CN107391790B - Green self-compacting concrete and preparation method thereof - Google Patents
Green self-compacting concrete and preparation method thereof Download PDFInfo
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- 239000011376 self-consolidating concrete Substances 0.000 title claims abstract description 65
- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 239000000463 material Substances 0.000 claims abstract description 166
- 239000000203 mixture Substances 0.000 claims abstract description 88
- 239000004576 sand Substances 0.000 claims abstract description 78
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 77
- 239000002245 particle Substances 0.000 claims abstract description 50
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 38
- 238000000034 method Methods 0.000 claims abstract description 30
- 239000007787 solid Substances 0.000 claims abstract description 11
- 238000003756 stirring Methods 0.000 claims abstract description 5
- 230000006835 compression Effects 0.000 claims abstract description 4
- 238000007906 compression Methods 0.000 claims abstract description 4
- 239000004567 concrete Substances 0.000 claims description 26
- 239000004568 cement Substances 0.000 claims description 20
- 239000010881 fly ash Substances 0.000 claims description 17
- 239000000843 powder Substances 0.000 claims description 14
- 238000005056 compaction Methods 0.000 claims description 13
- 238000012360 testing method Methods 0.000 claims description 13
- 238000009826 distribution Methods 0.000 claims description 12
- 238000012856 packing Methods 0.000 claims description 11
- 239000002253 acid Substances 0.000 claims description 4
- 210000000988 bone and bone Anatomy 0.000 claims description 4
- 238000011056 performance test Methods 0.000 claims description 4
- 229920001732 Lignosulfonate Polymers 0.000 claims description 3
- 125000001931 aliphatic group Chemical group 0.000 claims description 3
- UFWIBTONFRDIAS-UHFFFAOYSA-N Naphthalene Chemical compound C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 claims 2
- 229920000877 Melamine resin Polymers 0.000 claims 1
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims 1
- IIACRCGMVDHOTQ-UHFFFAOYSA-M sulfamate Chemical compound NS([O-])(=O)=O IIACRCGMVDHOTQ-UHFFFAOYSA-M 0.000 claims 1
- 238000009825 accumulation Methods 0.000 abstract description 15
- 239000002994 raw material Substances 0.000 abstract description 6
- 238000004364 calculation method Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 9
- 238000013461 design Methods 0.000 description 5
- 239000008187 granular material Substances 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 239000004575 stone Substances 0.000 description 4
- 238000013329 compounding Methods 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 150000007974 melamines Chemical class 0.000 description 2
- 150000002790 naphthalenes Chemical class 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- IIACRCGMVDHOTQ-UHFFFAOYSA-N sulfamic acid Chemical class NS(O)(=O)=O IIACRCGMVDHOTQ-UHFFFAOYSA-N 0.000 description 2
- 238000012795 verification Methods 0.000 description 2
- 230000003245 working effect Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 239000002956 ash Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 239000004574 high-performance concrete Substances 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B14/02—Granular materials, e.g. microballoons
- C04B14/04—Silica-rich materials; Silicates
- C04B14/06—Quartz; Sand
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B18/00—Use of agglomerated or waste materials or refuse as fillers for mortars, concrete or artificial stone; Treatment of agglomerated or waste materials or refuse, specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B18/04—Waste materials; Refuse
- C04B18/06—Combustion residues, e.g. purification products of smoke, fumes or exhaust gases
- C04B18/08—Flue dust, i.e. fly ash
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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Abstract
The invention discloses green self-compacting concrete and a preparation method thereof, wherein the preparation method comprises the following steps: calculating the stacking compactness of a cementing material system, an aggregate system and a mixture system according to the stacking mode of the solid particles and the compressible stacking model; obtaining a preselected cementing material combination, a preferred sand rate and a preselected volume ratio of a cementing material system to an aggregate system; determining the mass ratio of water to the cementing material system according to the compression strength requirement of the green self-compacting concrete and the stacking compactness of the cementing material system, and calculating the specific mixing amount of the cementing material system, the aggregate system and the water; determining the mixing amount of the water reducing agent according to the specific mixing amount of the cementing material system; stirring and mixing uniformly to obtain the green self-compacting concrete. The method starts from the solid particle accumulation angle, considers the properties of the actually selected raw materials, combines a compressible accumulation model, optimizes the accumulation compactness and obviously reduces the using amount of the cementing material.
