CN112331276A - High-performance recycled concrete mix proportion design method based on modified CPM model and nano calcium carbonate reinforcement - Google Patents

High-performance recycled concrete mix proportion design method based on modified CPM model and nano calcium carbonate reinforcement Download PDF

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CN112331276A
CN112331276A CN202011231918.9A CN202011231918A CN112331276A CN 112331276 A CN112331276 A CN 112331276A CN 202011231918 A CN202011231918 A CN 202011231918A CN 112331276 A CN112331276 A CN 112331276A
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recycled
recycled concrete
concrete
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aggregate
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CN112331276B (en
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孟涛
赵羽习
卢予奇
应侃君
郝旭
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Zhejiang University ZJU
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    • G—PHYSICS
    • G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
    • G16C—COMPUTATIONAL CHEMISTRY; CHEMOINFORMATICS; COMPUTATIONAL MATERIALS SCIENCE
    • G16C20/00—Chemoinformatics, i.e. ICT specially adapted for the handling of physicochemical or structural data of chemical particles, elements, compounds or mixtures
    • G16C20/30—Prediction of properties of chemical compounds, compositions or mixtures
    • 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
    • C04B20/00—Use of materials as fillers for mortars, concrete or artificial stone according to more than one of groups C04B14/00 - C04B18/00 and characterised by shape or grain distribution; Treatment of materials according to more than one of the groups C04B14/00 - C04B18/00 specially adapted to enhance their filling properties in mortars, concrete or artificial stone; Expanding or defibrillating materials
    • C04B20/10—Coating or impregnating
    • C04B20/1055—Coating or impregnating with inorganic materials
    • C04B20/107—Acids or salts thereof

Abstract

The invention provides a high-performance recycled concrete mix proportion design method based on a modified CPM model and nano calcium carbonate reinforcement3The amount of the slurry is used for carrying out nano reinforcement on the recycled coarse and fine aggregate, then, a CPM model correction form is provided, the stacking compactness after the recycled coarse and fine aggregate and the cementing material are mixed according to different proportions is calculated, and the sand rate and the gel-to-bone ratio of the recycled concrete are determined; thirdly, determining an effective water-cement ratio according to the design strength and the bauromid formula, and obtaining a primary calculated mix proportion of the recycled concrete by adopting a volume method; and finally, adjusting the mixing ratio according to the trial-matching condition of the recycled concrete. Under the combined action of the accumulation model and the nano slurry, the invention improves the macro-micro performance index of the recycled concrete and finally realizes high performance. The design method of the mixing proportion has clear operation steps, accords with the engineering practice, and fills the construction wasteThe separate utilization has good ecological benefit.

Description

High-performance recycled concrete mix proportion design method based on modified CPM model and nano calcium carbonate reinforcement
Technical Field
The invention relates to the field of high-valued utilization of construction waste in concrete, in particular to a high-performance recycled concrete mix proportion design method based on a modified CPM model and nano calcium carbonate reinforcement.
Background
China is currently in the process of vigorous development of the building industry and massive construction of urban infrastructure. As the most important building material, the annual average yield of commercial concrete has exceeded 2.5X 109m3This means a rapid depletion of natural sand resources. Meanwhile, the construction waste generated in China each year exceeds 30 hundred million tons, the resource utilization rate is less than 10 percent, and if the construction waste can be crushed into recycled coarse and fine aggregates, the construction waste can be popularized and applied to concrete production, the problems of sandstone resource shortage and construction waste disposal can be solved, the on-site utilization rate of concrete raw materials can be improved, and financial resources and material resources are saved.
The recycled aggregate has low apparent density and high water absorption and crushing indexes due to the adhesion of old mortar on the surface, and can generate negative effects on the mechanical property and the durability of concrete. If the recycled aggregate is used for preparing high-performance concrete, high-grade application is realized in structural members, a conventional mix proportion design flow is not suitable for direct application, the recycled aggregate needs to be subjected to strengthening treatment, and the mix proportion design flow of the concrete is improved.
In the conventional mix proportion design process, multiple parameters are determined according to a chart and depend on experience to a large extent, however, the performance index of the recycled aggregate has a large difference with that of the natural aggregate, and the previous experience is not suitable for being directly applied.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the limitation of the existing concrete design and providing a scientific and practical high-performance recycled concrete mix proportion design method based on an accumulation model and nano reinforcement.
