CN110156406B

CN110156406B - Method for manufacturing brick powder concrete by using waste sintered shale brick powder

Info

Publication number: CN110156406B
Application number: CN201910571872.6A
Authority: CN
Inventors: 黄榜彪; 刘灏; 黄秉章; 李晓; 谢伟标; 王俊云
Original assignee: Guangxi University of Science and Technology; Liuzhou Institute of Technology
Current assignee: Guangxi University of Science and Technology; Liuzhou Institute of Technology
Priority date: 2019-06-28
Filing date: 2019-06-28
Publication date: 2021-10-22
Anticipated expiration: 2039-06-28
Also published as: CN110156406A

Abstract

The invention discloses a method for preparing brick powder concrete by using waste sintered shale brick powder, which comprises the following steps: (1) removing impurities; (2) crushing and drying; (3) grinding, screening and drying to obtain waste sintered shale brick powder; (4) weighing the following raw materials in parts by weight: cement, medium sand, cobblestone, water, waste sintered shale brick powder, magnesium borate, zirconium oxide, hydroxypropyl methyl cellulose, bentonite and mica; (5) carrying out oscillation stirring on each raw material by using 100-200 Hz ultrasonic waves to obtain mixed slurry; (6) and (4) forming the mixed slurry. The product of the invention has the advantages that: the waste of the sintered shale brick is made into powder, and the powder is partially substituted for cement to produce brick powder concrete, and the overall performance of the brick powder concrete is effectively improved by comparing with common concrete.

Description

Method for manufacturing brick powder concrete by using waste sintered shale brick powder

Technical Field

The invention relates to the technical field of concrete, in particular to a method for preparing brick powder concrete by using waste sintered shale brick powder.

Background

Concrete is one of the basic materials widely used in the civil engineering industry. According to statistics of the national statistical bureau, the yield of the commercial concrete in 2016 years in China is up to 179200 ten thousand cubic meters, the commercial concrete is increased by 7.4 percent, and the commercial concrete is improved by 5.4 percent on year-on-year basis. With the high-speed development of economy, the more widespread the application of concrete. The old buildings are dismantled every day in China, and meanwhile, new buildings grow up. This results in a large amount of construction waste every day. The waste sintered shale bricks account for a large part of construction wastes, and manufacturers of shale bricks also produce a large amount of waste bricks, and the bricks have no reasonable treatment mode and become one of important pollutions for the environment and occupied land resources. Therefore, reasonable and resourceful treatment of the waste sintered shale bricks is required to be found.

Because the reserves of the shale in Guangxi province are rich, the sintered shale bricks in the local area have rich yield and wide application. The special regional characteristics make the sintered shale brick become a special industry in the local area of Guangxi. Experts have pointed out that: "there is no rubbish in the world, only misplaced resources". With the rapid development of economy and cities, the urbanization process is accelerated, and with the removal of a large number of buildings every day, new building plans emerge, and the updating of buildings creates a large number of waste sintered shale bricks. Meanwhile, the daily sintering of brickyards is not perfect, and a lot of unqualified sintered bricks always exist. The comprehensive reasons result in a large amount of waste sintered shale bricks. For waste sintered shale bricks, the treatment mode in the Guangxi district is to stack the bricks in place, and large-scale waste brick transportation generates a large amount of dust on the transportation route. Or for small volume landfill sites. There is no unified and reasonable resource treatment mode. And the waste sintered shale brick belongs to siliceous raw materials, has crystal phase activity after grinding, is high in resource waste undoubtedly due to an unreasonable treatment mode, and is seriously inconsistent with the strategy of resource shortage and sustainable green development in China. But at present, systematic research on the resource treatment of the waste sintered shale bricks is not carried out all the time at home and abroad.

In conclusion, the resource utilization of the waste sintered shale bricks and the energy conservation and consumption reduction of the cement industry are urgent.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a method for preparing brick powder concrete by using waste sintered shale brick powder. The invention can effectively recycle the waste sintered shale brick powder to replace part of cement to produce brick powder concrete, and the overall performance of the brick powder concrete is obviously improved after being compared with the common concrete, thereby achieving the purpose of improving the engineering quality, reducing the environmental pollution problem caused by the production of the cement, solving the environmental problem caused by related pollution in cities, increasing employment posts of industries undoubtedly by emerging industries, generating the industrial chain effect, driving the development of related industries, preparing building materials by utilizing the recycling of wastes, changing the wastes into valuables on the basis of solving the problem of waste treatment, protecting the environment and saving resources.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the method for preparing the brick powder concrete by using the waste sintered shale brick powder comprises the following steps:

(1) the method comprises the following steps of (1) recycling waste sintered shale bricks, hammering, primarily crushing and sorting by manpower, and removing impurities of the waste sintered shale bricks;

(2) crushing the waste sintered shale bricks after impurity removal by using a jaw crusher, and drying after crushing;

(3) grinding the crushed waste sintered shale bricks, sieving by using a vibrating screen machine, and drying by using an oven to obtain waste sintered shale brick powder, wherein the fineness of the waste sintered shale brick powder is 0.08-0.15 mm;

(4) weighing the following raw materials in parts by weight: cement 359-445 weight parts, medium sand 600-620 weight parts, stone 1100-1185 weight parts, water 190-210 weight parts, waste sintered shale brick powder 24-96 weight parts, magnesium borate 3-5 weight parts, zirconium oxide 3-5 weight parts, hydroxypropyl methyl cellulose 3-5 weight parts, bentonite 4-5 weight parts, mica 4-5 weight parts;

(5) mixing cement, medium sand, pebbles, water, waste sintered shale brick powder, magnesium borate, zirconia, hydroxypropyl methyl cellulose, bentonite and mica, and performing oscillation stirring by using 100-plus-200 Hz ultrasonic waves to obtain mixed slurry;

(6) and pouring the mixed slurry into a forming die for forming to obtain the brick powder concrete product.

