High-strength rubberized recycled concrete and method for preparing the same

Abstract

The application discloses high-strength rubber recycled concrete and a preparation method thereof, and belongs to the technical field of building materials. The recycled concrete comprises the following components: cement, rubber particles, recycled coarse aggregate, fine aggregate, fly ash, modified nano silicon dioxide, water reducing agent and mixing water; the application realizes the efficient resource utilization of solid waste and the high performance of concrete; through scientific proportioning design, the application introduces rubber particles, recycled coarse aggregate and industrial waste such as fly ash into a high-strength concrete system, thereby not only reducing environmental load, but also effectively overcoming the technical problems of weak interface bonding between the rubber particles and the cement matrix and the strength reduction caused by the high porosity of the recycled aggregate by adding modified silicon dioxide, so that the mechanical strength, toughness and durability of the concrete are significantly improved; and the application is a green building material with high strength and excellent freeze-thaw resistance.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a high-strength rubber recycled concrete and its preparation method. Background Technology

[0002] With the acceleration of urbanization, the amount of construction waste generated is increasing rapidly, and the recycling of waste concrete has become an important way for the construction industry to achieve sustainable development. Crushing and screening waste concrete to prepare recycled aggregates, which are then used to formulate recycled concrete, can not only reduce the mining of natural sand and gravel resources but also effectively solve the problems of construction waste dumping and environmental pollution.

[0003] Chinese patent document CN110776290A discloses a rubber recycled concrete and its preparation method. The rubber recycled concrete comprises the following components by weight: 400-550 parts cement, 950-1100 parts recycled coarse aggregate, 550-650 parts river sand, 25-30 parts rubber particles, 1-5 parts water-reducing agent, and 170-190 parts water. The recycled coarse aggregate is treated with a nano-SiO2 silica sol solution; the rubber particles are treated with a nano-SiO2 silica sol solution and a silane coupling agent. The rubber recycled concrete provided by this invention uses specially treated recycled coarse aggregate and rubber particles, combined with a certain amount of cement, river sand, water-reducing agent, and water. This rubber recycled concrete does not contain any admixtures; the recycled coarse aggregate, rubber particles, and gel material are tightly bonded, and the resulting rubber recycled concrete still possesses good mechanical properties. It can be widely used in various fields, effectively solving the defects of poor mechanical properties and limited application range of rubber recycled concrete.

[0004] However, compared to ordinary concrete, recycled concrete has higher porosity and water absorption due to the old mortar adhering to the aggregate surface, and contains numerous microcracks. This generally results in poorer mechanical strength and durability (especially frost resistance) of recycled concrete. To improve the toughness and crack resistance of recycled concrete, researchers often introduce waste rubber particles to prepare rubber-recycled concrete. While the addition of rubber particles can significantly improve the deformation capacity and damping performance of concrete, rubber, as an organic elastomer, has extremely weak interfacial adhesion with the inorganic cement matrix, leading to a significant decrease in the compressive strength of the concrete. Furthermore, the hydrophobicity of rubber particles makes the interfacial transition zone more porous, allowing water to easily penetrate, making it highly susceptible to spalling and cracking during freeze-thaw cycles in cold regions. Summary of the Invention

[0005] The main objective of this invention is to propose a high-strength recycled rubber concrete and its preparation method. By modifying nano-silica to enhance the bonding between rubber and cement, the strength and frost resistance are improved, thereby achieving efficient utilization of waste rubber particles and concrete.

[0006] To achieve the above objectives, this invention proposes a high-strength rubber recycled concrete, comprising the following components by weight: 350-450 parts cement, 10-30 parts rubber granules, 500-800 parts recycled coarse aggregate, 450-650 parts fine aggregate, 60-100 parts fly ash, 20-30 parts modified nano silica, 5-10 parts water-reducing agent, and 140-170 parts mixing water.

[0007] Based on the above technical solutions, preferably, the cement is ordinary Portland cement.

