CN114436601A - Recycled aggregate self-compacting concrete and preparation method thereof - Google Patents
Recycled aggregate self-compacting concrete and preparation method thereof Download PDFInfo
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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
- C04B28/04—Portland 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
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- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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Abstract
The application relates to the field of building materials, and particularly discloses recycled aggregate self-compacting concrete and a preparation method thereof. The recycled aggregate self-compacting concrete comprises the following components: cement, modified recycled aggregate, sand, fly ash, mineral powder, an additive, water and plant fiber; the modified recycled aggregate is prepared by the following method: crushing, sorting and sieving the waste concrete to prepare aggregate particles; uniformly mixing water glass, PVA, nano-silica, phosphoric acid and water to prepare a composite liquid, and placing aggregate particles into the composite liquid for soaking; placing the aggregate particles soaked in the composite liquid in a closed container, vacuumizing, introducing carbon dioxide gas, boosting the pressure to 0.1-0.4MPa, and maintaining the pressure for 20-24h to prepare reinforced aggregate particles; and soaking the reinforced aggregate particles in the water-based organic silicon resin emulsion, and drying. The recycled aggregate self-compacting concrete has the advantages of compact structure, high mechanical strength and strong freezing resistance.
Description
Technical Field
The application relates to the technical field of building materials, in particular to recycled aggregate self-compacting concrete and a preparation method thereof.
Background
Self-compacting concrete refers to concrete which can flow and be compact under the action of self gravity, can completely fill a template even if compact steel bars exist, and simultaneously obtains good homogeneity without additional vibration. The recycled aggregate is gradually recognized with good environmental protection benefits, not only reduces construction waste, but also reduces construction cost, and if the recycled aggregate is applied to the preparation of the self-compacting concrete, the advantages of the recycled aggregate and the self-compacting concrete are fully utilized, so good economic and social benefits are certainly brought.
In the prior art, Chinese patent application No. CN201410158353.4 discloses C30 single-particle grade recycled self-compacting concrete, wherein raw material components are cement in 1 weight part according to weight part; 0.70-1.53 parts by weight of regenerated coarse aggregate; 0.66-1.64 parts by weight of natural coarse aggregate; 1.90 parts by weight of fine aggregate; 0.47 parts by weight of water; 0.04-0.08 parts by weight of additional water; 0.26 part by weight of fly ash; 0.006-0.007 parts by weight of an additive.
Aiming at the related technologies, the inventor finds that the recycled coarse aggregate obtained by sorting, crushing and screening the waste concrete has large porosity, high water absorption rate and high water absorption speed, and the absorbed water participates in hydration reaction in the concrete mixing process, so that the water-cement ratio of a transition area of a recycled aggregate and a new cement interface is increased, the interface structure is loose, the porosity is large, and the mechanical property of the concrete is reduced.
Disclosure of Invention
In order to improve the compactness of self-compacting concrete prepared from recycled aggregate and improve the mechanical strength of the concrete, the application provides the recycled aggregate self-compacting concrete and a preparation method thereof.
In a first aspect, the application provides a recycled aggregate self-compacting concrete, which adopts the following technical scheme:
the recycled aggregate self-compacting concrete comprises the following components in parts by weight: 290-310 parts of cement, 800-900 parts of modified recycled aggregate, 700-800 parts of sand, 75-85 parts of fly ash, 80-100 parts of mineral powder, 5-9 parts of additive, 160-200 parts of water and 10-20 parts of plant fiber;
the modified recycled aggregate is prepared by the following method:
(1) crushing, sorting and sieving the waste concrete to prepare aggregate particles;
(2) uniformly mixing water glass, PVA, nano-silica, phosphoric acid and water to prepare a composite liquid, placing aggregate particles in the composite liquid, soaking for 1-2h at the temperature of 120-;
(3) placing the aggregate particles soaked in the composite liquid in a closed container, vacuumizing to- (0.1-0.2) MPa, maintaining the pressure for 1-1.5min, introducing carbon dioxide gas, increasing the pressure to 0.1-0.4MPa, and maintaining the pressure for 20-24h to prepare reinforced aggregate particles;
(4) soaking the reinforced aggregate particles in 25-50% water-based organic silicon resin emulsion for 30-40min, and drying at 160-180 ℃ for 3-4 h.
