CN111751188B - A Mesoscopic Fracture Mechanics Analysis Method for Large-volume Rubber Concrete - Google Patents

Abstract

The invention discloses a microscopic fracture mechanics analysis method of large-doped rubber concrete, which comprises the following steps: preparing a test piece, pretreating the test piece, slicing and scanning the test piece, simulating a microscopic structure of the test piece, and analyzing and comparing a real test with a simulated test; according to the invention, the cubic test piece with different rubber doping amounts is prepared through reasonable raw material proportion, the test piece is pretreated to be conveniently scanned by a full-automatic panoramic fluorescence microscope, so that the porosity of concrete is conveniently observed, the influence of the rubber doping amount on the mechanical property of the rubber concrete is further analyzed based on a microstructure, then the microstructure of the test piece is simulated according to a scanning image of a sample slice to generate a microstructure model of the rubber concrete, and then the real test of the test piece is analyzed and compared with the simulation test of the microstructure model of time, so that the influence of the rubber doping amount on the macroscopic fracture performance of the rubber concrete is analyzed based on the microstructure, and the method has better applicability and accuracy.

Description

A Mesoscopic Fracture Mechanics Analysis Method for Large-volume Rubber Concrete

technical field

The invention relates to the technical field of material performance analysis, in particular to a method for analyzing mesoscopic fracture mechanics of large-volume rubber concrete.

Background technique

Rubber concrete is a concrete formed by mixing and curing rubber emulsion and auxiliary admixtures with cement when preparing cement mortar or concrete. It has excellent impact resistance and wear resistance, and can better solve the problem of recycling waste rubber products. Compared with ordinary concrete, rubber concrete has better performance in terms of abrasion resistance, crack resistance, seepage resistance, frost resistance, and earthquake resistance, and can effectively reduce the use of natural aggregates and the accumulation of waste rubber products. It has a good application prospect in engineering, but with the increase of rubber content, the strength of rubber concrete continues to decrease, which limits its engineering application to a certain extent;

In order to promote the popularization and application of large-volume rubber concrete in water conservancy, civil engineering, transportation and other practical projects, it is necessary to analyze the fracture performance of rubber concrete to reveal the mechanism of rubber concrete fracture performance and prolong the service life of rubber concrete structures. There are few analyzes on the fracture process mechanism of large-volume rubber concrete, and most of the analysis results are not representative, because the macroscopic performance of material properties is often inseparable from its mesomechanics, and mesoscopic numerical simulation can effectively reflect the structure under load. Therefore, the present invention proposes a mesoscopic fracture mechanics analysis method of large-volume rubber concrete to solve the problems existing in the prior art.

Contents of the invention

For the problems referred to above, the object of the present invention is to propose a method for analyzing the mesoscopic fracture mechanics of large-volume rubber concrete. The multiphase composite material composed of the aggregate-mortar interface transition zone and the initial defects of the interface, and then based on the real microstructure of the rubber concrete interface, the two-dimensional rubber concrete mesostructure was established, so as to characterize the effect of rubber content on the rubber concrete macroscopic structure through the microstructure. The impact of fracture properties makes this analysis method have better applicability and accuracy.

In order to achieve the purpose of the present invention, the present invention is achieved through the following technical solutions: a method for analyzing the mesoscopic fracture mechanics of large-volume rubber concrete, comprising the following steps:

Step 1: Test piece preparation

Put Portland cement, fine aggregate, coarse aggregate, rubber granules and water into the mixer according to the specified ratio and mix them. After mixing evenly, it is poured into a shape with a length, width and height of 100×100×100mm and rubber granules. Different rubber concrete cube specimens, and then put the rubber concrete cube specimens with different rubber particle content obtained by pouring into the standard curing room for curing, and the curing period is 28 days;

Step 2: Specimen pretreatment

According to step 1, firstly take out the cube specimen whose curing age has reached and cut out a specimen slice whose length, width and height are 100×100×15 mm respectively, and use an automatic grinding and polishing machine to polish the observation surface of the specimen slice, and then Clean the polished sample slices and dry the surface water stains after cleaning, then put the dried sample slices into a vacuum drying oven for full drying, and then put the dried sample slices into a vacuum Vacuumize the dipping box and pour epoxy resin mixed with fluorescent powder to complete the impregnation. After impregnation, take out the sample slice and apply a layer of epoxy resin on the observation surface. After standing for 35 minutes, scrape off the residual epoxy resin on the surface And carry out secondary grinding on the sample slice;

