AU2020103285A4

AU2020103285A4 - A method for improving the properties of recycled concrete aggregates by using bacillus h4

Info

Publication number: AU2020103285A4
Application number: AU2020103285A
Authority: AU
Inventors: Shicong Kou; Feng XING; Yaguang ZHU
Original assignee: Shenzhen University
Current assignee: Shenzhen University
Priority date: 2020-11-06
Filing date: 2020-11-06
Publication date: 2021-01-14
Anticipated expiration: 2028-11-06

Abstract

The invention pertains to the field of concrete technology, and specially relates to a method for improving the properties of recycled concrete aggregates by using Bacillus H4. The method includes the following steps: (1) Mixing Bacillus H4 and a mineralized culture solution to obtain a mixed culture solution, wherein the collection number of the Bacillus H4 is CGMCC NO. 9629, and the mineralized culture solution is prepared from 3-12g/L sodium lactate, 3-10g/L calcium hydroxide and 10-45g/L N-Cyclohexyl-3-aminopropanesulfonic acid; (2) Using the mixed culture solution obtained in step (1) or the mineralized culture solution to spray on the recycled concrete aggregates to get the enhanced recycled concrete aggregates. The method provided by the invention has the following advantages: the water absorption rate of the enhanced recycled concrete aggregates is reduced, and the compression strength of the recycled mortar made from the enhanced recycled concrete aggregates is improved.

Description

A METHOD FOR IMPROVING THE PROPERTIES OF RECYCLED CONCRETE AGGREGATES

BY USING BACILLUS H4

FIELD OF THE INVENTION

[0001] The present invention pertains to the field of concrete technology, and in particular relates to a

method for improving the properties of recycled concrete aggregates by using Bacillus H4.

BACKGROUND OF THE INVENTION

[0002] With the acceleration of urbanization around the world, the construction industry has entered a

stage of rapid development. A great number of old buildings were demolished, and a large amount of

construction waste, of which waste concrete accounted for the largest share, were produced. From 1991 to

2000, the total amount of waste concrete all around the word (including products that were not qualified in

reinforced concrete factories) is over one billion tons. China has nearly 40 million tons of construction waste

every year, 34% of which are concrete blocks. That means there are over 13.6 million tons waste concrete

every year. Meanwhile, it shows an increasing trend with the acceleration of economic construction. Such a

huge number of concrete wastes will not only cost a great deal of money to dispose but also occupy a large

amount of open space to store and pollute the environment. It is a major public hazard in the city.

[0003] Waste concrete is high-quality concrete aggregates. There are many advantages to use waste

concrete blocks as aggregates. For example, after the building is dismantled, the concrete blocks and silt after

high-quality crushing and screening can be used as the materials of the recycled concrete. Therefore, the

production of recycled aggregates is an important development direction for the construction industry in the

future. The most valuable treatment for waste concrete is to reuse it as a renewable resource to produce

recycled aggregates and turn waste into treasure.

[0004] The application of recycled aggregates has good economic, social, environmental benefits and good

market application prospects. In the prior art, ball mills are used to activate the recycled aggregates and

improve the quality of the recycled aggregates so that they can be used to produce reinforced concrete

members. 5% concentration of glacial acetic acid and 3% hydrochloric acid solution are also used in the

manufacture of the recycled aggregates. The cement and fine mineral powder slurry (such as fly ash, silicon powder, silicon waterproofing agent or calcium sulphoaluminate expansive agents) can be used to soak and dry the regenerated aggregates. However, the pore or fracture of the recycled aggregates resulting from crushing or other treatment cause the water absorption rate of the recycled aggregates is large, which leads to the decline of the performance of the recycled concrete and restricts the development of the recycled aggregates production of recycled aggregates.

SUMMARY OF INVENTION

[0005] In order to solve the problems of the prior art mentioned above, the present invention provides a

method using Bacillus H4 to strengthen the recycled concrete aggregates, which can reduce the water

absorption rate and improve the properties of the recycled concrete aggregates.

[0006] The technical aspect of the present invention is as follows:

[0007] A method for improving the properties of recycled concrete aggregates by using Bacillus H4,

includes the following steps:

(1) Mixing Bacillus H4 and a mineralized culture solution to obtain a mixed culture solution, wherein

the collection number of the Bacillus H4 is CGMCC NO. 9629, and the mineralized culture solution

is prepared from 3-12g/L sodium lactate, 3-10g/L calcium hydroxide and 10-45g/L

N-Cyclohexyl-3-aminopropanesulfonic acid;

(2) Using the mixed culture solution obtained in the step (1) or the mineralized culture solution to spray

on the recycled concrete aggregates to get the enhanced recycled concrete aggregates.