Description
Technical Field
The invention relates to the field of concrete, in particular to green self-compacting concrete and a preparation method thereof.
Background
The self-compacting concrete is high-performance concrete which depends on the self-weight action of the self-compacting concrete without additional manual or mechanical vibration, has excellent working properties such as large fluidity, homogeneity and segregation resistance in pouring construction, and has good mechanical and durable properties after hardening. However, the self-compacting concrete has a large content of the cementing material in the design, which results in high hydration heat, large shrinkage and creep after hardening, and CO generated in the concrete production process2The environmental pollution is aggravated by large discharge amount, and CO2The main emission source of (A) is cement, which occupies approximately the total CO of concrete2The discharge amount is 74-81%, and coarse aggregate is used as the next material, which accounts for 13-20%. Therefore, the green self-sealing performance of the low-dosage cementing material which is more in line with the requirements of engineering economy and environment is developedSolid concrete will be an important direction in the future.
At present, self-compacting concrete mix proportion design methods based on different theories and control parameters are more at home and abroad, because the mix proportion parameters are more to meet the stricter requirements on the performance of the mixture, and the methods for acquiring the parameters are different. The use amount of cementing materials such as a fixed sand volume content method of European regulations and an advanced method proposed by Japan is larger, and the powder-rich self-compacting concrete has higher cost and larger carbon emission.
Therefore, the prior art has yet to be improved.
Disclosure of Invention
The invention mainly aims to provide a preparation method of green self-compacting concrete, and aims to solve the technical problems of high cost and heavy pollution caused by large using amount of cementing materials in the existing concrete.
The invention provides a preparation method of green self-compacting concrete, which comprises the following steps:
determining the compaction index of the green self-compacting concrete according to the solid particle stacking mode and the compressible stacking model, and respectively calculating the stacking compactness of a cementing material system, an aggregate system and a mixture system according to the compaction index;
obtaining a preselected cementing material combination according to the stacking compactness of the cementing material system; obtaining the optimal sand rate according to the stacking compactness of the aggregate system; determining the volume ratio of a preselected cementing material system to an aggregate system according to the stacking compactness of the mixture system, the preselected cementing material combination and the preferred sand rate;
determining the mass ratio of water to the cementing material system according to the compression strength requirement of the green self-compacting concrete and the stacking compactness of the cementing material system, and calculating the specific mixing amount of the cementing material system, the aggregate system and the water, wherein the specific mixing amount of the cementing material system is 340kg/m3To 380kg/m3；
Determining the mixing amount of the water reducing agent according to the specific mixing amount of the cementing material system;
and uniformly stirring and mixing the determined concrete mixing amount of the cementing material system, the aggregate system, the water and the water reducing agent to obtain the green self-compacting concrete.
Preferably, before the step of determining the compaction index of the green self-compacting concrete according to the solid particle stacking mode and the compressible stacking model, and calculating the stacking compactness of the cementing material system, the aggregate system and the mixture system according to the compaction index, the method comprises the following steps of: collecting performance parameters of a pre-selected cementing material and a pre-selected aggregate; the preselected aggregate comprising: coarse aggregate and fine aggregate; the performance parameters comprise: density, particle size fraction distribution and size fraction volume fraction.
Preferably, the pre-selected cementing material combination proportion is obtained according to the stacking compactness of the cementing material system; obtaining the optimal sand rate according to the stacking compactness of the aggregate system; the step of determining the volume ratio of the preselected cementitious material system to the aggregate system according to the bulk density of the mix system, the preselected cementitious material combination and the preferred sand rate comprises:
according to the combination of different volume ratios of the preselected cementing materials in the cementing material system, calculating the stacking compactness of the cementing material system combined by different volume ratios so as to determine the combination proportion of the preselected cementing materials to form the cementing material system;
calculating the stacking compactness of the bone material system under different sand rates, and determining the preferred sand rate;
and calculating the stacking compactness of the mixture system consisting of the aggregate system and the cementing material system in different volume ratios, and determining the volume ratio of the cementing material system to the aggregate system.
Preferably, the step of calculating the aggregate system packing compactness at different sand rates and determining the sand rate comprises the following steps: according to the sand rate, replacing the original sand mixing amount with the specified amount of superfine sand powder; the specified amount range is 0-20% of the volume mixing amount of the medium sand.
