the present invention is to provide a method for strengthening recycled aggregates using biological deposition to solve/improve that the calcium carbonate generated by biomineralization deposition during traditional soaking treatment cannot be targeted to repair holes, and the spray treatment equipment is complex and costly. High, difficult to large-scale industrial application of at least one of the current status of the problem.

In order to achieve the above object, the present invention provides the following technical solution: a method for strengthening recycled aggregates utilizing biological deposition, comprising the following steps:

(1) Filling and soaking: first soak the regenerated aggregate in the bacterial solution in a vacuum environment, then take out the regenerated aggregate from the bacterial solution, soak it in the mineralization culture solution, and place the regenerated bone after soaking The material is taken out, cleaned, and dried; the soaking time of the regenerated aggregate in the bacterial solution is 20-60min, and the vacuum degree of the vacuum environment is 0.6-0.8Mpa; the mass ratio of the regenerated aggregate to the bacterial solution is 2 : 1～2:1.2, the mass ratio of described mineralization culture fluid and described bacterial fluid is 1:1;

(2) Soaking for repairing: taking out the regenerated aggregate treated in step (1), cleaning and drying, and soaking in the mixed culture solution of the bacteria solution and the mineralization culture solution; the bacteria solution contains bacillus; The mass ratio of the regenerated aggregate to the mixed culture solution is 1:1 to 1:1.2; the mass ratio of the bacteria solution in the mixed culture solution to the mineralized culture solution is 1:1;

The bacillus includes colloid bacillus and subtilis bacillus, and the ratio of the effective number of viable bacteria of the two kinds of bacteria is 3:7-7:3.

Beneficial effects: The method for strengthening recycled aggregates using biodeposition of the present invention can be more targeted on the areas where recycled aggregates need to be repaired to obtain a better repair effect, and industrially produced bacterial powder is used to greatly reduce the process. The cost makes Microbial Mineralized Precipitation (MICP) technology more widely used.

The invention utilizes the recycled aggregate strengthening method of biological deposition to reduce the cost of the current microbial mineralization deposition (MICP) technology and optimizes the strengthening effect of the MICP technology on the recycled aggregate, and the strengthening process is more targeted for the repair of the recycled aggregate, thereby The pore structure and basic properties of the recycled aggregate are significantly changed, the water absorption of the recycled aggregate is reduced by about 30%, and the crushing index is improved by about 16%.

Description of drawings

Fig. 1 is the SEM figure of the calcite calcium carbonate that fills the interstices of recycled aggregate obtained after the treatment of comparative example 1 that comparative example 1 of the present invention provides; ;

Fig. 2 is the XRD pattern of the calcite calcium carbonate that fills the gap of recycled aggregate obtained after the comparative example 1 treatment provided by the comparative example 1 of the present invention;

Fig. 3 is the comparison chart of the crushing value and water absorption ratio of the recycled aggregates obtained by the methods of Example 1 and Comparative Examples 1 to 3 respectively provided by the present invention;

Fig. 4 is the scanning electron micrograph of the surface morphology of the recycled aggregate obtained by the method of Example 1 and Comparative Examples 1-3 respectively provided by the present invention; wherein, (a) is obtained after the treatment of Comparative Example 1 The scanning electron micrograph of the recycled aggregate, (b) is the scanning electron micrograph of the recycled aggregate obtained after the comparative example 2 treatment, (c) is the scanning electron microscopic image of the recycled aggregate obtained after the comparative example 3 treatment, (d ) is a scanning electron micrograph of the recycled aggregate obtained after the treatment of Example 1;

Fig. 5 is a comparison chart of the mineralization rate provided by the present invention after being treated with the mineralization liquid of Experimental Examples 1-3 respectively.

Detailed ways

The present invention will be described in detail below in conjunction with examples. It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

The present invention aims at the defects existing in the current recycled aggregate bio-augmentation technology, and makes up for the fact that the biologically generated calcium carbonate in the traditional immersion treatment cannot repair the holes in a targeted manner, and the spraying treatment equipment is complicated, the cost is high, and it is difficult for large-scale industrial application. , to provide a method for strengthening recycled aggregates using biodeposition, so as to solve or alleviate at least one of the above-mentioned problems.