Step 3: Sample slice scanning

According to step 2, scan the panoramic microscopic image of the sample slices with different rubber content after secondary grinding through the automatic panoramic fluorescence microscope and obtain the panoramic microscopic image of the observation surface, and then use the obtained panoramic microscopic image Observing the porosity of the sample slices with different dosages, the effect of the dosage of rubber particles on the mechanical properties of rubber concrete is obtained;

Step 4: Simulation of the mesostructure of the specimen

According to the third step, the coarse aggregate and rubber are placed on the two-dimensional plane through the Matlab software according to the panoramic microscopic image, and the coarse aggregate is simplified into a polygon based on the real structure, and the rubber is simplified into a circle for model building, and then according to The distribution of coarse aggregate and rubber is based on the Monte Carlo method, and the particle flow analysis program is written based on Matlab software to generate a two-dimensional rubber concrete rubber and coarse aggregate structure model, and further obtain the position information of the generated rubber and coarse aggregate particles. Expand a certain width, and then write a program to generate the rubber-mortar interface and coarse aggregate-mortar interface. After running, retrieve the center coordinates and radius of the rubber and rubber-mortar interface, and the multi-point position coordinates of the coarse aggregate and coarse aggregate-mortar interface. Then, after obtaining the position coordinates of the materials of each phase, based on the parametric design language of ANSYS software, the establishment of the mortar matrix and rubber, coarse aggregate, rubber-mortar interface transition zone, and coarse aggregate-mortar interface transition zone is completed, and finally the fine rubber concrete is generated. Visual structure model;

Step 5: Analysis and comparison between real test and simulated test

According to step 4, first use the universal testing machine to conduct real fracture strength tests on cube specimens with different rubber content and record the experimental results, and then simulate the fracture strength of the rubber concrete mesostructure model according to the real test Test and store the experimental conclusions, then compare and analyze the real test results and simulation test conclusions, and obtain the relationship between the mesomechanics and macroscopic performance of the fracture performance of rubber concrete with different dosages.

The further improvement is: in the first step, the coarse aggregate is mixed with limestone pebbles with a particle size of 5-10mm and large limestone stones with a particle size of 10-20mm in a ratio of 3:7, and the rubber particles are shredded from waste tires The obtained rubber crumbs with a particle diameter of 3-6mm, the fine aggregate is natural river sand.

The further improvement is: in the step 2, in the polishing process of the sample slice, the grinding material with a specification of 300# is firstly used for grinding for 20 minutes, and then the abrasive material with a specification of 800# is used for grinding for 10 minutes, and finally the grinding medium with a specification of 1000# is used. The grinding material of # was polished for 5 minutes, and the speed of the automatic grinding and polishing machine was set to 50r/min during the grinding process.

The further improvement is: in the second step, the vacuum degree in the vacuum drying oven is kept above 0.9, the temperature of the vacuum drying oven is set to 40°C, and the sample slices are taken out every 6 hours during the drying process for weighing. The drying is completed when the mass loss of slices is less than 0.1g within 24 hours.

The further improvement is: in the step 3, when scanning the sample slice, the selected sample slice observation area is within the range of 90mm×90mm, and at the same time, the observation area is divided into nine equal parts for observation, and the scanned image consists of nine All pixels are stitched together from 12664×12664 sub-images.

The further improvement is: in the step 4, the two-dimensional transformation formula conforming to the three-dimensional Fuller gradation curve derived by Walraven J.C based on the method of probability and statistics is used to ensure the convenience of two-dimensional rubber concrete numerical simulation. The formula is

In the formula, Pc is the probability that any point on the rubber concrete section has a diameter _d <d ₀ , P _K is the percentage of particle volume in the total volume of rubber concrete, d is the actual particle size required, and d ₀ is the limited particle size diameter, _dmax is the largest particle size.

