CN114195437A - Recycled concrete replaced by brick-concrete recycled coarse aggregate and preparation method thereof - Google Patents

Recycled concrete replaced by brick-concrete recycled coarse aggregate and preparation method thereof Download PDF

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CN114195437A
CN114195437A CN202111350702.9A CN202111350702A CN114195437A CN 114195437 A CN114195437 A CN 114195437A CN 202111350702 A CN202111350702 A CN 202111350702A CN 114195437 A CN114195437 A CN 114195437A
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concrete
recycled
coarse aggregate
brick
aggregate
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王淼
李岩凌
周伟
何强
陈向杰
刘文才
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BCEG Resources Recycling Co Ltd
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BCEG Resources Recycling Co Ltd
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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
    • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
    • 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
    • C04B18/16—Waste materials; Refuse from building or ceramic industry
    • 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
    • C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
    • C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
    • 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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  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Civil Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Inorganic Chemistry (AREA)
  • Environmental & Geological Engineering (AREA)
  • Curing Cements, Concrete, And Artificial Stone (AREA)

Abstract

The invention relates to recycled concrete replaced by brick-concrete recycled coarse aggregate, which comprises cement, fly ash, mineral powder, fine aggregate, coarse aggregate, a water reducing agent and water; the coarse aggregate comprises natural coarse aggregate and brick-concrete recycled coarse aggregate, and the mass percentage of the brick-concrete recycled coarse aggregate in the coarse aggregate is 20-30%; the brick-concrete recycled coarse aggregate is obtained by compounding recycled red brick coarse aggregate and recycled concrete coarse aggregate, wherein the mass percentage of the recycled red brick coarse aggregate is 50-75%. The brick-concrete recycled coarse aggregate is used for partially replacing natural coarse aggregate in concrete, and the prepared recycled concrete has better cubic compressive strength and axial compressive strength, and also has better elastic modulus, Poisson's ratio and frost resistance; the method is beneficial to relieving the current situation of shortage of natural aggregate supply at present and realizes the resource application of the construction waste.

Description

Recycled concrete replaced by brick-concrete recycled coarse aggregate and preparation method thereof
Technical Field
The invention relates to recycled concrete replaced by brick-concrete recycled coarse aggregate and a preparation method thereof, belonging to the technical field of concrete.
Background
The concrete is widely applied to various modern buildings and structures as the most common material, the research on the recycled concrete is increasing along with the shortage of concrete raw materials and the problems of reduction of building wastes, resource application and the like, the application research on the recycled concrete can not only reduce the use and exploitation of raw materials and relieve the environmental pressure, but also realize the resource application of building wastes, and therefore, the research on the recycled concrete has great significance.
At present, recycled concrete aggregate is mostly used in the research of recycled concrete, and in reality, the recycled aggregate often contains a large amount of red bricks, and compared with the pure recycled concrete aggregate, the performance of brick-concrete aggregate is larger in difference, related research is less, and the brick-concrete aggregate is difficult to be applied to the preparation of recycled concrete. Moreover, the separation technology of the brick-concrete aggregate is still not perfect, the labor cost for realizing brick-concrete separation is high, large-scale separation is difficult, the content of red bricks in the brick-concrete aggregate is greatly different, and the self performance dispersion degree of the aggregate is large. The brick-concrete recycled aggregate is mostly used as a base layer or made into a recycled product for use on roads, and resource utilization of the brick-concrete aggregate in cement concrete is difficult.
Therefore, the brick-concrete recycled aggregate is applied to concrete to replace natural aggregate with medium quality from the brick-concrete aggregate, so that the brick-concrete recycled concrete is prepared, and has wide application prospect.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide recycled concrete replaced by brick-concrete recycled coarse aggregate and a preparation method thereof.
In order to achieve the purpose, the invention adopts the technical scheme that: the recycled concrete substituted by the brick-concrete recycled coarse aggregate comprises cement, fly ash, mineral powder, fine aggregate, coarse aggregate, a water reducing agent and water; the coarse aggregate comprises natural coarse aggregate and brick-concrete recycled coarse aggregate, and the mass percentage of the brick-concrete recycled coarse aggregate in the coarse aggregate is 20-30%; the brick-concrete recycled coarse aggregate is obtained by compounding recycled red brick coarse aggregate and recycled concrete coarse aggregate, wherein the mass percentage of the recycled red brick coarse aggregate is 50-75%.
In a preferred embodiment of the recycled concrete of the present invention, the mass percentage of the brick-mixed recycled coarse aggregate in the coarse aggregate is 20%.
In a preferred embodiment of the recycled concrete of the present invention, the recycled red brick coarse aggregate in the brick-concrete recycled coarse aggregate is 50% by mass.
In a preferred embodiment of the recycled concrete of the present invention, the mass percentage of the brick-mixed recycled coarse aggregate in the coarse aggregate is 20%, and the mass percentage of the recycled red brick coarse aggregate in the brick-mixed recycled coarse aggregate is 50%.
As a preferred embodiment of the recycled concrete of the present invention, the recycled concrete comprises the following components in parts by weight: 220 parts of cement, 80 parts of fly ash, 80 parts of mineral powder, 800 parts of fine aggregate, 1100 parts of coarse aggregate, 1.9-5.7 parts of water reducing agent and 170 parts of water.
As a preferred embodiment of the recycled concrete of the present invention, the recycled concrete comprises the following components in parts by weight: 220 parts of cement, 80 parts of fly ash, 80 parts of mineral powder, 800 parts of fine aggregate, 1100 parts of coarse aggregate, 2.85 parts of water reducing agent and 170 parts of water.
In a preferred embodiment of the recycled concrete of the present invention, the fine aggregate has a particle size of 0 to 5mm, and the coarse aggregate has a particle size of 5 to 20 mm.
As a preferable embodiment of the recycled concrete of the present invention, the water reducing agent is a powdery polycarboxylic acid water reducing agent, and the fly ash is class II fly ash.
As a preferred embodiment of the recycled concrete, the brick-concrete recycled coarse aggregate has a crushing index of 20.00-25.00%, a 4.75-26.5 mm continuous gradation and an apparent density of 2300-2400 kg/m3The porosity is 53.00% -58.00%, and the water absorption is 3.00% -18.50%.