By adopting the technical scheme, after the waste concrete is crushed, the surface of the waste concrete is filled with fine cracks, the waste concrete is firstly put into an aqueous solution containing water glass, PVA, phosphoric acid and nano-silica, the composite liquid is acidic due to the addition of the phosphoric acid, the hydroxyl group of the polyvinyl alcohol reacts with sodium silicate under an acidic condition to form a cross-linked structure, the hydroxyl group of the PVA is reduced, the crystallinity is reduced, the water resistance of the PVA is improved, then when carbon dioxide is introduced, the carbon dioxide can react with the sodium silicate to generate amorphous gel, the introduced carbon dioxide can carry out carbonization reaction on the surface of aggregate particles, the pore structure of the aggregate particles is refined, the strength of mortar attached to the surface of the aggregate is increased, so that the strength of the recycled aggregate is improved, finally, the organic silicon resin emulsion is mixed with the reinforced aggregate particles, the organic silicon resin has excellent hydrophobicity, and after the organic silicon resin is wrapped on the reinforced aggregate particles, the organic silicon resin emulsion can effectively block the water from entering, the cured organic silicon resin emulsion seals the open pores of the aggregate particles, so that the open pores are gradually reduced and disappear, the organic silicon resin improves the overall performance of the recycled aggregate surface cement mortar, has a good filling effect on the pores, improves the strength of the recycled aggregate, improves the hydrophobicity, and ensures that the water is not easy to remain in the concrete, thereby improving the frost resistance of the concrete.
Preferably, when the modified recycled aggregate is prepared, the modified recycled aggregate is prepared from the following raw materials in parts by weight: 100 parts of aggregate particles, 30-40 parts of water glass, 15-20 parts of PVA, 20-30 parts of nano silicon dioxide, 4.5-9 parts of phosphoric acid, 90-100 parts of water and 20-35 parts of water-based organic silicon resin emulsion.
By adopting the technical scheme, the consumption of each raw material in the preparation of the modified recycled aggregate is reasonably controlled, the pores on the surfaces of the aggregate particles can be fully filled, the surface porosity is reduced, the density is improved, and the compressive strength of the concrete is improved.
Preferably, the water-based silicone resin emulsion comprises silicone resin emulsion, isobutyl triethoxysilane and gamma-aminopropyltriethoxysilane in a mass ratio of 1:0.3-0.5: 0.1-0.3.
By adopting the technical scheme, the isobutyl triethoxy silane is used as a penetrating agent, so that the permeability of the organic silicon resin emulsion can be improved, the filling rate of the organic silicon resin emulsion to pores on aggregate particles is enhanced, and the gamma-aminopropyl triethoxy silane is used as a tackifier, so that the binding power of the organic silicon resin emulsion and the aggregate particles can be improved, and the durability of concrete is improved.
Preferably, the nanosilica is pretreated with a silane coupling agent.
By adopting the technical scheme, the nano-silica has small size and is easy to agglomerate, so that the nano-silica cannot be well dispersed in the composite liquid formed by the water glass and the PVA, the nano-silica is pretreated by using the silane coupling agent to strengthen the interface effect of the nano-silica, and the dispersibility of the nano-silica, the water glass and the PVA is enhanced, so that the nano-silica can be well dispersed in the composite liquid, the pores on aggregate particles are effectively filled, the density of the aggregate particles is improved, and the mechanical strength of concrete is improved.
Preferably, the plant fiber is one or more of wood fiber, straw fiber and rice straw fiber.
By adopting the technical scheme, the plant fibers such as wood fibers and straw fibers are agricultural and forestry wastes, can cause resource waste and environmental pollution by direct abandonment, and can prevent the crack expansion in concrete and improve the crack resistance when being used in the concrete.
Preferably, the plant fiber is pretreated by the following steps:
mixing 0.5-1 part of pasteurella, 1-2 parts of urea, 3-5 parts of calcium chloride and 10-15 parts of water to prepare a deposition solution;
uniformly spraying the deposition solution on 7-10 parts of plant fiber, and standing at room temperature for 1-2h to obtain reinforced plant fiber;
mixing 1-3 parts of zein, 1-3 parts of sodium alginate and 3-5 parts of sodium hydroxide solution with the pH value of 12 to prepare impregnation liquid, adding the reinforced plant fiber into the impregnation liquid, impregnating for 8-10h at room temperature, fishing out the reinforced plant fiber, and drying.