In the recycled aggregate strengthening method provided by the present invention utilizing biodeposition, comprise the following steps:

(1) Filling and soaking: first soak the recycled aggregate in the bacterial solution in a vacuum environment, then take out the recycled aggregate from the bacterial solution, soak it in the mineralization culture solution, take out the recycled aggregate after soaking, and wash , dry; (2) repair soaking: soak the recycled aggregate treated in step (1) in the mixed culture solution of bacteria solution and mineralization culture solution; the bacteria solution contains bacillus.

In the recycled aggregate strengthening method using biological deposition provided by the present invention, during the filling and soaking treatment, the recycled aggregate is soaked in the bacterial solution in a vacuum environment, and the bacterial solution can better fill the internal pore structure of the recycled aggregate, and the microbial Calcium carbonate is mineralized and deposited in the pores of the attached mortar to fill the pore structure, which is named filling soaking; during repairing soaking, microorganisms focus on repairing the surface of the recycled aggregate, named repairing soaking.

Among them, the main function of Bacillus is to induce the generation of calcium carbonate to fill the cavity. The production of calcium carbonate is concentrated around the bacteria, and the mineralized culture solution provides calcium ions and nutrients for the bacteria to survive and produce calcium carbonate. Increase the concentration of bacteria in the holes inside the recycled aggregate to make the bacteria adhere to the inner wall of the hole, and then the calcium carbonate produced can fill the inner holes. The main purpose of repairing and soaking is to make the bacteria survive in a suitable environment. Nucleation site patching. The contact between mineralized culture fluid and bacteria during filling and soaking is not more effective than that of repairing soaking, so the activity of bacteria is not as good as that of repairing soaking, but the advantage of filling and soaking is that the repairing position is very targeted, and the calcium carbonate produced is in the position that needs to be repaired , the biological activity is better when repairing and soaking, and the speed of producing calcium carbonate is faster, but it is not targeted for the repair of aggregates, so we choose to fill and soak to repair the large internal defects of the aggregate, and then repair and soak to strengthen the recycled aggregate. .

In step (1), the soaking time of the recycled aggregate in the bacterial solution is 20-60 minutes (for example, 20 minutes, 30 minutes, 40 minutes, 50 minutes or 60 minutes).

In step (1), the mass ratio of the recycled aggregate to the bacterial solution is 2:1 to 2:1.2 (for example, 2:1, 2:1.1 or 2:1.2), and the mass ratio of the mineralized culture solution to the bacterial solution is 1:1.

In step (1), the vacuum degree of the vacuum environment is 0.6-0.8Mpa.

In step (2), the mass ratio of the recycled aggregate to the mixed culture solution is 1.5:2 to 3:2 (for example, 1.5:2, 2:2, 2.5:2 or 3:2), and the bacteria solution in the mixed culture solution is mixed with The mass ratio of mineralized culture medium is 1:1.

In a preferred embodiment of the present invention, the mass ratio of the recycled aggregate to the mixed culture solution in step (2) is 1:1 to 1:1.2 (for example, 1:1.2, 1:1.1, or 1:1)

Bacillus comprises colloid bacillus and bacillus subtilis, and the effective number ratio of two kinds of bacteria used is 3:7-7:3 (for example, 3:7, 5:7, 7:7 or 7:3 ), the metabolic effects of the two bacteria co-induced the production of calcium carbonate precipitates during the mineralization process.

The Bacillus colloidum is derived from the Bacillus colloidus powder, and the effective number of viable bacteria in the Bacillus coliformum powder is 1×10 ¹⁰ cfu/g bacterial powder.

The Bacillus subtilis comes from the Bacillus subtilis powder, and the effective number of viable bacteria of the Bacillus subtilis powder is 2×10 ¹¹ cfu/g bacteria powder.

The bacterial liquid is prepared according to the following method: dissolve the bacterial powder in deionized water, stir, adjust the pH, and filter after standing still to obtain the bacterial liquid.

When preparing the bacterial liquid, the stirring time is 5-15min (for example, 5min, 10min or 15min), the pH of the bacterial liquid is adjusted to 9.5-10.5 (for example, 9.5, 10 or 10.5) with NaOH, and the standing time is ≥30min .

