CN115477503B - Regenerated environment-friendly concrete and preparation process thereof - Google Patents
Regenerated environment-friendly concrete and preparation process thereof Download PDFInfo
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- CN115477503B CN115477503B CN202211167335.3A CN202211167335A CN115477503B CN 115477503 B CN115477503 B CN 115477503B CN 202211167335 A CN202211167335 A CN 202211167335A CN 115477503 B CN115477503 B CN 115477503B
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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
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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
- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Abstract
The application relates to the field of building materials, and particularly discloses recycled environment-friendly concrete and a preparation process thereof. The regenerated environment-friendly concrete comprises the following raw materials in parts by weight: cement, fly ash, mineral powder, water, recycled coarse aggregate, river sand, broken stone and water reducer; the recycled coarse aggregate is prepared by the following method: crushing and carbonizing the waste concrete to form regenerated particles; mixing glass powder, nano silicon dioxide and water to form a treatment solution, adding the regenerated particles, vacuumizing, maintaining the pressure for 2-3 hours, recovering to normal pressure, and drying to prepare pretreated particles; mixing the pretreated particles, the modified polyvinyl alcohol and the liquid alkali-free accelerator, oscillating for 15-20min, vacuumizing, maintaining the pressure for 1-3h, spraying molten thermal reversible glue on the surface, stirring while spraying, and drying to prepare the regenerated coarse aggregate. The recycled environment-friendly concrete has the advantages of high compressive strength and high impermeability.
Description
Technical Field
The application relates to the technical field of building materials, in particular to recycled environment-friendly concrete and a preparation process thereof.
Background
With the continuous acceleration of urban development, urban steps are faster and faster, old urban reconstruction projects are more and more, a large amount of waste building wastes are generated, most of the building wastes in China are not recycled in a scientific mode, and the vast majority of the building wastes are treated as wastes and are randomly piled in the open suburbs or are treated in a simple landfill mode, so that huge burden is generated on the environment.
The recycled concrete is prepared by cleaning, crushing, grading and matching waste concrete according to proportion, and can be used as concrete prepared by partial or all aggregates, so that raw materials for producing concrete, such as cement, sand and stone, and limestone and clay for producing cement are saved, exploitation of natural sand and stone is reduced, and concrete waste can be fully recycled, so that the difficulty in treating the concrete waste is effectively solved, and the environment-friendly idea is reflected.
In the prior art, the Chinese patent application number of which can be referred to as publication number CN2016107853485 discloses a recycled concrete produced by utilizing recycled aggregate, which comprises the following raw materials in percentage by mass: 37-55% of recycled coarse aggregate, 17-37% of recycled fine aggregate, 15-22% of P.O.42.5 cement and 8-12% of water; the particle size of the recycled coarse aggregate is 5-31.5mm, and the particle size of the recycled fine aggregate is less than 5mm; the recycled coarse aggregate consists of 35-40% by mass of recycled coarse aggregate with the particle size of 5-20mm and 60-65% by mass of recycled coarse aggregate with the particle size of 20-31.5 mm.
In view of the above-mentioned related art, the inventors found that, in the process of obtaining recycled coarse aggregate from waste concrete after crushing and sieving, the recycled coarse aggregate is subjected to impact and crushing forces, so that a large amount of microcracks are generated in the recycled coarse aggregate, the recycled aggregate has increased porosity, harmful gases, liquids and the like are more likely to permeate into the recycled concrete, the impermeability of the recycled concrete is poor, and meanwhile, old cement mortar is attached to the surface of the recycled coarse aggregate, so that the surface of the recycled coarse aggregate is rough, the pores are more and the edges are more, and the compressive strength of the prepared recycled concrete is lower.
Disclosure of Invention
In order to improve the strength and the impermeability of the recycled concrete, the application provides the recycled environment-friendly concrete and the preparation process thereof.