The technical proposal is adopted, firstly, the plant fiber is mixed with the deposition solution formed by the pasteurella bacillus, the urea and the calcium chloride, the pasteurella bacillus can decompose the urea to generate carbonate through the product of the metabolism of the pasteurella bacillus, namely urease at room temperature, the generated carbonate can combine with calcium ions in the calcium chloride to generate calcium carbonate deposition so as to be deposited on the plant fiber, the wet expansion and dry shrinkage of the plant and the water absorption are reduced, the strength of the plant fiber is also increased, then, the plant fiber deposited with the calcium carbonate is mixed with the impregnation solution formed by zein, sodium alginate and the like, and after the zein and the sodium alginate are mixed, carboxyl on zein is electrolyzed into carboxylate groups with negative charges, when an impregnation liquid is contacted with unreacted calcium chloride on plant fibers, sodium alginate and carboxylate groups on zein are rapidly combined with calcium ions to form a cross-linked network, in addition, molecular chains of the sodium alginate and the zein are mutually wound and can also form a certain cross-linking, the zein has certain elasticity and can inhibit the coagulation network formed by the sodium alginate from being decomposed in alkaline concrete, and a gel network formed by the zein and the sodium alginate after cross-linking has hydrophobicity, so that the water absorption of the plant fibers can be reduced, and the water permeating into the concrete is prevented from being remained on the surfaces of the plant fibers, thereby improving the frost resistance of the concrete.
Preferably, the admixture comprises a polycarboxylic acid high-efficiency water reducing agent and an organosilicon water repellent, and the mass ratio of the polycarboxylic acid high-efficiency water reducing agent to the organosilicon water repellent is 0.1-0.3: 2-5.
By adopting the technical scheme, the organic silicon water repellent can increase the hydrophobicity of the cementing material, so that moisture can be quickly seeped out of the concrete, and the frost resistance of the concrete in a severe cold area is improved; the polycarboxylic acid high-efficiency water reducing agent can enhance the compressive strength of concrete.
Preferably, the fly ash is I-grade fly ash, the ignition loss is less than or equal to 3.0 percent, the 45-micron screen residue is less than or equal to 12 percent, the water demand ratio is less than or equal to 95 percent, and the water content is less than or equal to 1.0 percent;
the sand is machine-made sand with the particle size of 800-1000 meshes and the apparent density of 1800-2000Kg/cm3。
By adopting the technical scheme, the grade I fly ash has small fineness and can be filled among modified recycled aggregate particles, so that the compactness of the self-compacting concrete is improved, bleeding and segregation of the concrete are reduced, and the flowability and the filling property are improved; when the particle size of the sand is larger, more coarse particles are obtained, the grading is unreasonable, the workability is poor, when the particle size of the sand is smaller, more fine powder is obtained, the water demand is increased, the concrete strength is reduced, the particle size of the sand is 800-plus-100 meshes, the grading is reasonable, and the concrete strength is high.
Preferably, the particle size of the aggregate particles is 9.5-13.2 mm.
By adopting the technical scheme, the particle size of the aggregate particles is reasonably controlled, the aggregate particles, the fly ash, the sand and the mineral powder can form reasonable gradation and are mutually overlapped, and the compactness of concrete is improved.
In a second aspect, the application provides a preparation method of recycled aggregate self-compacting concrete, which adopts the following technical scheme:
a preparation method of recycled aggregate self-compacting concrete comprises the following steps:
uniformly mixing cement, modified recycled aggregate, sand, fly ash, plant fiber and mineral powder to prepare a dry mixture;
and (3) uniformly mixing the admixture and water, adding the mixture into the dry mixture, and uniformly mixing to prepare the recycled aggregate self-compacting concrete.
By adopting the technical scheme, the components such as cement, sand and the like are firstly dry-mixed, and then the aqueous solution of the additive is added into the dry mixture, so that the components can be uniformly mixed, and the plant fibers can be prevented from agglomerating.
In summary, the present application has the following beneficial effects:
1. according to the method, the aggregate particles are treated by the acidic composite liquid formed by water glass, PVA, nano-silica and the like, hydroxyl groups on the PVA can form a cross-linked structure with the water glass to fill pores on the aggregate particles, the nano-silica adhered to the aggregate particles is filled in the pores of the aggregate particles by utilizing negative pressure to reduce the porosity, then carbon dioxide is introduced to carry out carbonization reaction, calcium carbonate and silica gel are formed on the aggregate particles to further reduce the porosity and enhance the strength of the recycled aggregate, and finally, the organic silicon resin emulsion is coated to improve the strength of the recycled aggregate, improve the hydrophobicity of the recycled aggregate, prevent water from being retained on the surface of the recycled aggregate to cause frost heaving and cracking inside the concrete, and improve the frost resistance of the concrete.
