CN116750997A - High-strength recycled aggregate concrete and preparation method thereof - Google Patents
High-strength recycled aggregate concrete and preparation method thereof Download PDFInfo
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- CN116750997A CN116750997A CN202310699150.5A CN202310699150A CN116750997A CN 116750997 A CN116750997 A CN 116750997A CN 202310699150 A CN202310699150 A CN 202310699150A CN 116750997 A CN116750997 A CN 116750997A
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- 239000004567 concrete Substances 0.000 title claims abstract description 88
- 238000002360 preparation method Methods 0.000 title abstract description 43
- 239000003575 carbonaceous material Substances 0.000 claims abstract description 42
- 239000000843 powder Substances 0.000 claims abstract description 38
- 239000011449 brick Substances 0.000 claims abstract description 32
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 27
- 239000004568 cement Substances 0.000 claims abstract description 26
- 239000002893 slag Substances 0.000 claims abstract description 19
- 229910052500 inorganic mineral Inorganic materials 0.000 claims abstract description 17
- 239000011707 mineral Substances 0.000 claims abstract description 17
- 239000010881 fly ash Substances 0.000 claims abstract description 14
- 239000004576 sand Substances 0.000 claims abstract description 13
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 10
- 239000002994 raw material Substances 0.000 claims abstract description 10
- 239000010902 straw Substances 0.000 claims description 41
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 19
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 19
- 239000007864 aqueous solution Substances 0.000 claims description 19
- 229910017604 nitric acid Inorganic materials 0.000 claims description 19
- 238000003756 stirring Methods 0.000 claims description 16
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 14
- 238000002156 mixing Methods 0.000 claims description 14
- RYAGRZNBULDMBW-UHFFFAOYSA-L calcium;3-(2-hydroxy-3-methoxyphenyl)-2-[2-methoxy-4-(3-sulfonatopropyl)phenoxy]propane-1-sulfonate Chemical compound [Ca+2].COC1=CC=CC(CC(CS([O-])(=O)=O)OC=2C(=CC(CCCS([O-])(=O)=O)=CC=2)OC)=C1O RYAGRZNBULDMBW-UHFFFAOYSA-L 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 12
- 229920005551 calcium lignosulfonate Polymers 0.000 claims description 11
- 238000010000 carbonizing Methods 0.000 claims description 11
- 239000011268 mixed slurry Substances 0.000 claims description 11
- 239000000243 solution Substances 0.000 claims description 10
- 239000002351 wastewater Substances 0.000 claims description 10
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 7
- 238000005470 impregnation Methods 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 241000209140 Triticum Species 0.000 claims description 4
- 235000021307 Triticum Nutrition 0.000 claims description 4
- 240000008042 Zea mays Species 0.000 claims description 4
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 claims description 4
- 235000002017 Zea mays subsp mays Nutrition 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 4
- 235000005822 corn Nutrition 0.000 claims description 4
- 244000025254 Cannabis sativa Species 0.000 claims description 3
- 235000012766 Cannabis sativa ssp. sativa var. sativa Nutrition 0.000 claims description 3
- 235000012765 Cannabis sativa ssp. sativa var. spontanea Nutrition 0.000 claims description 3
- 235000009120 camo Nutrition 0.000 claims description 3
- 235000005607 chanvre indien Nutrition 0.000 claims description 3
- 239000011487 hemp Substances 0.000 claims description 3
- 235000006408 oxalic acid Nutrition 0.000 claims description 3
- 241000196324 Embryophyta Species 0.000 claims description 2
- 240000007594 Oryza sativa Species 0.000 claims description 2
- 235000007164 Oryza sativa Nutrition 0.000 claims description 2
- 244000000231 Sesamum indicum Species 0.000 claims description 2
- 235000003434 Sesamum indicum Nutrition 0.000 claims description 2
- 235000009566 rice Nutrition 0.000 claims description 2
- 238000012360 testing method Methods 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 10
- 239000011148 porous material Substances 0.000 description 9
- 238000001723 curing Methods 0.000 description 8
- 238000006703 hydration reaction Methods 0.000 description 8
- 238000002791 soaking Methods 0.000 description 8
- 230000036571 hydration Effects 0.000 description 7
- 239000002699 waste material Substances 0.000 description 6