In a first aspect, the application provides recycled environment-friendly concrete, which adopts the following technical scheme:
the regenerated environment-friendly concrete comprises the following raw materials in parts by weight: 310-330 parts of cement, 50-55 parts of fly ash, 100-110 parts of mineral powder, 150-160 parts of water, 740-760 parts of recycled coarse aggregate, 435-445 parts of river sand, 1065-1075 parts of crushed stone and 10-15 parts of water reducer;
the recycled coarse aggregate is prepared by the following method:
crushing and carbonizing the waste concrete to form regenerated particles;
mixing glass powder, nano silicon dioxide and water to form a treatment solution, adding the regenerated particles, vacuumizing to- (1-3) MPa, maintaining the pressure for 2-3h, recovering to normal pressure, and drying to prepare pretreated particles;
mixing the pretreated particles, the modified polyvinyl alcohol and the water, oscillating for 15-20min, vacuumizing to- (4-5) MPa, maintaining the pressure for 1-3h, spraying the melted thermoreversible adhesive on the surface, stirring while spraying, and drying to prepare the regenerated coarse aggregate.
According to the technical scheme, after the waste concrete is crushed, the waste concrete is carbonized by using carbon dioxide to strengthen the waste concrete, and the carbon dioxide and calcium hydroxide and calcium silicate hydrate which are main components of the surface mortar of the waste concrete can react and react to produce a reaction product of calcium carbonate and silica gel microbeads, so that the solid phase volume of the waste concrete is increased, the compactness of the regenerated particle surface mortar is increased, the water absorption rate is reduced, and the strength is increased; the nano silicon dioxide has small size and large adsorption force, can permeate into pores and microcracks of the regenerated particles under the action of negative pressure of vacuumizing, so that the pores and microcracks are fully filled with the nano silicon dioxide and the pozzolanic effect is fully exerted, thereby reducing the porosity, and when the glass powder is ground to a certain degree, the nano silicon dioxide has alkali activity, can react with calcium hydroxide which is not completely carbonized on the regenerated particles to generate C-S-H gel, further improves the surface compactness of the regenerated particles, and can generate the C-S-H gel when the calcium hydroxide is generated by hydration of concrete, so that the strength and the compactness of the concrete are improved; coating the pretreated particles with a thermoreversible adhesive under the vacuumizing effect of modified polyvinyl alcohol and a liquid alkali-free accelerator; when the thermal reversible glue is hydrated in cement, the thermal reversible glue is slowly melted and releases liquid alkali-free accelerator and modified polyvinyl alcohol, the liquid alkali-free accelerator accelerates the solidification of the concrete, so that the setting time is shortened, and the modified polyvinyl alcohol can improve the dispersion uniformity of the recycled coarse aggregate, river sand and broken stone, so that the recycled coarse aggregate is uniformly dispersed in the cementing material, and after the thermal reversible glue is melted, glass powder on the surface of the recycled coarse aggregate reacts with calcium hydroxide generated by hydration, thereby further improving the density around the recycled coarse aggregate and improving the impermeability and the compressive strength.
Optionally, the recycled coarse aggregate comprises the following raw materials in parts by weight: 10-20 parts of regenerated particles, 1-2 parts of glass powder, 0.5-1 part of nano silicon dioxide, 1.5-3 parts of water, 3-5 parts of liquid alkali-free accelerator, 2-5 parts of modified polyvinyl alcohol and 5-10 parts of heat reversible glue.
By adopting the technical scheme, the consumption of each raw material is reasonably controlled, so that the compactness of the recycled coarse aggregate is better, and the compressive strength and the impermeability of the concrete are improved.
Optionally, the modified polyvinyl alcohol is prepared by performing ultrasonic dispersion on polyvinyl alcohol, acidified carbon nano tubes and deionized water for 2-3 hours at the temperature of 100-120 ℃ according to the mass ratio of 1:0.3-0.5:3-4, and then performing suction filtration and drying.
By adopting the technical scheme, the acidified carbon nano tube has a structure that openings at two ends are oxidized, a plurality of carboxyl groups, hydroxyl groups and other functional groups are generated on the side wall and the opening end of the oxidized carbon nano tube, the functional groups have high reactivity, so that the carbon nano tube and the polyvinyl alcohol have strong interaction, a modified polyvinyl alcohol film is formed after suction filtration and drying, the tensile strength and the elongation at break of the modified polyvinyl alcohol film are improved by adding the carbon nano tube, and when the thermal reversible glue is melted, the modified polyvinyl alcohol flows out along with a liquid alkali-free accelerator, is filled in concrete, and the impermeability of the concrete is improved.