2. In the application, the bacillus pasteurianus is preferably adopted to decompose urea on the plant fiber, then the urea and calcium ions in calcium chloride form calcium carbonate deposition, the strength of the plant fiber is improved, the water absorption rate of the plant fiber is reduced, and then a cross-linked gel network is formed on the plant fiber by using zein, sodium alginate and the like, so that the water absorption rate of the plant fiber can be reduced, the water is prevented from being retained on the surface of the plant fiber, the frost resistance of concrete is improved, the toughness of the plant fiber can be improved, and the crack resistance of the concrete is improved.
3. In the application, the cement, the plant fiber and the modified recycled aggregate are dry-mixed firstly, and then the admixture and the water are mixed to form a solution, and the solution is added into the dry mixture, so that the plant fiber can be prevented from agglomerating on the aggregate, and the uniformity of the concrete is improved.
Detailed Description
Preparation examples 1 to 9 of modified recycled aggregate
The raw materials in preparation examples 1-9 can all adopt commercial products, and the raw materials are taken as examples in the application, and the organic silicon resin emulsion is selected from Shanghai cellcept New Material science and technology Limited, with the model number of 8016; the nano silicon dioxide is selected from Jiangsu Tianxing new material company, and the model is TSP-L12; the PVA is selected from Kyoho chemical industry Co., Ltd, the model is N300; the water glass is selected from Shandong Chuancheng chemical industry Co., Ltd, and the model is 001.
Preparation example 1: (1) crushing, sorting and sieving the waste concrete to prepare aggregate particles with the particle size of 9.5 mm;
(2) uniformly mixing 30kg of water glass, 15kg of PVA, 20kg of nano-silica, 4.5kg of phosphoric acid and 90kg of water to prepare a composite liquid, putting 100kg of aggregate particles into the composite liquid, soaking at 120 ℃ for 2 hours, fishing out the aggregate particles, and mixing the nano-silica and a silane coupling agent according to a ratio of 1:0.5 for pretreatment;
(3) placing the aggregate particles soaked in the composite liquid in a closed container, vacuumizing to-0.1 MPa, maintaining the pressure for 1.5min, introducing carbon dioxide gas, boosting the pressure to 0.1MPa, and maintaining the pressure for 24h to prepare reinforced aggregate particles;
(4) and (3) soaking the reinforced aggregate particles prepared in the step (3) in 20kg of 25% aqueous organic silicon resin emulsion for 40min, and drying at 160 ℃ for 4h, wherein the aqueous organic silicon resin emulsion is prepared by mixing organic silicon resin emulsion and water.
Preparation example 2: (1) crushing, sorting and sieving the waste concrete to prepare aggregate particles with the particle size of 13.2 mm;
(2) uniformly mixing 40kg of water glass, 20kg of PVA, 30kg of nano-silica, 9kg of phosphoric acid and 100kg of water to prepare a composite liquid, putting 100kg of aggregate particles into the composite liquid, soaking for 1h at 140 ℃, fishing out the aggregate particles, and mixing the nano-silica and a silane coupling agent according to the proportion of 1:0.5 for pretreatment;
(3) placing the aggregate particles soaked in the composite liquid in a closed container, vacuumizing to-0.2 MPa, maintaining the pressure for 1min, introducing carbon dioxide gas, boosting the pressure to 0.4MPa, and maintaining the pressure for 20h to prepare reinforced aggregate particles;
(4) and (3) soaking the reinforced aggregate particles prepared in the step (3) in 35kg of water-based organic silicon resin emulsion with the mass concentration of 50% for 30min, and drying at 180 ℃ for 3h, wherein the water-based organic silicon resin emulsion is prepared by mixing organic silicon resin emulsion and water.
Preparation example 3: the difference from preparation example 1 is that the aqueous silicone resin emulsion comprises silicone resin emulsion, isobutyl triethoxysilane and gamma-aminopropyltriethoxysilane in a mass ratio of 1:0.3: 0.1.