- 230000007547 defect Effects 0.000 description 5
- 239000010410 layer Substances 0.000 description 5
- 238000004064 recycling Methods 0.000 description 5
- 238000003763 carbonization Methods 0.000 description 4
- 229920005646 polycarboxylate Polymers 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 238000005452 bending Methods 0.000 description 3
- 238000000465 moulding Methods 0.000 description 3
- 125000000962 organic group Chemical group 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 2
- 239000000920 calcium hydroxide Substances 0.000 description 2
- 229910001861 calcium hydroxide Inorganic materials 0.000 description 2
- XFWJKVMFIVXPKK-UHFFFAOYSA-N calcium;oxido(oxo)alumane Chemical compound [Ca+2].[O-][Al]=O.[O-][Al]=O XFWJKVMFIVXPKK-UHFFFAOYSA-N 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- DKAGJZJALZXOOV-UHFFFAOYSA-N hydrate;hydrochloride Chemical compound O.Cl DKAGJZJALZXOOV-UHFFFAOYSA-N 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- ZDYUUBIMAGBMPY-UHFFFAOYSA-N oxalic acid;hydrate Chemical compound O.OC(=O)C(O)=O ZDYUUBIMAGBMPY-UHFFFAOYSA-N 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 230000000704 physical effect Effects 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- 239000011398 Portland cement Substances 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004566 building material Substances 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000011083 cement mortar Substances 0.000 description 1
- 235000013339 cereals Nutrition 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000007676 flexural strength test Methods 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
Classifications
-
- 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
-
- 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
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00017—Aspects relating to the protection of the environment
-
- 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
Abstract
The application relates to the technical field of concrete, and in particular discloses high-strength recycled aggregate concrete and a preparation method thereof, wherein the high-strength recycled aggregate concrete comprises the following raw materials in parts by weight: 120-180 parts of cement; 150-170 parts of water; 60-100 parts of fly ash; 70-100 parts of mineral powder; 800-1000 parts of sand; 700-900 parts of recycled brick slag; 5-10 parts of water reducer; 50-60 parts of modified biochar; 70-80 parts of porous carbon material. The high-strength recycled aggregate concrete has the advantage of improving the strength of recycled brick aggregate concrete.
Description
Technical Field
The application relates to the technical field of concrete, in particular to high-strength recycled aggregate concrete and a preparation method thereof.
Background
According to statistics, the yield of the construction waste in China is about 40% of the total amount of the urban waste, 7000-12000 tons of construction waste can be produced when old buildings of 1 ten thousand square meters are dismantled, wherein the preparation of the recycled brick aggregate concrete after the waste bricks are crushed is an exploration for recycling the recycled brick aggregate concrete, and based on the related experimental results, the following main defects exist in the fully recycled brick aggregate concrete: the strength of the full-recycled brick aggregate concrete is relatively low, and the application of the full-recycled brick aggregate concrete in the engineering field is limited, so that the recycling utilization of waste bricks is severely restricted, the shrinkage rate of the full-recycled brick aggregate concrete is large and the full-recycled brick aggregate concrete is easy to crack, the comprehensive utilization rate of cement in the full-recycled brick aggregate concrete is low, generally only one hydration reaction is basically terminated, the cement strength and the performance of the cement are not fully exerted, and the key problem of urgent need to be solved is how to fully utilize the physical and chemical properties of the waste bricks, greatly improve the flexural strength and the compressive strength of the concrete, and realize the recycling and rationalization utilization of the concrete.
Disclosure of Invention
The application provides high-strength recycled aggregate concrete and a preparation method thereof in order to improve the strength of recycled brick aggregate concrete.