Optionally, the thermoreversible gum comprises 10-15 parts of paraffin wax, 1-1.5 parts of graphite, 3-5 parts of diatom ooze and 0.3-0.5 part of
Bacillus alcalophilus.
By adopting the technical scheme, the paraffin is used as the thermoreversible adhesive, the paraffin has better toughness, can be coated on the pretreated particles, the thermal conductivity of the graphite is strong, the thermal conductivity of the paraffin can be improved, the thermal melting of the paraffin is accelerated, the graphite can also be filled into the pores of the concrete along with the flow of the paraffin, the compactness of the concrete is improved, the basophilic bacillus takes diatom ooze as a carrier, when the paraffin is thermally melted, the basophilic bacillus generates carbon dioxide along with the flow of the paraffin in the concrete, the carbon dioxide reacts with hydroxyl ions in the concrete slurry to generate carbonate ions, then the carbonate ions continuously react with calcium ions in the cement slurry under alkaline conditions to generate calcium carbonate crystals, the calcium carbonate crystals are filled between the regenerated coarse aggregate and the cementing material to fill micro gaps, and the calcium carbonate crystals and the concrete have good compatibility and interface strength, so that the durability is good, and the impermeability of the concrete can be improved.
Optionally, the preparation method of the thermoreversible adhesive comprises the following steps:
heating paraffin to 60-65 ℃, adding graphite, and uniformly stirring to obtain a premix;
mixing diatom ooze and water according to a mass ratio of 1:1-1.5, uniformly stirring, then placing at 100-110 ℃ for drying to constant weight, crushing, and selecting diatom ooze blocks with the particle size of 3-8 mm;
inoculating Bacillus alcaligenes into a microorganism culture medium for culturing to obtain a microorganism culture solution, immersing the diatom ooze blocks into the microorganism culture solution, vacuum immersing and adsorbing for 20-25min under the negative pressure of 0.6-0.8MPa, drying, spraying a premix solution, stirring while spraying, and drying.
According to the technical scheme, graphite and paraffin are firstly melted and then mixed, then basophilic bacillus is loaded on the diatom ooze, finally, the mixture of the graphite and the paraffin is wrapped on the diatom ooze, when the paraffin is wrapped on the pretreated particles, the diatom ooze loaded with the basophilic bacillus is also adhered on the pretreated particles, when the paraffin flows under the action of hydration heat in a hot melting mode, the diatom ooze loaded with the basophilic bacillus also flows along with the process, and the basophilic bacillus generates respiration in the concrete, so that calcium carbonate crystals are generated, the concrete is filled, the compactness is increased, and the compressive strength and the impermeability are improved.
Optionally, the carbonization method specifically includes: placing the crushed waste concrete at 18-22 ℃ with 55-65% humidity and 18-22% carbon dioxide concentration, and carbonizing for 2-3h.
By adopting the technical scheme, the waste concrete is carbonized in the environment containing carbon dioxide after being crushed, and the carbon dioxide can react with calcium hydroxide and hydrated calcium silicate in the mortar layer on the surface of the waste concrete, so that the solid phase volume is increased, and the compactness of the recycled coarse aggregate is improved.
Optionally, the particle size of the glass powder is 0.08-0.6mm.
By adopting the technical scheme, the glass powder has smaller particle size, can be effectively filled into the gaps of the regeneration particles, reduces the roughness of the surfaces of the regeneration particles, improves the fluidity of the regeneration particles, improves the compactness of the concrete, and further improves the strength and the impermeability of the concrete.
Optionally, the fly ash is class F class II fly ash, the balance of the 45 μm square hole sieve is 8-12%, the water demand ratio is 95-98%, and the loss on ignition is 2-4.5%.