The invention is realized by adopting the following technical scheme:
a high-performance recycled concrete mix proportion design method based on a modified CPM model and nano calcium carbonate reinforcement comprises the following steps:
(1) determination of Nano CaCO3The slurry amount is used for carrying out nano modification on the recycled coarse and fine aggregate;
(2) calculating the stacking compactness of a mixture I obtained by mixing the recycled coarse aggregate and the recycled fine aggregate in different proportions by using a modified CPM model, and determining the volume sand rate of the recycled concrete according to the peak position;
(3) determining the composition of the cementing material, namely the proportion of cement and mineral admixture;
(4) on the premise of a set volume sand rate, calculating the stacking compactness of a mixture II obtained by mixing the recycled coarse and fine aggregate and the cementing material in different volume proportions by using a modified CPM model, and determining the volume ratio of the cementite of the recycled concrete (namely the volume ratio of the cementing material to the recycled coarse and fine aggregate) according to the peak position;
(5) calculating the preparation strength of the recycled concrete, and determining the effective water-cement ratio (namely the mass ratio of mixing water and a cementing material in the concrete when the water absorbed by the recycled coarse and fine aggregates is not counted) by utilizing a pallium formula;
(6) determining the primary calculation mixing proportion of the recycled concrete by using a volume method, namely the consumption of recycled coarse aggregate, the consumption of recycled fine aggregate, the consumption of cementing material and the consumption of mixing water;
(7) determining the additional water consumption of the recycled concrete in unit volume according to the water absorption characteristic of the recycled coarse and fine aggregate;
(8) trial preparation is carried out according to the preliminary calculated mixture ratio, the dosage of the water reducing agent is determined based on the fluidity requirement of the recycled concrete, and the effective water-cement ratio and the composition of the cementing material are allowed to be properly adjusted based on the mechanical and durability requirements of the recycled concrete.
Further, the nano CaCO in the step (1)3The slurry is alkalescent, has a pH value of 8-9, a solid content of 20%, an average particle size of 30-50 nm and nano CaCO3The slurry is made of nano CaCO3The emulsion being formed by partial dehydration, nano CaCO3The emulsion is produced by a carbonation reactor.
Further, the nano CaCO in the step (1)3The slurry is divided into two equal parts, one part of the slurry is uniformly sprayed on the surface of the recycled aggregate, the recycled aggregate is fully turned over after standing for 20-30 min, and the other part of the slurry is uniformly sprayed. And after spraying, the recycled aggregate is aired for 48 hours at least at the ventilation position, and can be used for preparing concrete after reaching an air drying state. Nano CaCO for modified recycled coarse aggregate by mass3The dosage of the serous fluid is 1.0-2.0 percent of the recycled coarse aggregate, and the nano CaCO used for modifying the recycled fine aggregate3The dosage of the slurry is 2.0-3.0% of the recycled fine aggregate.
Further, the corrected CPM model to-be-solved quantity in the step (2) and the step (4) is the actual stacking compactness phi of the mixture I and the mixture II respectively, and the calculation is carried out according to the following formula, and the key difference of the method compared with the conventional CPM model is that the compaction coefficient K takes a value:
Figure BDA0002765503430000021
Figure BDA0002765503430000022
βti-the virtual bulk density of the mix when the ith size fraction is taken as the leading factor;
βi-residual bulk density of the ith fraction;
rithe volume proportion of the ith fraction to all the particles,
Figure BDA0002765503430000031
aij-the loosening effect coefficient between the ith and jth grain,
Figure BDA0002765503430000032
bijthe coanda effect coefficient between the ith and jth grain levels, bij＝1-(1-di/dj)1.50；
di-the characteristic particle size of the ith fraction,
Figure BDA0002765503430000033
wherein d isimaxIs the upper limit particle diameter of the i-th fraction, diminThe lower limit particle size of the ith fraction;
k is the compaction coefficient of the mixture; the compaction coefficient K is related to the compaction energy provided by the outside to the mixture, and the mixture is vibrated in a dry state, wherein K is 9.0-6.2rCWherein r isCIn order to ensure that the volume proportion of the particles of the cementing material to all the particles is consistent with the process of mixture stacking and vibrating described in GB/T14685-2011 section 7.13.2.3 of pebble macadam for construction.
