CN112748004A - Analysis method for basic mechanics and frost-resistant durability of recycled concrete - Google Patents
Analysis method for basic mechanics and frost-resistant durability of recycled concrete Download PDFInfo
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- 238000004458 analytical method Methods 0.000 title claims description 8
- 238000012360 testing method Methods 0.000 claims abstract description 225
- 230000000399 orthopedic effect Effects 0.000 claims abstract description 37
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- DGVVJWXRCWCCOD-UHFFFAOYSA-N naphthalene;hydrate Chemical compound O.C1=CC=CC2=CC=CC=C21 DGVVJWXRCWCCOD-UHFFFAOYSA-N 0.000 claims description 3
- 239000002002 slurry Substances 0.000 claims description 3
- 238000005303 weighing Methods 0.000 claims description 3
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Abstract
The invention discloses a method for analyzing basic mechanics and frost-resistant durability of recycled concrete, which comprises the following steps: preparing raw materials, preparing a test piece, testing basic mechanical properties, testing anti-freezing durability and analyzing test results; according to the invention, the recycled concrete is prepared by the recycled coarse aggregate, the tests of the compressive strength, the splitting tensile strength and the bending strength are respectively carried out on the recycled concrete test piece and the natural orthopedic concrete, and the test results are compared and analyzed, so that the basic mechanical properties of the recycled concrete and the natural orthopedic concrete are convenient to compare, and the test of the freezing resistance durability and the comparative analysis of the test results are respectively carried out on the recycled concrete test piece and the natural orthopedic concrete, so that the freezing resistance durability of the recycled concrete and the natural orthopedic concrete are convenient to compare, thereby determining the feasibility of applying the recycled aggregate to the engineering structure, and having considerable practical significance on environmental protection, economic growth and social development.
Description
Technical Field
The invention relates to the technical field of concrete material performance analysis, in particular to a method for analyzing basic mechanics and frost-resistant durability of recycled concrete.
Background
The recycled concrete is used for recycling and reusing the waste concrete, as early as two war years, a plurality of developed countries begin to develop, research and recycle the waste concrete, so far, three meetings have been held internationally to discuss the recycling problem of the waste concrete, the recycled concrete has gradually become the subject of research of various countries, some countries, such as Japan, America, Switzerland and the like, also adopt a legislative form to ensure the development of the research and the application thereof, and in China, the economic and environmental-friendly characteristics of the recycled concrete attract the attention of people to the recycled concrete;
although the foreign research on the recycled aggregate and the recycled concrete has achieved great results, the cement and the aggregate used abroad have a certain reference value for researching the recycled concrete and cannot be used for guiding the domestic recycled concrete engineering application, so that the foreign research results have great significance and value for the systematic research on the performance of the recycled concrete, the basic mechanical properties and the frost resistance durability of the recycled concrete are not researched much at present, and the research method is not scientific and rigorous enough, so that the representativeness of the research result is not high.
Disclosure of Invention
In view of the above problems, the present invention is directed to a method for analyzing the basic mechanical and frost-resistant durability of recycled concrete, which comprises testing the compressive strength, the cleavage tensile strength and the bending strength of recycled concrete and natural orthopedic concrete respectively, and comparing the test results, so as to compare the basic mechanical properties of recycled concrete and natural orthopedic concrete, and performing the frost-resistant durability test and the comparative analysis on the test results, so as to compare the frost-resistant durability of recycled concrete and natural orthopedic concrete.