Through adopting above-mentioned technical scheme, the active ingredient of fly ash is silica and aluminium oxide, mixes with cement and water back, can produce comparatively stable cementing material to make concrete have higher intensity, 70% or more of granule in the fly ash is amorphous spherical vitreous body simultaneously, mainly plays ball bearing's effect, plays the lubrication effect in concrete mixture, improves concrete mixture's workability, and fly ash and rubble etc. constitute reasonable gradation, make each other pack mutually, can effectively increase concrete compactness, further improve concrete compressive strength and impermeability.
Optionally, the mineral powder is S95 grade mineral powder, and the specific surface area of the mineral powder is 400-450m 2 The activity index per kg for 28 days was 95% and the fluidity ratio was 99%.
By adopting the technical scheme, the mineral powder mineral admixture has a plurality of comprehensive effects such as an active effect, an interface effect, a micro-filling effect, a water reducing effect and the like, so that the mineral admixture such as mineral powder can improve rheological property, reduce hydration heat, reduce slump loss, reduce segregation and bleeding, improve the pore structure and mechanical property of a concrete structure, and improve compressive strength and durability.
In a second aspect, the application provides a preparation process of recycled environment-friendly concrete, which adopts the following technical scheme: a preparation process of recycled environment-friendly concrete comprises the following steps:
mixing the recycled coarse aggregate, river sand and crushed stone to obtain a first mixture;
mixing water, cement, fly ash and mineral powder, and adding a water reducing agent to obtain a second mixture;
and adding the first mixture into the second mixture, and uniformly stirring to obtain the regenerated environment-friendly concrete.
In summary, the application has the following beneficial effects:
1. according to the application, after the waste concrete is crushed and carbonized, glass powder and nano silicon dioxide are loaded under negative pressure, then modified polyvinyl alcohol and a liquid alkali-free accelerator are loaded under negative pressure, and finally, the recycled coarse aggregate is prepared by a hot-melt thermal reversible adhesive coating method, so that the glass powder and the nano silicon dioxide can reduce pores and microcracks on the surface of the recycled coarse aggregate, the compactness of the recycled coarse aggregate is improved, the thermal reversible adhesive is thermally melted when the cementing material generates hydration heat, the internally coated liquid alkali-free accelerator flows out of the modified polyvinyl alcohol, and the modified polyvinyl alcohol can be mutually overlapped in the concrete, so that the cracking resistance and the impermeability of the concrete are improved.
2. The application preferably adopts the polyvinyl alcohol, the acidified carbon nano tube and the deionized water to prepare the modified polyvinyl alcohol, the acidified carbon nano tube and the polyvinyl alcohol have stronger interaction, and the modified polyvinyl alcohol composite film is formed after suction filtration and drying, and after the heat reversible glue is melted, the heat reversible glue flows out along with the alkali-free liquid accelerator, is filled and lapped in the concrete, and improves the impermeability and crack resistance of the concrete.
3. According to the application, paraffin, graphite, diatom ooze and basophilic bacillus are preferably adopted to prepare the thermoreversible adhesive, the graphite can increase the thermal conductivity of the paraffin, so that the paraffin can flow fully in a hot melting way, the diatom ooze is used as a carrier of the basophilic bacillus, when the paraffin flows in a hot melting way, the diatom ooze and the basophilic bacillus can flow and fill in concrete, the respiration of the basophilic bacillus can generate carbon dioxide and react with hydroxyl ions in the concrete to generate carbonate ions, and finally calcium carbonate crystals are generated, so that tiny gaps are filled, the compactness of the concrete is improved, and the compressive strength and the impermeability of the concrete are improved.