The application provides high-strength recycled aggregate concrete, which adopts the following technical scheme:
the high-strength recycled aggregate concrete comprises the following raw materials in parts by weight:
120-180 parts of cement;
150-170 parts of water;
60-100 parts of fly ash;
70-100 parts of mineral powder;
800-1000 parts of sand;
700-900 parts of recycled brick slag;
5-10 parts of water reducer;
50-60 parts of modified biochar;
70-80 parts of porous carbon material;
the modified biochar is obtained by adding straw powder into nitric acid aqueous solution for pretreatment, then adding the pretreated straw powder into alumina sol for impregnation, and carbonizing at 300-400 ℃ for 2-3 h;
the porous carbon material is obtained by adding calcium lignosulfonate into oxalic acid solution, stirring, drying and carbonizing at 680-710 ℃ for 0.5-1 h.
By adopting the technical scheme, the solid waste recycled brick slag is used as the coarse aggregate of the concrete, so that the recycling of the concrete can be realized, the pressure of environmental management is reduced, meanwhile, the recycled brick slag can partially replace cement, but the cement mortar in the recycled aggregate is higher in content, the surface is much coarser than that of the natural aggregate, and the recycled aggregate is decomposed and crushed to generate a large number of microcracks in the process, so that the water absorption rate is much higher than that of the natural aggregate, the hydration process of the concrete is incomplete, the strength of the concrete is reduced, and the concrete is easy to crack.
Firstly, straw powder is immersed in alumina sol, alumina is loaded on the surface of biochar through high-temperature carbonization, the biochar obtained through carbonization at 300-400 ℃ is of an unordered stacked amorphous structure, a porous carbon material is obtained through carbonization of calcium lignosulfonate at high temperature, the structure of the porous carbon material is of a orderly stacked layered structure, a certain amount of alumina is loaded on the prepared modified biochar material, calcium hydroxide generated in the cement hydration process can form hydrated calcium aluminate on the surfaces of nano alumina particles, and the alumina is easy to chemically bond with hydration products of cement, so that the hydration products are formed among the layers of the porous carbon material, and the compactness and strength of concrete are improved. The modified biochar and the porous carbon material are compounded, so that the modified biochar is dispersed among the layers of the porous carbon material, wherein organic groups which are incompletely carbonized on the surface of the biochar form binding force with the surface of the porous carbon material, interface defects are reduced, the modified biochar and the porous carbon material form close stacking in the concrete, and the compressive strength and the flexural strength of the concrete are improved.
Along with the doping of the modified biochar and the porous carbon fiber, the two are compounded to improve the bending toughness of the concrete matrix, and the force required to resist bending fracture is increased due to layered close packing, so that the continuous bearing capacity of the composite material is increased after the maximum damage load is reached, and the bending toughness of the material is increased. In addition, the thermal conductivity of the biochar is low, so that the biochar has the effects of heat preservation and heat insulation, the combination of the biochar and the biochar has stable and high chemical properties, and the internal structure of the cement is not easy to be decomposed chemically, because of the existence of fixed carbon in the biochar and the reason that active groups are removed after high-temperature pyrolysis, the water retention property of the biochar and the porous carbon material due to the self pore structure can absorb the content of water added into the part during cement mixing, thereby reducing the content of free water of the cement and further reducing pores generated by water evaporation. Meanwhile, the water absorbed by the biochar and the porous carbon material can be used for curing the inside of the cement, so that the inside structure of the cement is more compact and the strength of the cement is increased.
Optionally, the mass concentration of nitric acid in the nitric acid aqueous solution is 55-64%, and the straw powder is added into the nitric acid aqueous solution for pretreatment for 10-15h and then added into the alumina sol for impregnation for 20-24h.
By adopting the technical scheme, the straw powder is pretreated in the nitric acid aqueous solution, so that the surface of the straw powder is oxidized in the acid solution to generate active sites, and more alumina is loaded on the surface of the biochar in the carbonization stage.
Optionally, the calcium lignosulfonate is carbonized at 680-710 ℃ for 0.5-1h and then soaked in 0.5-1mol/L hydrochloric acid aqueous solution for 8-10h.