[0008] As further defined, the pH value of the mineralized culture solution is between 10.1 to 10.9.

[0009] As further defined, the bacteria number of the mixed culture solution of the step(2) is between

Ix10 7 ~0l'cfu/L.

[0010] As further defined, the Bacillus H4 of the step(1) is cultured in a microbial medium;

[0011] The microbial medium includes beef extract peptone medium and

N-Cyclohexyl-3-aminopropanesulfonic acid medium; The beef extract peptone medium uses water as a

solvent, and includes 2.5-6.0 g/L beef extract and 8-20 g/L peptone;

The N-Cyclohexyl-3-aminopropanesulfonic acid medium uses water as a solvent, and includes 120 to 170

g/L of N-Cyclohexyl-3-aminopropanesulfonic acid.

[0012] As further defined, the pH value of the N-Cyclohexyl-3-aminopropanesulfonic acid medium is

between 9-10.5, and the volume ratio of the beef extract peptone medium to

N-Cyclohexyl-3-aminopropanesulfonic acid medium is (70-95): (10-20).

[0013] As further defined, the culture condition of the Bacillus H4 is: the speed of shaking culture is

between 120 to 180 rpm, the culture temperature is between 25 to 35 ° C, and the culture time is between 8

-48h.

[0014] As further defined, the Bacillus H4 is cultured in a microbial culture medium, and then the

microbial culture medium is centrifuged to obtain the bacterial precipitate; and then washing the bacterial

precipitate by the mineralized culture solution for 2 to 3 times and finally obtaining the Bacillus H4; The

rotational speed of the centrifugation is between 5000 to 7000 rpm, and the centrifugation time is between 8

to 12 minutes.

[0015] As further defined, if using the mix culture solution in step(2), the spraying period of the step(2)

when is between 15-30 days.

[0016] As further defined, if using the mineralized culture solution in the step(2), the recycled concrete

aggregates should be soaked in the mix culture solution obtained in the step(1) for 1-10 hours first, and then

taken out from the mix culture solution and sprayed with the mineralized culture solution for 10-35 days.

[0017] The ratio of the mass of the recycled concrete aggregates to the volume of the mixed culture

solution is (0.5 - 1.5) g: (15-25) ml.

[0018] As further defined, in step (2), each kilogram of the recycled concrete aggregates is sprayed at a

rate of 0.5 to 4 L/mmin, and the spraying cycle is: Spray every 4 to 12 hours for 0.5 to 4 hours.

[0019] The present invention provides a method for improving the properties of recycled concrete aggregates by using Bacillus H4, including the following steps: (1) Mixing Bacillus H4 and a mineralized culture solution to obtain a mixed culture solution, wherein the collection number of the Bacillus H4 is

CGMCC NO. 9629, and the mineralized culture solution is prepared from 3-12g/L sodium lactate, 3-10g/L

calcium hydroxide and 10-45g/L N-Cyclohexyl-3-aminopropanesulfonic acid; (2) Using the mixed culture

solution obtained in the step (1) or the mineralized culture solution to spray the recycled concrete aggregates

to get the enhanced recycled concrete aggregates. When the recycled concrete aggregates is sprayed with the

mixed culture solution or the mineralized culture solution, the calcium ions Ca in the culture solution will

be converted to calcium carbonate CaCO 3 by the metabolization of the microorganisms. The calcium

carbonate, CaCO3, will the deposited in the surface pores of the recycled concrete aggregates, and thereby

the surface pores of the recycled concrete aggregates will be blocked and the water absorption rate of the

recycled concrete aggregates will be reduced. By adopting the method provided by the present invention, the

water absorption rate of the obtained recycled concrete aggregates is reduced by 45.9%. The compressive

strength of the concrete made by the enhanced recycled concrete aggregates is increased by 17.2-20.1 %.

