A fiber reinforced concrete based on construction solid waste recycled aggregate and a preparation method thereof

Abstract

The application relates to the technical field of concrete building material preparation, in particular to a fiber reinforced concrete based on building solid waste recycled aggregate and a preparation method thereof, which comprises the following preparation steps: S1. Recycled coarse aggregate, silica fume, rice husk ash and metakaolin are mixed and stirred according to proportions to obtain cement mixture; S2. The cement mixture obtained in the step S1 is calcined for 2-3 hours to obtain cement clinker; S3. The cement clinker obtained in the step S2, polypropylene-vinyl aramid mixed fiber, polycarboxylic acid water reducing agent, modified pouring agent and tetrasodium iminodisuccinate are mixed according to proportions, then poured into a stirrer and stirred for 5-8 minutes; and S4. Water is added into the stirrer according to a proportion, and the mixture is continuously stirred for 6-12 minutes and then taken out to obtain the fiber reinforced concrete based on the building solid waste recycled aggregate. The application utilizes the building solid waste recycled aggregate, reduces natural resource consumption, reduces the building waste landfill amount (1.5-2 tons of natural sand and stone mining can be reduced per ton of recycled aggregate), and meets the sustainable development concept.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete building material preparation, in particular to a fiber reinforced concrete based on building solid waste recycled aggregate and a preparation method thereof. BACKGROUND

[0002] With the acceleration of global urbanization and the large-scale expansion of infrastructure construction, the demand for natural aggregate in the traditional building material industry continues to rise, leading to over-exploitation of resources and intensifying ecological pressure. For example, the over-exploitation of river sand not only causes river erosion and destruction of biological habitats, but also may induce regional water resource imbalance; mountain stone mining is prone to cause instability of mountain structure, aggravating soil erosion and geological disaster risk. Globally, about 40 billion tons of sand and stone resources are consumed annually, far exceeding the natural regeneration rate, highlighting the problem of resource unsustainability.

[0003] At the same time, the disposal of construction waste has become a serious challenge for urban management. Globally, more than 3 billion tons of construction waste are generated annually, of which more than 50% is waste concrete. Traditional landfill methods not only occupy land resources, but also may contaminate soil and groundwater systems due to heavy metal leaching. Under this background, building solid waste recycling technology has become a research hotspot. Through crushing, screening and other processes, waste concrete can be converted into recycled aggregate, which can replace natural sand and stone for building material production. Studies have shown that the large-scale application of recycled aggregate can reduce natural resource consumption by 40%-60% and reduce landfill by about 70%, in line with the concept of circular economy.

[0004] In the field of concrete performance optimization, fiber reinforcement technology has attracted attention due to its significant toughening and crack resistance effects. By incorporating high-strength fibers (such as steel fibers, carbon fibers or synthetic fibers), stress concentration can be effectively dispersed, and micro-crack propagation can be inhibited, thereby improving the impact resistance and durability of concrete. In recent years, the introduction of nanomaterials (such as carbon nanotubes, graphene) has further promoted the development of high-performance concrete. For example, the interfacial modification ability of nanoparticles can optimize the bonding performance of the cement matrix and aggregate, and the synergistic effect of functional additives (such as water reducing agents, toughening agents) can significantly improve the workability and long-term stability of concrete.

[0005] However, existing recycled aggregate concrete still faces the bottleneck of insufficient mechanical properties, high porosity and poor durability. Recycled aggregate has a high water absorption rate due to the attachment of old mortar on its surface, which can easily cause loose internal structure of concrete; in addition, traditional fiber reinforcement technology has limited adaptability to complex environments (such as high alkalinity, freeze-thaw cycles). Therefore, developing recycled aggregate concrete with high mechanical strength, excellent durability and environmental friendliness has become an urgent task in the building material field. Based on this, it is necessary to modify the material, innovate the process and optimize the components to build a multi-scale synergistic reinforcement system and promote the industrialization application of green building materials technology. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a fiber reinforced concrete based on building solid waste recycled aggregate and a preparation method thereof.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] A fiber reinforced concrete based on building solid waste recycled aggregate, comprising the following components by mass fraction: 150-200 parts of recycled coarse aggregate, 150-200 parts of silica fume, 270-300 parts of rice husk ash, 160-210 parts of water, 200-250 parts of metakaolin, 10-15 parts of polypropylene-aramid fiber mixture, 10-15 parts of polycarboxylate superplasticizer, 10-20 parts of modified pouring agent, and 10-20 parts of tetrasodium iminodisuccinate.

[0009] The preparation of the modified pouring agent comprises the following steps:

[0010] S21. 1-3 parts of a 60% mass concentration carboxymethyl cellulose sodium solution is added to 5-8 parts of modified nano-silica sol at a drop rate of 1-2 mL / min, and stirring is carried out at a speed of 300-400 r / min at a temperature of 40-50°C while dropping, to obtain a primary mixed solution;

[0011] S22. 10-15 parts of water-based epoxy resin emulsion is added to the primary mixed solution, and stirring is carried out at a speed of 600-700 r / min at a constant temperature of 50°C for 1-1.5 h to obtain a secondary mixed solution;

[0012] S23. 0.1-0.5 parts of a defoaming agent is added to the secondary mixed solution, and stirring is carried out at a speed of 400-500 r / min for 15-20 min to finally obtain the modified pouring agent.