In order to achieve the purpose of the invention, the invention is realized by the following technical scheme: a method for analyzing basic mechanical and frost-resistant durability properties of recycled concrete comprises the following steps:
the method comprises the following steps: raw material preparation
Firstly, crushing waste plain concrete blocks by adopting a crushing tool, sieving the crushed waste plain concrete blocks by a 50-mesh sieve, crushing the large aggregate which is not sieved again, sieving the crushed waste plain concrete blocks by a 25-mesh sieve, controlling the maximum particle size, sieving the coarse aggregate which is sieved below the 25-mesh sieve by a 5-mesh sieve, removing ash scraps and fine particles to prepare regenerated coarse aggregate, preparing cement, fine aggregate, natural coarse aggregate, regenerated coarse aggregate, a first water reducing agent and a second water reducing agent in specified weight parts as raw materials for preparing a regenerated concrete sample according to test requirements, and selecting natural orthopaedic concrete as test reference concrete;
step two: preparation of test pieces
According to the first step, firstly putting the recycled coarse aggregate into a stirrer, then putting 10% of the preset cement dosage into the stirrer, then adding weighed water in advance, stirring for 30 seconds, then sequentially adding sand, cement, a first water reducing agent and water, stirring for 60 seconds, then pouring concrete slurry into a test mould on a vibration table, vibrating and forming according to actual needs, after demoulding, putting into a standard curing room for curing, wherein the indoor temperature of the curing room is 20 +/-5 ℃, the relative humidity is 95 +/-5%, curing for a specified time, taking out, preparing a plurality of groups of recycled concrete test pieces for mechanical property tests, repeating the steps, and replacing the first water reducing agent with a second water reducing agent to prepare a plurality of groups of recycled concrete test pieces for durability tests;
step three: basic mechanical property test
Carry out compressive strength test to mechanical properties test with recycled concrete test piece and natural orthopedics concrete respectively earlier through compression testing machine to calculate the compressive strength of concrete test piece, the calculation formula is:
in the formula fccThe compressive strength is P, the breaking load is P, and the bearing area of the test piece is A;
and then the splitting tensile strength test is carried out on the recycled concrete test piece for the mechanical property test and the natural orthopedic concrete respectively through the universal testing machine, and the splitting tensile strength of the concrete test piece is calculated, and the calculation formula is as follows:
in the formula ftsThe fracture tensile strength is the splitting tensile strength, P is the breaking load, and A is the fracture surface area of the test piece;
then, respectively carrying out the bending strength test on the recycled concrete test piece for the mechanical property test and the natural orthopedic concrete through a pressure testing machine, and calculating the bending strength of the concrete test piece, wherein the calculation formula is as follows:
in the formula ffThe bending strength is P, the breaking load is P, the distance between the supports is l, the width of the section of the test piece is b, and the height of the section of the test piece is h;
step four: freezing resistance durability test
Respectively soaking a recycled concrete test piece for a durability test and natural orthopedic concrete in water for four days, taking out, wiping off water, weighing initial mass, measuring initial natural vibration frequency, then loading the test piece into a test piece box, injecting fresh water to immerse for 2cm, starting a machine to start a freeze-thaw test, detecting the mass and the natural vibration frequency of the test piece once for every 25 times of freeze-thaw cycles, calculating mass loss and relative dynamic elastic modulus, then turning the test piece to reload the test piece into the test piece box, repeating the steps, continuing the test, taking out a measurement test piece after the preset cycle number is reached, testing the mass and the relative dynamic elastic modulus, performing a strength test, and measuring the compression resistance test piece, the split tensile strength and the breaking strength of the concrete after freeze-thaw;
step five: analysis of test results
Firstly, the compressive strength, the splitting tensile strength and the bending strength which are calculated by the recycled concrete test piece for the mechanical property test and the natural orthopedic concrete test are compared and analyzed to obtain the difference of the basic mechanical property of the recycled concrete test piece and the natural orthopedic concrete, and then the anti-freezing durability which is calculated by the recycled concrete test piece for the durability test and the natural orthopedic concrete test is compared and analyzed to obtain the difference of the anti-freezing durability of the recycled concrete test piece and the natural orthopedic concrete.
The further improvement lies in that: in the first step, the strength of the waste plain concrete block is 30-40Mpa, the crushing tool is a hammer of 10 pounds, the cement is ordinary Portland 42.5 cement, the 28 balance average strength is 53.7MPa, the fine aggregate is natural river sand, the natural coarse aggregate is construction site gravel, the particle size is 5mm-20mm, the first water reducing agent is a JM-A type high-efficiency naphthalene water reducing agent, and the second water reducing agent is a construction 4 type air-entraining water reducing agent.