Detailed Description
Preparation examples 1 to 8 of recycled coarse aggregate
Preparation example 1: crushing waste concrete, carbonizing to form regenerated particles, and placing the crushed waste concrete for 2 hours under the conditions that the temperature is 22 ℃, the humidity is 55% and the carbon dioxide concentration is 18%;
mixing 2kg of glass powder, 1kg of nano silicon dioxide and 3kg of water to form a treatment solution, adding 20kg of regenerated particles, vacuumizing to-3 MPa, maintaining the pressure for 2 hours, recovering to normal pressure, and drying to prepare pretreated particles, wherein the particle size of the glass powder is 0.6mm;
mixing pretreated particles, 5kg of modified polyvinyl alcohol and 5kg of liquid alkali-free accelerator, oscillating for 20min, vacuumizing to-5 MPa, maintaining pressure for 1h, spraying molten thermoreversible adhesive on the surface, stirring while spraying, drying to prepare regenerated coarse aggregate, and carrying out ultrasonic treatment on the modified polyvinyl alcohol at 120 ℃ for 3h by using polyvinyl alcohol, acidified carbon nano tubes and deionized water in a mass ratio of 1:0.5:4, carrying out suction filtration and drying to obtain the modified polyvinyl alcohol.
Preparation example 2: crushing waste concrete, carbonizing to form regenerated particles, wherein the carbonization method is to place the crushed waste concrete at 18 ℃ under the conditions that the humidity is 65% and the carbon dioxide concentration is 22%, and carbonizing for 2 hours;
mixing 1kg of glass powder, 0.5kg of nano silicon dioxide and 1.5kg of water to form a treatment solution, adding 10kg of regenerated particles, vacuumizing to-1 MPa, maintaining the pressure for 3 hours, recovering to normal pressure, and drying to prepare pretreated particles, wherein the particle size of the glass powder is 0.08mm; mixing the pretreated particles, 2kg of modified polyvinyl alcohol and 3kg of liquid alkali-free accelerator, oscillating for 15min, vacuumizing to-4 MPa, maintaining pressure for 3h, spraying molten thermal reversible glue on the surface, stirring while spraying, drying to prepare the regenerated coarse aggregate, wherein the thermal reversible glue is paraffin, and the modified polyvinyl alcohol is prepared by carrying out ultrasonic treatment on polyvinyl alcohol, acidified carbon nano tube and deionized water at the mass ratio of 1:0.3:3 for 2h at the temperature of 100 ℃, and carrying out suction filtration and drying.
Preparation example 3: the difference from preparation example 1 is that no liquid alkali-free accelerator was added when preparing the modified polyvinyl alcohol.
Preparation example 4: the difference from preparation example 1 is that the acidified carbon nanotubes were not added when preparing the modified polyvinyl alcohol.
Preparation example 5: the difference from preparation example 1 is that the thermoreversible gel was prepared by the following method:
heating 15kg of paraffin to 65 ℃, adding 1.5kg of graphite, and uniformly stirring to prepare a premix;
mixing 5kg of diatom ooze and water according to a mass ratio of 1:1.5, uniformly stirring, then drying at 110 ℃ until the weight is constant, crushing, and selecting diatom ooze blocks with the particle size of 8mm;
inoculating 0.5kg of bacillus alcaligenes into a microbial culture medium for culturing to obtain a microbial culture solution, immersing diatom ooze blocks into the microbial culture solution, carrying out vacuum immersion and adsorption for 20min under the negative pressure of 0.8MPa, drying, spraying a premix solution, stirring while spraying, and drying, wherein the microbial culture medium comprises 10g of peptone, 3g of beef extract, 5g of sodium chloride, 12g of agar powder and 1000ml of water.
Preparation example 6: the difference from preparation example 1 is that the thermoreversible gel was prepared by the following method:
heating 10kg of paraffin to 60 ℃, adding 1kg of graphite, and uniformly stirring to prepare a premix;
3kg of diatom ooze and water are mixed according to the mass ratio of 1:1, and after being stirred uniformly, the mixture is dried to constant weight at 100 ℃, crushed and diatom ooze blocks with the particle size of 3mm are selected;
inoculating 0.3kg of bacillus alcaligenes into a microbial culture medium for culturing to obtain a microbial culture solution, immersing diatom ooze blocks into the microbial culture solution, carrying out vacuum immersion and adsorption for 25min under the negative pressure of 0.6MPa, drying, spraying a premix solution, stirring while spraying, and drying, wherein the microbial culture medium comprises 10g of peptone, 3g of beef extract, 5g of sodium chloride, 12g of agar powder and 1000ml of water.
Preparation example 7: the difference from preparation example 5 is that Bacillus alcalophilus was not added.