Preferably, the cementitious material system comprises: fly ash and cement; the volume mixing amount of the fly ash in the cementing material system is 20-40%.
Preferably, the volume ratio of the cementitious material system to the aggregate system is in the range of 1: 5.5 to 1: 6.5.
Preferably, the water reducing agent comprises: one or more of lignosulfonate, naphthalene series, melamine series, sulfamate series, aliphatic series and polycarboxylic acid series; the amount of the water reducing agent is 2-4% of the mass of the cementing material system.
Preferably, before the step of uniformly mixing the determined specific mixing amount of the cementing material system, the aggregate system, the water and the water reducing agent, the step of obtaining the green self-compacting concrete comprises the following steps:
forming a mixture by the determined concrete mixing amount of the cementing material system, the aggregate system, water and the water reducing agent, testing the working performance of the mixture, and verifying the compressive strength of the mixture;
and adjusting the specific mixing amounts of the cementing material system, the aggregate system, the water and the water reducing agent according to the working performance test result of the mixture and the compressive strength of the mixture to meet the requirements.
Preferably, the concrete mixing amount of the cementing material system, the aggregate system, the water and the water reducing agent is determined to form a mixture, the working performance of the mixture is tested, and the compressive strength of the mixture is verified; according to the testing result of the working performance of the mixture and the compressive strength of the mixture, the concrete mixing amounts of the cementing material system, the aggregate system, the water and the water reducing agent are adjusted to meet the requirements, and the method comprises the following steps:
respectively taking a cementing material system, an aggregate system, water and a water reducing agent with specific mixing amounts according to the specific mixing amounts to form a mixture, testing the working performance of the mixture, and adjusting the mixing amounts of the water reducing agent to enable the mixture to meet the working performance requirement;
verifying whether the mixture meets the requirement of compressive strength under the condition of meeting the working performance;
if not, adjusting the composition proportion of the cementing material system or the mass ratio of the water to the cementing material system to balance the working performance and the compressive strength of the mixture.
The invention also provides green self-compacting concrete prepared by the preparation method of the green self-compacting concrete.
The invention has the beneficial technical effects that: the method starts from the angle of solid particle accumulation and fully considers the properties of the actually selected raw materials, carries out calculation analysis by combining a compressible accumulation model, optimizes the accumulation compactness of the green self-compacting concrete mixture from the essence of particle accumulation, and obviously reduces the using amount of the cementing material on the premise of ensuring the working performance of the green self-compacting concrete. Theoretical analysis is utilized to calculate the optimal proportioning parameters of each component, and tests and verifications are combined with experiments, so that the trial-proportioning experiment times of the proportioning parameters are greatly reduced, and the production cost and CO of concrete can be fully reduced2The discharge amount meets the performance requirement of the self-compacting concrete. The cementing material system of the green self-compacting concrete comprises a certain amount of fly ash, so that the use amount of cement is reduced, and the green and environment-friendly effect is achieved; a certain amount of superfine sand powder volume is used for replacing medium sand in the aggregate of the green self-compacting concrete, so that the compactness of the mixture is improved. The green self-compacting concrete simultaneously meets the requirements of two aspects of target working performance and mechanical performance, and is green, environment-friendly and low in cost.
Drawings
FIG. 1 is a schematic flow chart of a method for preparing green self-compacting concrete according to an embodiment of the present invention;
FIG. 2 is a graph showing the variation of the wet bulk density of the slurry with the volume of the fly ash in an embodiment of the present invention;
FIG. 3 is a graph showing the variation of the degree of compaction of aggregate system with sand ratio S/A according to an embodiment of the present invention;
FIG. 4 shows the packing compactness of the mixture system with V according to an embodiment of the present inventiona/VbAnd (5) a variation trend graph.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, an embodiment of the present invention provides a method for preparing green self-compacting concrete, including:
s1: determining the compaction index of the green self-compacting concrete according to the solid particle stacking mode and the compressible stacking model, and respectively calculating the stacking compactness of a cementing material system, an aggregate system and a mixture system according to the compaction index;
s2: obtaining a preselected cementing material combination according to the stacking compactness of the cementing material system; obtaining the optimal sand rate according to the stacking compactness of the aggregate system; determining the volume ratio of a preselected cementing material system to an aggregate system according to the stacking compactness of the mixture system, the preselected cementing material combination and the preferred sand rate;
s3: determining the mass ratio of water to the cementing material system according to the compression strength requirement of the green self-compacting concrete and the stacking compactness of the cementing material system, and calculating the specific mixing amount of the cementing material system, the aggregate system and the water, wherein the specific mixing amount of the cementing material system is 340kg/m3To 380kg/m3；
S4: determining the mixing amount of the water reducing agent according to the specific mixing amount of the cementing material system;
s5: and uniformly stirring and mixing the determined concrete mixing amount of the cementing material system, the aggregate system, the water and the water reducing agent to obtain the green self-compacting concrete.