Preparation example 4: the difference from preparation example 1 is that the aqueous silicone resin emulsion comprises silicone resin emulsion, isobutyl triethoxysilane and gamma-aminopropyltriethoxysilane in a mass ratio of 1:0.5: 0.3.
Preparation example 5: the difference from preparation example 1 is that no nanosilica was added in step (2).
Preparation example 6: the difference from preparation example 1 is that, without performing step (3), the aggregate particles prepared in step (2) are mixed with an aqueous silicone resin emulsion and soaked.
Preparation example 7: the difference from preparation example 1 is that step (4) was not performed.
Preparation example 8: the difference from preparation example 1 is that no water glass was added in step (2).
Preparation example 9: the difference from preparation example 1 is that no PVA was added in step (2).
Examples
In the following examples, the polycarboxylic acid high-efficiency water reducing agent is selected from Wuhan Huaxuan high and new technology Limited company with the product number of KH-1, and the organosilicon water repellent is selected from Shanghai Zhuohui chemical industry Limited company with the product number of GPSHP-50; the Pasteurella pasteuris selected from Shanghai Shanzhu biological science and technology Limited, and has a model number of ATCC 11859; the zein is selected from Sienna-Yam Biotechnology GmbH, with product number YT-060506; the sodium alginate is selected from Qingdao Tuohai iodine products Co., Ltd, and has a product number of 9005-38-3.
Example 1: the raw material formulation of the recycled aggregate self-compacting concrete is shown in Table 1, wherein the cement is P.O42.5 portland cement, the modified recycled aggregate is prepared by the preparation example 1, the sand is machine-made sand, the particle size is 800 meshes, and the apparent density is 1800kg/cm3The fly ash is I-grade fly ash, the ignition loss is less than or equal to 3.0 percent, the 45-micron screen residue is less than or equal to 12 percent, the water demand ratio is less than or equal to 95 percent, the water content is less than or equal to 1.0 percent, the mineral powder is S95-grade mineral powder, the additive comprises a polycarboxylic acid high-efficiency water reducing agent and an organic silicon water repellent in a mass ratio of 0.1:2, and the plant fiber is straw fiber with the length of 10 mm.
The preparation method of the recycled aggregate self-compacting concrete comprises the following steps:
uniformly mixing cement, modified recycled aggregate, sand, fly ash, plant fiber and mineral powder to prepare a dry mixture;
and (3) uniformly mixing the admixture and water, adding the mixture into the dry mixture, and uniformly mixing to prepare the recycled aggregate self-compacting concrete.
TABLE 1 dosage of raw materials for recycled aggregate self-compacting concrete in examples 1-4
Examples 2 to 4: a recycled aggregate self-compacting concrete is different from the concrete of example 1 in that the raw materials are used in the amounts shown in Table 1.
Example 5: the self-compacting recycled aggregate concrete is different from the concrete in example 1 in that the additive comprises a polycarboxylic acid high-efficiency water reducing agent and an organosilicon water repellent in a mass ratio of 0.3: 5.
Example 6: a recycled aggregate self-compacting concrete is different from the concrete in example 1 in that the additive is a polycarboxylic acid high-efficiency water reducing agent.
Example 7: a recycled aggregate self-compacting concrete, which is different from example 1 in that a modified recycled aggregate was prepared from preparation example 2.
Example 8: a recycled aggregate self-compacting concrete, which is different from example 1 in that a modified recycled aggregate was prepared in preparation example 3.
Example 9: a recycled aggregate self-compacting concrete, which is different from example 1 in that a modified recycled aggregate was prepared from preparation example 4.
Example 10: a recycled aggregate self-compacting concrete, which is different from the concrete of example 9 in that plant fibers are pretreated by the following steps: (1) mixing 0.5kg of Bacillus pasteurii, 1kg of urea, 3kg of calcium chloride and 10kg of water to prepare a sediment solution; (2) uniformly spraying the deposition solution on 7kg of plant fiber, and standing at room temperature for 1h to prepare reinforced plant fiber;
(3) mixing 1kg zein, 1kg sodium alginate and 3kg sodium hydroxide solution with pH of 12 to obtain soaking solution, adding the reinforced plant fiber into the soaking solution, soaking at room temperature for 8 hr, taking out the reinforced plant fiber, and freeze drying at-45 deg.C for 4 hr.