In a second aspect, the present invention provides a method for preparing the recycled concrete, comprising the following steps:
(1) weighing fine aggregate, coarse aggregate, mineral powder, fly ash, cement, a water reducing agent and water according to the proportion;
(2) and pouring the mixture into a concrete mixer in sequence, and uniformly mixing to obtain the recycled concrete substituted by the brick-concrete recycled fine aggregate.
Compared with the prior art, the invention has the beneficial effects that: the brick-concrete recycled coarse aggregate is used for partially replacing natural coarse aggregate in concrete, and the prepared recycled concrete has better cubic compressive strength and axial compressive strength, and also has better elastic modulus, Poisson's ratio and frost resistance; the method is beneficial to relieving the current situation of shortage of natural aggregate supply at present and realizes the resource application of the construction waste.
Drawings
FIG. 1 is a picture of recycled concrete coarse aggregate and recycled red brick coarse aggregate.
FIG. 2 is a statistical chart of the content of fine powder and MB value of 3 kinds of recycled coarse aggregates.
FIG. 3 is a statistical chart of the impurity content of the brick-concrete coarse aggregate.
FIG. 4 is a graph of experimental results of organic content of brick-concrete coarse aggregates, wherein A is a graph of experimental results of 25% of red brick content, B is a graph of experimental results of 50% of red brick content, and C is a graph of experimental results of 75% of red brick content.
Fig. 5 is a statistical chart of the total mass loss percentage of the brick-mixed recycled coarse aggregate sample.
FIG. 6 is a graph showing the variation tendency of the brick-concrete coarse aggregate crushing index and the result of linear fitting.
Fig. 7 is a water absorption rate variation trend graph of the brick-concrete coarse aggregate.
Fig. 8 is an experimental result and a trend graph of the bulk density of the brick-concrete recycled coarse aggregate.
Fig. 9 is an experimental result and a trend graph of the apparent density of the brick-concrete recycled coarse aggregate.
Fig. 10 is an experimental result and a trend graph of the porosity of the brick-concrete recycled coarse aggregate.
FIG. 11 is a graph of recycled concrete density for the group having 50% red brick content.
FIG. 12 is a density chart of recycled concrete of a group with 75% of red brick content.
Fig. 13 is a graph of cubic compressive strength of recycled concrete with brick content of 50% and brick content of 75% in recycled aggregate, where a is the graph of cubic compressive strength of recycled concrete, and B is the graph of cubic compressive strength of recycled concrete with brick content of 75% in aggregate.
FIG. 14 is a graph showing axial compressive strength of recycled concrete containing 50% and 75% of bricks in recycled aggregate.
FIG. 15 is a B-group recycled concrete failure form diagram.
FIG. 16 is a failure pattern diagram for group C recycled concrete.
FIG. 17 is a graph showing the failure mode of the recycled concrete of group G.
FIG. 18 is a view showing a failure mode of recycled concrete in group H.
FIG. 19 is a graph showing the tendency of the brick contents of 50% and 75% to change in the elastic modulus and axial compressive strength of recycled aggregate.
FIG. 20 is a freeze-thaw appearance change diagram of brick-concrete recycled concrete with red brick content of 50%.
FIG. 21 is a freeze-thaw appearance change diagram of brick-concrete recycled concrete with red brick content of 75%.
FIG. 22 is a diagram showing the tendency of the quality loss of the recycled concrete in the freeze-thaw cycle, with brick contents of 50% and 75% in the recycled aggregate.
FIG. 23 is a graph showing the compressive strength loss rate of recycled concrete D50 in freeze-thaw cycles, wherein the recycled concrete contains 50% and 75% of bricks in the recycled aggregate.
Detailed Description
To better illustrate the objects, aspects and advantages of the present invention, the present invention will be further described with reference to the accompanying drawings and specific embodiments.
1. Raw material
The materials involved in the test of the invention mainly comprise cement, recycled coarse aggregate, natural coarse and fine aggregate, fly ash, mineral powder, water reducing agent, water and chemicals used in the testing of the physicochemical properties of the aggregates.
(1) Cement
The test of the invention uses two kinds of cement together for carrying out related tests, wherein the cement used in the reclaimed mortar test is P I42.5.5 standard cement provided by China general institute of building materials science, and the physical properties, chemical analysis and mineral composition of the standard cement are shown in tables 1, 2 and 3. The cement used for the recycled concrete product is P O42.5.5 cement, and the basic physical properties of the cement are shown in Table 4; the related performance indexes of the two kinds of cement meet the requirements of the current related standards.
TABLE 1 benchmark Cement physical Properties
Figure BDA0003355636110000041
TABLE 2 results of the chemical analysis of the reference cements
Figure BDA0003355636110000042
TABLE 3 basic Cement mineral composition
Figure BDA0003355636110000043
TABLE 4 Cement physical Properties
Figure BDA0003355636110000044
(2) Fly ash
Class II fly ash was used in the recycled concrete product experiments herein, the basic performance index is shown in Table 5, and the chemical composition is shown in Table 6; meets the relevant requirements of 'fly ash for cement and concrete' GB/T1596-2017.
TABLE 5 basic fly ash Properties
Figure BDA0003355636110000051
TABLE 6 chemical analysis of fly ash
Figure BDA0003355636110000052
(3) Mineral powder
The slag powder is used in the recycled concrete experiment, the basic performance index of the slag powder is shown in Table 7, and the slag powder meets the relevant requirements of 'granulated blast furnace slag powder used in cement, mortar and concrete' GB/T18046-charge 2017.
TABLE 7 basic properties of the slag powder
Figure BDA0003355636110000053
(4) Aggregate material
The coarse aggregates used in the invention are 3 in total, comprising a natural coarse aggregate and two recycled coarse aggregates; the natural coarse aggregate adopts crushed stone with 5-20mm continuous gradation, and related physicochemical indexes of the crushed stone meet the related requirements of I-class aggregate in construction pebble and crushed stone GB/T14685-2011.