The further improvement lies in that: and in the second step, the recycled coarse aggregate is soaked in water to be saturated before being put into a stirrer and then naturally dried, wherein the stirrer is a JZ250 type forced multifunctional stirrer, and the vibration table is a ZH-1 x 1 type vibration table.
The further improvement lies in that: in the third step, the pressure testing machine is a YA-3000 type electrohydraulic pressure testing machine, the universal testing machine is a WE-300 type hydraulic universal testing machine, the pressure testing machine is a NYL-300C type pressure testing machine, and three-point loading is adopted in the flexural strength test.
The further improvement lies in that: in the fourth step, the recycled concrete test pieces for the freeze resistance durability test are provided with 30 groups, each group is provided with 6 cube test pieces with the size of 100mm multiplied by 100mm and 3 prism test pieces with the size of 100mm multiplied by 400mm, and the number of times of freeze thawing is respectively set to be 0, 50, 75, 125 and 200.
The further improvement lies in that: in the fourth step, the calculation formula of the relative dynamic elastic modulus of the test piece is as follows:
in the formula PnIs the relative dynamic elastic modulus, f, of the test piece after n times of freeze-thaw cycles0Is the natural vibration frequency f before the freeze-thaw cycle of the test piecenThe natural vibration frequency of the test piece after n cycles of freezing and thawing is shown.
The further improvement lies in that: in the fourth step, the mass loss rate calculation formula of the test piece is as follows:
in the formula WnThe mass loss rate of the test piece after n times of freeze thawing cycles, G0The quality of the test specimen before the freeze-thaw cycle, GnThe mass of the test piece after n times of freeze-thaw cycles.
The invention has the beneficial effects that: the invention firstly prepares recycled concrete by recycled coarse aggregate, tests of compressive strength, splitting tensile strength and bending strength are respectively carried out on recycled concrete samples and natural orthopedic concrete, and test results are contrastively analyzed, so that the basic mechanical properties of the recycled concrete and the natural orthopedic concrete are convenient to compare, the frost resistance durability of the recycled concrete and the natural orthopedic concrete are convenient to compare by respectively carrying out the test of frost resistance durability and the comparative analysis of the test results on the recycled concrete samples and the natural orthopedic concrete, and therefore, the feasibility of applying the recycled aggregate to engineering structures can be determined, and the invention has considerable practical significance for environmental protection, economic growth and social development.
Drawings
FIG. 1 is a flow chart of the method of the present invention.
Detailed Description
In order to further understand the present invention, the following detailed description will be made with reference to the following examples, which are only used for explaining the present invention and are not to be construed as limiting the scope of the present invention.
According to FIG. 1, the present embodiment provides a method for analyzing basic mechanical and frost-resistant durability of recycled concrete, comprising the following steps:
the method comprises the following steps: raw material preparation
Firstly, crushing waste plain concrete blocks by adopting a crushing tool, sieving the crushed waste plain concrete blocks by a 50-mesh sieve, crushing the large aggregate which is not sieved again, sieving the crushed waste plain concrete blocks by a 25-mesh sieve, controlling the maximum particle size, sieving the coarse aggregate which is sieved below the 25-mesh sieve by a 5-mesh sieve, removing ash scraps and fine particles to prepare regenerated coarse aggregate, preparing cement, fine aggregate, natural coarse aggregate, regenerated coarse aggregate, a first water reducing agent and a second water reducing agent which are in specified weight parts according to test requirements as preparation raw materials of a regenerated concrete sample, simultaneously selecting natural bone concrete as test reference concrete, wherein the strength of the waste plain concrete blocks is 30-40Mpa, the crushing tool is a 10-pound hammer, the cement is common Portland No. 42.5 cement, the 28 balance average strength is 53.7MPa, the fine aggregate is natural river sand, the natural coarse aggregate is crushed stone, and the particle size is 5-20 mm, the first water reducing agent is a JM-A type high-efficiency naphthalene water reducing agent, and the second water reducing agent is a Jian 4 type air-entraining water reducing agent;