The embodiment of the invention starts from the solid particle accumulation angle, fully considers the properties of the actually selected raw materials, performs calculation analysis by combining a compressible accumulation model, and optimizes the accumulation compactness of the green self-compacting concrete mixture from the essence of particle accumulation. Theoretical analysis is utilized to calculate optimal proportioning parameters of each component, and tests and verifications are combined with experiments to greatly reduce the trial-mix experiment times of the proportioning parameters on one hand and fully reduce the usage amount of the cementing material in the concrete on the other hand, and the specific mixing amount range of the cementing material system in the embodiment of the invention is 340kg/m3To 380kg/m3Compared with the concrete of the prior concrete, the concrete mixing amount of the cementing material system is more than 400kg/m3Book, bookThe concrete mixing amount of the cementing material system in the embodiment of the invention is obviously reduced, and the requirements of green self-compacting concrete performance and green environmental protection are met.
Further, before the step of determining the compaction index of the green self-compacting concrete according to the solid particle stacking mode and the compressible stacking model, the method comprises the following steps: collecting performance parameters of a pre-selected cementing material and a pre-selected aggregate; the preselected aggregate described above, comprising: coarse aggregate and fine aggregate; the performance parameters comprise: density, particle size fraction distribution and size fraction volume fraction.
According to the embodiment of the invention, the cementing material system is formed by combining different preselected cementing materials, the aggregate system is formed by combining different preselected aggregates, then the cementing material system and the aggregate system are formed into a mixture system according to a certain proportion, and the cementing material system, the aggregate system and water are mixed to form a mixture. Collecting performance parameters of a preselected cementing material and a preselected aggregate so as to calculate the stacking compactness of a cementing material system, an aggregate system and a mixture system, and further determining the specific mixing amount of the cementing material system, the aggregate system and water. And selecting target working performance and compressive strength according to design requirements, existing specifications and engineering experience.
Determination of the Density of the gelled MaterialbThe size fraction distribution of the cement particles and the volume fraction y of the size fraction are determined by means of a laser granulometeri(ii) a Separately determining the coarse and fine aggregate densities rhog、ρsAnd the particle size distribution of the aggregate particles and the volume fraction y of each sizeiDetermining the bulk density of the aggregate fraction and calculating the residual bulk density β of each fraction of the granules by a compressible bulk modeli。
Calculating the residual stacking compactness and the actual stacking compactness related to the stacking compactness in the calculation process through a compressible stacking model, wherein the calculation process is as follows:
firstly, the volume fraction y of each grain size fraction of the gelled material particles is measured by a laser particle sizeriThe volume fraction y of each particle fraction of the sand particles is determined by a standard vibrating screeniCalculating the characteristic particle diameter d of each fraction according to each fraction intervaltThe calculation formula is asThe following:
log10(dt)＝[log10(dmax)+log10(dmin)]/2, in the formula dmaxAnd dminRespectively the maximum and minimum particle diameters of the size fraction interval.