By adopting the technical scheme, the layered orderly-stacked porous carbon material is formed at high temperature by the calcium lignosulfonate, and then the porous carbon material is activated by soaking in hydrochloric acid, so that the surface of the layered porous carbon material forms a pore structure, and the water retention property of the inside of the concrete is improved.
Optionally, the water is concrete mixing plant wastewater.
By adopting the technical scheme, as the porous material is doped in the concrete material, the porous material can adsorb harmful metal ions in the waste water of the mixing station, so that the waste water of the mixing station can be directly recycled, and the direct discharge is avoided, thereby causing environmental pollution.
Optionally, the particle size of the regenerated brick slag is 5-30mm.
By adopting the technical scheme, the recycled brick slag is used as coarse aggregate and serves as a framework material of concrete, and forms grain size grading with fine aggregate sand stone, so that the strength of the whole material of the concrete is improved.
Optionally, the straw is any one of hemp straw, wheat straw, corn straw, sesame straw and rice straw.
By adopting the technical scheme, carbon emission can be generated by straw incineration, the biochar is prepared by carbonizing the straw at high temperature under anaerobic environment, the emission of carbon dioxide is reduced, the biochar is used for replacing cement in building materials, the using amount of cement is reduced, and the greenhouse gas emission in the building industry is additionally reduced as a carbon fixing means.
Optionally, the density of the S95 mineral powder is more than or equal to 2.8g/cm 3 Specific surface area is more than or equal to 400m 2 The water content is less than or equal to 1.0, and the loss on ignition is less than or equal to 3.0.
By adopting the technical scheme, the S95 mineral powder and the fly ash are compounded to prepare the concrete, and the S95 mineral powder meets certain physical property indexes, so that the workability of the concrete mixture is good, the cohesiveness is strong, the shrinkage cracks of the concrete are less, and the later strength of the concrete is enhanced.
In a second aspect, the application provides a preparation method of high-strength recycled aggregate concrete, which adopts the following technical scheme:
the preparation method of the high-strength recycled aggregate concrete comprises the following steps:
step one, uniformly mixing cement, water, a water reducing agent, fly ash, S95 mineral powder, sand and recycled brick slag to obtain mixed slurry;
and secondly, stirring and mixing the modified biochar and the porous carbon material, then adding the mixture into the mixed slurry, uniformly stirring, pouring, forming and curing to obtain the concrete.
By adopting the technical scheme, the S95 mineral powder and the fly ash are compounded, the recycled brick slag is used as coarse aggregate, the sand is used as fine aggregate, the sand is mixed with the water reducing agent to form slurry, and the concrete obtained by mixing the modified biochar and the porous carbon material is added for recycling, so that the compressive strength and the flexural strength of the concrete meet certain requirements.
In summary, the application has the following beneficial effects:
1. the application adopts the modified biochar and the porous carbon material for compounding so as to solve the defect caused by adding the recycled aggregate. The modified biochar is dispersed among the porous carbon material layers, wherein organic groups which are not completely carbonized on the surface of the biochar form binding force with the surface of the porous carbon material, so that interface defects are reduced, the organic groups and the porous carbon material form close stacking in the concrete, and the compressive strength and the flexural strength of the concrete are improved.
2. According to the application, as the porous material is doped in the concrete material, the porous material can adsorb harmful metal ions in the waste water of the mixing station, so that the waste water of the mixing station can be directly reused, and the direct discharge is avoided, thereby causing environmental pollution.
3. The S95 mineral powder and the fly ash are compounded to prepare the concrete, and the S95 mineral powder meets certain physical property indexes, so that the concrete mixture has good workability and strong cohesiveness, and can reduce thermal shrinkage cracks of the concrete and enhance the later strength of the concrete.
Detailed Description
The present application will be described in further detail with reference to examples and comparative examples.