[0020] Biological preservation instructions:

[0021] Bacillus sp. H4, was deposited in the China General Microbiological Culture Collection Center

(CGMCC) on September 1, 2014, where the address is Building No. 3, Courtyard No. 1, Beichen West Road,

Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences, and the collection

number is CGMCC No. 9629.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

[0022] The technical solution and implementation of the present invention will be described in detail

hereafter with reference to accompanying examples, but the present invention is not limited to the

embodiments described hereafter.

[0023] The present invention provides a method for improving the properties of recycled concrete

aggregates by using Bacillus H4, includes the following steps

is prepared from 3-12g/L sodium lactate, 3-10g/L calcium hydroxide and 10-45g/L

N-Cyclohexyl-3-aminopropanesulfonic acid;

(2) Using the mixed culture solution obtained in the step (1) to spray on the recycled concrete

aggregates to get the enhanced recycled concrete aggregates.

[0024] In the present invention, the microbial medium includes beef extract peptone medium and

N-Cyclohexyl-3-aminopropanesulfonic acid. Beef extract peptone medium plays the role of activating the

strains, and provides substance for the strains to grow to the logarithmic phase. The

N-Cyclohexyl-3-aminopropanesulfonic acid plays a buffering role of keeping the pH value stable, and can

cultivate the strains to adapt to the environment during mineralization culture.

[00251 The beef extract peptone medium uses water as a solvent, and includes 2.5-6.0 g/L beef extract and

8-20 g/L peptone. Preferably, the beef extract is 2.9 to 5.3 g/L. More preferably the beef extract is 3.5 to 4.5

g/L, and most preferably is 3.53 g/L. Preferably, the peptone is 9.4 to 17.7 g/L. More preferably the peptone

is 10 to 13 g/L, and most preferably is 11.76 g/L.

[0026] In the present invention, the beef extract medium is preferably used after sterilization. The

sterilization is preferably high temperature sterilization. The sterilization temperature is preferably 1210 C

and the sterilization time is preferably 15 minutes. The present invention has no special requirements for the

sterilization equipment. Any conventional sterilization equipment by those skilled in the art can be used is

qualified, such as a high-pressure steam sterilizer.

[00271 In the present invention, the N-Cyclohexyl-3-aminopropanesulfonic acid medium uses water as a

solvent, and includes 120 to 170 g/L of N-Cyclohexyl-3-aminopropanesulfonic acid. Preferably, the

N-Cyclohexyl-3-aminopropanesulfonic acid is 66 to 160 g/L. More preferably the

N-Cyclohexyl-3-aminopropanesulfonic acid is 130 to 150 g/L, and most preferably is 147.53 g/L. In the

present invention, the pH value of the N-Cyclohexyl-3-aminopropanesulfonic acid medium is preferably

9-10.5, more preferably 9.5-10.

[0028] In the present invention, there is no specific way to control the pH value of the

N-Cyclohexyl-3-aminopropanesulfonic acid medium. Any conventional method known to those skilled in the art may be adopted. In the specific embodiment of the present invention, it is preferable to adjust the pH value of the N-Cyclohexyl-3-aminopropanesulfonic acid medium with NaOH. The NaOH is preferably an aqueous NaOH solution, and the concentration of the aqueous NaOH solution is preferably 1-10 mol/, more preferably 5-7 mol/l.

[0029] In the present invention, the N-Cyclohexyl-3-aminopropanesulfonic acid medium is preferably

used after sterilization. The sterilization is preferably high temperature sterilization. The sterilization

temperature is preferably 1210C and the sterilization time is preferably 15 minutes. The present invention

has no special requirements for the sterilization equipment. Any conventional sterilization equipment by

those skilled in the art can be used is qualified, such as a high-pressure steam sterilizer.

[0030] In the present invention, the volume ratio of the beef extract peptone medium to the

N-Cyclohexyl-3-aminopropanesulfonic acid medium is (70-95): (10-20), and preferably is (80~90):(12~

18), more preferably is 85:15.

[0031] In the present invention, the beef extract culture medium and the

N-Cyclohexyl-3-aminopropanesulfonic acid medium are mixed under aseptic conditions according to the

above-mentioned volume ratio to obtain a microbial culture medium.

[0032] Bacillus H4 is cultured in a microbial culture medium, and then the microbial culture medium is

centrifuged to obtain the bacterial precipitate. The rotational speed of the centrifugation is preferably

between 5000 to 7000 rpm, more preferably 6000rmp. The centrifugation time is preferably between 8 to 12

minutes, more preferably10min.