Two interaction scenarios between the particles of each fraction are then considered: the loosening effect and the wall effect are calculated according to the following formula:
bij＝1-(1-di/dj)1.50j ═ 1 (1, 2, 3.... i-1); in the formula, aijAnd bijThe coefficient of the loosening effect produced by the particle j on the particle i and the coefficient of the coanda effect produced by the particle j on the particle i, diAnd djThe particle sizes of particle fraction i and particle fraction j, respectively. Further, in the multi-component mixture, when the granules are mainly in the ith grade, the virtual stacking compactness gamma of the multi-component granule system of the granules in the ith grade can be calculated according to the determined basic parametersiThe formula is as follows:
Obtaining the virtual stacking compactness gamma of the multi-element particlesiAnd then, selecting different compaction indexes K according to different particle stacking modes, wherein in the embodiment of the invention, the K is 7 for green self-compacting concrete under the conditions of wet stacking and high-efficiency water reducing agent addition. Finally according to the K value and the virtual stacking compactness gammaiAnd calculating the actual stacking compactness αtThe formula is as follows:
β for cementitious materialsiAnd (3) determination: when the volume fraction y of each material is measurediAnd a characteristic particle diameter dtThereafter, assume each size fraction βiAre all equal, i.e. β1＝β2＝...＝βn＝βiThe actual bulk density of each material was then determined by minimum Water demand method αtβ for the cement was then back calculated by the above formulai。
β for sandstone materialsiAnd (3) determination: after the sand and stone are screened, the density rho and the bulk density rho can be carried out through each particle size fraction0Then by equation αt＝ρ0Rho, calculating the actual stacking compactness, and determining β of the sand materiali。
When the particle intervals of the cementing materials are overlapped, the volume fraction of the particles after compounding
And composite grade residual packing compactness
Calculated by the following calculation formula:
The cementing material system in the embodiment of the invention comprises cement and fly ash, so that the dosage of the cement is reduced, and the effect of green and environment protection is achieved; the pre-selected aggregate comprises coarse aggregate macadam, and the fine aggregate comprises superfine sand powder and medium sand. The thickness degree of the sand is divided into four grades of coarse, medium, fine and superfine according to the fineness modulus of the sand, wherein the fineness modulus of the superfine sand is between 0.2 and 0.3.
Cement and powdered coal in the embodiment of the inventionThe particle size distribution of the ash and the superfine sand powder is measured by a laser particle size distribution instrument, the particle size distribution of the sand aggregate is measured by screening of a standard vibrating screen machine, the particle size distribution result is shown in tables 1 to 3, the apparent density of each raw material is measured by a pycnometer drainage method, the result is shown in table 4, the actual stacking compactness of the cement, the fly ash and the superfine sand powder is measured by a minimum water demand method, the residual stacking compactness is calculated, the result is shown in table 5, the stacking compactness of each particle size of the medium sand and the crushed stone is calculated from the density and the stacking density, and the residual stacking compactness is calculated βiThe results are shown in Table 6.
TABLE 1 Cement and fly ash size distribution
TABLE 2 ultrafine Sand particle size distribution
Table 3 Sand and gravel size distribution
TABLE 4 Density of the respective raw materials
TABLE 5 actual stacking compactness α of cement, fly ash and superfine sand powdertAnd residual packing density βi
Table 6 shows the actual packing density α of each fraction of sand and crushed stonetAnd residual packing density βi
Further, obtaining a pre-selected cementing material combination ratio according to the stacking compactness of the cementing material system; obtaining the optimal sand rate according to the stacking compactness of the aggregate system; the step of determining the volume ratio of the preselected cementitious material system to the aggregate system according to the bulk density of the mix system, the preselected cementitious material combination, and the preferred sand rate comprises:
according to the combination of different volume ratios of the preselected cementing materials in the cementing material system, calculating the stacking compactness of the cementing material system combined by different volume ratios so as to determine the combination proportion of the preselected cementing materials to form the cementing material system;
calculating the stacking compactness of the bone material system under different sand rates, and determining the preferred sand rate;
and calculating the stacking compactness of the mixture system consisting of the aggregate system and the cementing material system in different volume ratios, and determining the volume ratio of the cementing material system to the aggregate system.
According to the combination of the pre-selected cementing materials with different volume ratios in the cementing material system, the stacking compactness α of different combinations is calculatedtAnd selecting the optimal cementing material system combination according to the above formula.