Preparation of raw materials
Preparation example 1
Preparing modified biochar: crushing hemp straws into straw powder, adding the straw powder into a nitric acid aqueous solution with the mass concentration of 60% for pretreatment for 12 hours, then adding the straw powder into alumina sol for soaking for 22 hours, and carbonizing for 2.5 hours at the temperature of 350 ℃ to obtain the hemp-straw-containing composite material;
preparing a porous carbon material: adding calcium lignosulfonate into oxalic acid aqueous solution with the mass concentration of 50%, stirring, drying, carbonizing for 0.8h at 700 ℃, then soaking in 0.8mol/L hydrochloric acid aqueous solution for 9h, and drying to obtain the calcium lignosulfonate.
Preparation example 2
Preparing modified biochar: crushing corn straw into straw powder, adding the straw powder into a nitric acid aqueous solution with the mass concentration of 55% for pretreatment for 10 hours, then adding the straw powder into alumina sol for soaking for 20 hours, and carbonizing for 2 hours at 300 ℃ to obtain the corn straw;
preparing a porous carbon material: adding calcium lignosulfonate into 50% oxalic acid water solution, stirring, drying, carbonizing at 680 deg.C for 0.5h, and soaking in 0.5mol/L hydrochloric acid water solution for 8h. Drying to obtain the final product.
Preparation example 3
Preparing modified biochar: crushing wheat straw into straw powder, adding the straw powder into a nitric acid aqueous solution with the mass concentration of 64% for pretreatment for 15 hours, then adding the straw powder into alumina sol for soaking for 24 hours, and carbonizing for 3 hours at 400 ℃ to obtain the wheat straw;
preparing a porous carbon material: adding calcium lignin sulfonate into 50% oxalic acid water solution, stirring, drying, carbonizing at 710 ℃ for 1h, and soaking in 1mol/L hydrochloric acid water solution for 10h. Drying to obtain the final product.
Preparation example 4
The difference from preparation example 1 is that the mass concentration of nitric acid in the nitric acid aqueous solution is 50%, and the straw powder is added into the nitric acid aqueous solution for pretreatment for 8 hours and then added into the alumina sol for impregnation for 18 hours.
Preparation example 5
The difference from preparation example 1 is that the mass concentration of nitric acid in the nitric acid aqueous solution is 68%, and the straw powder is added into the nitric acid aqueous solution for pretreatment for 18 hours and then added into the alumina sol for soaking for 27 hours.
Preparation example 6
The difference from preparation example 1 is that calcium lignosulfonate was carbonized and then immersed in a 0.3mol/L aqueous hydrochloric acid solution for 6 hours.
Preparation example 7
The difference from preparation example 1 is that calcium lignosulfonate was carbonized and then immersed in 1.3mol/L hydrochloric acid aqueous solution for 12 hours.
Examples
Example 1
The preparation method of the high-strength recycled aggregate concrete comprises the following steps:
stirring cement, waste water of a stirring station, a polycarboxylate water reducer, fly ash, mineral powder, sand and recycled brick slag for 10min, and uniformly mixing to obtain mixed slurry, wherein the particle size of the recycled brick slag is 20mm, the recycled brick slag is recovered from a removing site, and the density of S95 mineral powder is more than or equal to 2.8g/cm 3 Specific surface area is more than or equal to 400m 2 The water content is less than or equal to 1.0, the ignition loss is less than or equal to 3.0, the fineness modulus of sand is 2.5, the fly ash is II fly ash, and the cement is ordinary Portland cement;
and secondly, stirring the modified biochar and the porous carbon material for 10min, adding the mixture into the mixed slurry, stirring for 10min, pouring, forming and curing to obtain the concrete, wherein the modified biochar is prepared by adopting a preparation example 1, and the porous carbon material is prepared by adopting a preparation example 1.
Example 2
A preparation method of high-strength recycled aggregate concrete is different from example 1 in that modified biochar is prepared by adopting preparation example 2, a porous carbon material is prepared by adopting preparation example 2, and the particle size of recycled brick slag is 5mm.
Example 3
A preparation method of high-strength recycled aggregate concrete is different from example 1 in that modified biochar is prepared by adopting preparation example 3, a porous carbon material is prepared by adopting preparation example 3, and the particle size of recycled brick slag is 30mm.
Examples 1-3 the components of the raw materials and their corresponding parts by weight are shown in Table 1.