Preparation example 8: the difference from preparation example 5 is that no graphite was added.
Examples
Example 1: the raw material consumption of the regenerated environment-friendly concrete is shown in table 1, cement is silicate P.O42.5 cement, fly ash is class F class II fly ash, the balance of a 45 μm square-hole sieve is 8%, the water demand ratio is 98%, the loss on ignition is 2%, mineral powder is S95-grade mineral powder, and the specific surface area of the mineral powder is 400m 2 The activity index per kg for 28 days is 95%, the fluidity ratio is 99%, the particle size of the recycled coarse aggregate is 10mm, the recycled coarse aggregate is prepared by preparation example 1, the particle size of river sand is 2mm, the particle size of broken stone is 20mm, and the water reducer is a polycarboxylate water reducer.
The preparation process of the regenerated environment-friendly concrete comprises the following steps:
s1, mixing recycled coarse aggregate, river sand and crushed stone to obtain a first mixture;
s2, mixing water, cement, fly ash and mineral powder, and adding a water reducing agent to obtain a second mixture;
s3, adding the first mixture into the second mixture, and uniformly stirring to obtain the regenerated environment-friendly concrete.
TABLE 1 raw material usage of recycled Environment-friendly concrete
Examples 2-3: the regenerated environment-friendly concrete is different from example 1 in that the raw material amounts are shown in table 1.
Example 4: the recycled environment-friendly concrete is different from example 1 in that recycled coarse aggregate is prepared from preparation example 2.
Example 5: the recycled environment-friendly concrete is different from example 1 in that recycled coarse aggregate is prepared from preparation example 3.
Example 6: the recycled environment-friendly concrete is different from example 1 in that recycled coarse aggregate is prepared from preparation example 4.
Example 7: the recycled environment-friendly concrete is different from example 1 in that recycled coarse aggregate is prepared from preparation example 5.
Example 8: the recycled environment-friendly concrete is different from example 1 in that recycled coarse aggregate is prepared from preparation example 6.
Example 9: the recycled environment-friendly concrete is different from example 1 in that recycled coarse aggregate is prepared from preparation example 7.
Example 10: the recycled environment-friendly concrete is different from example 1 in that recycled coarse aggregate is prepared from preparation example 8.
Comparative example
Comparative example 1: the recycled environment-friendly concrete is different from example 1 in that the recycled coarse aggregate is prepared by crushing waste concrete.
Comparative example 2: the regenerated environment-friendly concrete is different from example 1 in that the polyvinyl alcohol is not modified.
Comparative example 3: the recycled environment-friendly concrete is different from the embodiment 1 in that the recycled coarse aggregate is prepared by the following method:
crushing waste concrete, carbonizing to form regenerated particles, and placing the crushed waste concrete for 2 hours under the conditions that the temperature is 22 ℃, the humidity is 55% and the carbon dioxide concentration is 18%;
mixing 20kg of regenerated particles, 5kg of modified polyvinyl alcohol and 16kg of water, oscillating for 20min, vacuumizing to-5 MPa, maintaining pressure for 1h, spraying molten thermal reversible glue on the surface, stirring while spraying, drying to prepare regenerated coarse aggregate, and carrying out ultrasonic treatment on the modified polyvinyl alcohol at 120 ℃ for 3h by using polyvinyl alcohol, acidified carbon nano tubes and deionized water in a mass ratio of 1:0.5:4, carrying out suction filtration and drying.
Preparation example 4: the regenerated environment-friendly concrete is different from the example 1 in that the waste concrete is carbonized after being crushed to form regenerated particles, and the crushed waste concrete is carbonized for 2 hours under the conditions that the temperature is 22 ℃, the humidity is 55% and the carbon dioxide concentration is 18%;
mixing 2kg of glass powder, 1kg of nano silicon dioxide and 2.5kg of water to form a treatment solution, adding 20kg of regenerated particles, vacuumizing to-3 MPa, maintaining the pressure for 2 hours, recovering to normal pressure, and drying, wherein the particle size of the glass powder is 0.6mm.