[0008] Based on the above technical solutions, preferably, the recycled coarse aggregate is obtained by crushing waste concrete.

[0009] Based on the above technical solutions, preferably, the fine aggregate is one of river sand, sea sand, manufactured sand, and quartz sand.

[0010] Based on the above technical solutions, preferably, the fly ash is Class II fly ash.

[0011] Based on the above technical solutions, the preferred method for preparing the modified nano-silica includes the following steps:

[0012] (1) Disperse nano-silica in an aqueous ethanol solution, add KH550, stir and react to obtain aminated nano-silica;

[0013] (2) Add aminated nano silica to water and mix evenly. Add epichlorohydrin, adjust the pH to 4-6, add alkyl glycoside and citronellol, and heat the reaction to obtain cross-linked modified nano silica.

[0014] (3) The cross-linked modified nano silica was dispersed in N,N-dimethylformamide, fumaric acid and an initiator were added, and a polymerization reaction was carried out under a nitrogen atmosphere to obtain modified nano silica.

[0015] Based on the above technical solutions, preferably, the mass ratio of nano-silica to KH550 in step (1) is 100:3-5.

[0016] In this step, active amino groups are introduced onto the surface of nano-silica using KH550, which effectively reduces the surface energy of the nanoparticles, solves the problem of their easy aggregation in the matrix, and provides reaction sites for subsequent polymerization.

[0017] Based on the above technical solutions, preferably, in step (2), the mass ratio of aminated nano-silica, epichlorohydrin, alkyl glycoside and citronellol is 10:3-5:2-3:2-3; the heating reaction temperature is 60-80℃ and the reaction time is 4-8h.

[0018] In this step, epichlorohydrin is used as a bifunctional crosslinking agent to undergo a ring-opening reaction under acid catalysis. One end of the crosslinking agent is anchored to the amino group on the surface of nano-silica, while the other end is grafted onto the surface of nano-silica via an etherification reaction, thereby achieving the loading of functional molecules and introducing polymerization active sites.

[0019] Based on the above technical solutions, preferably, in step (3), the mass ratio of crosslinked modified nano silica, fumaric acid and initiator is 10:1-3:0.05-0.2; the reaction temperature is 60-80℃ and the reaction time is 6-12h; the initiator is azobisisobutyronitrile.

[0020] In this step, the initiator decomposes upon heating to generate free radicals, which attack the citronellol double bonds grafted on the surface and the fumaric acid monomer double bonds in the solution. Through in-situ free radical grafting copolymerization, a polymer shell rich in carboxyl groups is grown on the surface of nano-silica, ultimately forming a modified nanocomposite material with a core-shell structure.

[0021] Based on the above technical solutions, preferably, the water-reducing agent is at least one of lignin sulfonate water-reducing agents, naphthalene-based water-reducing agents, melamine-based water-reducing agents, aminosulfonate-based water-reducing agents, fatty acid-based water-reducing agents, and polycarboxylate-based water-reducing agents.

[0022] The present invention also provides a method for preparing the above-mentioned high-strength rubber recycled concrete, comprising the following steps:

[0023] Weigh each raw material according to the formula, mix cement, rubber granules, recycled coarse aggregate, fine aggregate, fly ash, and modified nano-silica evenly, then add water-reducing agent and mixing water, and continue to mix evenly to obtain high-strength recycled rubber concrete.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1) This invention provides a high-strength rubber recycled concrete and its preparation method, realizing the synergistic unity of efficient resource utilization of solid waste and high-performance concrete. Through scientific proportioning design, this invention introduces industrial waste such as rubber particles, recycled coarse aggregate and fly ash into the high-strength concrete system, which not only reduces the environmental impact, but also effectively overcomes the technical problems of weak interfacial bonding between rubber particles and cement matrix and high porosity of recycled aggregate leading to strength reduction by adding modified silica. It significantly improves the mechanical strength, toughness and durability of concrete, and is a green building material with both high strength and excellent freeze-thaw resistance.