In the high-performance recycled concrete of the invention, the recycled coarse aggregate, the recycled fine aggregate, the cementing material and other various particles usually cover a plurality of grain fractions, and can be overlapped with each other, and the residual stacking compactness beta of the overlapped grain fractions is existediCalculated according to the following formula:
Figure BDA0002765503430000034
Rkthe volume proportion of the kth particles to all the particles,
Figure BDA0002765503430000035
rik-the volume fraction of the ith fraction of the kth type particles in the class of particles,
Figure BDA0002765503430000036
βikresidual bulk density of i-th fraction in type k granules, assuming β1k＝β2k＝...＝βnk＝βkRequire to obtain betakThe actual stacking compactness phi of various particles is obtained through a stacking testkAnd substituting the correction CPM model for inverse calculation.
Further, the cement composition in step (3) is determined based on past experience or with reference to general concrete related specifications or regulations, and it is recommended that the mineral admixture proportion does not exceed 40%.
Further, the recycled concrete formulated strength f in the step (5)cu,h＝fcu,k+ Δ f +1.645 σ, where fcu,kThe standard intensity value, σ, and Δ f are the standard intensity deviation and the formulated intensity adjustment coefficient, respectively. The adjustment coefficient is set by nano CaCO3After the calcium carbonate slurry is strengthened, the physical and mechanical properties of the recycled coarse and fine aggregates are probably still different from those of natural coarse and fine aggregates, so that the preparation strength of recycled concrete needs to be properly improved, and the adjustment coefficient delta f is recommended to be 10-15 MPa.
Further, the bauromid formula empirical coefficient value suggestion in the step (5) is equal to the crushed stone concrete, namely alphaa＝0.53，αb0.20, or determined by fitting experimental data.
Further, the additional water consumption in the step (6) is the water absorption capacity of the recycled coarse aggregate and the recycled fine aggregate within 2 hours, because the recycled coarse and fine aggregates can basically complete the water absorption process within 2 hours after the recycled concrete is cast and molded.
In the present invention, the cement may be portland cement, ordinary portland cement, portland slag cement, portland pozzolana cement, portland fly ash cement or the like, the mineral admixture may be fly ash, slag powder, silica fume, zeolite powder, metakaolin or the like, and the water reducing agent may be a polycarboxylic acid water reducing agent, a lignin water reducing agent, a naphthalene water reducing agent, a resin water reducing agent, an aliphatic water reducing agent or the like.
The invention principle of the invention is as follows:
according to the invention, a particle stacking model with stronger theoretical performance is adopted for carrying out mix proportion design, so that the stacking compactness after mixing in different proportions can be obtained through calculation under the condition of knowing the basic physical properties of coarse and fine aggregates and even cementing materials, the particle composition is optimized, the concrete compactness is improved, and various performance indexes of the concrete are indirectly improved. According to the method, a compressible stacking model (CPM) created by de Larrard is selected from a plurality of stacking models, the model has more consideration factors and higher calculation accuracy. The method makes necessary correction on the CPM model, and popularizes and applies the CPM model to the recycled concrete mix proportion design, so that the process of determining the sand rate and the rubber-bone ratio is more scientific and has evidence.
The strengthening treatment of the recycled aggregate comprises various ways such as physical strengthening, chemical strengthening, microorganism strengthening and the like, and the novel strengthening mode with application potential is realized by adopting nano materials to spray or dip the recycled aggregate. The nano material has special properties such as volume effect, surface effect, macroscopic quantum tunnel effect and the like, has high volcanic ash activity, can participate in hydration reaction of the cementing material, can be attached to the surface of the recycled aggregate to play a role in filling pores and microcracks, and thus, can improve various performance indexes of concrete. The invention adopts nano CaCO with lower price3The slurry is used for spraying the recycled coarse and fine aggregates, so that an ideal reinforcing effect can be achieved, and the high performance of recycled concrete is ensured.