[0013] Preferably, the preparation of the polypropylene-aramid fiber mixture comprises the following steps:

[0014] S11. 3-6 parts of nickel-plated carbon nanotubes are ultrasonically dispersed in a 1% mass concentration sodium dodecyl sulfate aqueous solution to obtain a nickel-plated carbon nanotube dispersion solution;

[0015] S12. 55-65 parts of polypropylene fibers are subjected to plasma treatment under an argon atmosphere for 3-5 min, and then the nickel-plated carbon nanotube dispersion solution is added to obtain a polypropylene fiber nanodispersion solution;

[0016] S13. Soak 8-12 parts of aramid fiber in concentrated nitric acid with a mass concentration of 65% for 1-2 hours at a temperature of 60-65℃, rinse with deionized water until neutral, then soak in a chitosan solution with a mass concentration of 2% for 10-15 minutes and a dopamine hydrochloride solution with a mass concentration of 0.3% for 10-12 hours, respectively, to obtain modified aramid fiber;

[0017] S14. Mix the propylene fiber nanodispersion with the modified aramid fiber, and add a silane coupling agent ethanol solution with a mass concentration of 1%, and disperse at a high speed of 2000-4000 r / min for 25-30 minutes to obtain polypropylene-aramid hybrid fiber.

[0018] Preferably, the preparation of the modified nanosilica sol comprises the following steps:

[0019] S211. Mix 1-3 parts of polycarboxylic acid water reducer with 10-15 parts of deionized water, and stir at a speed of 200-400 r / min under the condition of a 40℃ water bath until completely dissolved to obtain a polycarboxylic acid water reducer aqueous solution;

[0020] S212. Add 0.5-2 parts of sodium gluconate to the polycarboxylic acid water reducer aqueous solution, continue to stir for 5-8 minutes, and then add 50-60 parts of nanosilica sol at a dropwise addition rate of 1-2 mL / min to obtain a preliminary modified nanosilica sol;

[0021] S213. Adjust the pH of the preliminary modified nanosilica sol to 8.5-9.5 with a NaOH solution to obtain a modified nanosilica sol.

[0022] Preferably, in step S11, the power of ultrasonic dispersion is 400-600 W, and the time is 25-30 minutes.

[0023] Preferably, in step S12, the power of plasma treatment is 80-120 W.

[0024] Preferably, the defoaming agent in step S23 is an organic silicon-based defoaming agent.

[0025] A preparation method of a fiber reinforced concrete based on building solid waste recycled aggregate, for preparing the above-mentioned fiber reinforced concrete based on building solid waste recycled aggregate, comprising the following steps:

[0026] S1. Mix and stir the recycled coarse aggregate, silica fume, rice husk ash, and metakaolin according to the proportions to obtain a cement mixture;

[0027] S2. Calcine the cement mixture obtained in step S1 for 2-3 hours to obtain cement clinker;

[0028] S3. The cement clinker, polypropylene-aramid hybrid fiber, polycarboxylate superplasticizer, modified troweling agent, and tetrasodium iminodisuccinate obtained in step S2 are mixed in proportion, then poured into a stirrer and stirred for 5-8 min;

[0029] S4. Water is added to the stirrer in proportion, and stirring is continued for 6-12 min to obtain the fiber reinforced concrete based on building solid waste recycled aggregate.

[0030] A method for preparing a fiber reinforced concrete based on building solid waste recycled aggregate, characterized in that the stirring speed in step S1 is 100-300 r / min, and the time is 7-10 min.

[0031] Preferably, in step S2, the calcination temperature is 800-1000 DEG C.

[0032] Compared with the prior art, the beneficial effects of the present application are:

[0033] 1. The modified troweling agent prepared by modifying the nano-silica sol uniformly fills the micropores in the concrete, forms a densified network structure, and effectively reduces the porosity. At the same time, the surface hydroxyl group forms a chemical bond with the cement hydration product, enhances the strength of the aggregate-paste interface transition zone, improves the compressive strength, delays the interface deterioration in the alkaline environment, and significantly improves the durability.

[0034] 2. The nickel-plated carbon nanotubes and the plasma-treated polypropylene fibers in the polypropylene-aramid hybrid fiber form a nano-micron multi-scale reinforcing system through high-speed shearing dispersion. The bridging effect of the carbon nanotubes can disperse stress concentration and improve the tensile strength; after the aramid fibers are etched with nitric acid and coated with chitosan-dopamine, the surface roughness increases, and the mechanical engagement force with the cement matrix is enhanced. In addition, the introduction of silane coupling agent optimizes the chemical bonding between the fiber-matrix interface, so that the fiber remains stable in the alkaline environment for a long time.

[0035] 3. The synergistic effect of the polypropylene-aramid hybrid fiber and the modified troweling agent forms a steric hindrance effect in the paste, reduces the water-binder ratio, improves the compactness of the concrete, further strengthens the three-dimensional cross-linked structure of the cement matrix, inhibits dry shrinkage cracks, effectively eliminates the air bubbles generated during the stirring process, reduces the defect density, and effectively improves the frost resistance. The synergistic effect of the raw materials constructs a multi-level reinforcing network of "fiber toughening + resin filling + nano densification" in the concrete, optimizes the mechanical properties and durability simultaneously, significantly improves the rheological properties of the paste, ensures efficient wrapping of the recycled aggregate, reduces the early shrinkage rate, and meets the requirements of high-strength and complex environment engineering. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1A preparation process flow chart of the fiber reinforced concrete based on building solid waste recycled aggregate according to the present application is provided.