[0033] After the bacterial precipitate is obtained, the present invention uses the mineralized culture

solution to wash it for 2 to 3 times, and then discards the washed solution and get the washed Bacillus H4.

Mixing the washed Bacillus H4 and the mineralized culture solution and obtaining the mixed culture solution.

In the present invention, the purpose of washing bacterial precipitate by the mineralized culture solution is to

remove the residual microbial culture medium, which will inhibit the mineralization activity of alkaliphilic

bacillus and affect the effect of strengthening recycled concrete aggregates.

[0034] In the present invention, the culture method is preferably shaking culture; the shaking frequency is

preferably 12 to 180 rpm; more preferably 130 to 160 rpm; most preferably 150 rpm. The present invention

does not have any special restrictions on the instrument for shaking culture. Any conventional sterilization

equipment known to those skilled in the art is qualified, such as a constant temperature shaker.

[00351 In the present invention, the culture temperature is preferably 25-35°C; more preferably 28-32°C;

most preferably 29-31°C. The culture time is preferably 8-48 hours; more preferably10-24 hours; most

preferably 12-20 hours.

[00361 The present invention mixes Bacillus H4 and a mineralized culture solution to obtain the mixed

culture solution. The mineralized culture solution is prepared from 3-12g/L sodium lactate, 3-10g/L calcium

hydroxide and 10-45g/L N-Cyclohexyl-3-aminopropanesulfonic acid. And more preferably it includes 7.5g/L

sodium lactate, 6.67g/L calcium hydroxide and 22.13g/L N-Cyclohexyl-3-aminopropanesulfonic acid, and

the pH value is 10.5.

[0037] The preparation method of the mineralized culture solution of the present invention preferably

includes the following steps:

[0038] () Preparing a mixture of sodium lactate and calcium hydroxide to obtain liquid A;

[00391 @ Preparing the aqueous solution of N-Cyclohexyl-3-aminopropanesulfonic acid and adjusting the

pH value to obtain liquid B;

[00401 @ Mixing liquid A and liquid B in a volume ratio of 17:3 and obtaining a mineralized culture

solution.

[0041] The present invention has no limitation on the sequence of steps Jand @.

[0042] In the present invention, the mineralized culture liquid preferably includes liquid A and liquid B.

Liquid A includes 3.5 to 14.5 g/L sodium lactate and 3.5 to 12 g/L calcium hydroxide. Liquid B includes 66.5

to 300 g/L N-Cyclohexyl-3-aminopropanesulfonic acid.

[0043] Liquid A preferably includes 5 to 10 g/L sodium lactate and 4 to 9 g/L calcium hydroxide, more preferably 8.82 g/L sodium lactate and 7.85 g/L calcium hydroxide. The calcium hydroxide can provide a source for microorganisms to precipitate Ion Ca".

[00441 Liquid B preferably includes 90 to 160 g/L N-Cyclohexyl-3-aminopropanesulfonic acid, more

preferably 147.53 g/L N-Cyclohexyl-3-aminopropanesulfonic acid.

[0045] The pH value of Liquid A and Liquid B is preferably between 10.1-10.9, more preferably between

10.4-10.6, most preferably between 10.5. The present invention preferably adopts acetic acid solution or

sodium hydroxide solution to adjust the pH value.

[00461 Further, the present invention uses acetic acid solution to adjust the pH value of Liquid A and uses

sodium hydroxide solution to adjust the pH value of Liquid B. The mass concentration of acetic acid in the

acetic acid solution is preferably 10-100%, more preferably 50-99%, and most preferably 80-95%. The

concentration of the NaOH solution is preferably 1-10 mol/l, more preferably 5-7 mol/l. The purpose of the

present invention to adjust the pH values of Liquid A and Liquid B liquids separately is to prevent Liquid A

and Liquid B reacting with each other.

[0047] In the mineralized culture solution of the present invention, sodium lactate provides a carbon

source for bacteria growing, and at the same time provides carbon elements for the formation of calcium

carbonate. Calcium hydroxide provides calcium ions for bacterial mineralization and synthesis.

N-Cyclohexyl-3-aminopropanesulfonic acid is a buffer component to maintain the pH value of the

mineralized culture solution stable. In the present invention, the microorganisms use sodium lactate in the

mineralized culture solution as a nutrient to convert the sodium lactate into carbon dioxide/carbonate ions

through aerobic respiration or other metabolic pathways and release them to the outside of the cell, and

combine with calcium ions to form calcium carbonate, and then precipitate on the recycled aggregates to

improve the water absorption coefficient and other properties of the recycled concrete aggregates.