Compared with the prior art, the invention has the following beneficial effects:
according to the method, the conventional CPM model is popularized and applied to the optimization of the grain composition of the recycled concrete through coefficient correction, so that the process of determining the sand rate to the rubber-cement ratio has more theoretical basis. And the CPM model is corrected, so that the compactness of the recycled concrete can be practically improved, and the amount of slurry and mixing water required for filling gaps can be reduced. The invention adopts nano CaCO3The slurry is used for spraying the recycled coarse and fine aggregates, so that the high performance of the recycled concrete is guaranteed. Nano CaCO3The slurry can effectively strengthen the adhesion of old mortar and an interface transition area, and improve various macro and micro performance indexes of recycled concrete. The design method of the mixing proportion has clear operation steps, accords with the engineering practice, and has good ecological benefit for the full utilization of the construction waste.
Drawings
FIG. 1 is a calculated value of the packing compactness of the recycled coarse aggregate and the recycled fine aggregate in example 1;
FIG. 2 is the calculated packing compactness of the recycled coarse and fine aggregates and the cementitious material in example 1;
FIG. 3 is the calculated packing density of the recycled coarse aggregate and the recycled fine aggregate in example 3;
FIG. 4 is the calculated packing density of the recycled coarse and fine aggregates and the cement in example 3.
Detailed Description
For a better understanding of the invention, illustrated with reference to the examples, the properties of the raw materials of recycled concrete are as follows:
the recycled coarse aggregate I is obtained by crushing waste concrete and has the apparent density of 2230kg/m3The compact bulk density is 1310kg/m3The water absorption rate after 2h is 3.45 percent, the maximum particle size is 40mm, and the particle size distribution is shown in the following table:
Figure BDA0002765503430000051
the recycled coarse aggregate II is obtained by crushing waste concrete and has the apparent density of 2280kg/m3The compact bulk density is 1250kg/m3The water absorption rate of 2h is 2.58%, the maximum particle size is 31.5mm, and the particle size distribution is shown in the following table:
Figure BDA0002765503430000052
the recycled fine aggregate I is obtained by crushing waste concrete and has the apparent density of 2130kg/m3The compact bulk density is 1310kg/m3The water absorption rate after 2h is 6.20 percent, the fineness modulus is 3.3, and the particle size distribution is shown in the following table:
Figure BDA0002765503430000053
the recycled fine aggregate II is obtained by crushing waste concrete and has an apparent density of 2060kg/m3The compact bulk density is 1220kg/m3The water absorption rate of 2h is 8.13%, the fineness modulus is 2.9, and the particle size distribution is shown in the following table:
Figure BDA0002765503430000054
the reference cement is 42.5 grade, and the apparent density is 3150kg/m3A compact bulk density of 1230g/m3The particle size distribution of any grade was measured by a laser particle sizer as shown in the following table:
Figure BDA0002765503430000055
the micro silicon powder is BK93 grade, and the apparent density is 2110kg/m3The compact bulk density is 445kg/m3The particle size distribution of any grade was measured by a laser particle sizer as shown in the following table:
Figure BDA0002765503430000056
the water reducing rate of the polycarboxylic acid water reducing agent is within 25-35%, and the solid content is 40%.
Nano CaCO3The slurry had a pH of 8.0, a solids content of 20% and an average particle size of 30 nm.
Example 1
In the embodiment, the high-performance recycled concrete is prepared by adopting the recycled coarse aggregate I and the recycled fine aggregate I, the cementing material is composed of cement and silica fume, the slump is required to reach 150mm, and the strength reaches the C55 grade.
(1) Determination of Nano CaCO3The dosage of the slurry is the regenerated coarse aggregate nano CaCO by mass3The slurry dosage is 1.0 percent, the recycled fine aggregate dosage is 2.0 percent, and the recycled coarse and fine aggregates are subjected to nano modification in a spraying mode.
(2) And (3) calculating the stacking compactness of the recycled coarse aggregate and the recycled fine aggregate by using the modified CPM model, wherein a peak value of 0.665 is obtained when the volume proportion of the recycled fine aggregate is 46.1% as shown in figure 1, namely the volume sand rate of the recycled concrete is 46.1%.
(3) And determining the composition of the cementing material, wherein the cement accounts for 85 percent and the silica fume accounts for 15 percent based on volume.
(4) The volume sand rate is kept unchanged at 46.1%, the CPM model is corrected, and the stacking compactness of the recycled coarse and fine aggregates and the cementing material is calculated, as shown in FIG. 2, when the volume ratio of the cementing material is 20.3%, the peak value is 0.742, namely the volume ratio of the recycled concrete to the cementite is 0.255.