[0026] 2) The preparation of the modified silica in this invention first involves surface treatment with KH550 to introduce active amino groups onto the surface. Then, alkyl glycosides and citronellol containing carbon-carbon double bonds are grafted onto the nano-silica surface through the crosslinking effect of epichlorohydrin. This avoids the free migration, interfacial sliding, and large bubble defects caused by physical blending of alkyl glycosides. The grafted alkyl glycosides, with their amphiphilicity and large sugar ring steric hindrance, not only significantly improve the interfacial bonding and dispersibility between hydrophobic rubber and hydrophilic slurry, promoting water penetration and hydration, but also induce the formation of a fine and stable porous structure, thereby improving the density of rubber recycled concrete. To improve the strength, mechanical properties, and long-term freeze-thaw resistance, the double bonds of citronellol were used to polymerize with fumaric acid, growing a carboxyl-rich polymer layer on the surface of nano-silica. The carboxylic acid groups in the fumaric acid segments can be adsorbed onto the surface of cement particles, acting as an anchor. Through electrostatic repulsion, the cement particles are uniformly dispersed, increasing the hydration contact area, accelerating the hydration process, and allowing the hydration products to fill the internal voids and interface transition zones more densely. Furthermore, the long polymer chains form a flexible network support in the microstructure, playing a toughening and crack-resistant role, effectively compensating for the strength loss caused by the addition of rubber to rubber concrete. Detailed Implementation

[0027] To avoid unnecessary details, unless otherwise specified, all items used in the following examples are commercially available products, and all methods used are conventional methods unless otherwise specified.

[0028] The sources of some of the raw materials used in this invention are as follows:

[0029] Nano-silica, 20nm, purchased from Hangzhou Hengna New Materials Co., Ltd.

[0030] The cement, purchased from Hubei Yadong Co., Ltd., is grade P·O 42.5 with a specific surface area of ​​360 m². 2 / kg, standard consistency water consumption 0.26.

[0031] Polycarboxylate superplasticizer, model 2101, purchased from Jining Yuanlian Chemical Technology Co., Ltd.

[0032] Example 1

[0033] A method for preparing high-strength recycled rubber concrete includes the following steps:

[0034] Waste concrete is crushed and screened to obtain recycled coarse aggregate with a particle size of 5-20mm. 400g of cement, 20g of rubber granules, 710g of recycled coarse aggregate, 520g of fine aggregate, 80g of fly ash, and 25g of modified nano-silica are mixed evenly. Then, 8.2g of polycarboxylate superplasticizer and 150g of mixing water are added and mixed evenly to obtain high-strength rubber recycled concrete.

[0035] The method for preparing the modified nano-silica includes the following steps:

[0036] (1) 100g of nano silica was dispersed in 1000mL of 50wt% ethanol aqueous solution, 4g of KH550 was added, and the mixture was stirred at 40℃ for 4h. After centrifugation, the precipitate was collected, washed and dried to obtain aminated nano silica.

[0037] (2) Add 100g of aminated nano silica to 1000mL of water and mix well. Add 43.6g of epichlorohydrin and adjust the pH to 5 with 1mol / L hydrochloric acid aqueous solution. Add 21g of alkyl glycoside and 25g of citronellol. Heat to 70℃ and react for 6h. After the reaction is completed, centrifuge, collect the precipitate, wash and dry to obtain cross-linked modified nano silica.

[0038] (3) 100g of cross-linked modified nano silica was dispersed in 1000mL of N,N-dimethylformamide, 22g of fumaric acid and 1g of azobisisobutyronitrile were added, and a polymerization reaction was carried out at 65℃ for 10h under nitrogen atmosphere. After the reaction was completed, the mixture was filtered, the solid was collected, washed and dried to obtain modified nano silica.