The bacterial concentration of the bacterial liquid is 2×10 ⁸ -4×10 ⁸ cfu/mL (for example, 2×10 ⁸ cfu/mL, 3×10 ⁸ cfu/mL or 4×10 ⁸ cfu/mL).

The mineralizing nutrient solution comprises 4-6 (for example 4, 5 or 6) parts by weight of yeast extract powder, 3-5 (for example 3, 4 or 5) parts by weight of peptone, 45-55 parts of calcium chloride (for example 45, 50 or 55 ) parts by weight, calcium lactate 18-22 (

eg

18, 20 or 22) parts by weight and 500 parts by weight. Among them, calcium chloride and calcium lactate are mainly used to provide calcium ions, and calcium lactate can also serve as a carbon source in addition to providing calcium sources.

The mineralized nutrient solution is prepared according to the following method: dissolving yeast, peptone, calcium chloride and calcium lactate in deionized water, adjusting the pH, standing still and filtering to obtain the mineralized nutrient solution.

When preparing the mineralized nutrient solution, use NaOH to adjust the pH of the mineralized culture solution to 9.5-10.5 (for example, 9.5, 10 or 10.5), and let it stand for more than 30 minutes.

In step (1), the immersion of the regenerated aggregate in the mineralization culture solution is carried out in a ventilated environment at 25-35°C (such as 25°C, 30°C or 35°C), and the immersion time is 14 days; in step (2), the regenerated bone The immersion of the material in the mixed culture solution is carried out in a ventilated environment at 25-35°C (such as 25°C, 30°C or 35°C), and the soaking time is 7-14d (for example, 7d, 8d, 9d, 10d, 11d, 12d, 13d or 14d). The above-mentioned two-step immersion treatment can not get a good repair effect when the curing time is short. After the curing time exceeds 7-14d (for example, 7d, 8d, 9d, 10d, 11d, 12d, 13d or 14d), the solution basically loses minerals. ability to deposit calcium carbonate.

The method for strengthening recycled aggregates using biological deposition of the present invention will be described in detail below through specific examples.

In the following examples, the amount and source of each raw material are shown in Table 1 below:

Table 1 Sources of raw materials used

The bacteria solution used in the following examples (or comparative examples) was prepared according to the following method: 6.0 g of Bacillus colloidus bacteria powder (the number of effective viable bacteria was 6×10 ¹⁰ cfu) and 0.7 g of Bacillus subtilis ( The number of effective viable bacteria is 1.4×10 ¹¹ cfu) dissolved in 500 g of deionized water, stirred for 10 minutes, added NaOH to adjust the pH to 10, allowed to stand for 30 minutes, and then filtered to obtain the above bacteria solution.

The mineralized culture solution used in the following examples (or comparative examples) is prepared according to the following method: 5 g of yeast extract powder, 4 g of peptone, 50 g of calcium chloride and 20 g of calcium lactate are dissolved in 500 g of deionized water, and NaOH is added to adjust pH to 10.0, let it stand for 30 minutes and then filter to obtain the above mineralization culture solution.

Example 1

The regeneration aggregate strengthening method utilizing biological deposition in this embodiment includes the following steps:

(1) Filling and soaking: select the particle size of the recycled aggregate to be 9.5-16mm, add the bacterial solution to the recycled aggregate according to the mass ratio of the bacterial solution and the recycled aggregate at a ratio of 1:2, place it at 30°C, and the vacuum degree is 0.8 Soak in a vacuum drying oven of Mpa for 30 minutes, take the recycled aggregate out of the bacterial solution, and then soak it in the mineralized culture solution with a mass ratio of 1:1 to the bacterial solution, and place it in a ventilated environment at 25-35°C for 14 days. Take it out and wash it, and dry it in an oven at 40°C;

(2) Repair soaking: prepare mixed culture solution according to the mass ratio of mineralization culture solution and bacterial solution of 1:1, and then follow the step (1) according to the ratio of mixed culture solution and recycled aggregate mass ratio of 1:1 Soak the processed recycled aggregate in the mixed culture solution, and place it in a ventilated environment at 25-35°C for 14 days;

After that, take out the recycled aggregate, wash it, put it in an oven at 40°C and dry it to constant weight, weigh the quality change of the recycled aggregate before and after strengthening, and calculate according to GB/T14685-2011 "Pebbles and gravel for construction". It is stipulated to test its water absorption, apparent density and crushing value, and the test results are shown in Table 2.