Further, the chemical composition of the sintered shale brick powder is as follows by mass percent: SiO 2₂54.35-55.48％； Fe₂O₃10.21-11.82％；Al₂O₃14.22 to 15.31 percent; CaO2.10-2.52%; MgO1.00-1.20%, and the balance of other impurities.

Furthermore, the particle size of the stones is 18-22 mm.

Furthermore, the cement is ordinary portland cement, and the strength grade is 42.5 MPa.

Further, the water-cement ratio of the mixed slurry is 0.42-0.45.

Further, the raw materials are weighed according to the parts by weight as follows: 400 parts of cement, 610 parts of medium sand, 1135 parts of stones, 200 parts of water, 48 parts of waste sintered shale brick powder, 4 parts of magnesium borate, 4 parts of zirconium oxide, 4 parts of hydroxypropyl methyl cellulose, 4.5 parts of bentonite and 4.5 parts of mica.

Compared with the prior art, the invention has the following beneficial effects:

the invention can effectively recycle the waste sintered shale bricks to produce the brick powder concrete, and the performance of the brick powder concrete can be effectively improved, thereby achieving the purpose of improving the engineering quality, reducing the environmental pollution problem caused by the production of cement, solving the environmental problem caused by related pollution in cities, increasing employment posts of industries undoubtedly by emerging industries, generating the industrial chain effect, driving the development of related industries, preparing building materials by utilizing the recycling of wastes, changing wastes into valuables on the basis of solving the problem of waste treatment, protecting the environment and saving resources. The invention uses the waste sintered shale bricks to prepare the ecological cement, realizes the resource harmless treatment of the waste sintered shale bricks, and greatly improves the current situation that the waste sintered shale bricks in China are increased year by year.

The physical property inspection of the produced concrete is carried out, and the result shows that the cubic compressive strength, the splitting strength, the breaking strength and the elastic modulus of the concrete can be enhanced to a certain extent by the mixing amount of the waste sintered shale brick powder.

In the invention, magnesium borate, zirconium oxide, hydroxypropyl methyl cellulose, bentonite and mica are used for replacing cement, the total substitution rate accounts for 4-5%, and the cubic compressive strength, the splitting strength, the breaking strength and the elastic modulus of the obtained concrete are improved. The hydroxypropyl methyl cellulose and the bentonite have a certain bonding effect, so that the uniformly stirred mixture can not be layered during the oscillation treatment, and the waste brick powder and the cement are more uniformly mixed; after heating in the mixing and stirring process of the mixture, magnesium borate can excite magnesium borate whiskers, the hardness of the formed concrete is improved, zirconia can promote nucleation between the zirconia whiskers and the magnesium borate whiskers to enable the whiskers to be compact in structure and agglomerate, the crystal performance is improved, ultrasonic oscillation treatment is adopted in the stirring process to prevent the whiskers from agglomerating with other raw materials, in the mixing and stirring process and the forming process, the whiskers can be uniformly distributed in the brick powder concrete, and the fracture resistance and the elastic modulus of a brick powder concrete product are effectively improved.

Drawings

FIG. 1 is a diagram of a failure test piece;

FIG. 2 is a broken cross-sectional view of a test piece;

FIG. 3 is a graph showing the influence of different substitution rates on the splitting tensile strength of concrete for different fineness of brick powder; wherein, A is intensity diagram with same fineness and different substitution rates, B is intensity diagram with same substitution rates and different fineness;

FIG. 4 is a line graph of strength of concrete with the same fineness and different substitution rates;

FIG. 5 is a graph showing the influence of different degrees of substitution on the splitting tensile strength of concrete due to different fineness of brick powder; wherein, A is the splitting tensile strength with the same fineness of 28d, and B is the splitting tensile strength with the same substitution rate and different fineness;

FIG. 6 is a line graph showing the splitting strength of concrete with the same fineness and different substitution rates;

FIG. 7 is a graph showing the influence of different substitution rates on the flexural strength of concrete due to brick powder with different fineness; wherein A is a comparison graph of flexural strength with the same fineness and different doping amounts, and B is a comparison graph of flexural strength with the same doping amount and different fineness;

FIG. 8 is a line graph showing the bending strength of concrete with the same fineness and different substitution rates;

FIG. 9 is a graph showing the effect of different fineness of brick powder and different substitution rates on the elastic modulus of concrete;

FIG. 10 is a 2000 times electron microscope image of brick powder with different fineness, wherein A is 0.08mm brick powder x2000 times, B is 0.10mm brick powder x2000 times, and C is 0.15mm brick powder x2000 times;

FIG. 11 is a diagram of a normal concrete electron microscope, wherein A is a 1000-fold electron microscope diagram and B is a 1000-fold electron microscope diagram;

FIG. 12 is a diagram of a concrete electron microscope with a brick powder fineness of 0.08mm and a substitution rate of 5%, wherein A is a 1000-fold electron microscope diagram and B is a 2000-fold electron microscope diagram;

FIG. 13 is a diagram of a concrete electron microscope with a brick powder fineness of 0.08mm and a substitution rate of 10%, wherein A is a 1000-fold electron microscope diagram and B is a 2000-fold electron microscope diagram;

FIG. 14 is a diagram of a concrete electron microscope with a substitution rate of 20% and a brick powder fineness of 0.08mm, wherein A is a 1000-fold electron microscope diagram and B is a 2000-fold electron microscope diagram;

FIG. 15 is a diagram of a concrete electron microscope with a brick powder fineness of 0.10mm and a substitution rate of 5%, wherein A is a 1000-fold electron microscope diagram and B is a 2000-fold electron microscope diagram;

FIG. 16 is a diagram of a concrete electron microscope with a brick powder fineness of 0.15mm and a substitution rate of 5%, wherein A is a 1000-fold electron microscope diagram and B is a 2000-fold electron microscope diagram;

FIG. 17-A is an internal structural view (10000 times) of a concrete having a substitution rate of brick powder of 0%, and FIG. 17-B is an internal structural view of a concrete having a substitution rate of 5% and a fineness of brick powder of 0.08 mm;

FIG. 18 is a view showing an internal structure of a concrete having a substitution rate of brick powder of 5% (10000 times), wherein A is a view showing an internal structure of a concrete having a substitution rate of 5% and having a fineness of brick powder of 0.10mm, and B is a view showing an internal structure of a concrete having a substitution rate of 5% and having a fineness of brick powder of 0.15 mm.