Calculating the optimal stacking compactness α of the aggregate system under the condition of different sand rates S/AtDetermining an optimum sand rate, represented by the following sub-formula:
Calculating the volume ratio V of different aggregate systems and cementing material systems of the mixture systema/VbAnd the packing density of the powder is optimizedα 'of bulk density'tCorrespondingly determining the volume ratio omega of the optimal aggregate system to the cementing material system, wherein the calculation formula is as follows:
according to the target compressive strength fcDetermining the mass ratio theta of water and glue, and combining the optimal sand rate and the volume ratio omega of the aggregate system to the cementing material system to calculate the volume mixing amount V of the cementing material systembThe formula of the calculation process is as follows:
Vw+Vb+Vg+Vs＝1；
Calculating V according to the formulabThen, the mixing amount of each proportioning material can be obtained, and the calculation formula is as follows:
mb＝Vb·ρb；
mw＝mb·θ；
ma＝Va·ρa＝Vb·ω·ρa；
mg＝ma·；
ms＝ma-mg(ii) a In the formula, mbIs the quality of the cementing material system.
Further, after the step of calculating the packing compactness of the bone material system under different sand rates and determining the sand rate, the method comprises the following steps:
the sand rate is the percentage of the mass of sand in the concrete to the total mass of sand and stone. According to the sand rate, replacing the original sand mixing amount with the specified amount of superfine sand powder; the specified amount range is 0-20% of the volume mixing amount of the medium sand.
After the optimal sand rate is calculated, the original sand mixing amount is replaced by the ultrafine sand powder, according to the relationship between the stacking compactness and the sand rate of the aggregate system in the attached figure 3 in the embodiment of the invention, the stacking compactness of the used aggregate system is optimal when the sand rate is equal to 0.45, and α at the momenttWhen the mixture is 0.7264, the superfine sand powder volume doping amount of 15% is used to replace the medium sand, and the compactness of the mixture is improved.
Further, the above cement system, comprising: fly ash and cement; the volume mixing amount of the fly ash in the cementing material system is 20-40%.
According to the change trend graph of the wet stacking compactness of the slurry along with the volume doping amount of the fly ash in the attached figure 2 and the increase trend of the stacking compactness after the fly ash and the cement are compounded, the working performance and the mechanical property of the mixture are comprehensively considered, and the volume doping amount of the fly ash is selected to be 30%. The cement consumption is reduced as much as possible, and the effects of environmental protection and low cost are achieved.
Further, the volume ratio of the cementing material system to the aggregate system is 1: 5.5 to 1: 6.5.
According to the attached figure 4, the mixture stacking compactness and the volume ratio V of the aggregate to the cementing materiala/VbIn the relation of (1), the mixture used is 5.5 < V under different sand ratesa/VbThe stacking compactness of less than 6.5 is in a larger value, three groups of schemes are selected at equal intervals in the scheme, Va/Vb5.7, 6.0 and 6.3 respectively.
Further, the water reducing agent comprises: one or more of lignosulfonate, naphthalene series, melamine series, sulfamate series, aliphatic series and polycarboxylic acid series; the amount of the water reducing agent is 2-4% of the mass of the cementing material.
According to the target compressive strength fcMass ratio of the mixture to the water gel
According to the scheme, theta is 0.45, the water reducing agent is a Cika polycarboxylic acid water reducing agent, and the using amount of the water reducing agent is 3.5% of the mass of the cementing material. Combining optimum sand rate and Va/VbThen three groups m can be calculatedbAre 373kg/m each3、359kg/m3、347kg/m3. Compared with 400-550kg/m in the conventional design, the green self-compacting concrete provided by the embodiment of the invention has the advantages that the working performance and the mechanical property are balanced3The dosage of the cementing material is greatly reduced to 347kg/m by the embodiment of the invention3And the production cost and the carbon emission of the concrete are obviously reduced.
Further, before the step of uniformly stirring and mixing the determined concrete mixing amount of the cementing material system, the aggregate system, the water and the water reducing agent to obtain the green self-compacting concrete, the method comprises the following steps of:
forming a mixture by the determined concrete mixing amount of the cementing material system, the aggregate system, water and the water reducing agent, testing the working performance of the mixture, and verifying the compressive strength of the mixture;
and adjusting the specific mixing amounts of the cementing material system, the aggregate system, the water and the water reducing agent according to the working performance test result of the mixture and the compressive strength of the mixture to meet the requirements.