(5) Determination of recycled concrete formulation Strength fcu,h＝fcu,k+ Δ f +1.645 σ ═ 55+15+1.645 × 5 ═ 78.2MPa, and the empirical coefficient of the bauromil equation is taken as αa＝0.53，αbThe effective water-gel ratio of the recycled concrete was 0.313 by mass, which is 0.20.
(6) The preliminary calculation mixing proportion is determined by a volume method, the gas content is 1.0 percent, and the using amount of the recycled concrete recycled coarse aggregate in unit volume is 796.4kg/m3The amount of the recycled fine aggregate is 651.6kg/m3The dosage of the reference cement is 451.9kg/m3The dosage of the micro silicon powder is 53.4kg/m3The water consumption for mixing is 158.2kg/m3。
(7) According to the water absorption rate of the recycled coarse aggregate and the recycled fine aggregate for 2h, the additional water consumption of the recycled concrete per unit volume is 796.4 x 3.45% +651.6 x 6.20% -67.9 kg/m3The total water consumption is 158.2+67.9 ═ 226.1kg/m3。
(8) Trial preparation is carried out according to the preliminary calculated mixture ratio, the mixing amount of the polycarboxylate superplasticizer is 1.60 percent of the gelled material by mass, and the dosage of the polycarboxylate superplasticizer for the recycled concrete in unit volume is 8.1kg/m3At this point the blend slump reached 180 mm.
According to the above analytical calculation, the recycled concrete is formulated as shown in the following table:
Figure BDA0002765503430000061
preparing a cubic test piece of 100mm multiplied by 100mm, curing the test piece in a standard environment after removing a mold, detecting the mechanical property of the recycled concrete by using a press machine, and finding that the compressive strength of the test piece in the 3d age, the compressive strength of the test piece in the 7d age and the compressive strength of the test piece in the 28d age reach 36.9MPa, 49.0MPa and 63.7MPa respectively, and the cleavage tensile strength of the test piece in the 28d age reach 4.36 MPa.
Example 2
On the basis of example 1, recycled coarse aggregate nano CaCO3The dosage of the slurry is increased to 2.0 percent, the dosage of the recycled fine aggregate is increased to 3.0 percent, and other parameters are not changed. At the moment, the slump of the recycled concrete reaches 165mm, the compression strength at the age of 3d, 7d and 28d reaches 41.6MPa, 51.7MPa and 65.4MPa respectively, and the splitting tensile strength at the age of 28d reaches 4.50 MPa.
Example 3
In the embodiment, the high-performance recycled concrete is prepared by adopting the recycled coarse aggregate II and the recycled fine aggregate II, the cementing material is composed of cement and silica fume, the slump reaches 150mm, and the strength reaches the C50 grade.
(1) Determination of Nano CaCO3The dosage of the slurry is the regenerated coarse aggregate nano CaCO by mass3The slurry dosage is 1.0 percent, the recycled fine aggregate dosage is 2.0 percent, and the recycled coarse and fine aggregates are subjected to nano modification in a spraying mode.
(2) The compaction degree of the recycled coarse aggregate and the recycled fine aggregate is calculated by using the modified CPM model, and as shown in FIG. 3, when the volume proportion of the recycled fine aggregate is 44.8%, the peak value is 0.698, namely the volume sand rate of the recycled concrete is 44.8%.
(3) And determining the composition of the cementing material, wherein the cement accounts for 90 percent and the silica fume accounts for 10 percent based on volume.
(4) The volume sand rate is kept to be 44.8 percent, the CPM model is corrected, the stacking compactness of the recycled coarse and fine aggregates and the cementing material is calculated, as shown in figure 4, the peak value is 0.753 when the volume ratio of the cementing material is 17.9 percent, namely the volume ratio of the recycled concrete to the cementite is 0.218.
(5) Determination of recycled concrete formulation Strength fcu,h＝fcu,k+ Δ f +1.645 σ is 50+15+1.645 × 5 is 73.2MPa, and the empirical coefficient of the bauromi equation is taken as αa＝0.53，αbThe effective water-gel ratio of the recycled concrete was 0.333 in terms of mass when it was 0.20.