Detailed Description

The invention is further described with reference to the following figures and specific examples.

The cement of the invention is ordinary portland cement with the strength grade of 42.5 MPa.

Example 1

(3) grinding the crushed waste sintered shale bricks, sieving by using a vibrating screen machine, and drying by using an oven to obtain waste sintered shale brick powder, wherein the fineness of the waste sintered shale brick powder is 0.08 mm;

(4) weighing the following raw materials in parts by weight: 359 parts of cement, 600 parts of medium sand, 1100 parts of stones with the particle size of 18mm, 190 parts of water, 246 parts of waste sintered shale brick powder, 3 parts of magnesium borate, 3 parts of zirconia, 3 parts of hydroxypropyl methyl cellulose, 4 parts of bentonite and 4 parts of mica;

the sintered shale brick powder comprises the following chemical components in percentage by mass: SiO 2₂54.35％；Fe₂O₃10.21％； Al₂O₃14.22 percent; 2.10% of CaO2; MgO1.00%, the balance being other impurities;

(5) mixing cement, medium sand, pebbles, water, waste sintered shale brick powder, magnesium borate, zirconia, hydroxypropyl methyl cellulose, bentonite and mica, and oscillating and stirring by using 100 Hz ultrasonic waves to obtain mixed slurry;

Example 2

(3) grinding the crushed waste sintered shale bricks, sieving by using a vibrating screen machine, and drying by using an oven to obtain waste sintered shale brick powder, wherein the fineness of the waste sintered shale brick powder is 0.10 mm;

(4) weighing the following raw materials in parts by weight: 400 parts of cement, 610 parts of medium sand, 1135 parts of stones with the particle size of 20mm, 200 parts of water, 48 parts of waste sintered shale brick powder, 4 parts of magnesium borate, 4 parts of zirconia, 4 parts of hydroxypropyl methyl cellulose, 4.5 parts of bentonite and 4.5 parts of mica;

the sintered shale brick powder comprises the following chemical components in percentage by mass: SiO 2₂5485％；Fe₂O₃10.87％； Al₂O₃14.63%; 2.38% of CaO2; MgO1.04%, and the balance of other impurities;

(5) mixing cement, medium sand, pebbles, water, waste sintered shale brick powder, magnesium borate, zirconia, hydroxypropyl methyl cellulose, bentonite and mica, and oscillating and stirring by using ultrasonic waves of 150 Hz to obtain mixed slurry;

Example 3

The method for preparing the brick powder concrete by using the waste sintered shale brick powder is characterized by comprising the following steps:

(3) grinding the crushed waste sintered shale bricks, sieving by using a vibrating screen machine, and drying by using an oven to obtain waste sintered shale brick powder, wherein the fineness of the waste sintered shale brick powder is 0.15 mm;

(4) weighing the following raw materials in parts by weight: 445 parts of cement, 620 parts of medium sand, 1185 parts of stones with the particle size of 22mm, 210 parts of water, 96 parts of waste sintered shale brick powder, 5 parts of magnesium borate, 5 parts of zirconia, 5 parts of hydroxypropyl methyl cellulose, 5 parts of bentonite and 5 parts of mica;

the sintered shale brick powder comprises the following chemical components in percentage by mass: SiO 2₂55.48％；Fe₂O₃11.82％； Al₂O₃15.31 percent; CaO2.52%; MgO1.20%, the rest is other impurities;

(5) mixing cement, medium sand, pebbles, water, waste sintered shale brick powder, magnesium borate, zirconia, hydroxypropyl methyl cellulose, bentonite and mica, and oscillating and stirring by using 200 Hz ultrasonic waves to obtain mixed slurry;

In order to research the cubic compressive strength of the waste sintered shale brick powder concrete, a test specimen is manufactured according to the test requirement in the current national standard 'mechanical property test method standard of common concrete' (GB/T50081-2016), the test specimen is 150mm x150mm cubic standard specimen, the specimen is molded, the test specimen is maintained by natural sprinkling due to the limitation of test conditions, and finally, a TYE-A type digital display electro-hydraulic pressure tester is used for testing in a material strength laboratory of the university of science and technology in Guangxi, wherein the specific test process is as follows:

according to the calculated concrete mixing proportion, designing a test list and weighing required test materials;

(1) pouring the test materials into a stirrer, starting the stirrer to stir for 30s to fully mix the test materials, adding test water, and stirring again to form concrete;

(2) the concrete formed by stirring is filled into a test mould brushed with oil, and the test mould is placed on a vibration table to vibrate, so that air bubbles in the concrete of the test model are removed, the vibration is dense, and the influence on test data caused by improper test operation is reduced;

(3) removing the mold of the molded test piece after 2 days, and naturally spraying water to cover and maintain for 28 d;

(4) wiping the surface of the cured and formed test piece by using a rag, and cleaning the pressure-bearing surface of the test instrument;

(5) placing the side surface of the test piece at the central part of an upper bearing plate and a lower bearing plate of a bearing surface, adjusting the upper bearing plate to be in pre-contact with the test piece, and preloading for 5 s;

(6) after preloading, continuously loading the test piece at a loading speed of 0.5-0.8 MPa/s;

(7) according to the expected damage load, when the test piece is about to be damaged, an oil valve of the test instrument is adjusted, loading is continued until the test piece is damaged, the loading force value becomes a negative value, loading is stopped, and damage data are recorded;

(8) the cubic compressive strength value of the concrete test piece is calculated according to the following formula:

in the formula: f. of_ccCubic compressive strength (MPa), F-test piece breaking load (N), pressure bearing area (mm) of A-test piece²)

And (3) test results:

cube strength test 10 sets of tests were designed according to the test design, with 3 test pieces per set, totaling 30 test pieces. The analysis of the test results is carried out according to the value-taking requirements of the standard of the test method for the mechanical properties of common concrete (GB/T50081-2016), and the data obtained in the specific test are shown in Table 1.