step two: preparation of test pieces
According to the first step, firstly putting the recycled coarse aggregate into a stirrer, then putting 10% of the preset cement dosage into the stirrer, then adding weighed water in advance, stirring for 30 seconds, then sequentially adding sand, cement, a first water reducing agent and water, stirring for 60 seconds, then pouring concrete slurry into a test mould on a vibration table, vibrating and forming according to actual needs, after demoulding, putting into a standard curing room for curing, wherein the indoor temperature of the curing room is 20 +/-5 ℃, the relative humidity is 95 +/-5%, curing for a specified time, taking out, preparing a plurality of groups of recycled concrete test pieces for mechanical property tests, repeating the steps, replacing the first water reducing agent with a second water reducing agent, preparing a plurality of groups of recycled concrete test pieces for durability tests, soaking the recycled coarse aggregate into water for saturation before putting into the stirrer, then naturally airing, and the stirrer is a JZ250 type forced multifunctional stirrer, the vibration table is a ZH-1 × 1 type vibration table;
step three: basic mechanical property test
Firstly, respectively carrying out compressive strength tests on a recycled concrete test piece for mechanical property tests and natural orthopedic concrete through a YA-3000 electrohydraulic pressure tester, and calculating the compressive strength of the concrete test piece, wherein the calculation formula is as follows:
in the formula fccThe compressive strength is P, the breaking load is P, and the bearing area of the test piece is A;
and then, respectively carrying out splitting tensile strength tests on the recycled concrete test piece for the mechanical property test and the natural orthopedic concrete through a WE-300 type hydraulic universal testing machine, and calculating the splitting tensile strength of the concrete test piece, wherein the calculation formula is as follows:
in the formula ftsThe fracture tensile strength is the splitting tensile strength, P is the breaking load, and A is the fracture surface area of the test piece;
and then, respectively carrying out a bending strength test on the recycled concrete test piece for the mechanical property test and the natural orthopedic concrete through an NYL-300C type pressure testing machine, wherein three-point loading is adopted in the bending strength test, the bending strength of the concrete test piece is calculated, and the calculation formula is as follows:
in the formula ffThe bending strength is P, the breaking load is P, the distance between the supports is l, the width of the section of the test piece is b, and the height of the section of the test piece is h;
step four: freezing resistance durability test
Firstly, respectively soaking a recycled concrete test piece for durability test and natural orthopedic concrete in water for four days, taking out, wiping off water, weighing initial mass, measuring initial natural vibration frequency, then placing the test piece into a test piece box, injecting fresh water to immerse the test piece for 2cm, starting a machine to start a freeze-thaw test, detecting the mass and the natural vibration frequency of the test piece for every 25 times of freeze-thaw cycles, calculating mass loss and relative dynamic elastic modulus, then turning the test piece to re-place into the test piece box, repeating the steps, continuing the test, taking out a measurement test piece, measuring the mass and the relative dynamic elastic modulus after reaching the preset cycle number, performing a strength test, and measuring the compression strength, the split tensile strength and the breaking strength of the concrete after freeze-thaw, wherein each group of the recycled concrete test piece for frost-resistant durability test is provided with 30 groups, each group is provided with 6 cubic test pieces of 100mm × 100mm × 100mm and 3 prismatic test pieces of 100mm × 100mm × 400mm, the number of freeze-thaw times is respectively set to 0, 50, 75, 125 and 200;
the relative dynamic elastic modulus calculation formula of the test piece is as follows:
in the formula PnIs the relative dynamic elastic modulus, f, of the test piece after n times of freeze-thaw cycles0Is the natural vibration frequency f before the freeze-thaw cycle of the test piecenThe self-vibration frequency of the test piece after n cycles of freeze thawing is obtained;
the mass loss rate calculation formula of the test piece is as follows:
in the formula WnThe mass loss rate of the test piece after n times of freeze thawing cycles, G0The quality of the test specimen before the freeze-thaw cycle, GnThe mass of the test piece after n times of freeze-thaw cycles.