Table 2 Basic properties of the biodeposition-enhanced recycled aggregate (9.5-16mm particle size) prepared in Example 1

Example 2

(1) Filling and soaking: select the particle size of the recycled aggregate to be 9.5-16mm, add the bacterial solution to the recycled aggregate according to the ratio of the mass ratio of the bacterial solution to the recycled aggregate of 1.2:2, place it at 30°C, and the vacuum degree is 0.8 Soak in a vacuum drying oven of Mpa for 30 minutes; take the recycled aggregate out of the bacterial solution and then soak it in the mineralized culture solution with a mass ratio of 1:1 to the bacterial solution, and place it in a ventilated environment at 25-35°C for 14 days Take it out and wash it, and dry it in an oven at 40°C;

(2) Repair soaking: prepare mixed culture solution according to the mass ratio of mineralized culture solution and bacterial solution of 1:1, and then follow the step (1) according to the ratio of mixed culture solution and recycled aggregate mass ratio of 1.2:1 Soak the processed recycled aggregate in the mixed culture solution, and place it in a ventilated environment at 25-35°C for 14 days;

After that, take out the recycled aggregate, wash it, and dry it in an oven at 40°C until it reaches a constant weight. Weigh the change in the quality of the recycled aggregate before and after strengthening, and calculate according to the relevant regulations in GB/T14685-2011 "Pebbles and Crushed Stones for Construction". Test its weight gain, water absorption, apparent density and crushing value, and the test results are shown in Table 3.

Table 3 Basic properties of biodeposition-enhanced recycled aggregate (9.5-16mm particle size) prepared in Example 2

Example 3

(1) Filling and soaking: select the particle size of the recycled aggregate to be 4.75-9.5mm, add the bacterial solution to the recycled aggregate according to the mass ratio of the bacterial solution and the recycled aggregate at a ratio of 1:2, place it at 30°C, and the vacuum degree is Soak in a 0.8Mpa vacuum drying oven for 30 minutes, take the regenerated aggregate out of the bacterial solution, and then soak it in a mineralized culture solution with a mass ratio of 1:1 to the bacterial solution, and place it in a ventilated environment at 25-35°C for curing. After 14 days, take it out and wash it, and dry it in an oven at 40°C;

(2) Repair soaking: prepare mixed culture solution according to the mass ratio of mineralization culture solution and bacterial solution of 1:1, and then follow the step (1) according to the ratio of mixed culture solution and recycled aggregate mass ratio of 1:1 The processed recycled aggregates were soaked in the mixed culture solution, placed in a ventilated environment at 25-35°C for 14 days, then taken out and washed, dried in an oven at 40°C to constant weight, and the weight of the recycled aggregates before and after strengthening was weighed. Change, and test its weight gain, water absorption, apparent density and crushing value according to the relevant regulations in GB/T14685-2011 "Pebbles and Gravels for Construction". The test results are shown in Table 4.

Table 4 Basic properties of the biodeposition-enhanced recycled aggregate (4.75-9.5mm particle size) prepared in Example 3

Example 4

(1) Filling and soaking: select the particle size of the recycled aggregate to be 16-19mm, add the bacterial solution to the recycled aggregate according to the mass ratio of the bacterial solution and the recycled aggregate at a ratio of 1:2, and place it in a vacuum drying oven (vacuum degree is 0.6Mpa) for 30 minutes, take out the recycled aggregate from the bacterial solution, then soak it in the mineralized culture solution with a mass ratio of 1:1 to the bacterial solution, place it in a ventilated environment at 25-35°C for 14 days, take it out and wash it. Clean and dry in an oven at 40°C;

After that, take out the recycled aggregate, wash it, put it in an oven at 40°C and dry it to constant weight, weigh the quality change of the recycled aggregate before and after strengthening, and calculate according to GB/T14685-2011 "Pebbles and gravel for construction". It is stipulated to test its weight gain, water absorption, apparent density and crushing value, and the test results are shown in Table 5.