The beneficial effects of the present invention are as follows: the present invention firstly prepares rubber concrete cube specimens with different rubber content through reasonable raw material ratio, and then cuts, polishes, cleans, dries, vacuum impregnates and grinds the specimens twice. The treatment makes the sample slices easy to be scanned and observed by a fully automatic panoramic fluorescence microscope, so that it is convenient to observe the porosity of the concrete, and then analyze the influence of the amount of rubber added on the mechanical properties of the rubber concrete based on the microstructure, and then carry out according to the scanned images of the sample slices. The mesoscopic structure of the specimen is simulated and the rubber concrete microstructure model is generated, and then the real test of the specimen is analyzed and compared with the simulation experiment of the mesostructural model of time, so that based on the mesostructure analysis of the effect of the rubber content on the rubber concrete In this method, the rubber concrete is regarded as a multiphase composite material composed of rubber, coarse aggregate, mortar matrix, rubber-mortar interface transition zone, coarse aggregate-mortar interface transition zone, and initial defects in the interface. Based on the real microstructure of the rubber-concrete interface, the two-dimensional rubber-concrete mesostructure is established, so as to characterize the effect of rubber content on the macro-fracture properties of rubber-concrete through the mesostructure, so that the analysis method has good applicability and accuracy.

Description of drawings

Fig. 1 is a flow chart of steps of the present invention.

detailed description

In order to deepen the understanding of the present invention, the present invention will be further described below in conjunction with the examples, which are only used to explain the present invention, and do not constitute a limitation to the protection scope of the present invention.

As shown in Figure 1, the present embodiment provides a method for analyzing the mesoscopic fracture mechanics of large-volume rubber concrete, comprising the following steps:

Step 1: Test piece preparation

Portland cement, fine aggregate composed of natural river sand, limestone pebbles with a particle size of 5-10mm and large limestone stones with a particle size of 10-20mm are mixed in a ratio of 3:7 to form a coarse aggregate. The 3-6mm rubber particles and water obtained by chopping waste tires are put into the mixer according to the specified ratio for stirring and mixing. Rubber concrete cube specimens, and then put the rubber concrete cube specimens with different rubber particle content obtained by pouring into the standard curing room for curing, and the curing period is 28 days;

Step 2: Specimen pretreatment

According to step 1, first take out the cube test piece that has reached the curing age and cut out a sample slice with a length, width, and height of 100×100×15mm, and use an automatic grinding and polishing machine to polish the observation surface of the sample slice. In the process, the grinding material with a specification of 300# is firstly used for grinding for 20 minutes, then the grinding material with a specification of 800# is used for grinding for 10 minutes, and finally the grinding material with a specification of 1000# is used for grinding for 5 minutes. During the grinding process, the speed of the automatic polishing machine is uniform. Set it to 50r/min, then clean the polished sample slices and dry the surface water stains after cleaning, then put the dried sample slices into a vacuum drying oven for full drying, the drying process The vacuum degree in the medium-vacuum drying oven is kept above 0.9, and the temperature is set at 40°C. During the drying process, the sample slices are taken out every 6 hours and weighed. When the mass loss of the sample slices is less than 0.1g within 24 hours, the drying is completed. , and then put the dried sample slices into a vacuum impregnation box to evacuate and pour epoxy resin mixed with fluorescent powder to complete the impregnation. After the impregnation, take out the sample slices and apply a layer of epoxy resin on the observation surface, statically After standing for 35 minutes, scrape off the residual epoxy resin on the surface and perform secondary grinding on the sample slice;

Step 3: Sample slice scanning

According to step 2, first scan the panoramic microscopic images of the sample slices with different rubber content after secondary grinding through the automatic panoramic fluorescence microscope and obtain the panoramic microscopic images of the observation surface. When scanning the sample slices, The selected sample slice observation area is within the range of 90mm×90mm, and the observation area is divided into nine equal parts for observation. The scanned image is composed of nine sub-images whose pixels are all 12664×12664, and then through the acquired The porosity of sample slices with different dosages was observed by panoramic microscopic images, and the effect of the dosage of rubber particles on the mechanical properties of rubber concrete was obtained;