The two recycled coarse aggregates used in the test are respectively from 5-20mm continuously assembled recycled aggregates formed by selecting, crushing, screening and the like waste concrete and waste red bricks; combining the two aggregates according to different mass ratios to form various recycled brick-concrete coarse aggregates.
The natural coarse aggregate adopts crushed stone with 5-20mm continuous gradation, and related physicochemical indexes of the crushed stone meet the related requirements of I-class aggregate in construction pebble and crushed stone GB/T14685-2011.
The natural fine aggregate used in the invention adopts natural river sand with fineness modulus of 2.4, and related physical and chemical indexes of the natural fine aggregate are shown in Table 8, and all meet the related requirements of II-class aggregates in GB/T14684-2011 building sand.
TABLE 8 basic Properties of Natural river Sand
Figure BDA0003355636110000061
(5) Additive agent
The polycarboxylic acid high-performance powder water reducer is used in the concrete experiment, and the related performance indexes are shown in the following table 9.
TABLE 9 polycarboxylate superplasticizer Performance index
Figure BDA0003355636110000062
(6) Other materials
The test water is divided into two types; the water used in concrete and mortar experiments is tap water from Beijing, and the water used in the related reagent is distilled water in the aggregate basic materialization experiment.
Methylene blue solution: methylene blue powder (C) produced by Tianjin Beichen Fangzheng is used16H18ClN3S·3H2O), drying and weighing, and weighing 10g to prepare 1L methylene blue solution.
Zinc chloride: chemical pure (ZnCl) produced by Tianjin Fuchen2)
Sodium hydroxide: analytical pure sodium hydroxide (NaOH) from Tianjin permanent production
Tannic acid: analytical pure tannic acid (tannic acid) produced by Tianjin Yongda
Anhydrous ethanol: analytically pure absolute ethyl alcohol produced by national medicine group
Barium chloride: analytically pure barium chloride produced in Beijing chemical plant
Sodium chloride: analytically pure sodium chloride produced in Beijing chemical plant
Dilute hydrochloric acid: the dilute hydrochloric acid used herein is concentrated hydrochloric acid
Silver nitrate solution: dissolving solid silver nitrate in water in brown bottle to obtain
5% potassium chromate indicator: prepared by potassium chromate produced in Tianjin Fuchen and distilled water.
Saturated solution of sodium sulfate: prepared by adding 350g of anhydrous sodium sulfate into 1L of water by using analytically pure anhydrous sodium sulfate produced in Tianjin Fuchen.
Related experimental equipment such as a measuring cylinder, a volumetric flask, a beaker, a triangular flask, a burette, a pipette and the like, measuring instruments and the like used in the recycled aggregate performance test all accord with relevant national standards.
2. Recycled aggregate testing method
(1) Particle size distribution
In a coarse aggregate particle grading experiment, 500g of coarse aggregate to be tested after being dried for 24 hours at 105 ℃ is weighed, poured into a sleeve sieve with a sieve bottom and a sieve cover of 0.15-4.75 mm, placed on a sieve shaker to shake for 10min, and the sieve residue is weighed out, wherein the sieve residue on each particle size sieve is not more than the calculated amount of the formula 2-1; the fineness modulus was calculated according to equation 2-2.
Figure BDA0003355636110000071
In the formula: g-the reject (G) on a single sieve;
a-area of the sieve surface (mm)2)；
d-mesh size (mm).
Figure BDA0003355636110000072
In the formula: mx-fineness modulus;
A1、A2、A3、A4、A5、A6-cumulative percent rejects for sieves ranging from 4.75mm to 0.15mm, respectively.
(2) Content of micropowder MB value and content of clod
The content of the micro powder of the recycled coarse aggregate and the content of the mud block are respectively tested according to a stone powder content and a mud block test method in GB/T14684 + 2011 building sand; the MB value is measured by referring to the measurement of methylene blue MB value; the content of the micro-powder is calculated according to the formula 2-3, the MB value is calculated according to the formula 2-4, and the content of the mud lumps is calculated according to the formula 2-5.
Figure BDA0003355636110000073
In the formula: qa-micropowder content (%); g0-drying the sample mass (g) before testing;
G1-oven dry sample mass after test (g).
Figure BDA0003355636110000081
In the formula: MB-methylene blue value (g/kg); g-sample mass (G);
v-total amount of methylene blue used (ml); 10-scaling factor.
Figure BDA0003355636110000082
In the formula: qb-mud mass content (%); g1-mass (g) of oversize sample of 1.18mm sieve; g2-oven dry sample mass after test (g).
(3) Content of harmful substance
The light material content in the recycled coarse aggregate is prepared by a specific gravity method, and the density is 2000kg/m3Weighing the sample according to the requirement, pouring the sample into the solution, fully stirring and precipitating, fishing out the floating substance, cleaning, drying, weighing, and calculating the content of the light substance according to the formula 2-6.
Figure BDA0003355636110000083
In the formula: qd-light matter content (%); g1-sample mass (g) 0.3mm to 4.75 mm; g2-beakerAnd drying the total mass (g) of the light materials; g3Beaker mass (g).
Preparing a standard solution according to the test requirement of the organic matter content in GB/T14684-2011 of building sand by adopting a colorimetric method for the organic matter content; and (4) carrying out color comparison on the sample solution and the standard solution, wherein the organic matter content is qualified if the color is lighter than that of the standard solution.
Measuring the content of sulfide and sulfate, grinding a sample to be measured, sieving the ground sample through a 0.075mm sieve, drying the ground sample at 105 ℃ for 24 hours, weighing 1g of sample powder, adding a proper amount of distilled water and dilute hydrochloric acid, heating the sample to slightly boil and keeping the boiling for 5min, filtering the solution through medium-speed filter paper, adding a prepared 10% barium chloride solution, filtering and precipitating the solution after boiling, transferring the solution and the filter paper to a crucible, burning the mixture in a high-temperature furnace for 30min, taking the mixture out and placing the mixture in a dryer, weighing the sample with the mass being accurate to 0.001g, and calculating the content of water-soluble sulfide and sulfate by using the formula 2-7.
Figure BDA0003355636110000084
In the formula: qe-sulphide and sulphate content (%);
G1-sample mass (g);
G2-mass (g) of the precipitate after high temperature ignition;
0.343 — conversion factor.