Comparative example 5: the recycled concrete produced by utilizing the recycled aggregate consists of the following raw materials in percentage by mass: 53.18 percent of recycled coarse aggregate, 17.72 percent of recycled fine aggregate, 18.77 percent of P.O.42.5 cement and 10.33 percent of water; wherein the recycled coarse aggregate consists of 40.05 percent by mass of recycled coarse aggregate with the grain diameter of 5-20mm and 59.95 percent by mass of recycled coarse aggregate with the grain diameter of 20-31.5 mm.
Performance test
Recycled concrete was prepared according to the methods in examples and comparative examples, and the properties of the concrete were measured with reference to the following methods, and the measurement results are recorded in table 2.
1. Compressive strength: the 28d compressive strength (MPa) of the recycled environment-friendly concrete is detected according to the compressive strength test in GB/T50081-2019 Standard of physical and mechanical Properties test method of concrete.
2. Water seepage height: the water penetration depth of the standard test block is tested according to the progressive pressurization method in GB/T50082-2009 Standard for test method of the long-term performance and durability of common concrete.
TABLE 2 Performance test results of recycled Environment-friendly concrete
The recycled coarse aggregates prepared in preparation example 1 are used in different amounts in examples 1-3, and the compressive strength of the concrete prepared in examples 1-3 reaches more than 40MPa and the water seepage height reaches less than 9mm, so that the concrete has better compressive strength and impermeability.
In example 4, the recycled coarse aggregate prepared in preparation example 2 was used, and the concrete 28d prepared in example 3 was similar in compressive strength and water penetration height to those of example 1.
In example 5, the recycled coarse aggregate prepared in preparation example 3 was used, and preparation example 3 was different from preparation example 1 in that no liquid alkali-free accelerator was added in preparation of the modified polyvinyl alcohol, and the compressive strength was decreased in example 5 as compared with example 1, indicating that the use of the liquid alkali-free accelerator can enhance the compressive strength of concrete.
In example 6, the recycled coarse aggregate prepared in preparation example 4 was used, and in preparation example 4, the acidified carbon nanotubes were not added, so that the compressive strength of the concrete prepared in example 6 was reduced and the water penetration height was not greatly changed, as compared with example 1.
In examples 7 and 8, the recycled coarse aggregate prepared in preparation examples 5 and 6 was used, respectively, and the thermally reversible glue prepared in preparation examples 5 and 6 was prepared using paraffin wax, graphite, etc., and the data in table 2 shows that the compressive strength of the recycled mix-packaged concrete prepared in examples 7 and 8 was increased and the water penetration height was reduced, indicating that the thermally reversible glue prepared in preparation examples 5 and 6 was effective in improving the compressive strength of the recycled aggregate.
In example 9, the recycled coarse aggregate prepared in preparation example 7 was used, and the compressive strength of the concrete prepared in example 9 was decreased, the water penetration height was increased, and the impermeability was deteriorated, as compared with example 7, in which Bacillus alcalophilus was not added, as compared with preparation example 5.
In example 10, the recycled coarse aggregate prepared in preparation example 8 was used, and compared with preparation example 5, graphite was not added thereto, and it is shown in table 2 that the compressive strength and the impermeability of the concrete prepared in example 10 were both inferior to those of example 7, indicating that the addition of graphite could improve the compactibility of the recycled coarse aggregate.
In comparative example 1, the recycled coarse aggregate obtained by crushing the waste concrete was used, and the concrete obtained in comparative example 1 was significantly reduced in compressive strength, increased in water penetration height and reduced in impermeability, as compared with example 1.
Comparative example 2 in comparison with example 1, the recycled coarse aggregate was prepared without modifying the polyvinyl alcohol, and it is shown in table 2 that the concrete prepared in comparative example 2 was reduced in compressive strength and in impermeability.
In comparative example 3, the recycled particles were treated under negative pressure without using glass frit and nano silica, and the recycled coarse aggregate used in comparative example 4 was prepared without using a solution containing modified polyvinyl alcohol to spray-treat the pretreated particles under negative pressure, and the concrete prepared in comparative example 3 and comparative example 4 had significantly reduced compressive strength and impermeability as compared to example 1.