TABLE 2 cube compressive strength test data

The test method of the cubic compressive strength test of the waste sintered shale brick powder concrete obtained by partially replacing cement with the waste sintered shale brick powder is the same as the cubic compressive strength test of common concrete. Therefore, the waste sintered shale brick powder concrete in the test can be used for uniaxial compressive strength test. During the test, the test piece is found to be compressed longitudinally under the application of load, and the compression is accompanied by the transverse extension; it is obvious in the test process that in the process of continuously increasing the load, criss-cross fine cracks are generated on the surface of the test piece, then the cracks are continuously expanded, so that the surface of the waste sintered shale brick powder concrete test piece begins to bulge and even fall off, and the shape after the fall-off is similar to that of a quadrangular pyramid in a mathematical model. Experimental research shows that the concrete with the brick powder or the common concrete has almost no difference in damage model and is similar to a quadrangular pyramid. Observing the fracture section of the test piece can find that the stones on the surface of the fractured test piece are also fractured, so that the crack can be directly penetrated in the stones and does not bypass the stones when the test piece is fractured. See fig. 1, 2.

The waste sintered shale brick powder is used for partially replacing the cement consumption in the concrete, and the brick powder is not added in the reference control group. A28-day cube compressive strength test is carried out on the brick powder, and test data show that when the fineness of the brick powder is 0.08mm, along with the gradual increase of the substitution rate from 5%, 10% and 20%, the strength increase of the waste sintered shale brick powder concrete is gradually reduced, the optimal strength mixing amount is 5%, and the strength increase is 15.29%. The strength increase of the 10 percent and 20 percent substitution rate is less, but the 28d cube compressive strength is higher than that of the base without the brick powder, the 28d cube compressive strength is higher than that of the base, the increase is not great, and the strength value of the brick powder concrete with the 10 percent substitution rate is lower than that of the standard group. When the fineness of the brick powder is 0.15mm, the difference between the 28d of the brick powder concrete at the substitution rate of 5 percent and 10 percent and the strength value of a reference group is not large along with the gradual increase of the substitution rate of 5 percent, 10 percent and 20 percent, and the strength value of the brick powder concrete at the substitution rate of 20 percent is reduced more and reaches 13.72 percent. The general trend of the brick powder fineness of 0.15mm is that the cubic compressive strength value of 28d concrete is gradually reduced along with the increase of the substitution rate. Under the same substitution rate, the compressive strength value of the 28d cube generally shows a decreasing trend along with the increase of the fineness of the brick powder. See fig. 3(A, B), fig. 4.

The analysis of test data can obtain that 5%, 10% and 20% of waste sintered shale brick powder with the thickness of 0.08mm is really feasible to replace cement as a concrete admixture, and the strength performance of concrete can be better improved; the strength of the waste sintered shale brick powder with the thickness of 0.10mm is improved to some extent under the cement substitution rate of 10 percent and 20 percent, and the method is really feasible; the concrete strength of the waste sintered shale brick powder with the thickness of 0.15mm is almost not different from that of the concrete obtained by the common mixing ratio under the cement substitution rate of 5 percent and 10 percent.

Axial compressive strength test

Test method

The axial compressive strength test procedure of the waste sintered shale brick powder concrete is similar to a cubic compressive strength test. According to the test requirements in the national standard of mechanical property test method standard of common concrete (GB/T50081-2016), a standard prism test piece with the size of 150mm x300mm is manufactured in a laboratory of Guangxi science and technology university, standard curing is carried out on the test piece in a strength laboratory, after 28d of curing period, the test piece is taken out from a curing pool, and an axial pressure strength test is carried out by using a microcomputer control electro-hydraulic type pressure tester of YAW-3000 type, wherein the specific test steps are as follows:

(1) taking out the cured and molded test piece from the curing pool, and cleaning and drying the surface of the test piece;

(2) fixing a test specimen on a testing machine according to a test standard placing form, adjusting an upper bearing plate of the testing machine to enable the test specimen to be in contact with the upper bearing plate, and aligning the center of the test specimen with the upper bearing plate;

(3) opening a test information acquisition system of a microcomputer control system, selecting a concrete axle center compressive strength test, and modifying and storing test parameter data according to each calculated test parameter;

(4) clicking an experiment starting button to start an experiment, starting loading of load until a test piece is loaded and damaged, and recording the maximum load during damage;

(5) the test strength calculation formula of the axial compressive strength test of the prism is as follows:

in the formula: f. of_cpCubic compressive strength (MPa), F-test piece breaking load (N), pressure bearing area (mm) of A-test piece²)

Test results

The axial compression test is characterized in that 10 groups are designed according to a test design scheme, 30 test pieces are counted, data calculation is carried out according to the calculation standard of the axial compression strength, namely the standard of the test method for the mechanical property of common concrete (GB/T50081-2016), and the obtained test data are calculated to obtain the following data:

TABLE 3-1 axial compressive Strength test data

2. Form of destruction of the test piece

Laboratory test researches show that the damage form of a test piece of the prismatic axial compressive strength test of the concrete doped with the waste sintered shale brick powder is not much different from that of common concrete, and the damage form is not greatly influenced by different waste brick powder doping amounts and different fineness substitutions.