And (2) measuring the chloride content, dissolving 500g of a sample in 500ml of distilled water, standing for 2 hours to dissolve chloride ions in the solution, sucking 50ml of the solution by using a pipette, adding 1ml of a potassium chromate indicator, titrating by using a prepared 0.01mol/L silver nitrate solution until brick red precipitates appear, recording the using amount of a silver nitrate standard solution at the moment, simultaneously performing a blank titration experiment by using distilled water, and calculating the chloride ion content according to the formula 2-8.
Figure BDA0003355636110000091
In the formula: qf-chloride ion content (%); n-nitreConcentration of silver acid solution (mol/L);
a-consumption of silver nitrate volume (ml) upon titration of sample solution;
b-blank titration consumes silver nitrate volume (ml); 0.0355-conversion factor.
(4) Firmness of use
The firmness of the recycled coarse aggregate is carried out according to a sodium sulfate solution method in GB/T14684-2011 of construction sands.
(5) Crush index
The crushing index of the recycled coarse aggregate is tested according to the crushing index methods in GB/T14685 plus 2011 and GB/T14684 plus 2011 of construction sand respectively.
(6) Apparent density, bulk density and void fraction
The apparent density and the bulk density of the recycled coarse aggregate are tested according to 'macadam and pebble for construction' GB/T14685-.
3. Test piece manufacturing and maintenance
(1) Sample preparation
Strength test block: the test blocks used in the strength test are manufactured into two types, and the axial compression test adopts a 100mm multiplied by 100mm triple test mould to manufacture the test blocks with reduced size; the prism has the test block size of 150mm multiplied by 300mm for the prism compressive strength, elastic modulus, Poisson's ratio and stress-strain full curve test; the testing machine used in the experiment is a HJW-60 type forced concrete mixer, slump and expansion meet the test requirements by adjusting the using amount of the water reducing agent, the testing machine is put into a test mold and placed on a compaction table for compaction, and then maintenance is carried out, wherein the test mold is required to be coated with a release agent in advance or mineral oil which does not react with concrete.
Freezing and thawing the test block: the test piece is used for detecting the D50 label by a slow freezing method, according to the requirement of the test method standard for the long-term performance and the durability of common concrete GB/T50082-2009, the test adopts a cubic test block with the size of 100mm multiplied by 100mm, and the test is uniformly matched with brick-mixed recycled concrete samples to manufacture 3 groups, wherein one group is used for 28D strength identification, one group is used for a freeze-thaw test, and the other group is used for comparing test pieces.
(2) Test block maintenance
Strength test block: and putting the compacted concrete test block into a curing room, curing for 24h, demolding, and continuing curing the test block until the age is finished after demolding, wherein the curing condition is controlled to be 20 +/-2 ℃ and the humidity is over 95 percent.
Freezing and thawing the test block: firstly, concrete mixture prepared according to the brick-concrete recycled concrete mixing proportion and the aggregate substitution scheme is put into a test mould for forming after slump and other indexes are tested, the concrete mixture is placed in a standard curing room for curing for 24 hours and then is demoulded for standard curing, a freeze-thaw test piece is taken out from the curing room in advance after being cured in the standard curing room for 24 days, a test block is placed in water with the temperature of 20 +/-2 ℃ for soaking, and the test block is placed into a freeze-thaw testing machine for freeze-thaw testing after being soaked for 4-28 days.
4. Performance testing
(1) Slump constant
The slump test is carried out according to the standard of the performance test method of common concrete mixtures GB/T50081-2019. The slump test is that after the concrete is placed for 1h, the slump is measured according to the standard GB/T50081-2019 of the test method for the performance of the common concrete mixture.
(2) Degree of expansion
The concrete expansion degree test is carried out according to the standard of the performance test method of common concrete mixtures GB/T50081 plus 2019. The method for the loss of the expansion degree with time is consistent with the concrete slump, the method is used for testing the expansion degree with time for 1h and calculating the loss with time.
(3) Density of
The main method of concrete density is that the concrete after being cured to the age is taken out from the curing room and wiped to dry the water stain on the surface by a rag, the mass is weighed by an electronic scale, and the concrete density is calculated.
(4) Strength of
Cubic compressive strength
The compressive strength is tested by adopting a concrete cubic non-standard test block with the side length of 100mm, 3 blocks are prepared in each group of tests, the compressive strength test is tested by adopting an WEW-200 type electro-hydraulic servo universal tester produced by a tin-free tester, and the maximum pressure is 2000 kN; the loading is controlled by stress, and the value range refers to the relevant regulations of the Experimental method Standard for physical and mechanical Properties of concrete GB/T50081-2019. The compressive strength was calculated according to equation 5-1.
Figure BDA0003355636110000101
Wherein: f. ofcc-compressive strength (MPa) of the concrete cubic specimen;
f is the load (N) when the test piece is damaged;
a-test piece bearing area under stress (mm)2)。
The compressive strength values for each set were averaged over 3 trials when one of them exceeded 15% of the median value. Discarding the maximum value and the minimum value, and taking a median; the set of test pieces was not effective when both the maximum and minimum values exceeded 15% of the median. The experiment adopts a non-standard cube test block with the side length of 100mm, so the measured intensity value needs to be multiplied by a reduction coefficient, and the reduction coefficient takes a standard recommended value of 0.95.
Axial compressive strength
The size of the test piece for the axial compressive strength test adopts 150mm multiplied by 300mm prism standard test pieces, each group of test pieces is 3, the test pieces are cured to the age according to standard curing conditions, a YAW6306 type microcomputer control electro-hydraulic servo pressure tester produced by Meitess industry is used for carrying out the compressive strength test, and the test only tests the strength of the age of 28 d.
(5) Modulus of elasticity
The elastic modulus reflects the relation of stress and strain of a concrete material, the deformation capacity of the elastic stage is reflected to a certain extent, the test is carried out according to a static compression elastic modulus test in GB/T50081-plus 2019 of Experimental method Standard of physical and mechanical Properties of concrete, the test block adopts a prism standard test block of 150mm multiplied by 300mm, and each group of test pieces is 3; firstly, the axial compressive strength of the same group of test pieces is measured as a reference for elastic modulus loading. The test uses a resistance-type strain gauge to measure the longitudinal strain, the strain gauge is an SZ150-150AA type resistance strain gauge produced by Beijing Spool, the resistance is 150.0 ohm +/-0.2 ohm, the sensitivity coefficient is 2.06 +/-1 percent, and the length is 150 mm; the surface of the sample is clean and stuck to the middle of two sides of the test piece by using 502 glue.