Example 11: a recycled aggregate self-compacting concrete, which is different from the concrete of example 9 in that plant fibers are pretreated by the following steps: (1) mixing 1kg of Paenibacillus pasteurii, 2kg of urea, 5kg of calcium chloride and 15kg of water to prepare a sediment solution; (2) uniformly spraying the deposition solution on 10kg of plant fibers, and standing at room temperature for 2h to prepare reinforced plant fibers;
(3) mixing 3kg zein, 3kg sodium alginate and 5kg sodium hydroxide solution with pH of 12 to obtain soaking solution, adding the reinforced plant fiber into the soaking solution, soaking at room temperature for 10 hr, taking out the reinforced plant fiber, and freeze drying at-45 deg.C for 4 hr.
Example 12: a recycled aggregate self-compacting concrete, which is different from the concrete of example 9 in that plant fibers are pretreated by the following steps: (1) mixing 1kg of Paenibacillus pasteurii, 2kg of urea, 5kg of calcium chloride and 15kg of water to prepare a sediment solution; (2) the deposition solution is evenly sprayed on 10kg of plant fiber and is kept stand for 2h at room temperature.
Example 13: a recycled aggregate self-compacting concrete, which is different from the concrete of example 9 in that plant fibers are pretreated by the following steps: mixing 3kg zein, 3kg sodium alginate and 5kg sodium hydroxide solution with pH of 12 to obtain soaking solution, adding 10kg plant fiber into the soaking solution, soaking at room temperature for 10 hr, taking out the plant fiber, and freeze drying at-45 deg.C for 4 hr.
Example 14: a recycled aggregate self-compacting concrete, which is different from example 11 in that zein is not added in the step (3).
Comparative example
Comparative example 1: a recycled aggregate self-compacting concrete, which is different from example 1 in that a modified recycled aggregate was prepared from preparation example 5.
Comparative example 2: a recycled aggregate self-compacting concrete, which is different from example 1 in that a modified recycled aggregate was prepared from preparation example 6.
Comparative example 3: a recycled aggregate self-compacting concrete, which is different from example 1 in that a modified recycled aggregate was prepared from preparation example 7.
Comparative example 4: a recycled aggregate self-compacting concrete, which is different from example 1 in that a modified recycled aggregate was prepared from preparation example 8.
Comparative example 5: a recycled aggregate self-compacting concrete, which is different from example 1 in that a modified recycled aggregate was prepared from preparation example 9.
Comparative example 6: a high-strength self-compacting concrete is prepared by weighing the following raw materials in parts by weight:
cementing material 23 (the mass percentage of cement in the cementing material is 60%), aggregate 32, sand 27 (the ratio of medium sand to fine sand is 2:1), expanded vermiculite 5, water reducing agent 0.2, thickening agent 0.1, thixotropic lubricant 0.3%, straw fiber 0.3 and water 12.
After the raw materials are prepared, the preparation method comprises the following steps:
(1) putting the cementing material, the straw fiber and the thickening agent which are required by the ingredients together, stirring and mixing for 3-6 minutes, then sequentially adding the water, the water reducing agent and the thixotropic lubricant which are required by the ingredients, and continuously stirring for 5-10 minutes to obtain a slurry mixture;
(2) and (2) adding aggregate, sand and expanded vermiculite into the slurry mixture obtained in the step (1), and stirring for 3-6 minutes to obtain the self-compacting concrete, wherein the 28-day compressive strength of the self-compacting concrete is 43MPa, and the slump expansion is 710 mm.
Performance test
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: detecting according to GB/T50081-2002 standard of common concrete mechanical property test method; 2. the expansion degree is as follows: detecting the expansion degree of the machine and the expansion degree of the machine after 30min of machine output according to GB/T50080-2002 standard of a common concrete mixture performance test method;
3. freezing resistance: performing a freeze-thaw cycle test according to GB/T50082-2009 Standard test method for testing long-term performance and durability of common concrete, wherein the freeze-thaw cycle test adopts a slow freezing method in the common concrete durability test, a test block adopts a cube of 100mm multiplied by 100mm poured by concrete, the freeze-thaw cycle is set for 300 times, and the test piece after the freeze-thaw test for 300 times is subjected to compression strength and quality test.
Table 2 performance testing of recycled aggregate self-compacting concrete
In examples 1 to 4, the modified recycled aggregate prepared in preparation example 1 was used in different amounts of raw materials, and table 2 shows that the concrete prepared in examples 1 to 4 had high mechanical strength, large mechanical elongation, small time loss, and frost resistance.