Experimental research shows that the destruction process of the waste sintered shale brick powder concrete is similar: under the action of a small load at the initial loading stage, no obvious crack appears on the surface of the test piece; along with the continuous time, the loading load of the test piece is continuously increased, the internal stress of the test piece is gradually increased, and short and small fine cracks are found to appear on the surface of the test piece; with the continuous loading of the load, the cracks are found to continuously extend along the axial direction, and a through inclined crack is slowly formed; the load is continuously increased, new cracks are continuously developed inwards, and the surface of the axial compression test piece made of the waste sintered shale brick powder concrete is found to be gradually bulged, and even some axial compression test pieces are peeled off; when the damage is close to, a 'clattering' sound can be heard, and the test piece is damaged.

TABLE 4 compressive Strength test data

After testing the qualified axis compressive strength test specimen in a laboratory, collecting relevant experimental data, obtaining an axis compressive strength test value of the waste sintered shale brick powder concrete through calculation and analysis of the experimental data, and analyzing the obtained axis compressive strength data and cube compressive strength data as shown in tables 3-4. The specification of cubic compressive strength test values and axial compressive strength test values of concrete test pieces in the concrete design Specification (GB50010-2010) in China is as follows: f. of_cpThe calculation of the test values shows that the proportionality coefficients of the test values are all less than 0.76, and the analysis reason is as follows: the first method is that the brick powder partially replaces cement, so that the cubic compressive strength value is improved to a certain extent, but the corresponding axial compressive strength value is not improved in the same proportion; in the second experiment process, due to the manual operation of a tester, the generated centering error causes the eccentricity of the test piece to be pressed, so that the measured value is lower than the theoretical value.

In general, the axial compressive strength of the waste sintered shale brick powder concrete with the 0.08mm fineness and the brick powder with the 0.15mm fineness, which has the substitution rate of 5 percent and 20 percent, and the substitution rate of the 0.10mm brick powder is 10 percent, 20 percent and 5 percent, is not greatly different from the strength of the common concrete; longitudinal analysis shows that under the condition that the fineness of the brick powder is the same, the strength of the concrete after the cement is partially replaced by the brick powder with the thickness of 0.08mm changes in an inverted triangle form, and the strength of the waste brick powder concrete with the substitution rate of 5 percent and 20 percent is higher than that of the waste brick powder concrete with the substitution rate of 10 percent; the strength of concrete after the cement is partially replaced by the brick powder with the thickness of 0.10mm is not much different from that of ordinary concrete in the brick powder concrete with the replacement rate of 10 percent and 20 percent, and the reduction of 5 percent is about 9.8 percent.

Split tensile strength test

Test method

The splitting tensile strength test is carried out according to relevant requirements in the national standard 'ordinary concrete mechanical property test method' (GB/T50081-2016), a cubic test piece of 150mm x150mm is manufactured, the test piece is maintained for 28d under standard maintenance conditions, a YES-300 digital display type hydraulic pressure tester is used for carrying out the test in a strength test room, and the specific test steps are as follows:

(1) taking out the test piece after maintenance from the maintenance pool, and drying and cleaning the surface of the test piece;

(2) carrying out center line marking processing on the surface of the test piece;

(3) placing an arc base plate and a three-layer plywood base strip (the base strip is cut into a shape with the width of 20mm and the length of not less than 150mm by a wood plate cutting knife before the test) on a lower bearing plate of a testing machine;

(4) aligning the center line of the side bearing surface of the test piece with the center of the lower bearing plate, placing the arc-shaped base plate and the backing strip of the upper bearing plate, and adjusting the upper bearing plate of the press machine to contact with the test piece;

(5) opening a switch of the testing machine, loading at a loading speed of 0.05-0.08 MPa/s until the test piece is damaged, and recording damage load data;

(6) a splitting tensile strength calculation formula specified by a specification;

in the formula (I); f. of_ts-concrete split tensile strength (MPa); f-breaking load (N) of the test piece;

a-area of cleavage plane of test piece (mm 2);

test data

In the test, 10 groups of test pieces are manufactured according to the test scheme, the total number of the test pieces is 30, the test values are calculated according to the calculation method in the standard of the ordinary concrete mechanical test method (GB/T50081-2016), and the cleavage tensile strength data of the waste sintered shale brick powder concrete obtained by calculation is shown in Table 5.

TABLE 5 tensile strength at split

Assay analysis

The obtained test data are analyzed, and the influence of the replacement of the waste sintered shale brick powder for cement on the splitting tensile strength of the concrete is found to be small. The tensile strength of common concrete is 1/10-1/20 of the cubic compressive strength of the common concrete, and the highest strength of 10 groups of test pieces is L4(4.25 MPa); when the brick powder with the fineness of 0.08mm is used at the substitution rate of 5%, the splitting strength is highest (3.48MPa), the substitution rate of 20% is equal to that of common concrete, and the splitting strength of the concrete with the substitution rate of 10% is lower than that of the common concrete and is reduced by 9.8%; the cleavage strength of the brick powder with the fineness of 0.10mm is higher than that of common concrete at 5% and 20% of substitution rate, the increase value of 20% is as high as 26.8%, the cleavage strength value of 10% of substitution rate is lower than that of common concrete, and the reduction rate is 13.1%. The brick powder with the fineness of 0.15mm has the slightly lower degree at the substitution rate of 5 percent than that of common concrete, and the brick powder with the fineness of 10 percent and 20 percent than that of the common concrete. See fig. 5(A, B), fig. 6.