Table 5 Basic properties of the biodeposition-enhanced recycled aggregate (16-19mm particle size) prepared in Example 4

Comparative example 1

Soak the recycled aggregate in deionized water, the specific steps are as follows:

Three kinds of recycled aggregates with particle sizes ranging from 4.75 to 9.5, 9.5 to 16 and 16 to 19 were selected, and the above three recycled aggregates were added to deionized water with a mass ratio of 1:1 to the recycled aggregate, and placed in Soak the recycled aggregate in a ventilated environment at 25-35°C for 28 days; after soaking, take out the recycled aggregate, rinse it, and dry it in an oven at 40°C to constant weight, and weigh the quality change of the recycled aggregate before and after strengthening , and test its weight gain, water absorption, apparent density and crushing value according to the relevant regulations in GB/T14685-2011 "Pebbles and Gravels for Construction". The test results are shown in Table 6.

Table 6 Basic properties of recycled aggregates soaked in deionized water

Comparative example 2

Repair and soak the recycled aggregate twice, the specific steps are as follows:

(1) The first repair soaking: select the particle size of the recycled aggregate to be 9.5, prepare a mixed culture solution according to the mass ratio of the mineralized culture solution and the bacterial solution at a ratio of 1:1, and then follow the mass ratio of the mixed culture solution and the recycled aggregate to Soak the recycled aggregate directly at a ratio of 1:1, put it in a ventilated environment at 25-35°C for 14 days, take it out, wash it, and dry it in an oven at 40°C;

(2) The second repair soaking: Repeat the above steps again, soak the recycled aggregate and place it in a ventilated environment at 25-35°C for 14 days (the specific method is the same as the above step (1)). After curing, clean the recycled aggregate, put it in an oven at 40°C and dry it to constant weight, weigh the quality change of the recycled aggregate before and after strengthening, and calculate according to GB/T14685-2011 "Pebbles and Gravels for Construction" It is stipulated to test its weight gain, water absorption, apparent density and crushing value, and the test results are shown in Table 7.

Table 7 Basic properties of recycled aggregate after two repair immersions

Comparative example 3

Fill and soak the recycled aggregate twice, the specific steps are as follows:

(1) Filling and soaking for the first time: select the particle size of the recycled aggregate to be 9.5-16mm, add the bacterial solution to the recycled aggregate according to the mass ratio of the bacterial solution and the recycled aggregate at a ratio of 1:2, and place it in a vacuum drying oven ( Take it out after immersing in a vacuum (0.8MPa) for 30 minutes; take out the recycled aggregate from the bacterial solution, then soak it in the mineralized culture solution with a mass ratio of 1:1 to the bacterial solution, and place it in a ventilated environment at 25-35°C for curing After 14 days, take it out and wash it, and dry it in an oven at 40°C;

(2) Filling and soaking for the second time: Add the recycled aggregate obtained by the above step (1) into the bacterial solution according to the mass ratio of the bacterial solution and the recycled aggregate at a ratio of 1:2, and place it in a vacuum drying oven (vacuum degree is 0.8MPa) and take it out after soaking for 30min; Take out the recycled aggregate from the bacteria solution and then soak it in the mineralized culture solution with a mass ratio of 1:1 to the bacteria solution, and place it in a ventilated environment at 25-35°C Conservation 14d. After curing, clean the recycled aggregate, put it in an oven at 40°C and dry it to constant weight, weigh the quality change of the recycled aggregate before and after strengthening, and calculate according to GB/T14685-2011 "Pebbles and Gravels for Construction" It is stipulated to test its weight gain, water absorption, apparent density and crushing value, and the test results are shown in Table 8.

Table 8 Basic properties of recycled aggregates after two filling immersions

Experimental example

Experimental example 1

Dissolve 6.0g of Bacillus colloidus powder (the effective number of viable bacteria is 6×10 ¹⁰ cfu) and 0.7g of Bacillus subtilis (the effective number of viable bacteria is 1.4×10 ¹¹ cfu) in 500g of deionized water, stir for 10min, add Adjust the pH to 10 with NaOH, filter after standing for 30min, mix the filtered bacterial solution and mineralized culture solution according to the mass ratio of 1:1 (to obtain the mineralized solution of this experimental example), take a small amount of mineralized solution and use ICP (inductor Coupled plasma) to test its calcium ion concentration, after curing the remaining solution in a sterile laboratory at 37°C for 14 days, the calcium ion concentration of the mineralization solution was tested again, and the test results are shown in Table 9. The change rate of calcium ion concentration before and after the mineralization reaction is the mineralization rate of the mineralization solution, that is, the ability of the solution to produce calcium carbonate.