[0048] In the present invention, the bacteria number of the mixed culture solution of the step(2) is

preferably between xI107~109cfu/L, more preferably x108 cfu/L.

[0049] After getting the mixed culture solution, the present invention uses it or the mineralized culture solution to spray the recycled concrete aggregates to get the enhanced recycled concrete aggregates. There is

no specific limitation for the particle size of the recycled concrete aggregates. In the present invention, the

particle size of the recycled concrete aggregates is preferably 0.10-25 mm. In the embodiment of the present

invention, the particle size of the recycled aggregates is 0.15 to 4.75 mmor 5 to 10 mm or 10 to 20 mm.

[0050] The present invention has no special restrictions on the source of the recycled concrete aggregates,

and it is prepared from waste concrete by adopting technical solutions well known to those skilled in the art.

Specifically, in the embodiment of the present invention, the preparation method of the recycled aggregates

preferably includes the following steps:

[0051] Crushing the waste concrete and taking out the steel bars in the crushed concrete to obtain

unreinforced concretes. And then crushing the unreinforced concretes again and obtaining recycled concrete

aggregates with the size of 0.10-25 mm.

[0052] In the present invention, the size of the unreinforced concrete is 5-20 mm or less than 4.75 mm; the

method of crushing the waste concrete is preferably to use a breaking hammer to break out the steel bars, or

to take out the steel bars after manual crushing. In the present invention, there is no special limitation on the

method of breaking the unreinforced concrete again, and conventional methods in the field may be used.

[0053] In the present invention, the spray method is preferably intermittent spray. Specifically, the

preferred interval time is 0.5-4h spraying every 4-12h, more preferably 1-2h spraying every 7-11h. The

mixed culture solution or the mineralized culture solution of the present invention is sprayed on per kilogram

of the recycled concrete aggregates at a rate of 0.5-4 mL/min, preferably 2-3 mL/min.

[0054] In the present invention, when the mixed culture solution is used to spray on the recycled concrete

aggregates, the spray period is preferably 10 to 35 days, more preferably 15 to 25 days, and most preferably

days. In the present invention, when the mixed culture solution is used to spray on the recycled concrete

aggregates, the microorganisms in the mixed culture solution will metabolize the calcium ion in the culture

solution and Ca 2 will turn into calcium carbonate CaCO 3 . CaCO3 settles in the surface pores of the recycled concrete aggregates, and thereby blocks the surface pores of the recycled concrete aggregates and reduces the water absorption rate of the recycled concrete aggregates.

[0055] In the present invention, when the mineralized culture solution is used to spray on the recycled

concrete aggregates, the recycled concrete aggregates should be soaked in the mixed culture solution for

1-10 hours first. After that, the recycled concrete aggregates which are taken out from the mixed culture

solution should be sprayed with the mineralized culture solution for 10-35 days, more preferably 20 days. In

the present invention, when the mineralized culture solution is used to spray on the recycled concrete

aggregates, soaking the recycled concrete aggregates in the mixed culture solution first will make the

Bacillus H4 adhere to the recycled concrete aggregates, and then when the mineralized culture solution is

sprayed, the microorganism in the surface of the recycled concrete aggregates will turn the calcium ions in

the mineralized culture solution into calcium carbonate by its metabolism. The calcium carbonate settles in

the in the surface pores of the recycled concrete aggregates and thereby blocks the surface pores of the

recycled concrete aggregates and reduces the water absorption rate of the recycled concrete aggregates. In

the present invention, the use of the mineralized culture solution to spray can further save the amount of

microorganisms and save the cost.

[0056] In the present invention, it is preferable to soak the recycled concrete aggregates in the mixed

culture solution for 2 to 8 hours, more preferably 3 to 6 hours. The spraying time of the mineralized culture

solution of the present invention is preferably 15-25 days, most preferably 20 days.

[0057] In the present invention, the mass ratio of the recycled concrete aggregates to the volume of the

mixed culture solution is preferably (0.51.5)g:(15-25)mL, more preferably (0.8-1.2)g:(18-22) mL, most

preferably 1g:20mL.