TABLE 1 raw materials and weights (kg) of the raw materials in examples 1 to 3
Example 4
A preparation method of high-strength recycled aggregate concrete is different from example 1 in that modified biochar is prepared by adopting preparation example 4, and porous carbon material is prepared by adopting preparation example 4.
Example 5
A preparation method of high-strength recycled aggregate concrete is different from example 1 in that modified biochar is prepared by adopting preparation example 5, and porous carbon material is prepared by adopting preparation example 5.
Example 6
A preparation method of high-strength recycled aggregate concrete is different from example 1 in that modified biochar is prepared by adopting preparation example 6, and porous carbon material is prepared by adopting preparation example 6.
Example 7
A preparation method of high-strength recycled aggregate concrete is different from example 1 in that modified biochar is prepared by adopting preparation example 7, and porous carbon material is prepared by adopting preparation example 7.
Comparative example
Comparative example 1
A method for preparing high-strength recycled aggregate concrete, which is different from example 1 in that the raw materials do not include modified biochar. The method comprises the following steps: step one, 160kg of cement, 140kg of waste water of a stirring station, 8kg of polycarboxylate water reducer, 80kg of fly ash, 85kg of mineral powder, 900kg of sand and 800kg of regenerated brick slag are stirred for 10min and uniformly mixed to obtain mixed slurry, step two, 75kg of porous carbon material is stirred for 10min and then added into the mixed slurry to be stirred for 10min, and then pouring, molding and curing are carried out to obtain the concrete, wherein the porous carbon material is prepared by adopting preparation example 1.
Comparative example 2
A method for preparing high-strength recycled aggregate concrete, which is different from example 1 in that the raw material does not include a porous carbon material. The method comprises the following steps: step one, 160kg of cement, 140kg of waste water of a stirring station, 8kg of polycarboxylate water reducer, 80kg of fly ash, 85kg of mineral powder, 900kg of sand and 800kg of regenerated brick slag are stirred for 10min and uniformly mixed to obtain mixed slurry, step two, 55kg of modified biochar is stirred for 10min and then added into the mixed slurry to be stirred for 10min, and then pouring, molding and curing are carried out to obtain the concrete, wherein the modified biochar is prepared by adopting preparation example 1.
Comparative example 3
A method for preparing high-strength recycled aggregate concrete, which is different from example 1 in that the raw materials do not include modified biochar and porous carbon materials. The method comprises the following steps: step one, 160kg of cement, 140kg of waste water of a stirring station, 8kg of polycarboxylate water reducer, 80kg of fly ash, 85kg of mineral powder, 900kg of sand and 800kg of recycled brick slag are stirred for 10min, and the mixed slurry is obtained after uniform mixing, and the concrete is obtained after casting, molding and curing.
Performance test
Detection method
Preparing 150mm multiplied by 150mm cubic standard test blocks serving as test blocks from the concrete prepared in the examples 1-7 and the comparative examples 1-3, pouring 3 standard test blocks in each group, placing the standard test blocks into a standard curing room for curing, testing the 3 standard test blocks by a pressure tester after 28 days, taking the arithmetic average value of the three obtained values as the test value of the group of regenerated concrete test blocks, and testing according to the compression strength test in GB/T50081-2019 test method Standard for physical and mechanical properties of concrete; the test is carried out according to the flexural strength test in GB/T50081-2019 Standard of test method for physical and mechanical properties of concrete.
TABLE 2 Performance test results
| Compressive Strength/MPa | Flexural Strength/MPa | |
| Example 1 | 51.1 | 5.5 |
| Example 2 | 51. | 5.3 |
| Example 3 | 49 | 5.1 |
| Example 4 | 46.1 | 4.8 |
| Example 5 | 46.5 | 4.7 |
| Example 6 | 47 | 4.5 |
| Example 7 | 47.8 | 4.51 |
| Comparative example 1 | 33.1 | 3.1 |
| Comparative example 2 | 34.5 | 2.9 |
| Comparative example 3 | 22.9 | 2 |
The compressive strength of the recycled aggregate concrete is generally larger than 40Mpa, the better the strength grade of the common concrete C40 is, the larger the mechanical property of the concrete is, the larger the compressive strength and the flexural strength are in terms of numerical value.