Table 9 The calcium ion concentration of the mixed solution prepared in Experimental Example 1

The mineralized product after 14 days was dried in a vacuum drying oven at a temperature of 40 °C and a vacuum degree of 0.06 MPa for 24 hours to obtain calcite-type calcium carbonate, an important component for filling aggregate pores. The results of the SEM and XRD tests are shown in Figures 1 and 2, respectively.

Experimental example 2:

The only difference from Experimental Example 1 is that all the bacillus used are Bacillus colloidus powder (the effective number of viable bacteria is 2×10 ¹¹ cfu), and the rest are consistent with Experimental Example 1. The calcium ion concentration of the mixed solution obtained after adopting the proportioning mineralization reaction of Experimental Example 2 is shown in Table 10:

Calcium ion concentration of the mixed solution prepared in Table 10 Experimental Example 2

Experimental example 3:

The only difference from Experimental Example 1 is that all the bacillus used are Bacillus subtilis powder, with a mass of 1 g (the effective number of viable bacteria is 2×10 ¹¹ cfu), and the rest are consistent with Experimental Example 1. The calcium ion concentration of the mixed solution obtained after adopting the proportioning mineralization reaction of Experimental Example 3 is shown in Table 11:

Table 11 Calcium ion concentration of the mixed solution prepared in Experimental Example 3

To sum up: (1) Summarize the testing results of water absorption and crushing values of Example 1 and Comparative Examples 1-3, and the results are shown in Figure 3 of the accompanying drawing.

It can be seen from Figure 3 that when the recycled aggregate is treated with the methods of Comparative Example 2 (twice repair soaking) and Comparative Example 3 (twice filling soaking), the performance of the recycled aggregate is improved (compared to Comparative Example 1 for Regenerated aggregates are soaked in deionized water), but the effect is relatively limited; and embodiment 1 (filling and soaking the recycled aggregates first, and then repairing and soaking) has a significantly better biodeposition strengthening effect on the recycled aggregates. With the treatment of Example 1, the water absorption of the recycled aggregate decreased by about 20% compared with Comparative Example 1, and the crushing value decreased by about 16.4% compared with Comparative Example 1.

(2) The scanning electron microscope results of the recycled aggregate obtained after the treatment of Comparative Examples 1 to 3 and Example 1 are shown in Figure 4, wherein: (a) is the scanning electron microscope of the recycled aggregate obtained after the treatment of Comparative Example 1 Figure, (b) is the scanning electron micrograph of the recycled aggregate obtained after the treatment of Comparative Example 2, (c) is the scanning electron micrograph of the recycled aggregate obtained after the treatment of Comparative Example 3, (d) is the scanning electron micrograph of the recycled aggregate obtained after the treatment of Comparative Example 2 Scanning electron micrographs of recycled aggregates obtained after treatment.

It can be seen from Figure 4 that the surface structure of the recycled aggregate after the treatment in Comparative Example 1 is loose; the surface of the aggregate after the treatment in Comparative Example 2 is covered, but because the two times are repair soaking, according to the crystal nucleation theory, the secondary soaking produced Calcium carbonate is more inclined to nucleate with the calcium carbonate produced by one soaking, so the rate of calcium carbonate production is faster and the shape is looser; the pores of the recycled aggregate after treatment in Comparative Example 3 are filled with calcium carbonate, but the aggregate The surface is still a loose structure, and the surface morphology of the aggregate has not been improved; after the treatment in Example 1, the surface of the recycled aggregate is completely covered with calcium carbonate precipitates produced by biodeposition, and the spherical calcium carbonate is closely connected, and a few growth The faster calcium carbonate is attached to the surface of the spherical calcium carbonate, and the surface morphology of the aggregate is significantly improved.