(6) Poisson ratio
The poisson ratio is the ratio of transverse strain to axial strain, and is also called as a transverse deformation coefficient, and the index can reflect the transverse deformation capacity of the concrete material; the Poisson's ratio test uses a test block and the modulus of elasticity test uses a prism test block of 150mm by 300 mm. The test needs to collect transverse strain and axial strain at the same time, in the test, the strain gauges are collected by using resistance strain gauges, and the axial strain gauges and the elastic modulus are kept consistent; the transverse strain gauge adopts a resistance-type strain gauge with the length of 100mm according to the specification, the strain gauge is a BZ120-100AA type resistance strain gauge produced by Beijing Spatiel, the resistance is 120.0 omega +/-0.2 omega, the sensitivity coefficient is 2.08 +/-1 percent, the length is 100mm, and the transverse strain gauge is attached to two surfaces adjacent to the axial strain gauge.
(7) Freezing resistance
The freeze-thaw test is marked by a slow-freeze method D50, namely the freeze-thaw cycle of the slow-freeze method is carried out for 50 times, the freeze-thaw equipment adopted in the test is CLD type full-automatic low-temperature freeze-thaw test equipment produced by Tianjin Mingda architectural instrument company, the equipment has the functions of automatically controlling and implementing dynamic curve memory, storage and display, and the equipment also supports the function of power-off memory; the frost resistance of the concrete is evaluated according to the strength loss by a freeze-thaw experiment slow freezing method, so that the test method is the same as that of common concrete, and the test of 28d age and the compressive strength of a freeze-thaw experiment and a control group are required.
Example 1 brick-concrete recycled coarse and fine aggregate Performance test
The recycled aggregate used in the test is from Beijing construction and resource company, and the aggregate is divided into recycled concrete coarse aggregate and recycled red brick coarse aggregate according to the particle size and raw materials, as shown in figure 1.
Drying the obtained recycled aggregate, and compounding 25%, 50% and 75% of recycled red brick aggregate by mass with recycled concrete aggregate to obtain 3 kinds of brick-mixed fully recycled coarse aggregates with different proportions, and respectively performing performance tests on the fully recycled coarse aggregates with different brick contents; the method mainly comprises the following steps: the indexes of particle composition, harmful substance content, micro powder and mud block content, firmness, crushing index, apparent density, stacking density, porosity and the like.
(1) Particle size distribution
The invention only carries out the screening experiment on the recycled concrete coarse aggregate and the recycled red brick coarse aggregate independently, and the recycled concrete coarse aggregate and the recycled red brick coarse aggregate are not mixed. The results of the sieving experiments are shown in Table 10.
TABLE 10 recycled coarse aggregate screening test results
Figure BDA0003355636110000121
The experimental results show that the particle size distribution of the two coarse aggregates is relatively consistent and has no large difference; and the two kinds of recycled coarse aggregates meet the requirements of the recycled coarse aggregates for concrete GB/T25177-2010 on grading placement.
(2) Content of micropowder and MB value
FIG. 2 shows the content of fine powder in 3 kinds of recycled coarse aggregates and MB value.
(3) Content of harmful substance
FIG. 3 is a statistical graph of the impurity content of the brick-concrete coarse aggregate, and FIG. 4 is a graph of the experimental result of the organic matter content of the brick-concrete coarse aggregate.
Through analysis of the detection result of the content of harmful substances in the coarse aggregate, the recycled red brick aggregate has low density, and the harmful indexes meet the requirements.
(4) Firmness of use
The coarse aggregate is divided into the mass loss of three grain size grades of 4.75mm-9.50mm, 9.50 mm-19.0 mm and 19.0 mm-25.0 mm in a test, and the comprehensive mass loss is calculated according to the mass ratio of each grain size grade. Figure 5 is a statistical plot of the percent total mass loss for the brick-concrete recycled coarse aggregate samples.
It can be seen that the aggregate with the grain size of 4.75mm-9.50mm has the largest mass loss which is more than 14%, the mass loss rate reaches 15.43% when the brick content is 25%, and the mass loss is reduced along with the increase of the red brick content in the brick-concrete aggregate; the mass loss rate of aggregates with two grain sizes of 9.50-19.0 mm and 19.0-25.0 mm is reduced more than that of aggregates with two grain sizes of 4.75-9.50 mm, wherein the mass loss rate of the aggregates with different brick contents and grain sizes of 9.50-19.0 mm is less than 2%, and the mass loss rate of the aggregates with brick contents of 50% is only 1.12%; the mass loss of the 9.50 mm-19.0 mm and 19.0 mm-25.0 mm size fractions did not show a relationship with the content of red bricks in the aggregate. In the experiment, the aggregate is more difficult to break by the sodium sulfate solution method along with the increase of the particle size, mainly the increase of the particle size of the aggregate, the reduction of the specific surface area of the sample and the contact area of the aggregate, the reduction of the probability of the breakage of the aggregate and the low quality loss rate.
(5) Crush index
The crushing index of the coarse aggregate is only one particle size range of 9.5 mm-19.0 mm, and the index is used as the crushing index of the coarse aggregate. Table 11 is the crushing index of the brick concrete aggregate of 25%, 50% and 75% of the red brick content, and fig. 6 is the variation tendency of the crushing index of the brick concrete coarse aggregate and the linear fitting result.