By combining example 1 and examples 4-5 and combining Table 2, it can be seen that by fully oxidizing the straw powder in nitric acid solution and fully impregnating the alumina sol, the prepared modified biochar material is loaded with a certain amount of alumina, calcium hydroxide generated in the hydration process of cement can form calcium aluminate hydrate on the surfaces of nano alumina particles, and the alumina is easy to generate chemical bonding with hydration products of cement, so that the hydration products are formed between porous carbon material layers, and the compactness and strength of the concrete are improved.
It can be seen from the combination of examples 1 and examples 6 to 7 and the combination of Table 2 that the carbonized porous carbon material is fully activated in the hydrochloric acid solution, and the surface of the layer forms a pore structure, so that water molecules are reserved in the interlayer pores, the loss of free water in the concrete is reduced, and the later strength of the concrete is improved.
It can be seen from the combination of example 1 and comparative examples 1 to 3 and the combination of table 2 that the combination of the modified biochar and the porous carbon material greatly improves the compressive strength and the flexural strength compared with the single addition, thereby explaining that the combination of the two can improve the defect of the recycled aggregate and also ensure the strength of the concrete.
The present embodiment is only for explanation of the present application and is not to be construed as limiting the present application, and modifications to the present embodiment, which may not creatively contribute to the present application as required by those skilled in the art after reading the present specification, are all protected by patent laws within the scope of claims of the present application.
Claims (8)
1. The high-strength recycled aggregate concrete is characterized in that: the material comprises the following raw materials in parts by weight:
120-180 parts of cement;
150-170 parts of water;
60-100 parts of fly ash;
70-100 parts of mineral powder;
800-1000 parts of sand;
700-900 parts of recycled brick slag;
5-10 parts of water reducer;
50-60 parts of modified biochar;
70-80 parts of porous carbon material;
the modified biochar is obtained by adding straw powder into nitric acid aqueous solution for pretreatment, then adding the pretreated straw powder into alumina sol for impregnation, and carbonizing at 300-400 ℃ for 2-3 h;
the porous carbon material is obtained by adding calcium lignosulfonate into oxalic acid solution, stirring, drying and carbonizing at 680-710 ℃ for 0.5-1 h.
2. The high strength recycled aggregate concrete of claim 1, wherein: the mass concentration of nitric acid in the nitric acid aqueous solution is 55-64%, and the straw powder is added into the nitric acid aqueous solution for pretreatment for 10-15h and then added into the alumina sol for impregnation for 20-24h.
3. The high strength recycled aggregate concrete of claim 1, wherein: the calcium lignosulfonate is carbonized at 680-710 ℃ for 0.5-1h and then soaked in 0.5-1mol/L hydrochloric acid aqueous solution for 8-10h.
4. The high strength recycled aggregate concrete of claim 1, wherein: the water is concrete mixing plant wastewater.
5. The high strength recycled aggregate concrete of claim 1, wherein: the particle size of the regenerated brick slag is 5-30mm.
6. The high strength recycled aggregate concrete of claim 1, wherein: the straw is any one of hemp straw, wheat straw, corn straw, sesame straw and rice straw.
7. The high strength recycled aggregate concrete of claim 1, wherein: the density of the S95 mineral powder is more than or equal to 2.8g/cm 3 Specific surface area is more than or equal to 400m 2 The water content is less than or equal to 1.0, and the loss on ignition is less than or equal to 3.0.
8. The method for preparing the high-strength recycled aggregate low-carbon concrete according to any one of claims 1 to 7, which is characterized in that: the method comprises the following steps:
step one, uniformly mixing cement, water, a water reducing agent, fly ash, mineral powder, sand and recycled brick slag to obtain mixed slurry;
and secondly, stirring and mixing the modified biochar and the porous carbon material, then adding the mixture into the mixed slurry, uniformly stirring, pouring, forming and curing to obtain the concrete.
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