(6) The preliminary calculation mixing proportion is determined by a volume method, the gas content is 1.0 percent, and the using amount of the recycled concrete recycled coarse aggregate in unit volume is 866.2kg/m3The amount of the recycled fine aggregate is 635.0kg/m3The dosage of the reference cement is 424.7kg/m3The dosage of the micro silicon powder is 31.6kg/m3The mixing water consumption is 152.0kg/m3。
(7) According to the water absorption rate of the recycled coarse aggregate and the recycled fine aggregate for 2h, the additional water consumption of the recycled concrete per unit volume is 866.2 multiplied by 2.58% +635.0 multiplied by 8.13% >, 74.0kg/m3The total water consumption is 152.0+74.0 ═ 226.0kg/m3。
(8) Trial preparation is carried out according to the preliminary calculated mixture ratio, the mixing amount of the polycarboxylate superplasticizer is 1.80 percent of the gelled material by mass, and the dosage of the polycarboxylate superplasticizer for the recycled concrete in unit volume is 7.3kg/m3At this point the blend slump reached 175 mm.
According to the above analytical calculation, the recycled concrete is formulated as shown in the following table:
Figure BDA0002765503430000071
preparing a cubic test piece of 100mm multiplied by 100mm, curing the test piece in a standard environment after removing a mold, detecting the mechanical property of the recycled concrete by using a press machine, and finding that the compressive strength of the test piece in the 3d age, the compressive strength of the test piece in the 7d age and the compressive strength of the test piece in the 28d age reach 32.7MPa, 45.6MPa and 57.2MPa respectively, and the cleavage tensile strength of the test piece in the 28d age reach 4.23 MPa.
Example 4
On the basis of example 3, recycled coarse aggregate nano CaCO3The dosage of the slurry is increased to 2.0 percent, the dosage of the recycled fine aggregate is increased to 3.0 percent, and other parameters are not changed. At the moment, the slump of the recycled concrete reaches 170mm, the compression strength at the age of 3d, 7d and 28d reaches 35.4MPa, 49.3MPa and 59.4MPa respectively, and the splitting tensile strength at the age of 28d reaches 4.20 MPa.
Mortar fragments were chiseled in the 4 examples of the high-performance recycled concrete test pieces, and the pore structure was examined by mercury porosimetry, wherein the pore diameter of harmful pores exceeded 200nm, the pore diameter of harmless pores did not exceed 50nm, and the less harmful pores were between the two.
Figure BDA0002765503430000081
From the detected data, the basisIn the correction of CPM model and nano-CaCO3The recycled concrete with the slurry reinforced design can meet the requirements of rheological property and mechanical property and has a compact pore structure. In addition, as the substitution rate of the recycled coarse aggregate and the recycled fine aggregate is 100 percent, the in-situ utilization rate of the raw materials exceeds 65 percent, and the method has good ecological benefit.
The above description is only exemplary of the preferred embodiment, and the present invention is not limited thereto, and any modification and equivalent replacement of the present invention within the spirit and scope of the claims are within the scope of the present invention.

Claims (7)

1. A high-performance recycled concrete mix proportion design method based on a modified CPM model and nano calcium carbonate reinforcement is characterized by specifically adopting the following technical scheme:
(1) determination of Nano CaCO3The slurry amount is used for carrying out nano modification on the recycled coarse and fine aggregate;
(2) calculating the stacking compactness of a mixture I obtained by mixing the recycled coarse aggregate and the recycled fine aggregate in different proportions by using a modified CPM model, and determining the volume sand rate of the recycled concrete according to the peak position;
(3) determining the composition of the cementing material, namely the proportion of cement and mineral admixture;
(4) on the premise of a set volume sand rate, calculating the stacking compactness of a mixture II obtained by mixing the recycled coarse and fine aggregate and the cementing material in different volume proportions by using a modified CPM model, and determining the volume ratio of the cementite of the recycled concrete according to the peak position;
(5) calculating the preparation strength of the recycled concrete, and determining the effective water-cement ratio by using a bauromid formula;
(6) determining the primary calculation mixing proportion of the recycled concrete by using a volume method, namely the consumption of recycled coarse aggregate, the consumption of recycled fine aggregate, the consumption of cementing material and the consumption of mixing water;
(7) determining the additional water consumption of the recycled concrete according to the water absorption characteristic of the recycled coarse and fine aggregate;
(8) trial preparation is carried out according to the preliminary calculated mixture ratio, the dosage of the water reducing agent is determined based on the fluidity requirement of the recycled concrete, and the effective water-cement ratio and the cementing material composition are adjusted based on the mechanical and durability requirements of the recycled concrete.