[0039] Example 2

[0040] A method for preparing high-strength recycled rubber concrete includes the following steps:

[0041] Waste concrete is crushed and screened to obtain recycled coarse aggregate with a particle size of 5-20mm. 350g of cement, 10g of rubber granules, 500g of recycled coarse aggregate, 450g of fine aggregate, 60g of fly ash, and 20g of modified nano-silica are mixed evenly. Then, 5g of polycarboxylate superplasticizer and 140g of mixing water are added and mixed evenly to obtain high-strength rubber recycled concrete.

[0042] The method for preparing the modified nano-silica includes the following steps:

[0043] (1) 100g of nano silica was dispersed in 1000mL of 50wt% ethanol aqueous solution, 3g of KH550 was added, and the mixture was stirred at 40℃ for 4h. After centrifugation, the precipitate was collected, washed and dried to obtain aminated nano silica.

[0044] (2) Add 100g of aminated nano silica to 1000mL of water and mix and stir evenly. Add 30g of epichlorohydrin, adjust the pH value to 4 with 1mol / L hydrochloric acid aqueous solution, add 20g of alkyl glycoside and 20g of citronellol, heat to 60℃ and react for 8h. After the reaction is completed, centrifuge, collect the precipitate, wash and dry to obtain cross-linked modified nano silica.

[0045] (3) 100g of cross-linked modified nano silica was dispersed in 1000mL of N,N-dimethylformamide, 10g of fumaric acid and 0.5g of azobisisobutyronitrile were added, and a polymerization reaction was carried out at 60℃ for 12h under nitrogen atmosphere. After the reaction was completed, the mixture was filtered, the solid was collected, washed and dried to obtain modified nano silica.

[0046] Example 3

[0047] A method for preparing high-strength recycled rubber concrete includes the following steps:

[0048] Waste concrete is crushed and screened to obtain recycled coarse aggregate with a particle size of 5-20mm. 450g of cement, 30g of rubber granules, 800g of recycled coarse aggregate, 650g of fine aggregate, 100g of fly ash, and 30g of modified nano-silica are mixed evenly. Then, 10g of polycarboxylate superplasticizer and 170g of mixing water are added and mixed evenly to obtain high-strength rubber recycled concrete.

[0049] The method for preparing the modified nano-silica includes the following steps:

[0050] (1) 100g of nano silica was dispersed in 1000mL of 50wt% ethanol aqueous solution, 5g of KH550 was added, and the mixture was stirred at 40℃ for 4h. After centrifugation, the precipitate was collected, washed and dried to obtain aminated nano silica.

[0051] (2) Add 100g of aminated nano silica to 1000mL of water and mix and stir evenly. Add 50g of epichlorohydrin, adjust the pH value to 6 with 1mol / L hydrochloric acid aqueous solution, add 30g of alkyl glycoside and 30g of citronellol, heat to 80℃ and react for 4h. After the reaction is completed, centrifuge, collect the precipitate, wash and dry to obtain cross-linked modified nano silica.

[0052] (3) 100g of cross-linked modified nano silica was dispersed in 1000mL of N,N-dimethylformamide, 30g of fumaric acid and 2g of azobisisobutyronitrile were added, and a polymerization reaction was carried out at 80℃ for 6h under nitrogen atmosphere. After the reaction was completed, the mixture was filtered, the solid was collected, washed and dried to obtain modified nano silica.

[0053] Comparative Example 1

[0054] A method for preparing high-strength recycled rubber concrete includes the following steps:

[0055] Waste concrete is crushed and screened to obtain recycled coarse aggregate with a particle size of 5-20mm. 400g of cement, 20g of rubber granules, 710g of recycled coarse aggregate, 520g of fine aggregate, 80g of fly ash, and 25g of modified nano-silica are mixed evenly. Then, 8.2g of polycarboxylate superplasticizer and 150g of mixing water are added and mixed evenly to obtain high-strength rubber recycled concrete.

[0056] The preparation method of the modified nano-silica is similar to that of Example 1, except that no alkyl glycosides are added, and specifically includes the following steps:

[0057] (1) 100g of nano silica was dispersed in 1000mL of 50wt% ethanol aqueous solution, 4g of KH550 was added, and the mixture was stirred at 40℃ for 4h. After centrifugation, the precipitate was collected, washed and dried to obtain aminated nano silica.