Flexural strength test

In order to research and determine the flexural strength of the waste sintered shale brick powder concrete, according to the relevant requirements in the flexural strength test national standard 'ordinary concrete mechanical property test method' (GB/T50081-2016), a cubic test piece of 150mm x 600mm is manufactured, the test piece is maintained for 28 days under the standard maintenance condition, a YES-300 digital display type hydraulic pressure tester is used for testing in a strength test room, and the specific test steps are as follows:

(2) marking the surface of the test specimen with a marking line

(3) Adjusting a support of the testing machine to a proper position;

(4) aligning a marking line of a test piece with a support of the testing machine, and adjusting an upper bearing plate of the pressing machine to enable the upper bearing plate to be in contact with the test piece;

(6) the formula for calculating the splitting tensile strength specified by the specification is as follows:

in the formula: f. of_tFlexural strength (MPa), breaking load (N) of the F-test specimen, l-span between supports (mm), h-section height of the specimen (mm), b-section width of the specimen (mm)

Test results

In the test, 10 groups of test pieces are manufactured according to the test scheme, the total number of the test pieces is 30, the test values are calculated according to the calculation method in the standard of the general concrete mechanical test method (GB/T50081-2016), and the flexural strength data of the waste sintered shale brick powder concrete obtained by calculation is shown in Table 6.

TABLE 6 flexural Strength test data

Assay analysis

Analysis of test data shows that the breaking load of 10 groups of test specimens reaches 1/5-1/10 of cubic compressive strength, the breaking strength of only Z1 group is slightly lower than that of common concrete, the reduction rate is about 8.2%, and the breaking strength of Z2 group is the highest (5.58MPa) and is about 11.8% higher than that of common concrete. Therefore, analysis of test data shows that partial replacement of cement by the waste sintered shale brick powder has little influence on the flexural resistance of concrete, and the flexural strength of the waste sintered shale brick powder is improved to a certain extent, so that the waste sintered shale brick powder concrete is favorably influenced. See fig. 7(A, B), fig. 8.

Modulus of elasticity test

Test method

The partial replacement of cement by the waste sintered shale brick powder can not influence the deformation state of concrete for researching. According to the test requirements in the national standard of general concrete mechanical property test method standard (GB/T50081-2016), a 150mmx150mmx300mm prism is manufactured in a laboratory for testing. In the test, 10 groups of test pieces are manufactured, each group comprises 6 test pieces, the total number of the test pieces is 60, and the test pieces are maintained under the standard condition. Of the 6 test pieces in each group, 3 were used for the axial compressive strength test and 3 were used for the elastic modulus test. This test was carried out in a strength laboratory using a TYE-A type digital display electrohydraulic compression tester.

The calculation formula of the elastic modulus of the concrete is as follows:

in the formula:

E_c-concrete modulus of elasticity (MPa);

F₀-an initial load (N) at a stress of 0.5 MPa;

a-test piece bearing area (mm2)⁾；

L-measurement mark (mm);

Δn＝εa

in the formula:

last time from F₀Average (mm) of the deformation of both sides of the test piece when loaded to Fa;

ε_adeformation values (mm) of both sides of the test piece;

ε₀deformation values (mm) of both sides of the test piece;

test results

The test designed 10 test pieces in total, and 60 test pieces in total. In the experiment, when the difference between the axial compressive strength value of the test specimen and the axial compressive strength value of the control load for inspection exceeds 20%, the test value is invalid, the average value of the test values of the other two groups of test specimens is calculated, and if the requirement cannot be met, the group of test values is invalid.

TABLE 7 axial compressive strength values

TABLE 8 modulus of elasticity test data

Assay analysis

The test age of the elastic modulus test specimen in the test is 28d, and the test result is shown in fig. 9, which can be obviously seen from the figure: the elastic modulus of the waste sintered shale brick powder concrete is partially changed under the condition of partial substitution of cement by different substitution rates and fineness. Under the condition of unchanged fineness, along with the increase of the substitution rate of the brick powder for the cement, the elastic modulus of the concrete is reduced from 5 percent, 10 percent and 20 percent. The elastic modulus value of the blank control group is 31904.79MPa, and the reduction rate of the brick powder fineness of 0.08mm is 7%, 13% and 21% in sequence by taking the elastic modulus value as a reference; the brick powder fineness of 0.10mm is taken as an example, and the reduction rates are found to be 9.7%, 14% and 16% in sequence; the reduction rate of the concrete with the brick powder fineness of 0.15mm is 15 percent, 17 percent and 18 percent in sequence. At the same substitution rate, the change in elastic modulus was not significant.

Full immersion water absorption test

The water absorption test tests the age of the test piece to be 28 d. During testing, firstly, drying a test piece with a maintenance expiration period by using a drying box, then placing the dried test piece in a water tank, adding water until the test piece is completely immersed, continuously adding water until the water level is about 30mm higher than the surface of the test piece, stopping adding water, weighing the test piece at intervals of 24h by taking the water level as a time axis, recording the mass of the test piece, and stopping the test when the mass of the test piece is not increased. Analysis on the data shows that the water absorption of the concrete doped with the waste sintered shale brick powder is basically the same as that of the common concrete, and is about 2 percent.

TABLE 9 test value of concrete full-immersion water absorption

Table9Testvalueoftotalimmersionwaterabsorptionofconcrete

Tests show that when the fineness of the waste sintered shale brick powder is the same, the overall rule is as follows under different substitution rates: the water absorption of the concrete gradually increases with the increase of the substitution rate of the brick powder. The water absorption of the powdered brick concrete with a fineness of 0.08mm is lower than that of the reference group as a whole. Under the different substitution rates of 5%, 10% and 20%, the reduction rates of the brick powder with the fineness of 0.08mm are 4.9%, 3.0% and 1.97% in sequence. The surface of the ground brick powder is zigzag and not smooth, can be well occluded with other materials of concrete, and can play a good role in filling pores, which is more obvious when the fineness of the brick powder is smaller. The smaller the fineness of the brick powder is, the larger the surface area of the brick powder is, the larger the contact area with a cement material is, and the hydration effect of the cement is further promoted.