[0058] In the present invention, after the spraying, the sprayed recycled concrete aggregates is preferably

dried to obtain a reinforced recycled concrete aggregates. The present invention does not specifically limit

the drying method. Any technical solution of aggregates drying known to those skilled in the art can be used.

In the embodiment of the present invention, a drum dryer can be used, or just drying the recycled concrete

aggregates by natural way. When using a drum dryer, the drying temperature is preferably 25-35°C.

[0059] In the present invention, the test method which is used to test the water absorption rate of the recycled concrete aggregates is based on the standard GB/T25176-2010 "Recycled Aggregates for Concrete

and Mortar".

[0060] Detailed description of the microorganism-enhanced recycled concrete aggregates provided in the present invention and its preparation method will be given below in conjunction with examples, but they

cannot be understood as limiting the protection scope of the present invention.

Example 1

[0061] Preparation of recycled concrete aggregates: Using a crusher to preliminarily crush the waste concrete and break out the steel bars. The hard-to-take out steel bars are manually crushed and then taken out

to obtain the preliminary crushed non-reinforced concrete. After that, using a jaw crusher to crush the

preliminary crushed non-reinforced concrete and then screening out the aggregates with the size of 5-10mm.

[0062] Preparation of the mineralized culture solution: Weighing calcium hydroxide, sodium lactate and water. The concentration of calcium hydroxide and sodium lactate are 7.85g/L and 8.82g/L separately. Using

acetic acid solution to adjust the pH of Liquid A and the pH value of Liquid A is adjusted to 10.5. Taking

N-Cyclohexyl-3-aminopropanesulfonic acid to prepare Liquid B and the concentration of

N-Cyclohexyl-3-aminopropanesulfonic acid is 147.53g/L. Using sodium hydroxide solution to adjust the pH

of Liquid B and the pH value of liquid B is adjusted to 10.5. Mix Liquid A and Liquid B at a volume ratio of

17:3 to form a mineralized culture solution.

[0063] Preparation of the microbial culture medium: Weighing beef extract, peptone and water to prepare a beef extract medium containing 3.53g/L beef extract and 11.76g/L peptone. The beef extract medium should

be sterilized at 121°C for 15 minutes and then cooled to the room temperature. Weighing

N-Cyclohexyl-3-aminopropanesulfonic acid and water, and adjusting the pH value of it to 10 by 6mol/L

sodium hydroxide to obtain a medium containing 147.53g/L N-Cyclohexyl-3-aminopropanesulfonic. The

medium should be sterilized at 121°C for 15 minutes and then cooled to the room temperature. Mixing the

beef extract medium and the N-Cyclohexyl-3-aminopropanesulfonic acid medium in a volume ratio of 85:15 to obtain a microbial medium.

[0064] The Bacillus H4 is inoculated into the microbial culture medium, and cultured with shaking at 30°C for 24h at a frequency of 150rpm. After cultivation, the microbial culture medium is centrifuged at 6000rpm

for 60min to obtain the bacterial precipitate; and then washing the bacterial precipitate by the mineralized

culture solution for 3 times and finally obtaining the Bacillus H4. Adding the Bacillus H4 to the mineralized

culture solution and obtaining a mixed culture solution, so that the number of bacteria in the mixed culture

solution is 1x10 8 cfu/L; Using the mixed culture solution to spray on the recycled concrete aggregates for 2

hours every 10 hours with the spray rate of 2 ml per minute on per kilogram of the recycled concrete

aggregates. The spraying period is 20 days. According to the method of the standard GB/T25176-2010

"Recycled Aggregates for Concrete and Mortar", the water absorption and other properties of the reinforced

recycled concrete aggregates before and after microbial treatment were tested. The results are shown in Table

1:

Table 1: Comparison of the properties of the recycled concrete aggregates before and after dealing

Name Particle Water Absorption Apparent Density Crush Index

Size Rate(%) (kg/m 3) (%)

(mm)

The recycled 4.75-20 7.4 2530 17.3

concrete

aggregates before

the treatment

The reinforced 4.75-20 4.0 2565 12.8

recycled concrete

aggregates

[0065] It can be concluded from Table 1 that the water absorption rate of the reinforced recycled concrete aggregates before the treatment is 7.4%, and the water absorption rate after the microbial treatment is 4.0%,

which is 45.9% lower than that before the microbial treatment.