TABLE 11 crushing index of brick-concrete coarse aggregate
Figure BDA0003355636110000131
The crushing value of the brick-concrete coarse aggregate is only tested for the aggregate with the grain diameter of 9.5 mm-19.0 mm to represent the firmness of the aggregate, and as can be seen from the table 11, the numerical value difference of 3 times of tests of the aggregate with the same brick content is smaller, the related requirements are met, and the data dispersion degree is lower; fig. 6 shows that in addition to the 3 sets of coarse aggregate data in table 11, a set of crushing indexes of 0% red brick content, namely pure recycled concrete coarse aggregate, is added, and it can be seen that the increase of red brick content leads to the increase of quality loss, and when the red brick content in the brick-mixed coarse aggregate is 75%, the quality loss reaches 24.23%; the mass loss of the pure recycled concrete coarse aggregate is 11.26 percent, and is reduced by 13 percent compared with the content of 75 percent of red bricks; the content of red bricks and the mass loss shown in FIG. 6 show a certain linear relationship, and the linear fitting is carried out on the red bricks, and the fitting result is shown in formula 3-1, lineCoefficient of sexual fitness R20.988, exhibiting a highly linear relationship.
y＝4.221x+7.637 (3-1)
In the formula: y-mass loss; and x is the content of red bricks in the brick-mixed coarse aggregate.
(6) Water absorption rate
Carrying out water absorption tests on samples with grain sizes of 4.75mm-9.50mm and 9.50mm-26.5mm of the brick-concrete aggregate, wherein the content of red bricks with each grain size is 0-100 percent, and 5 experiments are carried out; 0% of the red brick is pure recycled concrete aggregate, and 100% of the red brick is pure recycled red brick aggregate; table 12 shows the water absorption test results, and fig. 7 is a water absorption trend graph.
TABLE 12 Water absorption of brick-concrete aggregates
Figure BDA0003355636110000141
As can be seen from both FIG. 7 and Table 12, the water absorption of the brick-concrete aggregate with the same brick content in the 4.75mm-9.50mm size fraction is generally higher than that of the 9.50mm-26.5mm size fraction, and the difference is about 1% -3%, mainly because the specific surface area of the aggregate is increased due to the reduction of the particle size of the aggregate, the contact area with liquid is increased due to the increase of the area, and the water absorption is slightly higher than that of the aggregate with large particle size; the result also shows that the water absorption rate increases along with the increase of the content of red bricks in the brick-concrete aggregate, the water absorption rate of 0 percent of the content of red bricks (pure recycled concrete aggregate) is only 5.42 percent and 3.87 percent, the water absorption rate of 100 percent of red bricks (pure recycled red brick aggregate) is as high as 18.01 percent and 15.88 percent, and the water absorption rate of the content of red bricks in the aggregate presents a certain linear relation; this further illustrates the reason why brick concrete aggregates are less used in cement concrete, and the high water absorption of the aggregates causes more problems.
(7) Apparent density, bulk density and void fraction
Fig. 8, 9 and 10 are experimental results and a trend graph of the bulk density, apparent density and porosity of the brick-mixed recycled coarse aggregate, respectively.
The bulk density test results of FIG. 8 show that recycled aggregate is recycledThe content of the red bricks is increased, the stacking density of the recycled coarse aggregate is reduced, and the dry stacking density of the pure red brick coarse aggregate is 923kg/m3The bulk density of the pure concrete coarse aggregate is 1369kg/m3The difference between the two is small. In the results of the apparent density experiment of FIG. 9, the recycled brick-mixed coarse aggregate decreased with the increase of the content of red bricks, and when the content of red bricks was 75%, the apparent density of the brick-mixed coarse aggregate with 25% of red bricks was 2484kg/m at the maximum3(ii) a This is mainly due to the red brick pores and internal water absorption characteristics. The porosity results of fig. 10 show that recycled aggregate porosity increases with red brick content. When the content of the red bricks is 25%, the gaps of the brick-mixed coarse aggregates are 50.73%, when the content of the red bricks is 75%, the gaps of the brick-mixed coarse aggregates are 57.49%, and when the content of the red bricks is increased, the gap ratio difference value of the brick-mixed coarse aggregates tends to be reduced, which is related to the grading characteristics of the aggregates.
Example 2 preparation of recycled concrete
According to the test result of the recycled aggregate, respectively selecting 2 kinds of brick-mixed recycled coarse aggregates (the red brick content is 50% and 75%), and preparing recycled concrete by replacing natural coarse aggregates with the brick-mixed recycled coarse aggregates; the influence of different substitution rates, coarse aggregate substitution modes and different brick contents in the coarse aggregates on the strength, the working performance (slump, expansion and time loss) and the freeze-thaw resistance (quality loss and strength loss) of the recycled concrete at each age is researched.
As shown in Table 13, the total water consumption of the recycled concrete foundation is controlled to be unchanged in the test, the slump is adjusted by adjusting the using amount of the water reducing agent, the slump is controlled to be 20 +/-2 mm, the slump is controlled to be 45 +/-3 mm, and the water reducing agent for the test is a powder water reducing agent in order to ensure that the total water consumption is unchanged; when the water reducing agent reaches 300% of the reference group dosage, if the slump still can not meet the requirement, water and a cementing material are added in the same proportion to adjust the slump. Table 14 shows a specific alternative scheme of the brick-concrete recycled concrete aggregate, where the sample numbers are simple numbers in the experiment, and the numbers are numbers in the form of "red brick content-fine aggregate substitution rate-coarse aggregate substitution rate" for better distinguishing the test blocks, where 50-25-0 represents that the red brick content in the recycled aggregate is 50%, the fine aggregate substitution rate is 25%, and the coarse aggregate substitution rate is 0, i.e., all natural coarse aggregates are used; the detailed numbering details are shown in table 14.
TABLE 13 base mix ratio (kg/m) of recycled concrete3)
Figure BDA0003355636110000151
TABLE 14 brick-concrete recycled concrete aggregate alternatives
Figure BDA0003355636110000152
Figure BDA0003355636110000161
Example 3 Performance testing of recycled concrete
(1) Slump constant
In the concrete test, the slump is controlled to be about 20cm by adjusting the dosage of the water reducing agent, so that the difference of slump of each group is small and is about 20cm, and detailed data are shown in the following table 15.
TABLE 15 slump of recycled concrete under coarse aggregate substitution and amount of water reducer
Figure BDA0003355636110000162
It can be seen from the data that under the condition of keeping the water consumption unchanged, along with the increase of the measured aggregate substitution rate, the using amount of the recycled concrete water reducing agent is gradually increased, and the higher the red brick content in the aggregate is, the more the required water reducing agent is.