Further, the concrete mixing amount of the cementing material system, the aggregate system, water and the water reducing agent are combined to form a mixture, the working performance of the mixture is tested, and the compressive strength of the mixture is verified; according to the working performance test result of the mixture and the compressive strength of the mixture, the concrete mixing amounts of the cementing material system, the aggregate system, the water and the water reducing agent are adjusted to meet the requirements, and the method comprises the following steps:
respectively taking a cementing material system, an aggregate system, water and a water reducing agent with specific mixing amounts according to the specific mixing amounts to form a mixture, testing the working performance of the mixture, and adjusting the mixing amounts of the water reducing agent to enable the mixture to meet the working performance requirement;
verifying whether the mixture meets the requirement of compressive strength under the condition of meeting the working performance;
if not, adjusting the composition proportion of the cementing material system or the mass ratio of the water to the cementing material system to balance the working performance and the compressive strength of the mixture.
In the examples of the present invention, tests such as slump spread SF, spreading time T500, visual stability index VSI, etc. of green self-compacting concrete were carried out according to the mix proportion shown in table 7 with reference to specifications of ASTM C1610, ASTM C1611 and ASTM C1621; compressive strengths 7 days and 28 days after hardening were measured according to the ACI 318 specification and the results are shown in Table 8. The test results in Table 8 show that the prepared green self-compacting concrete has good working performance, SF is larger than or equal to 650mm, T is larger than 2s and smaller than T500 and smaller than 8s, the mixture is uniform, and the segregation phenomenon is avoided, namely VSI is smaller than or equal to 1. For the aspect of mechanical property, the compressive strength of the prepared green self-compacting concrete is f after 28 days of hardeningcIs more than 35 MPa. Therefore, the prepared green self-compacting concrete simultaneously meets the requirements of two aspects of target working performance and mechanical performance, and the practicability and feasibility of the green self-compacting concrete mix proportion design method with low gel material consumption are verified.
TABLE 7 Green self-compacting concrete mix proportion (kg/m)3)
TABLE 8 test results of working properties and mechanical properties of green self-compacting concrete
The embodiment of the invention also provides green self-compacting concrete which is prepared by the preparation method of the green self-compacting concrete.
In the embodiment of the invention, the cementing material system of the green self-compacting concrete is 70% of cement and 30% of fly ash by volume, so that the consumption of the cement is reduced, and the effect of green environmental protection is achieved; the aggregate of the green self-compacting concrete comprisesThe coarse aggregate is crushed, the fine aggregate comprises superfine sand powder and medium sand, and 15% of superfine sand powder volume is used for replacing the medium sand, so that the compactness of the mixture is improved. The green self-compacting concrete provided by the embodiment of the invention starts from the solid particle accumulation angle and fully considers the properties of the actually selected raw materials, and is calculated and analyzed by combining the compressible accumulation model, the mixture accumulation compactness is optimized from the essence of particle accumulation, the slump expansion SF of the prepared green self-compacting concrete is more than or equal to 650mm, T500 is more than 2s and less than 8s, VSI is less than or equal to 1, the compressive strength reaches above C30, the requirements of two aspects of target working performance and mechanical performance are met, and the green self-compacting concrete is green, environment-friendly and low in cost. The dosage of the cementing material of the green self-compacting concrete in the embodiment of the invention is as low as 347kg/m3Wherein the cement dosage is only 243kg/m3Compared with the lowest cementing material dosage of JGJ/T283-3Compared with the prior art, the method reduces 14.25 percent, and reduces the production cost by at least 22.5 yuan/m3。
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (9)
1. A preparation method of green self-compacting concrete is characterized by comprising the following steps:
determining the compaction index of the green self-compacting concrete according to the solid particle stacking mode and the compressible stacking model, and respectively calculating the stacking compactness of a cementing material system, an aggregate system and a mixture system according to the compaction index;
obtaining a preselected cementing material combination according to the stacking compactness of the cementing material system; obtaining the optimal sand rate according to the stacking compactness of the aggregate system; determining the volume ratio of a preselected cementing material system to an aggregate system according to the stacking compactness of the mixture system, the preselected cementing material combination and the preferred sand rate;
determining the mass ratio of water to the cementing material system according to the compression strength requirement of the green self-compacting concrete and the stacking compactness of the cementing material system, and calculating the specific mixing amount of the cementing material system, the aggregate system and the water, wherein the specific mixing amount of the cementing material system is 340kg/m3To 380kg/m3；
Determining the mixing amount of the water reducing agent according to the specific mixing amount of the cementing material system;
uniformly stirring and mixing the determined concrete mixing amount of the cementing material system, the determined aggregate system, water and the water reducing agent to obtain green self-compacting concrete;
the cementing material system comprises 30% of fly ash and 70% of cement by volume;
the volume ratio range of the cementing material system to the aggregate system is 1: 5.5 to 1: 6.5.