Example 2

[0066] Preparation of recycled concrete aggregates: Using a crusher to preliminarily crush the waste

concrete and break out the steel bars. The hard-to-take out steel bars are manually crushed and then taken out

to obtain the preliminary crushed non-reinforced concrete. Then using a jaw crusher to crush the preliminary

crushed non-reinforced concrete and then screening out the aggregates with the size under 10mm. After that,

a compound crusher is used for secondary crushing. Aggregates smaller than 4.75mm are screened out, and

finally aggregates of 0.15 to 4.75mm are obtained.

[0067] Preparation of the mineralized culture solution: Weighing calcium hydroxide, sodium lactate and

water. The concentration of calcium hydroxide and sodium lactate are 7.85g/L and 8.82g/L separately. Using

of Liquid B and the pH value of liquid B is adjusted to 10.5. Mixing Liquid A and Liquid B in a volume ratio

of 17:3 and obtaining a mineralized culture solution.

[0068] Preparation of the microbial culture medium: Weighing beef extract, peptone and water to prepare a

beef extract medium containing 3.53g/L beef extract and 11.76g/L peptone. The beef extract medium should

beef extract medium and the N-Cyclohexyl-3-aminopropanesulfonic acid medium in a volume ratio of 85:15

to obtain a microbial medium.

[0069] The Bacillus H4 is inoculated into the microbial culture medium, and cultured with shaking at 30°C

for 24h at a frequency of 150rpm. After cultivation, the microbial culture medium is centrifuged to obtain the

bacterial precipitate; and then washing the bacterial precipitate by the mineralized culture solution for 3

times. Adding the bacterial precipitate to the mineralized culture solution to obtain a mixed culture solution, so that the number of bacteria in the mixed culture solution is 1x10 8cfu/L. Weighing the recycled concrete aggregates, and the mass ratio of the recycled concrete aggregates to the volume of the mixed culture solution is 1g:20mL. Using the mixed culture solution to spray on the recycled concrete aggregates for 2 hours every 10 hours with the spray rate of 2 ml per minute on per kilogram of the recycled concrete aggregates. The spraying period is 20 days. According to the method of the standard GB/T25176-2010

below:

Table 2 Particle Size of the Reinforced Recycled Aggregates in Example 2 of the present invention

Nominal Accumulated Retained Percentage (%) Fineness Standard Grading

Size of Side Length of the hole in the square hole Module Zone

Aggregates screen

(mm) 0 0.1 0.3 0.60 1.18 2.36 4.75

-4.75 100 90 70 45 18 4 0 2.3 Medium II

Table 3: Comparison of the Properties of the Reinforced Recycled Aggregates Before and After the

Microbial Treatment

Item Particle Apparent Density Packing Density (kg/m3)

Size (kg/m3 ) Loose Bulk Tap Bulk (mm) Density Density

Before treatment 4.75-20 2258 2258 17.3

After treatment 4.75-20 2416 2416 12.8

[0070] It can be concluded from Table 3 that the water absorption rate of the reinforced recycled concrete

aggregates after the microbial treatment is 3.7%, and the water absorption rate before the treatment is 6.0%.

Compared with the recycled concrete aggregates before the microbial treatment, the water absorption rate of

the reinforced recycled concrete aggregates is reduced by 38.3%.

Example 3

[0071] The untreated recycled aggregates and the reinforced recycled aggregates in Example 1 were used

as recycled concrete aggregates to prepare the recycled concrete. The ratio is shown in Table 2. The recycled

concrete aggregates of Example 1 is used as recycled coarse aggregates. The water absorbed by the recycled

aggregates is directly added to the mixing ratio as additional water, and the additional water is 60% of the

water absorption rate of the recycled aggregates. The effect of microbial treatment of the recycled aggregates

on the compressive strength of recycled concrete was investigated. The results are shown in Table 4.

Table 4: Mix ratio of recycled concrete (1m 3)

Item Water Cement Water Additional Recycled Recycled

cement water Coarse Fine

ratio Aggregates Aggregates

Concrete Made 0.47 409 192 74 720 1079

of the Untreated

Recycled

Aggregates

Concrete Made 0.47 409 192 49 771 1096

of the

Reinforced

Recycled

Aggregates

Table 5: Compressive Strength of Recycled Mortar /MPa

Item Age

28 days 56 days

Mortar made of the untreated 32.8MPa 35.4MPa

recycled aggregates

Mortar made of the reinforced 39.4MPa 41.5MPa recycled aggregates

Increase of the compressive 20.1 17.2

strength

[0072] It can be concluded from Table 5 that after microbial treatment, the compressive strength of

recycled mortar increased by 17.2-20.1 %.