[0037] Figure 2 A preparation process flow chart of the polypropylene-aramid hybrid fiber according to the present application is provided.

[0038] Figure 3 A preparation process flow chart of the modified pouring agent according to the present application is provided.

[0039] Figure 4 A preparation process flow chart of the modified nano-silica sol according to the present application is provided. DETAILED DESCRIPTION

[0040] The present application will be described in detail below with reference to the embodiments thereof, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0041] Please refer to Figures 1-4 The present application provides a technical solution:

[0042] Embodiment 1

[0043] A preparation method of a fiber reinforced concrete based on building solid waste recycled aggregate:

[0044] S1. 15 kg of recycled coarse aggregate, 15 kg of silica fume, 27 kg of rice husk ash, and 20 kg of metakaolin are mixed in proportion and stirred for 7 min at a stirring speed of 100 r / min to obtain a cement mixture;

[0045] S2. The cement mixture obtained in step S1 is calcined for 2 h at a temperature of 800℃ to obtain a cement clinker;

[0046] S3. The cement clinker obtained in step S2, 1 kg of polypropylene-aramid hybrid fiber, 1 kg of polycarboxylate superplasticizer, 1 kg of modified pouring agent, and 1 kg of iminodisuccinic acid tetrasodium are mixed and then poured into a stirrer for stirring for 5 min;

[0047] S4. 16 kg of water is added to the stirrer and continues to stir for 6 min to obtain a fiber reinforced concrete based on building solid waste recycled aggregate;

[0048] The preparation of the polypropylene-aramid hybrid fiber includes the following steps:

[0049] S11. 3 parts of nickel-plated carbon nanotubes are ultrasonically dispersed in a 1% sodium dodecyl sulfate aqueous solution at a power of 400 W for 25 min to obtain a nickel-plated carbon nanotube dispersion;

[0050] S12. 55 parts of polypropylene fibers were plasma treated under argon atmosphere for 3 min at a power of 80 W, and then a nickel-coated carbon nanotube dispersion solution was added to obtain a polypropylene fiber nanodispersion;

[0051] S13. 8 parts of aramid fibers were soaked in concentrated nitric acid with a mass concentration of 65% for 1 h at a temperature of 60°C, washed with deionized water until neutral, and then soaked in a chitosan solution with a mass concentration of 2% for 10 min and a dopamine hydrochloride solution with a mass concentration of 0.3% for 10 h, respectively, to obtain modified aramid fibers;

[0052] S14. The polypropylene fiber nanodispersion was mixed with the modified aramid fibers, and a silane coupling agent ethanol solution with a mass concentration of 1% was added, and high-speed shearing dispersion was performed at 2000 r / min for 25 min to obtain polypropylene-aramid hybrid fibers;

[0053] The preparation of the modified pouring agent includes the following steps:

[0054] S21. 1 part of a sodium carboxymethyl cellulose solution with a mass concentration of 60% was added to 5 parts of the modified nanosilica sol at a dropping speed of 1 mL / min, and stirring was performed at a rotation speed of 300 r / min at 40°C while dropping to obtain a primary mixture;

[0055] S22. 10 parts of an aqueous epoxy resin emulsion were added to the primary mixture, and stirring was performed at a rotation speed of 600 r / min at a constant temperature of 50°C for 1 h to obtain a secondary mixture;

[0056] S23. 0.1 parts of a silicone-based defoaming agent were added to the secondary mixture, and stirring was performed at a rotation speed of 400 r / min for 15 min to finally obtain a modified pouring agent;

[0057] The preparation of the modified nanosilica sol includes the following steps:

[0058] S211. 1 part of a polycarboxylic acid water reducer was mixed with 10 parts of deionized water, and stirring was performed at a rotation speed of 200 r / min at a water bath temperature of 40°C until complete dissolution to obtain a polycarboxylic acid water reducer aqueous solution;

[0059] S212. 0.5 parts of sodium gluconate were added to the polycarboxylic acid water reducer aqueous solution, and stirring was continued for 5 min, and then 50 parts of nanosilica sol were added at a dropping speed of 1 mL / min to obtain a preliminary modified nanosilica sol;

[0060] S213. The pH of the preliminary modified nanosilica sol was adjusted to 8.5 with a NaOH solution to finally obtain a modified nanosilica sol.