2. The method for designing the mix proportion of modified CPM model and nano calcium carbonate reinforced high-performance recycled concrete according to claim 1, wherein the step (1) is nano CaCO3The slurry is alkalescent, has a pH value of 8-9, a solid content of 20%, an average particle size of 30-50 nm and nano CaCO3The slurry is made of nano CaCO3The emulsion being formed by partial dehydration, nano CaCO3The emulsion is produced by a carbonation reactor.
3. The method for designing the mix proportion of modified CPM model and nano calcium carbonate reinforced high-performance recycled concrete according to claim 1, wherein the step (1) is nano CaCO3The slurry is uniformly sprayed on the surface of the recycled aggregate, the recycled aggregate can be used for preparing concrete after being sprayed and aired for at least 48 hours, and the nano CaCO used for modifying the recycled coarse aggregate is calculated by mass3The serous fluid is 1.0-2.0 percent of the recycled coarse aggregate, and the nano CaCO of the modified recycled fine aggregate3The size is 2.0-3.0% of the recycled fine aggregate.
4. The method for designing the mixing proportion of the high-performance recycled concrete based on the modified CPM model and the nano calcium carbonate reinforcement according to claim 1, wherein the amount to be solved by the modified CPM model in the steps (2) and (4) is the actual stacking compactness phi of the mixture I and the mixture II respectively, and the actual stacking compactness phi is calculated according to the following formula:
Figure FDA0002765503420000021
Figure FDA0002765503420000022
βtiwhen the ith size fraction is taken as the main factorThe virtual stacking compactness of the mixture;
βi-residual bulk density of the ith fraction;
rithe volume proportion of the ith fraction to all the particles,
Figure FDA0002765503420000023
aij-the loosening effect coefficient between the ith and jth grain,
Figure FDA0002765503420000024
bijthe coanda effect coefficient between the ith and jth grain levels, bij＝1-(1-di/dj)1.50；
di-the characteristic particle size of the ith fraction,
Figure FDA0002765503420000025
wherein d isimaxIs the upper limit particle diameter of the i-th fraction, diminThe lower limit particle size of the ith fraction;
k-compaction coefficient of the mix, K ═ 9.0-6.2rCWherein r isCThe volume ratio of the gelled material particles to all the particles is shown;
the granules of the recycled coarse aggregate, the recycled fine aggregate and the cementing material cover a plurality of size fractions, and can be overlapped with each other, and the residual stacking compactness beta of the overlapped size fractions isiCalculated according to the following formula:
Figure FDA0002765503420000026
Rkthe volume proportion of the kth particles to all the particles,
Figure FDA0002765503420000027
rik-the ith fraction of the kth granulesThe volume ratio of the particles is the same as the volume ratio of the particles,
Figure FDA0002765503420000028
βikresidual bulk density of i-th fraction in type k granules, assuming β1k＝β2k＝…＝βnk＝βkRequire to obtain betakThe actual stacking compactness phi of various particles is obtained through a stacking testkAnd substituting the correction CPM model for inverse calculation.
5. The method for designing the mix proportion of high-performance recycled concrete based on modified CPM model and nano calcium carbonate reinforcement according to claim 1, wherein the step (5) of preparing the recycled concrete with the strength fcu,h＝fcu,k+ Δ f +1.645 σ, where fcu,kThe standard value of the strength is, sigma is the standard deviation of the strength, and delta f is the adjustment coefficient of the prepared strength, and the value is 10 MPa-15 MPa.
6. The method for designing the mix proportion of the high-performance recycled concrete based on the modified CPM model and the nano calcium carbonate reinforcement in the claim 1, wherein the empirical coefficient value of the Baulomi formula in the step (5) is equal to that of the crushed stone concrete or determined by fitting test data.
7. The method for designing the mixing proportion of the high-performance recycled concrete based on the modified CPM model and the nano calcium carbonate reinforcement in claim 1, wherein the additional water consumption in the step (7) is 2h of water absorption of the recycled coarse aggregate and the recycled fine aggregate.
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