(3) The mineralization rate of the mineralization solution after the mineralization reaction in Experimental Examples 1-3 is shown in Figure 5. The mineralization capacity of the solution determines the amount of calcium carbonate generated. Calcium carbonate is a raw material for repairing and strengthening recycled aggregates. , the higher the mineralization rate of the solution, the more calcium carbonate will be produced, and the formation of calcium carbonate depends on the physiological activities of bacteria. The solution has a higher mineralization rate under the synergistic effect of the two bacteria, which helps to improve the biodeposition strengthening effect on the recycled aggregate.

Claims

A method for strengthening recycled aggregates utilizing biological deposition, characterized in that it comprises the following steps:

(1) Filling and soaking: first soak the regenerated aggregate in the bacterial solution in a vacuum environment, then take out the regenerated aggregate from the bacterial solution, soak it in the mineralization culture solution, and place the regenerated bone after soaking The material is taken out, cleaned, and dried; the soaking time of the regenerated aggregate in the bacterial solution is 20-60min, and the vacuum degree of the vacuum environment is 0.6-0.8Mpa; the mass ratio of the regenerated aggregate to the bacterial solution is 2 : 1～2:1.2, the mass ratio of described mineralization culture fluid and described bacterial fluid is 1:1;

(2) Soaking for repairing: taking out the regenerated aggregate treated in step (1), cleaning and drying, and soaking in the mixed culture solution of the bacteria solution and the mineralization culture solution; the bacteria solution contains bacillus; The mass ratio of the regenerated aggregate to the mixed culture solution is 1:1 to 1:1.2; the mass ratio of the bacteria solution in the mixed culture solution to the mineralized culture solution is 1:1;

The bacillus includes colloid bacillus and subtilis bacillus, and the ratio of the effective number of viable bacteria of the two kinds of bacteria is 3:7-7:3.
The method for strengthening recycled aggregates utilizing biological deposition according to claim 1, characterized in that,

The colloidal bacillus is from the colloidal bacillus bacteria powder, and the effective number of viable bacteria of the colloidal bacillus bacteria powder is 1×10 10 cfu/g bacteria powder;

The Bacillus subtilis is derived from Bacillus subtilis powder, and the effective number of viable bacteria in the Bacillus subtilis powder is 2×10 11 cfu/g bacteria powder.
The method for strengthening recycled aggregates utilizing biodeposition according to claim 1, wherein the bacterial solution is prepared according to the following method: dissolving bacterial powder in deionized water, stirring, adjusting pH, and filtering after standing , to obtain the bacterial liquid.
According to claim 3, the regeneration aggregate strengthening method utilizing biological deposition is characterized in that, when preparing the bacterial solution, the stirring time is 5-15 minutes, and NaOH is used to adjust the pH of the bacterial solution to 9.5 ~10.5, the standing time ≥30min.
The method for strengthening recycled aggregates using biological deposition according to claim 1, characterized in that the bacterial concentration of the bacterial solution is 2×10 8 -4×10 8 cfu/mL.
According to claim 1, the regeneration aggregate strengthening method utilizing biological deposition is characterized in that the mineralized nutrient solution includes 4-6 parts by weight of yeast extract powder, 3-5 parts by weight of peptone, 45-55 parts by weight of calcium chloride parts by weight, 18-22 parts by weight of calcium lactate and 500 parts by weight of water.
According to claim 6, the regeneration aggregate strengthening method utilizing biological deposition is characterized in that, the mineralized nutrient solution is prepared according to the following method: dissolving the yeast, peptone, calcium chloride and calcium lactate in desiccated In ionized water, adjust the pH, filter after standing still, and obtain the mineralized culture solution.
The method for strengthening recycled aggregates using biodeposition according to claim 7, characterized in that when preparing the mineralized nutrient solution, NaOH is used to adjust the pH of the mineralized culture solution to 9.5-10.5, and the static Set time ≥ 30min.
According to any one of claims 1-8, the method for strengthening recycled aggregates using biological deposition is characterized in that, in step (1), the soaking of the recycled aggregates in the mineralization culture solution is carried out at 25-35°C Carried out in a ventilated environment, the soaking time is 7-14 days;

and / or,

The soaking of the regenerated aggregate in the mixed culture solution in the step (2) is carried out in a ventilated environment at 25-35° C., and the soaking time is 7-14 days.