[0061] Example 2

[0062] A preparation method of a fiber reinforced concrete based on building solid waste recycled aggregate:

[0063] S1. 20 kg of recycled coarse aggregate, 20 kg of silica fume, 30 kg of rice husk ash, and 25 kg of metakaolin are mixed in proportion and stirred for 10 min at a stirring speed of 300 r / min to obtain a cement mixture;

[0064] S2. The cement mixture obtained in step S1 is calcined for 3 h at a temperature of 1000 DEG C to obtain a cement clinker;

[0065] S3. The cement clinker obtained in step S2, 1.5 kg of polypropylene-aramid hybrid fiber, 1.5 kg of polycarboxylate superplasticizer, 2 kg of modified pouring agent, and 2 kg of tetrasodium iminodisuccinate are mixed and then poured into a stirrer for stirring for 8 min;

[0066] S4. 21 kg of water is added to the stirrer for continuous stirring for 12 min to obtain a fiber reinforced concrete based on building solid waste recycled aggregate;

[0067] The preparation of the polypropylene-aramid hybrid fiber comprises the following steps:

[0068] S11. 6 parts of nickel-plated carbon nanotubes are ultrasonically dispersed in a 1% sodium dodecyl sulfate aqueous solution at a power of 600 W for 30 min to obtain a nickel-plated carbon nanotube dispersion;

[0069] S12. 65 parts of polypropylene fibers are subjected to plasma treatment under an argon atmosphere for 5 min at a power of 120 W, and then the nickel-plated carbon nanotube dispersion is added to obtain a polypropylene fiber nanodispersion;

[0070] S13. 12 parts of aramid fibers are soaked in a 65% concentrated nitric acid solution at a temperature of 65 DEG C for 2 h, washed with deionized water until neutral, and then soaked in a 2% chitosan solution and a 0.3% dopamine hydrochloride solution for 15 min and 12 h respectively to obtain modified aramid fibers;

[0071] S14. The polypropylene fiber nanodispersion and the modified aramid fibers are mixed, and a 1% silane coupling agent ethanol solution is added and subjected to high-speed shearing dispersion at 4000 r / min for 30 min to obtain polypropylene-aramid hybrid fibers;

[0072] The preparation of the modified pouring agent comprises the following steps:

[0073] S21. 3 parts of a 60% carboxymethyl cellulose sodium solution are added to 8 parts of a modified nano-silica sol at a dropping speed of 2 mL / min while stirring at a speed of 400 r / min at a temperature of 50 DEG C to obtain a primary mixture;

[0074] S22. Add 15 parts of water-based epoxy resin emulsion to the primary mixture, stir at a constant temperature of 50℃ and a speed of 700r / min for 1.5h to obtain a secondary mixture;

[0075] S23. Add 0.5 parts of silicone-based defoaming agent to the secondary mixture, stir at a speed of 500r / min for 20min to finally obtain the modified pouring agent;

[0076] The preparation of the modified nanometer silicon sol includes the following steps:

[0077] S211. Mix 3 parts of polycarboxylic acid water reducer with 15 parts of deionized water, stir at a speed of 400r / min under the condition of 40℃ water bath until completely dissolved to obtain a polycarboxylic acid water solution;

[0078] S212. Add 2 parts of sodium gluconate to the polycarboxylic acid water solution, continue to stir for 8min, and then add 60 parts of nanometer silicon sol at a dropping speed of 2mL / min to obtain a preliminary modified nanometer silicon sol;

[0079] S213. Adjust the pH of the preliminary modified nanometer silicon sol to 9.5 with NaOH solution to finally obtain the modified nanometer silicon sol.

[0080] Example 3

[0081] A preparation method of a fiber reinforced concrete based on building solid waste recycled aggregate:

[0082] S1. Mix 16kg of recycled coarse aggregate, 16kg of silica fume, 28kg of rice husk ash, and 21kg of metakaolin according to the proportion and stir for 8min at a stirring speed of 150r / min to obtain a cement mixture;

[0083] S2. Calcine the cement mixture obtained in step S1 for 2.2h at a temperature of 850℃ to obtain a cement clinker;

[0084] S3. Mix the cement clinker obtained in step S2, 1.2kg of polypropylene-aramid mixed fiber, 1.2kg of polycarboxylic acid water reducer, 1.5kg of modified pouring agent, and 1.5kg of iminodisuccinic acid tetrasodium, and then pour them into a blender and stir for 6min;

[0085] S4. Add 18kg of water to the blender and continue to stir for 8min, and then take out to obtain the fiber reinforced concrete based on building solid waste recycled aggregate;

[0086] The preparation of the polypropylene-aramid mixed fiber includes the following steps:

[0087] S11. Ultrasonic dispersion of 4 parts of nickel-plated carbon nanotubes in a 1% sodium dodecyl sulfate aqueous solution at a power of 450 W for 26 min to obtain a nickel-plated carbon nanotube dispersion;

[0088] S12. Plasma treatment of 58 parts of polypropylene fibers under an argon atmosphere for 4 min at a power of 90 W, and then adding the nickel-plated carbon nanotube dispersion to obtain a polypropylene fiber nanodispersion;

[0089] S13. Immersion of 9 parts of aramid fibers in 65% concentrated nitric acid for 1.2 h at a temperature of 62°C, washing with deionized water until neutral, and then immersing in 2% chitosan solution and 0.3% dopamine hydrochloride solution for 12 min and 10.5 h, respectively, to obtain modified aramid fibers;

[0090] S14. Mixing of the polypropylene fiber nanodispersion and the modified aramid fibers, and adding 1% silane coupling agent ethanol solution, and high-speed shearing dispersion at 3000 r / min for 27 min to obtain polypropylene-aramid hybrid fibers;

[0091] The preparation of the modified pouring agent includes the following steps:

[0092] S21. Adding 2 parts of 60% carboxymethyl cellulose sodium solution to 6 parts of modified nanosilica sol at a dropping rate of 1.5 mL / min, and stirring at a speed of 350 r / min at 42°C to obtain a primary mixture;

[0093] S22. Adding 12 parts of water-based epoxy resin emulsion to the primary mixture, and stirring at a speed of 650 r / min at 50°C for 1.2 h to obtain a secondary mixture;

[0094] S23. Adding 0.2 parts of silicone-based defoamer to the secondary mixture, and stirring at a speed of 450 r / min for 17 min to finally obtain a modified pouring agent;

[0095] The preparation of the modified nanosilica sol includes the following steps:

[0096] S211. Mixing 2 parts of polycarboxylic acid water reducer with 12 parts of deionized water, and stirring at a speed of 250 r / min at 40°C until completely dissolved to obtain a polycarboxylic acid water solution;

[0097] S212. Adding 1 part of sodium gluconate to the polycarboxylic acid water solution, and continuing to stir for 6 min, and then adding 55 parts of nanosilica sol at a dropping rate of 1.5 mL / min to obtain a preliminary modified nanosilica sol;

[0098] S213. Adjust the pH of the preliminary modified nanometer silicon sol to 9 with NaOH solution, finally obtain modified nanometer silicon sol.

[0099] Example 4

[0100] A preparation method of a fiber reinforced concrete based on building solid waste recycled aggregate:

[0101] S1. Mix 19 kg of recycled coarse aggregate, 19 kg of silica fume, 29 kg of rice husk ash, and 24 kg of metakaolin according to the proportion and stir for 9 min at a stirring speed of 250 r / min to obtain a cement mixture;

[0102] S2. Calcine the cement mixture obtained in step S1 for 2.5 h at a calcination temperature of 900℃ to obtain a cement clinker;

[0103] S3. Mix the cement clinker obtained in step S2, 1.3 kg of polypropylene-aramid hybrid fiber, 1.3 kg of polycarboxylate superplasticizer, 1.8 kg of modified grouting agent, and 1.8 kg of iminodisuccinic acid tetrasodium, and then pour them into a stirrer and stir for 7 min;

[0104] S4. Add 20 kg of water into the stirrer and continue to stir for 11 min, and then take out to obtain a fiber reinforced concrete based on building solid waste recycled aggregate;

[0105] The preparation of the polypropylene-aramid hybrid fiber comprises the following steps:

[0106] S11. Ultrasonically disperse 5 parts of nickel-plated carbon nanotubes in a 1% sodium dodecyl sulfate aqueous solution at a power of 550 W for 28 min to obtain a nickel-plated carbon nanotube dispersion;

[0107] S12. Plasma treat 63 parts of polypropylene fiber under an argon atmosphere for 4.5 min at a power of 110 W, and then add the nickel-plated carbon nanotube dispersion to obtain a polypropylene fiber nanodispersion;

[0108] S13. Soak 11 parts of aramid fiber in a 65% concentrated nitric acid solution at a temperature of 64℃ for 1.5 h, rinse with deionized water until neutral, and then soak in a 2% chitosan solution and a 0.3% dopamine hydrochloride solution for 14 min and 11.5 h respectively to obtain modified aramid fiber;

[0109] S14. Mix the polypropylene fiber nanodispersion with the modified aramid fiber, and add a 1% silane coupling agent ethanol solution, and then disperse at a high speed of 3500 r / min for 28 min to obtain polypropylene-aramid hybrid fiber;

[0110] The preparation of the modified grouting agent comprises the following steps:

[0111] S21. 2 parts of a 60% mass concentration sodium carboxymethyl cellulose solution was added to 7 parts of modified nanosilica sol at a dropping speed of 1.5 mL / min, and stirring was performed at a rotation speed of 350 r / min under the condition of 53°C during the dropping, to obtain a primary mixed solution;

[0112] S22. 14 parts of an aqueous epoxy resin emulsion was added to the primary mixed solution, and stirring was performed at a rotation speed of 650 r / min under the condition of 50°C for 1.4 h, to obtain a secondary mixed solution;

[0113] S23. 0.4 parts of a silicone-based defoaming agent was added to the secondary mixed solution, and stirring was performed at a rotation speed of 450 r / min for 19 min, to finally obtain a modified pouring agent;

[0114] The preparation of the modified nanosilica sol comprises the following steps:

[0115] S211. 2 parts of a polycarboxylic acid water reducing agent was mixed with 14 parts of deionized water, and stirring was performed at a rotation speed of 350 r / min under the condition of a 40°C water bath until complete dissolution, to obtain a polycarboxylic acid water reducing agent aqueous solution;

[0116] S212. 1.5 parts of sodium gluconate was added to the polycarboxylic acid water reducing agent aqueous solution, and after 7 min of continuous stirring, 58 parts of nanosilica sol was added at a dropping speed of 1.5 mL / min, to obtain a preliminary modified nanosilica sol;

[0117] S213. The pH of the preliminary modified nanosilica sol was adjusted to 9.3 by using a NaOH solution, to finally obtain a modified nanosilica sol.