[0058] (2) Add 100g of aminated nano silica to 1000mL of water and mix and stir evenly. Add 43.6g of epichlorohydrin, adjust the pH value to 5 with 1mol / L hydrochloric acid aqueous solution, add 25g of citronellol, heat to 70℃ and react for 6h. After the reaction is completed, centrifuge, collect the precipitate, wash and dry to obtain cross-linked modified nano silica.

[0059] (3) 100g of cross-linked modified nano silica was dispersed in 1000mL of N,N-dimethylformamide, 22g of fumaric acid and 1g of azobisisobutyronitrile were added, and a polymerization reaction was carried out at 65℃ for 10h under nitrogen atmosphere. After the reaction was completed, the mixture was filtered, the solid was collected, washed and dried to obtain modified nano silica.

[0060] Comparative Example 2

[0061] A method for preparing high-strength recycled rubber concrete includes the following steps:

[0062] Waste concrete is crushed and screened to obtain recycled coarse aggregate with a particle size of 5-20mm. 400g of cement, 20g of rubber granules, 710g of recycled coarse aggregate, 520g of fine aggregate, 80g of fly ash, and 25g of modified nano-silica are mixed evenly. Then, 8.2g of polycarboxylate superplasticizer and 150g of mixing water are added and mixed evenly to obtain high-strength rubber recycled concrete.

[0063] The preparation method of the modified nano-silica is similar to that of Example 1, except that the alkyl glycosides are physically mixed, and specifically includes the following steps:

[0064] (1) 100g of nano silica was dispersed in 1000mL of 50wt% ethanol aqueous solution, 4g of KH550 was added, and the mixture was stirred at 40℃ for 4h. After centrifugation, the precipitate was collected, washed and dried to obtain aminated nano silica.

[0065] (2) Add 100g of aminated nano silica to 1000mL of water and mix and stir evenly. Add 43.6g of epichlorohydrin, adjust the pH value to 5 with 1mol / L hydrochloric acid aqueous solution, add 25g of citronellol, heat to 70℃ and react for 6h. After the reaction is completed, centrifuge, collect the precipitate, wash and dry to obtain cross-linked modified nano silica.

[0066] (3) 100g of cross-linked modified nano silica was dispersed in 1000mL of N,N-dimethylformamide, 22g of fumaric acid and 1g of azobisisobutyronitrile were added, and a polymerization reaction was carried out at 65℃ for 10h under nitrogen atmosphere. After the reaction was completed, the mixture was filtered, the solid was collected, washed and dried, and mixed with 21g of alkyl glycoside to obtain modified nano silica.

[0067] Comparative Example 3

[0068] A method for preparing high-strength recycled rubber concrete includes the following steps:

[0069] Waste concrete is crushed and screened to obtain recycled coarse aggregate with a particle size of 5-20mm. 400g of cement, 20g of rubber granules, 710g of recycled coarse aggregate, 520g of fine aggregate, 80g of fly ash, and 25g of modified nano-silica are mixed evenly. Then, 8.2g of polycarboxylate superplasticizer and 150g of mixing water are added and mixed evenly to obtain high-strength rubber recycled concrete.

[0070] The preparation method of the modified nano-silica is similar to that of Example 1, except that fumaric acid is not added, and specifically includes the following steps:

[0071] (1) 100g of nano silica was dispersed in 1000mL of 50wt% ethanol aqueous solution, 4g of KH550 was added, and the mixture was stirred at 40℃ for 4h. After centrifugation, the precipitate was collected, washed and dried to obtain aminated nano silica.

[0072] (2) Add 100g of aminated nano silica to 1000mL of water and mix evenly. Add 43.6g of epichlorohydrin and adjust the pH to 5 with 1mol / L hydrochloric acid aqueous solution. Add 21g of alkyl glycoside and 25g of citronellol. Heat to 70℃ and react for 6h. After the reaction is completed, centrifuge, collect the precipitate, wash and dry to obtain modified nano silica.