Comparative example 5 is a concrete prepared using recycled coarse aggregate in the prior art, and the concrete prepared in comparative example 5 has low compressive strength and poor impermeability as compared with example 1.
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 (6)
1. The regenerated environment-friendly concrete is characterized by comprising the following raw materials in parts by weight: 310-330 parts of cement, 50-55 parts of fly ash, 100-110 parts of mineral powder, 150-160 parts of water, 740-760 parts of recycled coarse aggregate, 435-445 parts of river sand, 1065-1075 parts of crushed stone and 10-15 parts of water reducer;
the recycled coarse aggregate is prepared by the following method:
crushing and carbonizing the waste concrete to form regenerated particles;
mixing glass powder, nano silicon dioxide and water to form a treatment solution, adding the regenerated particles, vacuumizing to negative pressure, maintaining the pressure for 2-3 hours, recovering to normal pressure, and drying to prepare pretreated particles;
mixing the pretreated particles, the modified polyvinyl alcohol and the liquid alkali-free accelerator, oscillating for 15-20min, vacuumizing to negative pressure, maintaining the pressure for 1-3h, spraying molten thermoreversible adhesive on the surface, stirring while spraying, and drying to prepare the recycled coarse aggregate;
the recycled coarse aggregate comprises the following raw materials in parts by weight: 10-20 parts of regenerated particles, 1-2 parts of glass powder, 0.5-1 part of nano silicon dioxide, 1.5-3 parts of water, 3-5 parts of liquid alkali-free accelerator, 2-5 parts of modified polyvinyl alcohol and 5-10 parts of heat reversible glue;
the modified polyvinyl alcohol is prepared by performing ultrasonic dispersion on polyvinyl alcohol, acidified carbon nano tubes and deionized water for 2-3 hours at the temperature of 100-120 ℃ according to the mass ratio of 1:0.3-0.5:3-4, and then performing suction filtration and drying;
the thermoreversible gum comprises 10-15 parts of paraffin, 1-1.5 parts of graphite, 3-5 parts of diatom ooze and 0.3-0.5 part of bacillus alcalophilus;
the preparation method of the thermoreversible adhesive comprises the following steps: heating paraffin to 60-65 ℃, adding graphite, and uniformly stirring to obtain a premix;
mixing diatom ooze and water according to a mass ratio of 1:1-1.5, uniformly stirring, then placing at 100-110 ℃ for drying to constant weight, crushing, and selecting diatom ooze blocks with the particle size of 3-8 mm;
inoculating Bacillus alcaligenes into a microorganism culture medium for culturing to obtain a microorganism culture solution, immersing the diatom ooze blocks into the microorganism culture solution, vacuum immersing and adsorbing for 20-25min under negative pressure, drying, spraying a premix solution, stirring while spraying, and drying.
2. The recycled environment-friendly concrete according to claim 1, wherein the carbonization method specifically comprises the following steps: placing the crushed waste concrete at 18-22 ℃ with 55-65% humidity and 18-22% carbon dioxide concentration, and carbonizing for 2-3h.
3. The recycled environment-friendly concrete according to claim 1, wherein the particle size of the glass powder is 0.08-0.6mm.
4. The recycled environment-friendly concrete according to claim 1, wherein the fly ash is class-F class-II fly ash, the balance of the 45 μm square-hole sieve is 8-12%, the water demand ratio is 95-98%, and the loss on ignition is 2-4.5%.
5. The recycled environment-friendly concrete according to claim 1, wherein the mineral powder is S95 grade mineral powder, and the specific surface area of the mineral powder is 400-450m 2 The activity index per kg for 28 days was 95% and the fluidity ratio was 99%.
6. The process for preparing recycled concrete according to any one of claims 1 to 5, comprising the steps of:
mixing the recycled coarse aggregate, river sand and crushed stone to obtain a first mixture;
mixing water, cement, fly ash and mineral powder, and adding a water reducing agent to obtain a second mixture;
and adding the first mixture into the second mixture, and uniformly stirring to obtain the regenerated environment-friendly concrete.
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