[0118] Comparative Example 1

[0119] A preparation method of a fiber reinforced concrete based on construction solid waste recycled aggregate:

[0120] S1. 15 kg of recycled coarse aggregate, 15 kg of silica fume, 27 kg of rice husk ash, and 20 kg of metakaolin were mixed and stirred at a stirring speed of 100 r / min for 7 min, to obtain a cement mixture;

[0121] S2. The cement mixture obtained in step S1 was calcined for 2 h at a temperature of 800°C, to obtain a cement clinker;

[0122] S3. The cement clinker obtained in step S2, 1 kg of a polycarboxylic acid water reducing agent, 1 kg of a modified pouring agent, and 1 kg of tetrasodium iminodisuccinate were mixed and then poured into a stirrer for stirring for 5 min;

[0123] S4. 16 kg of water was added into the stirrer for continuous stirring for 6 min, and then taken out, to obtain a fiber reinforced concrete based on construction solid waste recycled aggregate.

[0124] The preparation of the modified irrigation agent comprises the following steps:

[0125] S21. 1 part of a 60% mass concentration sodium carboxymethyl cellulose solution is added to 5 parts of the modified nanosilica sol at a dropping speed of 1 mL / min, and stirring is performed at a speed of 300 r / min at 40°C while dropping, to obtain a primary mixed solution;

[0126] S22. 10 parts of an aqueous epoxy resin emulsion is added to the primary mixed solution, and stirring is performed at a speed of 600 r / min at a constant temperature of 50°C for 1 h, to obtain a secondary mixed solution;

[0127] S23. 0.1 part of a silicone-based defoaming agent is added to the secondary mixed solution, and stirring is performed at a speed of 400 r / min for 15 min, to finally obtain the modified irrigation agent;

[0128] The preparation of the modified nanosilica sol comprises the following steps:

[0129] S211. 1 part of a polycarboxylic acid water reducing agent is mixed with 10 parts of deionized water, and stirring is performed at a speed of 200 r / min at a water bath temperature of 40°C until complete dissolution, to obtain a polycarboxylic acid water reducing agent aqueous solution;

[0130] S212. 0.5 part of sodium gluconate is added to the polycarboxylic acid water reducing agent aqueous solution, and after 5 min of continuous stirring, 50 parts of nanosilica sol is added at a dropping speed of 1 mL / min, to obtain a preliminary modified nanosilica sol;

[0131] S213. The pH of the preliminary modified nanosilica sol is adjusted to 8.5 with a NaOH solution, to finally obtain the modified nanosilica sol.

[0132] Comparative Example 2

[0133] A preparation method of a fiber reinforced concrete based on building solid waste recycled aggregate:

[0134] S1. 15 kg of recycled coarse aggregate, 15 kg of silica fume, 27 kg of rice husk ash, and 20 kg of metakaolin are mixed according to the proportions and stirred for 7 min at a stirring speed of 100 r / min, to obtain a cement mixture;

[0135] S2. The cement mixture obtained in step S1 is calcined for 2 h at a temperature of 800°C, to obtain a cement clinker;

[0136] S3. The cement clinker obtained in step S2, 1 kg of polypropylene-aramid mixed fiber, 1 kg of polycarboxylic acid water reducing agent, and 1 kg of tetrasodium iminodisuccinate are mixed and then poured into a stirrer and stirred for 5 min;

[0137] S4. 16 kg of water was added into the blender and continued to stir for 6 min, then taken out to obtain the fiber reinforced concrete based on construction solid waste recycled aggregate;

[0138] The preparation of the polypropylene-aramid hybrid fiber comprises the following steps:

[0139] S11. 3 parts of nickel-plated carbon nanotubes were ultrasonically dispersed in a 1% sodium dodecyl sulfate aqueous solution at a power of 400 W for 25 min to obtain a nickel-plated carbon nanotube dispersion;

[0140] S12. 55 parts of polypropylene fibers were plasma treated under an argon atmosphere for 3 min at a power of 80 W, and then the nickel-plated carbon nanotube dispersion was added to obtain a polypropylene fiber nanodispersion;

[0141] S13. 8 parts of aramid fibers were soaked in 65% concentrated nitric acid for 1 h at a temperature of 60°C, washed with deionized water until neutral, and then soaked in 2% chitosan solution and 0.3% dopamine hydrochloride solution for 10 min and 10 h respectively to obtain modified aramid fibers;

[0142] S14. The polypropylene fiber nanodispersion was mixed with the modified aramid fibers, and 1% silane coupling agent ethanol solution was added, and high-speed shearing dispersion was carried out at 2000 r / min for 25 min to obtain polypropylene-aramid hybrid fibers.

[0143] Performance test:

[0144] Comparative Example 1 did not add polypropylene-aramid hybrid fibers compared to Example 1, and Comparative Example 2 did not add modified grouting agent compared to Example 1. The silica ash in Examples 1-4 and Comparative Examples 1-2 is granulated blast furnace silica ash with a maximum particle size ≤ 50 mm, a specific surface area ≥ 300 m² / kg (S95 grade: specific surface area not less than 350 m² / kg; S105 grade: specific surface area not less than 400 m² / kg; S115 grade: specific surface area not less than 500 m² / kg), and the particle size of the powdery particulate cementitious material is described by the average particle size DAV and the median particle size D50 (the particle size corresponding to the cumulative volume fraction of 50%), wherein the median particle size D50 is 11.86-68.05 μm; the particle size of rice husk ash is less than or equal to 50 μm. The curing was carried out under the conditions that the temperature was 18-22°C, the relative humidity was more than 95%, the test pieces were placed on the support with a distance of 10-20 mm from each other, and the surface of the test pieces was kept moist. After the test pieces were formed, they should be placed in a room with a temperature of 15-25°C and a relative humidity of more than 50% for 2 d, and during the standing period, they should be protected from vibration and impact. After standing, the test pieces were numbered, demolded, and when the test pieces had serious defects, they should be treated as waste.