The difference between the concrete prepared in the example 5 and the concrete prepared in the example 1 is that the compressive strength and the mass loss are reduced and the frost resistance is enhanced after the concrete prepared in the example 5 is subjected to freeze-thaw cycles for 300 times.
The difference between the concrete prepared in the example 6 and the example 1 is that the concrete prepared in the example 6 has increased compressive strength loss rate and mass loss rate after 300 freeze-thaw cycles compared with the concrete prepared in the example 1 because the admixture is a polycarboxylic acid high-efficiency water reducing agent and no organosilicon water repellent is used.
In example 7, the modified recycled aggregate prepared in preparation example 2 was used, and compared with example 1, the concrete prepared in example 7 also had higher compressive strength, large expansion degree, good fluidity, less time loss, good stability, and better freeze-thaw resistance.
In example 8 and example 9, the modified recycled aggregates prepared in preparation examples 3 and 4 were used, respectively, and the concrete in example 8 and example 9 had an increased compressive strength compared to example 1 because the aqueous silicone resin emulsion in preparation examples 3 and 4 contained not only the silicone resin emulsion but also a tackifier and a penetrating agent.
In examples 10 and 11, compared to example 9, the modified recycled aggregate prepared in preparation example 4 was used, and the plant fiber was pretreated with urea, zein, and other components, and it is shown in table 2 that the compressive strength of the concrete prepared in examples 10 and 11 was increased, and the compressive strength loss rate and the quality loss rate were decreased after 300 freeze-thaw cycles, and the freezing resistance was further improved.
Example 12 differs from example 9 in that the deposition solution formed by urea and calcium chloride is sprayed on the plant fibers, and the data in table 2 shows that compared with example 11, the concrete prepared in example 12 has insignificant changes in mechanical properties, but the mass loss and compressive strength loss of the concrete are obviously increased after 300 freeze-thaw cycles.
The difference between example 13 and example 9 is that the mechanical properties of the concrete prepared in example 13 were reduced, as shown in table 2, without spraying the plant fibers with the sediment solution formed of urea, calcium chloride, etc.
Example 14 differs from example 11 in that, without addition of zein, the concrete made in example 14, as shown in table 2, had compressive strength similar to that of example 11, but significantly decreased compressive strength and quality after freeze-thawing.
Comparative example 1 compared with example 1, the compressive strength of concrete was reduced and freezing resistance was reduced using the modified recycled aggregate prepared in preparation example 5, in which nano-silica was not added.
Comparative example 2 compared with example 1, with the modified recycled aggregate prepared in preparation example 6, the compressive strength of the concrete prepared in comparative example 2 was significantly reduced without placing the aggregate particles in a closed container and introducing carbon dioxide gas.
Comparative example 3 using the modified recycled aggregate prepared in preparation example 7, in which the reinforcing aggregate particles were not impregnated in the aqueous silicone resin emulsion, compared to example 1, the concrete prepared in comparative example 3 had significantly reduced freezing resistance, increased compressive strength, and increased mass loss rate, compared to example 1.
Comparative example 4 and comparative example 5 compared with example 1, the modified recycled aggregates prepared in preparation examples 8 and 9 were used, respectively, no water glass was added in preparation example 8, no PVA was added in preparation example 9, and the compressive strength and freezing resistance of the concrete prepared in examples 8 and 9 were reduced.
Comparative example 6 is the recycled aggregate self-compacting concrete prepared by the prior art, the compressive strength of which is 43MPa, although the compressive strength is higher, the mass loss rate is large after freeze thawing, the compressive strength loss is serious, and the frost resistance is insufficient.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
Claims (10)
1. The recycled aggregate self-compacting concrete is characterized by comprising the following components in parts by weight: 290-310 parts of cement, 800-900 parts of modified recycled aggregate, 700-800 parts of sand, 75-85 parts of fly ash, 80-100 parts of mineral powder, 5-9 parts of additive, 160-200 parts of water and 10-20 parts of plant fiber;
the modified recycled aggregate is prepared by the following method:
(1) crushing, sorting and sieving the waste concrete to prepare aggregate particles;
(2) uniformly mixing water glass, PVA, nano-silica, phosphoric acid and water to prepare a composite liquid, placing aggregate particles in the composite liquid, soaking for 1-2h at the temperature of 120-;
(3) placing the aggregate particles soaked in the composite liquid in a closed container, vacuumizing to- (0.1-0.2) MPa, maintaining the pressure for 1-1.5min, introducing carbon dioxide gas, increasing the pressure to 0.1-0.4MPa, and maintaining the pressure for 20-24h to prepare reinforced aggregate particles;
(4) soaking the reinforced aggregate particles in 25-50% water-based organic silicon resin emulsion for 30-40min, and drying at 160-180 ℃ for 3-4 h.