2. the method for preparing green self-compacting concrete according to claim 1, wherein the step of determining the compaction index of green self-compacting concrete according to the solid particle stacking mode and the compressible stacking model, and calculating the stacking compactness of the cementing material system, the aggregate system and the mixture system according to the compaction index comprises the following steps:
collecting performance parameters of a pre-selected cementing material and a pre-selected aggregate; the preselected aggregate comprising: coarse aggregate and fine aggregate; the performance parameters comprise: density, particle size fraction distribution and size fraction volume fraction.
3. The method for preparing green self-compacting concrete according to claim 1, wherein the pre-selected binding material combination ratio is obtained according to the packing compactness of the binding material system; obtaining the optimal sand rate according to the stacking compactness of the aggregate system; the step of determining the volume ratio of the preselected cementitious material system to the aggregate system according to the bulk density of the mix system, the preselected cementitious material combination and the preferred sand rate comprises:
according to the combination of different volume ratios of the preselected cementing materials in the cementing material system, calculating the stacking compactness of the cementing material system combined by different volume ratios so as to determine the combination proportion of the preselected cementing materials to form the cementing material system;
calculating the stacking compactness of the bone material system under different sand rates, and determining the preferred sand rate;
and calculating the stacking compactness of the mixture system consisting of the aggregate system and the cementing material system in different volume ratios, and determining the volume ratio of the cementing material system to the aggregate system.
4. The method for preparing green self-compacting concrete according to claim 3, wherein the step of calculating the aggregate system packing compactness at different sand rates and determining the sand rate comprises the following steps:
according to the sand rate, replacing the original sand mixing amount with the specified amount of superfine sand powder; the specified amount range is 0-20% of the volume mixing amount of the medium sand.
5. The method for preparing green self-compacting concrete according to claim 1, wherein the cementitious material system comprises: fly ash and cement; the volume mixing amount of the fly ash in the cementing material system is 20-40%.
6. The method for preparing green self-compacting concrete according to claim 1, wherein the water reducing agent comprises:
one or more of lignosulfonate, naphthalene, melamine, sulfamate, aliphatic or polycarboxylic acid; the amount of the water reducing agent is 2-4% of the mass of the cementing material system.
7. The preparation method of the green self-compacting concrete according to claim 1, wherein the step of uniformly mixing the determined specific mixing amount of the cementing material system, the aggregate system, the water and the water reducing agent comprises the following steps:
forming a mixture by the determined concrete mixing amount of the cementing material system, the aggregate system, water and the water reducing agent, testing the working performance of the mixture, and verifying the compressive strength of the mixture;
and adjusting the specific mixing amounts of the cementing material system, the aggregate system, the water and the water reducing agent according to the working performance test result of the mixture and the compressive strength of the mixture to meet the requirements.
8. The preparation method of the green self-compacting concrete according to claim 7, wherein the concrete mixture is prepared from the cementing material system, the aggregate system, water and the water reducing agent with specific mixing amounts, the working performance of the mixture is tested, and the compressive strength of the mixture is verified; according to the testing result of the working performance of the mixture and the compressive strength of the mixture, the concrete mixing amounts of the cementing material system, the aggregate system, the water and the water reducing agent are adjusted to meet the requirements, and the method comprises the following steps:
respectively taking a cementing material system, an aggregate system, water and a water reducing agent with specific mixing amounts according to the specific mixing amounts to form a mixture, testing the working performance of the mixture, and adjusting the mixing amounts of the water reducing agent to enable the mixture to meet the working performance requirement;
verifying whether the mixture meets the requirement of compressive strength under the condition of meeting the working performance;
if not, adjusting the composition proportion of the cementing material system or the mass ratio of the water to the cementing material system to balance the working performance and the compressive strength of the mixture.
9. A green self-compacting concrete, characterized in that it is prepared by the method of any one of claims 1-8.
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| CN113836738B (en) * | 2021-09-29 | 2023-06-23 | 中铁二十四局集团有限公司 | SCC mix proportion design method based on aggregate filling and efficiency factors |
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