[0145] 1. Mechanical property test

[0146] According to the standard GB / T 50081-2002 Standard for testing the mechanical properties of ordinary concrete and JC / T 2461 Standard for testing the mechanical properties of high ductility fiber reinforced cementitious composites, the specimens of the fiber reinforced concrete based on construction waste recycled aggregate prepared in the above Examples 1-4 and Comparative Examples 1-2 were cured for 28 days, and the performance of the specimens was tested, and the results are shown in Table 1. Figure 1

[0147] Table 1

[0148]

[0149] As can be seen from the data in the table, the mechanical properties of the fiber reinforced concrete based on construction waste recycled aggregate prepared in Comparative Examples 1-2 are poorer than those of Examples 1-4. The addition of polypropylene-aramid hybrid fibers and modified troweling agent can significantly improve the mechanical strength and toughness of the fiber reinforced concrete based on construction waste recycled aggregate, and enhance its tensile strength, compressive strength and equivalent bending strength.

[0150] 2. Durability test

[0151] According to the standard GB / T 50082-2009 Standard for testing the long-term performance and durability of ordinary concrete, the specimens were alternately cycled in dry and humid environments to simulate the dry and wet changes of concrete in actual use. Each cycle includes drying the specimen at 60°C for 24 hours, then soaking in water at 20°C for 24 hours, and the cycle number is 50 times. After 50 dry and wet cycles, the mass loss rates of the specimens of Examples 1-4 are 1.0%, 0.8%, 0.9% and 1.0%, respectively, while the mass loss rates of Comparative Examples 1-2 are 1.7% and 1.9%, respectively. This shows that the concrete mixed with polypropylene-aramid hybrid fibers and modified troweling agent has better durability.

[0152] 3. Permeability test

[0153] According to the standard GB / T 50082-2009 Standard for testing the long-term performance and durability of ordinary concrete, the water pressure method was used to test the permeability of the concrete. The specimens obtained from Examples 1-4 and Comparative Examples 1-2 were placed in a water pressure testing machine, and the water pressure was increased from 0.1 MPa every 8 hours until the specimen showed water seepage, and the maximum water pressure value was recorded. The maximum water pressure values of Examples 1-4 are 2.0 MPa, 2.2 MPa, 2.1 MPa and 1.9 MPa, respectively, while the maximum water pressure values of Comparative Examples 1-2 are 1.2 MPa and 1.0 MPa, respectively. This shows that the concrete mixed with polypropylene-aramid hybrid fibers and modified troweling agent has better permeability. ​

[0154] 4. Anti-freezing test

[0155] According to the standard of GB / T 50082-2009, the test pieces obtained from Examples 1-4 and Comparative Examples 1-2 were placed in a freeze-thaw test machine for freeze-thaw cycles. Each cycle included freezing the test pieces at -18°C for 4 hours, and then thawing in 20°C water for 4 hours, with 100 cycles. The mass loss rate and relative dynamic elastic modulus of the test pieces were tested. The mass loss rates of Examples 1-4 were 1.4%, 1.1%, 1.2%, and 1.3%, respectively, while the mass loss rates of Comparative Examples 1-2 were 2.6% and 2.8%, respectively, indicating that the concrete mixed with polypropylene-aramid hybrid fiber and modified tamping agent had better anti-freezing properties.

[0156] 5. Acid resistance

[0157] According to the standard of GB / T 50082-2009, the test pieces obtained from Examples 1-4 and Comparative Examples 1-2 were respectively immersed in 5% hydrochloric acid, sulfuric acid, and nitric acid solutions for 150 days, and the mass loss rate and compressive strength change of the test pieces were tested. The mass loss rates of Examples 1-4 in hydrochloric acid, sulfuric acid, and nitric acid were 1.3%, 1.4%, and 1.6%, respectively, while the mass loss rates of Comparative Examples 1-2 were 3.3% and 3.4%, respectively. This indicated that the concrete mixed with polypropylene-aramid hybrid fiber and modified tamping agent had better acid resistance.

[0158] 6. Early compressive strength performance test

[0159] According to the standard of GB / T 50081-2002, the compressive strength of the test pieces of fiber reinforced concrete based on construction solid waste recycled aggregate prepared from Examples 1-4 and Comparative Examples 1-2 above were tested after curing for 3d, 7d, and 28d, and the results are shown in Table 2 below:

[0160] Table 2

[0161]

[0162] From the data, it can be seen that the concrete mixed with polypropylene-aramid hybrid fiber and modified tamping agent is significantly superior to the concrete without mixing in terms of early strength development, especially in the early strength performance at 3 days and 7 days.