Step 4: Simulation of the mesostructure of the specimen

According to the third step, the coarse aggregate and rubber are placed on the two-dimensional plane through the Matlab software according to the panoramic microscopic image, and the coarse aggregate is simplified into a polygon based on the real structure, and the rubber is simplified into a circle for model building, and then according to The distribution of coarse aggregate and rubber is based on the Monte Carlo method, and the particle flow analysis program is written based on Matlab software to generate a two-dimensional rubber concrete rubber and coarse aggregate structure model, and further obtain the position information of the generated rubber and coarse aggregate particles. Expand a certain width, and then write a program to generate the rubber-mortar interface and coarse aggregate-mortar interface. After running, retrieve the center coordinates and radius of the rubber and rubber-mortar interface, and the multi-point position coordinates of the coarse aggregate and coarse aggregate-mortar interface. Then, after obtaining the position coordinates of the materials of each phase, based on the parametric design language of ANSYS software, the establishment of the mortar matrix and rubber, coarse aggregate, rubber-mortar interface transition zone, and coarse aggregate-mortar interface transition zone is completed, and finally the fine rubber concrete is generated. In order to ensure the convenience of two-dimensional rubber concrete numerical simulation in the process of model simulation, the two-dimensional conversion formula derived by WalravenJ.C based on the method of probability and statistics conforms to the three-dimensional Fuller grading curve, and the formula is

In the formula, Pc is the probability that any point on the rubber concrete section has a diameter _d <d ₀ , P _K is the percentage of particle volume in the total volume of rubber concrete, d is the actual particle size required, and d ₀ is the limited particle size diameter, d _max is the largest particle size;

Step 5: Analysis and comparison between real test and simulated test

According to step 4, first use the universal testing machine to conduct real fracture strength tests on cube specimens with different rubber content and record the experimental results, and then simulate the fracture strength of the rubber concrete mesostructure model according to the real test Test and store the experimental conclusions, then compare and analyze the real test results and simulation test conclusions, and obtain the relationship between the mesomechanics and macroscopic performance of the fracture performance of rubber concrete with different dosages.

The mesoscopic fracture mechanics analysis method of large-volume rubber concrete first prepares rubber concrete cube specimens with different rubber content through reasonable raw material ratio, and then cuts, grinds, cleans, dries, vacuum-impregnates and The secondary grinding treatment makes the sample slices easy to be scanned and observed by a fully automatic panoramic fluorescence microscope, so that it is convenient to observe the porosity of the concrete, and then analyze the influence of rubber content on the mechanical properties of rubber concrete based on the microstructure, and then according to the sample slices Scan the image to simulate the mesostructure of the specimen and generate a rubber concrete mesostructure model, then analyze and compare the real test of the specimen with the simulation experiment of the mesostructure model of time, so as to analyze the amount of rubber incorporated based on the mesostructure Influence on the macro-fracture properties of rubber concrete, this method regards rubber concrete as a multiphase consisting of rubber, coarse aggregate, mortar matrix, rubber-mortar interface transition zone, coarse aggregate-mortar interface transition zone, and initial defects in the interface Composite materials and based on the real microstructure of the rubber-concrete interface, the two-dimensional rubber-concrete mesostructure was established, in order to characterize the effect of rubber content on the macro-fracture properties of rubber-concrete through the microstructure, so that the analysis method has good applicability and accuracy.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (6)

1. A method for analyzing the microscopic fracture mechanics of large-doped rubber concrete is characterized by comprising the following steps: the method comprises the following steps:

the method comprises the following steps: preparation of test pieces

Putting portland cement, fine aggregate, coarse aggregate, rubber particles and water into a stirrer according to a specified proportion for stirring and mixing, pouring and molding after uniform mixing to obtain rubber concrete cubic test pieces with length, width and height of 100 multiplied by 100mm and different rubber particle mixing amounts, and then putting the poured rubber concrete cubic test pieces with different rubber particle mixing amounts into a standard curing chamber for curing, wherein the curing age is 28 days;

step two: pretreatment of test pieces

According to the first step, taking out a cubic test piece which is reached in the maintenance age, cutting a test piece slice with the length, width and height of 100 multiplied by 15mm, polishing the observation surface of the test piece slice by using an automatic polishing machine, cleaning the polished test piece slice, wiping the surface water stain after the cleaning is finished, putting the wiped test piece slice into a vacuum drying box for fully drying, putting the dried test piece slice into a vacuum impregnation box for vacuumizing, filling epoxy resin doped with fluorescent powder for finishing impregnation, taking out the test piece slice after the impregnation is finished, coating a layer of epoxy resin on the observation surface of the test piece slice, standing for 35 minutes, scraping the residual epoxy resin on the surface, and performing secondary polishing on the test piece slice;