Under the condition that the substitution rate of the brick powder is the same, the water absorption rate of the brick powder concrete is increased along with the increase of the fineness of the brick powder. Taking the substitution rate of brick powder of 5% as an example, the water absorption rate reduction rates of the brick powder with the fineness of 0.08mm, 0.10mm and 0.15mm are 4.9%, 2.5% and 0.09% in sequence. The water absorption of the concrete having a substitution rate of 10% is more than that of the general concrete at a fineness of 0.15 mm. The small amount of the brick powder can promote the hydration of cement to a certain extent, but when the amount is large, the hydration of cement is inhibited, so that the water absorption rate is increased.

Overview of microscopic examination

This test was performed using a femtocel scanning electron microscope (full-automatic electron microscope). The specific test steps are as follows:

(1) selecting a sample part with proper size and material from a test sample, and fixing the selected sample on a nail-shaped sample table by using conductive adhesive;

(2) carrying out metal spraying treatment on the selected concrete material sample;

(3) clamping a sample by using a special forceps, vertically inserting the sample into the sample ring, and rotating the metal ring clockwise to enable the highest point of the sample to be level with the plane of the ring buckle; continuously rotating the four scales to enable the sample to descend by four 20 mm; opening the cabin door, inserting the sample ring, and closing the cabin door when the sample lamp is automatically turned on;

(4) adjusting various parameters of an electron microscope to achieve a proper photographing mode, switching to the electron microscope mode, adjusting the electronic competition multiple, and photographing a test sample;

(5) the sample was unloaded.

Scanning test by electron microscope

Powder electron microscope scanning test for waste sintered shale bricks

The waste sintered shale sticky powder is used as a research object of the test, and the apparent characteristics of the waste sintered shale sticky powder are analyzed through electron microscope scanning tests under different times, so that the influence research on the concrete performance is researched.

As can be clearly seen from 2000-fold electron microscope pictures (figure 10-A, figure 10-B and figure 10-C) of the brick powder with different fineness, the uniformity of the brick powder is smaller and smaller along with the increase of the fineness, more large particles exist in brick powder particles which are obviously seen in the brick powder with 0.15mm, and the particle distribution of the brick powder with 0.08mm is more uniform.

As can be seen from the magnified electron microscope pictures of the brick powder with different fineness, because the waste sintered shale brick powder is obtained after the brick body is crushed, the instrument is continuously ground and sieved, the fractures on the surface of the waste sintered shale brick powder are not regular and have irregular shapes. The surface characteristics of the brick powder can enhance the mechanical interlocking action among various materials when the waste sintered shale brick powder concrete is formed, thereby improving various excellent performances of the waste sintered shale brick powder concrete. This is well verified in the mechanical properties studies described above.

From the microscopic image analysis of 1 group, 2 groups and 3 groups of doped brick powder in the 12-14 microscopic images, when the fineness of the brick powder is 0.08mm, along with the increase of the substitution rate of the brick powder, the micro cracks exist in the concrete of the brick powder in the three groups from the enlarged microscopic images, but the width of the micro cracks is reduced compared with that of the common concrete. The analysis shows that the brick powder with irregular surface shape enhances the cementation with cement materials, so that the viscosity of concrete materials formed by adding the brick powder is increased, and the mechanical occlusion effect is enhanced. The analysis of the slump of the freshly mixed brick powder concrete combined with the development situation of cracks shows that the addition of the brick powder increases the viscosity of the freshly mixed concrete, so that the occlusion effect among materials is enhanced, and the filling effect is obvious. The micro cracks generated in the early stage of the poured concrete are reduced to a certain degree, and the method is favorable for the mechanical property of the waste sintered shale brick powder concrete.

From the microscopic analysis of the 0 group of ordinary concrete in fig. 11-a and 11-B, it is found that when the cement is not partially replaced by the waste sintered shale brick powder, many dense small holes are distributed in the interior of the concrete structure test piece, and the gaps are partially communicated, but the distribution is not uniform and has different sizes. Therefore, the porosity of the concrete test piece is large, and the use function of the concrete structure is greatly reduced.

From the microscopic image analysis of the 1 group of brick dust concrete of fig. 12-a and 12-B, it is found that after the cement is partially replaced by the brick dust of 0.08mm, under the condition of 5% substitution rate, compared with the internal structure of the ordinary concrete, the internal porosity concentration of the brick dust concrete is obviously reduced, the internal defects are reduced, the compactness of the concrete structure is enhanced, and the use of the brick dust concrete is favorably influenced.

From the microscopic image analysis of the 2 groups of brick powder concrete in fig. 13-a and fig. 13-B, after the brick powder with 0.08mm is partially substituted for the cement, under the condition of 10% substitution rate, compared with the internal structure of the common concrete, the internal pores of the brick powder concrete structure are not much different from the common concrete, the internal distribution is more, the part is communicated but the shape is irregular, and the compactness is not much different.

From the microscopic image analysis of the 3 sets of brick dust concrete of fig. 14-a and 14-B, it is found that after the cement is partially replaced by the brick dust of 0.08mm, under the condition of 15% substitution rate, compared with the internal structure of the ordinary concrete, the brick dust concrete has relatively fewer structural voids and cracks and higher compactness.

The brick powder concrete of the

groups

1, 2 and 3 is analyzed, and the concrete with the 10% substitution rate has more pores, so that the formed brick powder concrete structure is loose, the strength is reduced, and the result is consistent with the test result of the cubic compressive strength.