(2) Degree of expansion
Table 16 shows the results of the extension degree and the extension degree with time of the recycled concrete fine aggregate replacement scheme and the amount of the water reducing agent, wherein the amount of the water reducing agent is 5% of the cementitious material, and the extension degree is the average of the extension degrees in two perpendicular directions.
TABLE 16 expansion degree of recycled concrete and amount of water reducer used in coarse aggregate substitution
Figure BDA0003355636110000163
Figure BDA0003355636110000171
It can be seen that the expansion degree of the recycled concrete, the dosage of the water reducing agent and the law presented in the slump test are relatively consistent; the slump and the expansion degree with time are not obviously lost compared with the slump and the expansion degree with time, and the data with time of a part of groups are larger than the initial values, which is mainly the reason of the water reducing agent and shows that the recycled concrete with the mixing ratio has small loss with time.
(3) Density of
The density of part of recycled concrete is tested in the test, the test data is divided into 50% of red brick content and 75% of red brick content, and relevant data are shown in tables 17 and 18.
TABLE 17 Density of partially recycled concrete containing 50% of red bricks
Figure BDA0003355636110000172
TABLE 18 Density of partially recycled concrete having a content of red bricks of 75%
Figure BDA0003355636110000173
FIGS. 11 and 12 show the variation of the density of the recycled concrete, and the detailed alternatives for each group are shown in the above table, and the density of the recycled concrete for each group is lower than that of the reference group by analyzing the density of the recycled concrete; the density of the concrete of the reference group is 2523kg/m3(ii) a The density of each group of recycled concrete decreases with the increase of the substitution rate.
Example 4 Strength analysis of recycled concrete
(1) Cubic compressive strength
Table 19 shows the cubic compression strength test results of the recycled concrete with coarse aggregate replaced, and fig. 1 shows the compression strengths of the recycled concrete with red brick contents of 50% and 75%.
TABLE 19 cubic compressive strength of recycled concrete with coarse aggregate as a substitute
Figure BDA0003355636110000181
It can be seen from table 19 that the amount of the recycled concrete water-reducing agent is gradually increased with the increase of the replacement rate of the recycled aggregate; the recycled concrete with 75% of red brick content, 20% (G group) of coarse aggregate substitution rate and 30% (H group) is additionally added with additional water and cementing materials besides the water reducing agent. As can be seen from FIG. 13, the compressive strength of the recycled concrete with higher content of red bricks at all ages is lower than that of the recycled concrete with lower content of red bricks at the same substitution rate; it can also be seen from the graph that the compressive strength of both groups B, G, measured at 20% aggregate replacement, is greater than the strength of the baseline group; the compressive strength of the brick-concrete aggregate recycled concrete with 75% of red brick content shows a trend of ascending and then descending along with the increase of the replacement rate of the aggregate, which is mainly caused by the change of the effective water-cement ratio; in addition, the 50% and 75% red brick content recycled concrete 3d and 28d compressive strength trends were generally consistent, and the G, H group 3d strength increased faster than the other groups, mainly because the two groups added 5% and 15% more water cement during the test, and thus the early strength increased faster.
(2) Axial compressive strength
In order to explore the compressive strength of the prism, on the basis of the cubic compressive strength of the recycled concrete, part of the recycled concrete is selected to further carry out the compressive strength of the axis of the recycled concrete, and the specific groups are shown in table 20.
Axial compressive strength of brick-concrete recycled concrete of table 20
Figure BDA0003355636110000182
FIG. 14 shows the axial compressive strength of the recycled concrete with brick-concrete aggregate when the content of red bricks is 50% and 75%. When the content of the red bricks is 50%, the maximum axial compressive strength of the recycled concrete reaches 45.8MPa for the B group; the cubic compressive strength under the same proportion is also drawn in the figure, the result shows that the compressive strength variation trend of the recycled concrete axle center under different red brick contents and different substitution modes is consistent with the compressive strength variation trend of the cubic, and only the variation amplitude of part of the group strength has small difference.
(3) Analysis of recycled concrete destruction morphology
FIGS. 15 to 18 are views showing the failure states of recycled concrete in groups B, C, G and H, respectively. B. The group C is recycled concrete with 50 percent of red brick content in the brick-concrete coarse aggregate and 20 percent and 30 percent of replacement rate respectively; G. and the H group is recycled concrete with 75 percent of red brick content in the brick-concrete coarse aggregate and 20 percent and 30 percent of replacement rate respectively.
The overall damage form of the recycled concrete in each group is consistent with that of common concrete (reference group), the surface of the test block at the initial stage of compression resistance has no obvious change, fine cracks begin to appear on the surface of the concrete along with the continuous increase of load, and the cracks are further expanded and penetrated along with the increase of the load and are finally damaged; due to the hoop effect in the compression resisting process, the upper part and the lower part of the test piece form a pyramid respectively after being damaged. In addition, compared with common concrete, the damage of the brick-concrete recycled concrete can penetrate through red brick aggregate, which is mainly caused by the low strength of the red brick aggregate, while the natural aggregate is rarely damaged, mostly caused by the damage of the aggregate and a slurry bonding surface, and the phenomenon is consistent with the damage form in the fully recycled mortar.
Example 5 modulus of elasticity and Poisson's ratio of recycled concrete
(1) Modulus of elasticity
The elastic modulus is shown in Table 21, and FIG. 19 is a graph showing the variation of the elastic modulus and the axial compressive strength.
TABLE 21 modulus of elasticity of brick-concrete recycled concrete
Figure BDA0003355636110000191
Table 21 and fig. 19 show the elastic modulus data and the variation trend of the recycled concrete, from which it can be seen that the overall variation trend of the elastic modulus of the recycled concrete is more consistent with the overall variation trend of the axial compressive strength, and only the variation amplitudes of the elastic modulus of a part of groups of recycled concrete are different, and the elastic modulus of the recycled concrete is smaller than that of the reference group of recycled concrete.
(2) Poisson ratio
Table 22 shows experimental data on poisson's ratio of the recycled concrete with brick-concrete aggregate.