[0073] It can be observed from the above examples that using the method for preparing

microbial-enhanced recycled concrete aggregates of the present invention, the water absorption of the

obtained recycled concrete aggregates is reduced by 13.2 to 17.2%. The compressive strength of the recycled

mortar which is made of the enhanced recycled concrete aggregates is increased by 17.220.1 %.

[0074] Other features, advantages and embodiments of the invention disclosed herein will be readily

apparent to those exercising ordinary skill after reading the foregoing disclosures. In this regard, while

specific embodiments of the invention have been described in considerable detail, variations and

modifications of these embodiments can be effected without departing from the spirit and scope of the

invention as described and claimed.

Claims

1. A method for improving the properties of recycled concrete aggregates by using Bacillus H4, includes

the following steps:

(1) Mixing Bacillus H4 and a mineralized culture solution to obtain a mixed culture solution, wherein the

collection number of the Bacillus H4 is CGMCC NO. 9629, and the mineralized culture solution is prepared

from 3-12g/L sodium lactate, 3-10g/L calcium hydroxide and 10-45g/L

N-Cyclohexyl-3-aminopropanesulfonicacid;

(2) Using the mixed culture solution obtained in the step (1) or the mineralized culture solution to spray on

the recycled concrete aggregates to get the enhanced recycled concrete aggregates.

2. The method for improving the properties of recycled concrete aggregates by using Bacillus H4

according to claim 1, wherein the pH value of the mineralized culture solution is between 10.1 to 10.9.

3. The method for improving the properties of recycled concrete aggregates by using Bacillus H4

according to claim 1, wherein the bacteria number of the mixed culture solution of the step(1) is between

1x10 7 ~'10'fu/L.

4. The method for improving the properties of recycled concrete aggregates by using Bacillus H4

according to any one of claims 1 to 3, wherein the Bacillus H4 of the step(1) is cultured in a microbial

medium;

The microbial medium includes beef extract peptone medium and N-Cyclohexyl-3-aminopropanesulfonic

acid medium;

The beef extract peptone medium uses water as a solvent, and includes 2.5-6.0 g/L beef extract and 8-20 g/L

peptone;

g/L of N-Cyclohexyl-3-aminopropanesulfonic acid.

5. The method for improving the properties of recycled concrete aggregates by using Bacillus H4

according to claim 4, wherein the pH value of the N-Cyclohexyl-3-aminopropanesulfonic acid medium is

between 9-10.5, and the volume ratio of the beef extract peptone medium to the

N-Cyclohexyl-3-aminopropanesulfonic acid medium is (70-95): (10-20).

6. The method for improving the properties of recycled concrete aggregates by using Bacillus H4

according to any one of claims 4 to 5, wherein the culture condition of the Bacillus H4 is: the speed of

shaking culture is between 120 to 180 rpm, the culture temperature is between 25 to 35 0 C, and the culture

time is between 8 -48h.

7. The method for improving the properties of recycled concrete aggregates by using Bacillus H4

according to claim 4, wherein the Bacillus H4 is cultured in the microbial culture medium, and then the

precipitate by the mineralized culture solution for 2 to 3 times and finally obtaining the Bacillus H4;The

to 12 minutes.

8. The method for improving the properties of recycled concrete aggregates by using Bacillus H4

according to claim 1, wherein if using the mix culture solution in the step(2), the spraying period of the

step(2) is between 15-30 days.

9. The method for improving the properties of recycled concrete aggregates by using Bacillus H4

according to claim 1, wherein if using the mineralized culture solution in the step(2), the recycled concrete

The ratio of the mass of the recycled concrete aggregates to the volume of the mixed culture solution is (0.5

1.5) g: (15-25) ml.

10. The method for improving the properties of recycled concrete aggregates by using Bacillus H4

according to any one of claims, 4 or 9, wherein in step (2), each kilogram of the recycled concrete

aggregates is sprayed at a rate of 0.5 to 4 L/mmin, and the spraying cycle is: spraying every 4 to 12 hours for

0.5 to 4 hours.