The analysis and summary of the microscopic images show that compared with the common concrete of group 0, the concrete cast and molded by replacing cement with the waste sintered shale brick powder has small and dense pores, and the concrete doped with the brick powder has small pore density. From the microscopic analysis of the brick dust concretes of groups 1 (FIG. 12-A, FIG. 12-B), 4 (FIG. 15-A, FIG. 15-B) and 7 (FIG. 16-A and FIG. 16-B), it was found that under the condition of the same substitution rate, the compactness of the brick dust concrete of 0.08mm is the highest, the compactness of the concrete of the brick dust substitution rates of 0.01mm and 0.15mm is relatively lower, and the substitution rate of the brick dust of 0.01mm is more compact than that of the brick dust of 0.15 mm.

Research on influence of waste sintered shale brick powder on internal structure of concrete

From the comparison analysis of the ordinary concrete in FIG. 17-A, it was found that when no brick powder is added, the product of the ordinary concrete after hydration of cement is mainly connected by C-S-H gel with different forms, there are lots of needle-like ettringite with different lengths among the gaps of CSH gel, and it can be seen from the picture that these needles are mainly distributed on the periphery of some holes or pores, and at the same time, some hexagonal plate-like Ca (OH) are spread on the surface of the hydration product₂. From the micro-morphology picture of the hydration product in the picture, it can be found that the internal structure of the common concrete is relatively loose, has more pores and cracks, and has low compactness.

From the picture of fig. 17-B, it is found that after a part of the brick powder is added to replace cement, most of CSH gels connected in series are connected on the surface of the hydration product in the brick powder concrete, even the CSH gels are distributed in a flaky shape, the CH spread on the surface is obviously increased, but needle-shaped hydration product ettringite is difficult to find from the CSH gels, which indicates that the added brick powder promotes the hydration of the cement to a certain extent, the hydration product is increased to make the surface compact, and the ettringite is covered, so that the excellent performance of the brick powder concrete is improved to a certain extent.

It is found from the pictures in fig. 18-a and 18-B that the distribution of the hydration products is not very different from that of the ordinary concrete, calcium silicate hydrate gels with different shapes on the surfaces are connected with each other, a large amount of acicular ettringite with different shapes and sizes are distributed around the holes and gaps, and calcium hydroxide crystals are scattered on different positions on the surfaces. The internal structure of the powdered concrete formed from these dispersed gels and irregularly shaped, acicular ettringite is not favorably improved, and the functional effects of the concrete in use are far from being affected.

In conclusion, the pictures of different magnifications of a scanning electron microscope show that the partial replacement of the cement by the waste sintered shale brick powder can fully play the mechanical occlusion of the brick powder to the cement material and the filling effect of the brick powder to concrete pores, reduce the development of internal microcracks at the initial stage of concrete pouring, reduce the internal porosity of the concrete, promote the hydration of the cement to a certain extent, increase the compactness of the concrete, and further improve the excellent performance of the concrete.

Therefore, the concrete is feasible to be prepared by mixing a certain amount of waste sintered shale brick powder with specific fineness.

After further research, the applicant finds that magnesium borate, zirconium oxide, hydroxypropyl methyl cellulose, bentonite and mica replace part of cement besides waste sintered shale brick powder replaces part of cement, the total substitution rate accounts for 4-5%, and results of detection show that the cubic compressive strength, the splitting strength, the breaking strength and the elastic modulus of the obtained concrete are improved.

Comparative example 1: the preparation scheme is the same as that of example 1, except that magnesium borate, zirconium oxide, hydroxypropyl methyl cellulose, bentonite and mica are replaced by waste sintered shale brick powder instead of part of cement.

Comparative example 2: the raw materials were the same as in example 1, except that the ultrasonic oscillation was not performed in the step, and the raw materials were stirred uniformly by a general stirring method.

The products prepared in examples 1 to 3 of the present application were subjected to performance testing, and the tested products all used:

from the above table, it can be seen that the physical properties are improved to some extent by further studying the improved formula, ratio and process.

Although the present invention has been described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. The method for preparing the brick powder concrete by using the waste sintered shale brick powder is characterized by comprising the following steps:

(4) weighing the following raw materials in parts by weight: cement 359-445 weight parts, medium sand 600-620 weight parts, stone 1100-1185 weight parts, water 190-210 weight parts, waste sintered shale brick powder 24-96 weight parts, magnesium borate 3-5 weight parts, zirconium oxide 3-5 weight parts, hydroxypropyl methyl cellulose 3-5 weight parts, bentonite 4-5 weight parts, mica 4-5 weight parts; (ii) a

(5) Mixing cement, medium sand, pebbles, water, waste sintered shale brick powder, magnesium borate, zirconia, hydroxypropyl methyl cellulose, bentonite and mica, and performing oscillation stirring by using 100-plus-200 Hz ultrasonic waves to obtain mixed slurry; the water-cement ratio of the mixed slurry is 0.42-0.45;

2. The method for making brick powder concrete by using the waste sintered shale brick powder as claimed in claim 1, wherein the method comprises the following steps: the sintered shale brick powder comprises the following chemical components in percentage by mass: SiO 2₂54.35-55.48％；Fe₂O₃10.21-11.82％；Al₂O₃14.22-15.31％；CaO₂10-2.52%; MgO1.00-1.20%, and the balance of other impurities.

3. The method for making brick powder concrete by using the waste sintered shale brick powder as claimed in claim 1, wherein the method comprises the following steps: the particle size of the stones is 18-22 mm.

4. The method for making brick powder concrete by using the waste sintered shale brick powder as claimed in claim 1, wherein the method comprises the following steps: the cement is ordinary portland cement with the strength grade of 42.5 MPa.

5. The method for making brick powder concrete by using the waste sintered shale brick powder as claimed in claim 1, wherein the method comprises the following steps: weighing the following raw materials in parts by weight: 400 parts of cement, 610 parts of medium sand, 1135 parts of stones, 200 parts of water, 48 parts of waste sintered shale brick powder, 4 parts of magnesium borate, 4 parts of zirconium oxide, 4 parts of hydroxypropyl methyl cellulose, 4.5 parts of bentonite and 4.5 parts of mica.