2. The recycled aggregate self-compacting concrete according to claim 1, wherein: when the modified recycled aggregate is prepared, the modified recycled aggregate comprises the following raw materials in parts by weight: 100 parts of aggregate particles, 30-40 parts of water glass, 15-20 parts of PVA, 20-30 parts of nano silicon dioxide, 4.5-9 parts of phosphoric acid, 90-100 parts of water and 20-35 parts of water-based organic silicon resin emulsion.
3. The recycled aggregate self-compacting concrete according to claim 1, wherein the aqueous silicone resin emulsion comprises silicone resin emulsion, isobutyl triethoxysilane, and gamma-aminopropyltriethoxysilane in a mass ratio of 1:0.3-0.5: 0.1-0.3.
4. The recycled aggregate self-compacting concrete according to claim 1, wherein the nano silica is pretreated with a silane coupling agent.
5. The recycled aggregate self-compacting concrete according to claim 1, wherein the plant fiber is one or more of wood fiber, straw fiber and straw fiber.
6. The recycled aggregate self-compacting concrete according to claim 1, wherein the plant fibers are pretreated by:
mixing 0.5-1 part of pasteurella, 1-2 parts of urea, 3-5 parts of calcium chloride and 10-15 parts of water to prepare a deposition solution;
uniformly spraying the deposition solution on 7-10 parts of plant fiber, and standing at room temperature for 1-2h to obtain reinforced plant fiber;
mixing 1-3 parts of zein, 1-3 parts of sodium alginate and 3-5 parts of sodium hydroxide solution with the pH value of 12 to prepare impregnation liquid, adding the reinforced plant fiber into the impregnation liquid, impregnating for 8-10h at room temperature, fishing out the reinforced plant fiber, and drying.
7. The concrete recycled by wastes according to claim 1, wherein the admixture comprises a polycarboxylic acid high-efficiency water reducing agent and an organosilicon water repellent, and the mass ratio of the polycarboxylic acid high-efficiency water reducing agent to the organosilicon water repellent is 0.1-0.3: 2-5.
8. The recycled aggregate self-compacting concrete according to claim 1, wherein the fly ash is class I fly ash, the loss on ignition is less than or equal to 3.0%, the 45 μm screen residue is less than or equal to 12%, the water demand ratio is less than or equal to 95%, and the water content is less than or equal to 1.0%;
the sand is machine-made sand, the particle size is 800-1000 meshes, and the apparent density is 1800-2000Kg/cm 3.
9. The recycled aggregate self-compacting concrete according to claim 1, wherein the aggregate particles have a particle size of 9.5-13.2 mm.
10. The method for preparing the recycled aggregate self-compacting concrete according to any one of claims 1 to 9, which comprises the following steps:
uniformly mixing cement, modified recycled aggregate, sand, fly ash, plant fiber and mineral powder to prepare a dry mixture;
and (3) uniformly mixing the admixture and water, adding the mixture into the dry mixture, and uniformly mixing to prepare the recycled aggregate self-compacting concrete.
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| CN115073097A (en) * | 2022-07-11 | 2022-09-20 | 杭州余杭恒力混凝土有限公司 | High-strength recycled aggregate concrete and preparation method thereof |
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| CN115806414A (en) * | 2023-01-07 | 2023-03-17 | 成都新豪鼎盛建材有限公司 | Anti-cracking concrete and preparation method thereof |
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| CN115806414A (en) * | 2023-01-07 | 2023-03-17 | 成都新豪鼎盛建材有限公司 | Anti-cracking concrete and preparation method thereof |
| CN116553876A (en) * | 2023-06-01 | 2023-08-08 | 中建新城建设工程有限公司 | Energy-saving green building material and preparation method thereof |
| CN116553876B (en) * | 2023-06-01 | 2024-01-09 | 中建新城建设工程有限公司 | Energy-saving green building material and preparation method thereof |
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