[0163] The recycled coarse aggregate has strong water absorption, in the process of concrete hardening, it can absorb the excess water in the cement paste, reduce the porosity in the concrete, thereby improving the impermeability and frost resistance of the concrete, and due to the good bonding of the recycled coarse aggregate and the cement paste, the invasion of harmful substances can be effectively prevented, and the durability of the concrete is enhanced.

[0164] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely divergences of the principles and spirit of the application and that numerous modifications, changes, substitutions, and alterations can be made thereto without departing from the spirit and scope of the application as defined by the appended claims and their equivalents.

Claims

1. A fiber-reinforced concrete based on recycled aggregates from construction solid waste, characterized in that, The composition by weight is as follows: 150-200 parts recycled coarse aggregate, 150-200 parts silica fume, 270-300 parts rice husk ash, 160-210 parts water, 200-250 parts metakaolin, 10-15 parts polypropylene-aramid blended fiber, 10-15 parts polycarboxylate superplasticizer, 10-20 parts modified grouting agent, and 10-20 parts tetrasodium iminodisuccinate. The preparation of the modified grouting agent includes the following steps: S21. Add 1-3 parts of 60% sodium carboxymethyl cellulose solution to 5-8 parts of modified nano-silica sol at a dropping rate of 1-2 mL / min, while stirring at 300-400 r / min at 40-50℃ to obtain a primary mixture. S22. Add 10-15 parts of waterborne epoxy resin emulsion to the primary mixture, and stir at a speed of 600-700 r / min for 1-1.5 h under constant temperature of 50℃ to obtain the secondary mixture. S23. Add 0.1-0.5 parts of defoamer to the secondary mixture and stir at 400-500 r / min for 15-20 min to finally obtain the modified grouting agent; The preparation of the polypropylene-aramid blended fiber includes the following steps: S11. Disperse 3-6 parts of nickel-plated carbon nanotubes in a 1% sodium dodecyl sulfate aqueous solution by ultrasonication to obtain a nickel-plated carbon nanotube dispersion. S12. Plasma treatment of 55-65 parts of polypropylene fiber under argon atmosphere for 3-5 min, then add nickel-plated carbon nanotube dispersion to obtain polypropylene fiber nano dispersion. S13. Immerse 8-12 parts of aramid fiber in concentrated nitric acid with a mass concentration of 65% for 1-2 hours at a temperature of 60-65℃, rinse with deionized water until neutral, and then immerse in chitosan solution with a mass concentration of 2% for 10-15 minutes and dopamine hydrochloride solution with a mass concentration of 0.3% for 10-12 hours to obtain modified aramid fiber. S14. Mix the polypropylene fiber nano-dispersion with the modified aramid fiber, and add a 1% (w / w) silane coupling agent ethanol solution. Disperse the mixture under high-speed shear at 2000-4000 r / min for 25-30 min to obtain polypropylene-aramid mixed fiber. The preparation of the modified nano-silica sol includes the following steps: S211. Mix 1-3 parts of polycarboxylate superplasticizer with 10-15 parts of deionized water, and stir at 200-400 r / min in a 40℃ water bath until completely dissolved to obtain an aqueous solution of polycarboxylate superplasticizer. S212. Add 0.5-2 parts of sodium gluconate to the aqueous solution of polycarboxylate superplasticizer, continue stirring for 5-8 min, and then add 50-60 parts of nano-silica sol at a dropping rate of 1-2 mL / min to obtain the preliminarily modified nano-silica sol. S213. The pH of the preliminarily modified nano-silica sol was adjusted to 8.5-9.5 using NaOH solution to finally obtain the modified nano-silica sol.

2. The fiber-reinforced concrete based on recycled aggregate from construction solid waste according to claim 1, characterized in that, In step S11, the ultrasonic dispersion power is 400-600W and the time is 25-30min.

3. The fiber-reinforced concrete based on recycled aggregate from construction solid waste according to claim 1, characterized in that, In step S12, the power of the plasma treatment is 80-120W.

4. The fiber-reinforced concrete based on recycled aggregate from construction solid waste according to claim 1, characterized in that, The defoamer in step S23 is an organosilicon defoamer.

5. A method for preparing fiber-reinforced concrete based on recycled aggregate from construction solid waste, used to prepare the fiber-reinforced concrete based on recycled aggregate from construction solid waste as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Mix and stir the recycled coarse aggregate, silica fume, rice husk ash, and metakaolin in a certain proportion to obtain cement mixture; S2. Calcine the cement mixture obtained in step S1 for 2-3 hours to obtain cement clinker; S3. Mix the cement clinker obtained in step S2, polypropylene-aramid mixed fiber, polycarboxylate superplasticizer, modified grouting agent, and tetrasodium iminodisuccinate in proportion, and then pour them into a mixer and stir for 5-8 minutes. S4. Add water to the mixer according to the ratio and continue mixing for 6-12 minutes. Then remove the mixer to obtain fiber-reinforced concrete based on recycled aggregates from construction solid waste.

6. The method for preparing fiber-reinforced concrete based on recycled aggregate from construction solid waste according to claim 5, characterized in that, The stirring speed in step S1 is 100-300 r / min, and the time is 7-10 min.

7. The method for preparing fiber-reinforced concrete based on recycled aggregate from construction solid waste according to claim 5, characterized in that, In step S2, the calcination temperature is 800-1000℃.

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