[0073] Performance testing

[0074] Specimen preparation and curing: The high-strength rubber recycled concrete prepared in Examples 1-3 and Comparative Examples 1-3 were cured and molded into standard-sized specimens. All specimens were cured in a standard curing room at a temperature of (20±2)℃ and a relative humidity of >95% for 28 days, and then subjected to frost resistance tests.

[0075] Freeze-thaw resistance test: Take a set of cured specimens, soak them in water for 4 days, wipe the surface dry and weigh their initial mass. Then, place the weighed concrete specimens into the specimen box of the freeze-thaw cycle machine. According to the test provisions in GB / T50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", the freeze-thaw resistance of the concrete specimens is tested. The smaller the mass loss rate, the stronger the freeze-thaw resistance. The test results are shown in Table 1.

[0076] Table 1. Test results of the freeze-thaw resistance of high-strength rubber recycled concrete

[0077]

[0078] Compressive strength testing: The compressive strength of the high-strength rubber recycled concrete prepared in Examples 1-3 and Comparative Examples 1-3 was tested according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The test results are shown in Table 2.

[0079] Table 2. Test results of compressive strength of high-strength rubber recycled concrete

[0080]

[0081] As can be seen from the experimental results in Tables 1 and 2, the high-strength rubber recycled concrete obtained by this invention has good frost resistance and mechanical properties.

[0082] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A high-strength recycled rubber concrete, characterized in that, It includes the following components by weight: 350-450 parts cement, 10-30 parts rubber granules, 500-800 parts recycled coarse aggregate, 450-650 parts fine aggregate, 60-100 parts fly ash, 20-30 parts modified nano silica, 5-10 parts water-reducing agent, and 140-170 parts mixing water; The method for preparing the modified nano-silica includes the following steps: (1) Disperse nano-silica in an aqueous ethanol solution, add KH550, stir and react to obtain aminated nano-silica; (2) Add aminated nano silica to water and mix evenly. Add epichlorohydrin, adjust the pH to 4-6, add alkyl glycoside and citronellol, and heat the reaction to obtain cross-linked modified nano silica. (3) The cross-linked modified nano silica was dispersed in N,N-dimethylformamide, fumaric acid and an initiator were added, and a polymerization reaction was carried out under a nitrogen atmosphere to obtain modified nano silica.

2. The recycled concrete according to claim 1, characterized in that: The cement is ordinary Portland cement.

3. The recycled concrete according to claim 1, characterized in that: The recycled coarse aggregate is obtained by crushing waste concrete.

4. The recycled concrete according to claim 1, characterized in that: The fine aggregate is one of river sand, sea sand, manufactured sand, or quartz sand.

5. The recycled concrete according to claim 1, characterized in that: The fly ash is Class II fly ash.

6. The recycled concrete according to claim 1, characterized in that: In step (1), the mass ratio of nano-silica to KH550 is 100:3-5.

7. The recycled concrete according to claim 1, characterized in that: In step (2), the mass ratio of aminated nano-silica, epichlorohydrin, alkyl glycoside and citronellol is 10:3-5:2-3:2-3.

8. The recycled concrete according to claim 1, characterized in that: In step (3), the mass ratio of crosslinked modified nano silica, fumaric acid and initiator is 10:1-3:0.05-0.2; the reaction temperature is 60-80℃ and the reaction time is 6-12h; the initiator is azobisisobutyronitrile.

9. A method for preparing recycled concrete according to any one of claims 1-8, characterized in that, The process includes the following steps: Weigh each raw material according to the formula, mix cement, rubber granules, recycled coarse aggregate, fine aggregate, fly ash, and modified nano-silica evenly, then add water-reducing agent and mixing water, and continue to mix evenly to obtain high-strength recycled rubber concrete.

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