Step five: analysis of test results
Firstly, the compressive strength, the splitting tensile strength and the bending strength which are calculated by the recycled concrete test piece for the mechanical property test and the natural orthopedic concrete test are compared and analyzed to obtain the difference of the basic mechanical property of the recycled concrete test piece and the natural orthopedic concrete, and then the anti-freezing durability which is calculated by the recycled concrete test piece for the durability test and the natural orthopedic concrete test is compared and analyzed to obtain the difference of the anti-freezing durability of the recycled concrete test piece and the natural orthopedic concrete.
The analysis method of the basic mechanics and the frost-resistant durability of the recycled concrete comprises the steps of firstly preparing the recycled concrete by using recycled coarse aggregate, the basic mechanical properties of the recycled concrete and the natural orthopaedics concrete are convenient to compare by respectively testing the compressive strength, the splitting tensile strength and the bending strength of the recycled concrete test piece and the natural orthopaedics concrete and comparing and analyzing the test results, by respectively carrying out the test on the frost resistance and the durability of the recycled concrete test piece and the natural orthopedic concrete and comparing and analyzing the test results, the frost resistance and the durability of the recycled concrete and the natural orthopedic concrete are convenient to compare, thereby determining the feasibility of applying the recycled aggregate to the engineering structure, the method has considerable practical significance for environmental protection, economic growth and social development, and the method is simple, scientific and rigorous in flow and representative and persuasive in analysis result.
The foregoing illustrates and describes the principles, general features, and advantages of the present invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (7)
1. A method for analyzing basic mechanics and frost-resistant durability of recycled concrete is characterized by comprising the following steps: the method comprises the following steps:
the method comprises the following steps: raw material preparation
Firstly, crushing waste plain concrete blocks by adopting a crushing tool, sieving the crushed waste plain concrete blocks by a 50-mesh sieve, crushing the large aggregate which is not sieved again, sieving the crushed waste plain concrete blocks by a 25-mesh sieve, controlling the maximum particle size, sieving the coarse aggregate which is sieved below the 25-mesh sieve by a 5-mesh sieve, removing ash scraps and fine particles to prepare regenerated coarse aggregate, preparing cement, fine aggregate, natural coarse aggregate, regenerated coarse aggregate, a first water reducing agent and a second water reducing agent in specified weight parts as raw materials for preparing a regenerated concrete sample according to test requirements, and selecting natural orthopaedic concrete as test reference concrete;
step two: preparation of test pieces
According to the first step, firstly putting the recycled coarse aggregate into a stirrer, then putting 10% of the preset cement dosage into the stirrer, then adding weighed water in advance, stirring for 30 seconds, then sequentially adding sand, cement, a first water reducing agent and water, stirring for 60 seconds, then pouring concrete slurry into a test mould on a vibration table, vibrating and forming according to actual needs, after demoulding, putting into a standard curing room for curing, wherein the indoor temperature of the curing room is 20 +/-5 ℃, the relative humidity is 95 +/-5%, curing for a specified time, taking out, preparing a plurality of groups of recycled concrete test pieces for mechanical property tests, repeating the steps, and replacing the first water reducing agent with a second water reducing agent to prepare a plurality of groups of recycled concrete test pieces for durability tests;
step three: basic mechanical property test
Carry out compressive strength test to mechanical properties test with recycled concrete test piece and natural orthopedics concrete respectively earlier through compression testing machine to calculate the compressive strength of concrete test piece, the calculation formula is:
in the formula fccThe compressive strength is P, the breaking load is P, and the bearing area of the test piece is A;
and then the splitting tensile strength test is carried out on the recycled concrete test piece for the mechanical property test and the natural orthopedic concrete respectively through the universal testing machine, and the splitting tensile strength of the concrete test piece is calculated, and the calculation formula is as follows:
in the formula ftsThe fracture tensile strength is the splitting tensile strength, P is the breaking load, and A is the fracture surface area of the test piece;
then, the recycled concrete test piece for mechanical property test is tested through a pressure testerAnd respectively carrying out the bending strength test on the natural orthopedic concrete, and calculating the bending strength of the concrete test piece, wherein the calculation formula is as follows:
in the formula ffThe bending strength is P, the breaking load is P, the distance between the supports is l, the width of the section of the test piece is b, and the height of the section of the test piece is h;
step four: freezing resistance durability test
Respectively soaking a recycled concrete test piece for a durability test and natural orthopedic concrete in water for four days, taking out, wiping off water, weighing initial mass, measuring initial natural vibration frequency, then loading the test piece into a test piece box, injecting fresh water to immerse for 2cm, starting a machine to start a freeze-thaw test, detecting the mass and the natural vibration frequency of the test piece once for every 25 times of freeze-thaw cycles, calculating mass loss and relative dynamic elastic modulus, then turning the test piece to reload the test piece into the test piece box, repeating the steps, continuing the test, taking out a measurement test piece after the preset cycle number is reached, testing the mass and the relative dynamic elastic modulus, performing a strength test, and measuring the compression resistance test piece, the split tensile strength and the breaking strength of the concrete after freeze-thaw;
step five: analysis of test results
Firstly, the compressive strength, the splitting tensile strength and the bending strength which are calculated by the recycled concrete test piece for the mechanical property test and the natural orthopedic concrete test are compared and analyzed to obtain the difference of the basic mechanical property of the recycled concrete test piece and the natural orthopedic concrete, and then the anti-freezing durability which is calculated by the recycled concrete test piece for the durability test and the natural orthopedic concrete test is compared and analyzed to obtain the difference of the anti-freezing durability of the recycled concrete test piece and the natural orthopedic concrete.
2. The method for analyzing basic mechanical and frost-resistant durability of recycled concrete according to claim 1, wherein the method comprises the following steps: in the first step, the strength of the waste plain concrete block is 30-40Mpa, the crushing tool is a hammer of 10 pounds, the cement is ordinary Portland 42.5 cement, the 28 balance average strength is 53.7MPa, the fine aggregate is natural river sand, the natural coarse aggregate is construction site gravel, the particle size is 5mm-20mm, the first water reducing agent is a JM-A type high-efficiency naphthalene water reducing agent, and the second water reducing agent is a construction 4 type air-entraining water reducing agent.
3. The method for analyzing basic mechanical and frost-resistant durability of recycled concrete according to claim 1, wherein the method comprises the following steps: and in the second step, the recycled coarse aggregate is soaked in water to be saturated before being put into a stirrer and then naturally dried, wherein the stirrer is a JZ250 type forced multifunctional stirrer, and the vibration table is a ZH-1 x 1 type vibration table.
4. The method for analyzing basic mechanical and frost-resistant durability of recycled concrete according to claim 1, wherein the method comprises the following steps: in the third step, the pressure testing machine is a YA-3000 type electrohydraulic pressure testing machine, the universal testing machine is a WE-300 type hydraulic universal testing machine, the pressure testing machine is a NYL-300C type pressure testing machine, and three-point loading is adopted in the flexural strength test.
5. The method for analyzing basic mechanical and frost-resistant durability of recycled concrete according to claim 1, wherein the method comprises the following steps: in the fourth step, the recycled concrete test pieces for the freeze resistance durability test are provided with 30 groups, each group is provided with 6 cube test pieces with the size of 100mm multiplied by 100mm and 3 prism test pieces with the size of 100mm multiplied by 400mm, and the number of times of freeze thawing is respectively set to be 0, 50, 75, 125 and 200.
6. The method for analyzing basic mechanical and frost-resistant durability of recycled concrete according to claim 1, wherein the method comprises the following steps: in the fourth step, the calculation formula of the relative dynamic elastic modulus of the test piece is as follows:
in the formula PnFor n freeze-thaw cyclesRelative dynamic elastic modulus of test piece behind ring, f0Is the natural vibration frequency f before the freeze-thaw cycle of the test piecenThe natural vibration frequency of the test piece after n cycles of freezing and thawing is shown.
7. The method for analyzing basic mechanical and frost-resistant durability of recycled concrete according to claim 1, wherein the method comprises the following steps: in the fourth step, the mass loss rate calculation formula of the test piece is as follows:
in the formula WnThe mass loss rate of the test piece after n times of freeze thawing cycles, G0The quality of the test specimen before the freeze-thaw cycle, GnThe mass of the test piece after n times of freeze-thaw cycles.
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