step three: specimen slice scanning

According to the second step, firstly, scanning panoramic microscopic images of sample slices with different rubber mixing amounts after secondary polishing through a full-automatic panoramic fluorescence microscope, obtaining the panoramic microscopic images of observation surfaces of the sample slices, and observing the porosity of the sample slices with different mixing amounts through the obtained panoramic microscopic images to obtain the influence of the mixing amount of the rubber particles on the mechanical property of the rubber concrete;

step four: test piece mesoscopic structure simulation

According to the third step, firstly, according to a panoramic microscopic image, throwing the coarse aggregate and the rubber on a two-dimensional plane through Matlab software, simplifying the coarse aggregate into a polygon based on a real structure, simplifying the rubber into a circle, establishing a model, writing a particle flow analysis program based on Matlab software by means of a Monte Carlo method according to the distribution rule of the coarse aggregate and the rubber to generate a two-dimensional rubber concrete rubber and coarse aggregate structural model, further acquiring position information of the generated rubber and coarse aggregate particles, expanding the position information to a certain width, then writing the program to generate a rubber-mortar interface and a coarse aggregate-mortar interface, adjusting the center coordinates and the radius of the rubber and rubber-mortar interface after running, obtaining the multipoint position coordinates of the coarse aggregate and the coarse aggregate-mortar interface, then carrying out parametric design language based on ANSYS software after obtaining the position coordinates of each phase of materials, completing establishment of a mortar matrix and rubber, the coarse aggregate, the rubber-mortar interface transition area and the coarse aggregate-mortar interface transition area, and finally generating a rubber concrete microscopic structural model;

step five: analysis and comparison of real test and simulation experiment

According to the fourth step, firstly, a universal testing machine is adopted to carry out real fracture resistance tests on cubic test pieces with different rubber mixing amounts and record the test results, then simulated fracture resistance tests are carried out on the microscopic structure models of the rubber concrete according to the real tests and the test conclusions are stored, and then the real test results and the simulated test conclusions are compared and analyzed to obtain the relationship between microscopic mechanics and macroscopic performances of the fracture performance of the rubber concrete with different mixing amounts.

2. The method for mechanical analysis of microscopic fracture of rubber concrete with large content according to claim 1, wherein the method comprises the following steps: in the first step, the coarse aggregate is formed by mixing small limestone stones with the particle size of 5-10mm and large limestone stones with the particle size of 10-20mm according to the proportion of 3.

3. The method for mechanical analysis of microscopic fracture of rubber concrete with large content according to claim 1, wherein the method comprises the following steps: in the second step, in the polishing process of the sample slice, firstly polishing for 20 minutes by using the abrasive with the specification of 300#, then polishing for 10 minutes by using the abrasive with the specification of 800#, and finally polishing for 5 minutes by using the abrasive with the specification of 1000#, wherein the rotating speed of the automatic polishing machine is set to be 50r/min in the polishing process.

4. The method for mechanical analysis of microscopic fracture of rubber concrete with large content according to claim 1, wherein the method comprises the following steps: and in the second step, the vacuum degree in the vacuum drying oven is kept above 0.9, the temperature of the vacuum drying oven is set to be 40 ℃, sample slices are taken out every 6 hours in the drying process and weighed, and when the mass loss of the sample slices in 24 hours is less than 0.1g, the drying is finished.

5. The method for mechanical analysis of microscopic fracture of rubber concrete with large content according to claim 1, wherein the method comprises the following steps: in the third step, when the sample slice is scanned, the observation area of the selected sample slice is within the range of 90mm multiplied by 90mm, meanwhile, the observation area is equally divided into nine equal parts for observation, and the image obtained by scanning is formed by splicing nine sub-images of which the pixels are 12664 multiplied by 12664.

6. The method for mechanical analysis of microscopic fracture of rubber concrete with large content according to claim 1, wherein the method comprises the following steps: in the fourth step, a two-dimensional conversion formula which is derived by a Walraven J.C probability statistics-based method and accords with a three-dimensional Fuller grading curve is adopted to ensure the convenience of numerical simulation of the two-dimensional rubber concrete, and the formula is

In the formula P _c The diameter d of any point on the cross section of the rubber concrete is less than d ₀ Probability of (P) _K The volume of the particles is the percentage of the total volume of the rubber concrete, d is the actually required particle diameter of the particles, d ₀ For a defined particle size, d _max The largest particle size.

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