TABLE 22 Poisson's ratio of brick-concrete recycled concrete
Figure BDA0003355636110000201
As can be seen, the Poisson ratio of each group of the brick-concrete aggregate recycled concrete is between 0.203 and 0.229.
EXAMPLE 6 Frost resistance of recycled concrete
(1) Change in appearance
Fig. 20 is a freeze-thaw appearance change diagram of brick-concrete recycled concrete with the red brick content of 50%, and fig. 21 is a freeze-thaw appearance change diagram of brick-concrete recycled concrete with the red brick content of 75%. It can be seen that after each group of brick-concrete recycled concrete is subjected to freeze-thaw cycle, the appearance of the test piece is not obviously changed, only a small amount of cavities appear on the surface of the recycled concrete along with the increase of the number of times of the freeze-thaw cycle on the surface of the test piece, but the cavities are not obvious, and a small amount of silt-like substances exist at the bottom of the freeze-thaw cycle box.
(2) Loss of mass
The average mass of the test pieces at each cycle is shown in Table 23. Because the quality loss of each group of recycled concrete test blocks in the experiment is small, the lower graph only shows the quality change of each test block under each freeze-thaw cycle number, and the trend of the quality loss of each group of recycled concrete freeze-thaw cycle is shown in FIG. 22.
TABLE 23 quality of test piece for freeze-thaw test of recycled concrete
Figure BDA0003355636110000202
It can be seen that each group of recycled concrete increases with the freeze-thaw cycle coefficient, the mass loss of the test block is small and far less than 5%, and we also find that each group of test block does not change greatly in the freeze-thaw cycle process, only part of fine particles are separated from the surface of the test block, and the mass loss of the test block meets the requirement.
(3) Loss of strength
The compressive strength data of the recycled concrete freeze-thaw tests are shown in table 24, and fig. 23 is the compressive strength loss rate of the recycled concrete D50 under the freeze-thaw cycles.
TABLE 24 compressive strength data of freeze-thaw test of recycled concrete
Figure BDA0003355636110000211
Test results show that the loss of compressive strength of the reference group concrete is maximum and reaches 11.9 percent after 50 times of freeze-thaw cycles; the compressive strength loss of the recycled concrete is less than that of the concrete of the reference group, which shows that the frost resistance of the brick-concrete aggregate recycled concrete is improved to a certain extent compared with that of the reference group.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims (10)

1. The recycled concrete substituted by the brick-concrete recycled coarse aggregate comprises cement, fly ash, mineral powder, fine aggregate, coarse aggregate, a water reducing agent and water; the method is characterized in that the coarse aggregate comprises natural coarse aggregate and brick-concrete recycled coarse aggregate, and the mass percentage of the brick-concrete recycled coarse aggregate in the coarse aggregate is 20-30%; the brick-concrete recycled coarse aggregate is obtained by compounding recycled red brick coarse aggregate and recycled concrete coarse aggregate, wherein the mass percentage of the recycled red brick coarse aggregate is 50-75%.
2. The recycled concrete of claim 1, wherein the mass percentage of the brick-mixed recycled coarse aggregate in the coarse aggregate is 20%.
3. The recycled concrete of claim 1, wherein the recycled red brick coarse aggregate is 50% by mass of the brick-mixed recycled coarse aggregate.
4. The recycled concrete of claim 1, wherein the mass percentage of the brick-concrete recycled coarse aggregate in the coarse aggregate is 20%, and the mass percentage of the recycled red brick coarse aggregate in the brick-concrete recycled coarse aggregate is 50%.
5. The recycled concrete of claim 1, wherein the recycled concrete comprises the following components in parts by weight: 220 parts of cement, 80 parts of fly ash, 80 parts of mineral powder, 800 parts of fine aggregate, 1100 parts of coarse aggregate, 1.9-5.7 parts of water reducing agent and 170 parts of water.
6. The recycled concrete of claim 4, wherein the recycled concrete comprises the following components in parts by weight: 220 parts of cement, 80 parts of fly ash, 80 parts of mineral powder, 800 parts of fine aggregate, 1100 parts of coarse aggregate, 2.85 parts of water reducing agent and 170 parts of water.
7. The recycled concrete of claim 1, wherein the fine aggregate has a particle size of 0 to 5mm, and the coarse aggregate has a particle size of 5 to 20 mm.
8. The recycled concrete of claim 1, wherein the water reducer is a powdered polycarboxylic acid water reducer and the fly ash is a class II fly ash.
9. The recycled concrete of claim 1, wherein the brick-concrete recycled coarse aggregate has a crush index of 20.00% to 25.00%,4.75-26.5 mm continuous gradation with apparent density of 2300-2400 kg/m3The porosity is 53.00% -58.00%, and the water absorption is 3.00% -18.50%.
10. The method for producing recycled concrete according to any one of claims 1 to 9, comprising the steps of:
(1) weighing fine aggregate, coarse aggregate, mineral powder, fly ash, cement, a water reducing agent and water according to the proportion;
(2) and pouring the mixture into a concrete mixer in sequence, and uniformly mixing to obtain the recycled concrete substituted by the brick-concrete recycled fine aggregate.
CN202111350702.9A 2021-11-15 2021-11-15 Recycled concrete replaced by brick-concrete recycled coarse aggregate and preparation method thereof Pending CN114195437A (en)

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CN116496056A (en) * 2023-03-14 2023-07-28 北京工业大学 Fully regenerated semi-rigid road base material containing red brick construction waste and preparation method and application thereof

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CN108706928A (en) * 2018-05-30 2018-10-26 郑州大学 A kind of brick concrete mixed regeneration coarse aggregate concrete and preparation method thereof
CN112876175A (en) * 2021-03-26 2021-06-01 北京建筑材料科学研究总院有限公司 Self-curing recycled brick-concrete aggregate concrete and preparation method thereof

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108706928A (en) * 2018-05-30 2018-10-26 郑州大学 A kind of brick concrete mixed regeneration coarse aggregate concrete and preparation method thereof
CN112876175A (en) * 2021-03-26 2021-06-01 北京建筑材料科学研究总院有限公司 Self-curing recycled brick-concrete aggregate concrete and preparation method thereof

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