A production process and application of concrete

Abstract

The present invention belongs to the field of concrete processing technology, and specifically relates to a concrete production process and application. The production process comprises the following steps: S1, mixing rice straw fiber with a low eutectic solvent, ultrasonicating, obtaining pretreated rice straw fiber, and then soaking the pretreated rice straw fiber in a dopamine hydrochloride solution to obtain modified rice straw fiber; S2, dry-mixing coarse aggregate, fine aggregate, Portland cement, the modified rice straw fiber, and admixtures to obtain a dry mix; S3, adding a polyurethane emulsion, a water reducer, and micro-nano bubble water to the dry mix and stirring to obtain a concrete product. This production process can significantly improve the comprehensive performance of concrete, and the process is simple, economical, and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete processing, and in particular relates to a production process and application of concrete. Background Art

[0002] As an important protective material, concrete has been widely used in construction, road, and bridge engineering due to its abundant raw materials, low cost, excellent durability, and good mechanical properties. However, the mechanical and durability properties of concrete have long been a topic of considerable interest to researchers. The implementation of the Sustainable Development Goals initiative has boosted the use of recycled concrete. Recycled concrete generally offers two major advantages: First, it increases the utilization rate of construction waste, promotes waste reuse, significantly reduces the mining of natural aggregate, and reduces the environmental pollution and damage caused by construction waste. Second, the relatively low production cost of recycled concrete facilitates cost reduction and efficiency gains for concrete manufacturers. However, research by numerous researchers both domestically and internationally has shown that the apparent density and bulk density of recycled coarse aggregate are lower than those of natural aggregate. This is because, compared to natural coarse aggregate, recycled coarse aggregate is often coated or partially coated with hardened cement mortar. Cement mortar has high porosity and low density, resulting in lower apparent and bulk densities of recycled coarse aggregate than those of natural aggregate. Compared to natural aggregate, recycled aggregate has a higher water absorption rate, a higher crushing value, and a large amount of surface mortar residue, which to some extent affects the performance of recycled concrete. Furthermore, the multi-interface structure, high porosity, and high water absorption of recycled concrete reduce its mechanical properties and durability, severely restricting its application in new structures.

[0003] Currently, a series of experimental studies have been conducted on the mechanical properties of recycled concrete. For example, a related technical report analyzed the influence of the interface transition zone morphology on the mechanical properties of recycled concrete and found that when the recycled aggregate replacement rate was 100%, the cubic compressive strength was about 30% lower than that of natural aggregate concrete, and the splitting tensile strength was about 25% to 35% lower.

[0004] Therefore, how to improve the mechanical properties and durability of recycled concrete has become a hot topic and focus of research on recycled concrete today. Summary of the Invention

[0005] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a concrete production process and application. This production process can significantly improve the overall performance of concrete and is simple in process.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A first aspect of the present invention provides a concrete production process comprising the following steps:

[0009] S1. Mixing rice straw fibers with a deep eutectic solvent and subjecting the mixture to ultrasonic treatment to obtain pretreated rice straw fibers, and then soaking the pretreated rice straw fibers in a dopamine hydrochloride solution to obtain modified rice straw fibers;

[0010] S2, dry-mixing the coarse aggregate, fine aggregate, Portland cement, the modified rice straw fiber, and an admixture to obtain a dry mix;

[0011] S3, adding polyurethane emulsion, water reducing agent and micro-nano bubble water to the dry mix, stirring, and obtaining;

[0012] The raw materials for preparing the concrete include the following components in parts by mass:

[0013] 1000-1600 parts of coarse aggregate, 400-1000 parts of fine aggregate, 400-600 parts of Portland cement, 20-50 parts of modified rice straw fiber, 20-80 parts of admixture, 100-400 parts of polyurethane emulsion, and 1-5 parts of water reducer.

[0014] First of all, plant fibers are not suitable for being directly added to cement-based materials. This is because the lignin present in the plant fibers will precipitate and hydrolyze in aqueous or alkaline solutions, and the hydrolyzate will hinder cement hydration, and the compatibility of untreated plant fibers with cement-based materials is poor. The present invention uses a low-melting-point solvent treatment to help reduce the lignin in the fiber, while retaining the cellulose component and fiber structure in the biomass, maintaining its excellent tensile and compressive properties. The fiber is further treated with dopamine, and the fiber surface is coated with a dopamine layer, which plays a role in protecting the fiber and increasing its compatibility with the matrix. The modified rice straw fiber has good dispersibility and compatibility in dry mixes. Polyurethane emulsion can fill the microcracks in the structure, and may also form a network structure together with the modified rice straw fiber, which is conducive to enhancing the mechanical properties of concrete.

[0015] Secondly, coarse aggregate typically accounts for a large proportion of concrete and is much larger than fine aggregate. Therefore, the addition of fine aggregate to fill the concrete helps enhance the mechanical strength of the concrete. The admixture fills the pores on the surface of the modified fiber, thereby reducing the fiber porosity and improving the overall performance of the concrete.

[0016] Micro-nano bubble water can promote cement hydration and the production of hydration products, improve the mechanical properties and durability of concrete, and reduce mortar shrinkage. The reason is that it has fewer water molecule clusters than ordinary water and is easier to disperse in cementitious materials. While promoting cement hydration, it increases the density of the slurry, thereby improving the strength of the specimen. In addition, the independent, closed micro-nano bubbles remaining in the concrete can block the capillary penetration path, which manifests itself as improved durability on a macro scale.

[0017] Finally, the present invention prepares concrete by a dry method, and the obtained concrete has better comprehensive properties, which is related to the fact that the dry method of preparing concrete promotes the dispersion of fibers.

[0018] In some embodiments of the present invention, in step S1, the deep eutectic solvent is prepared by heating choline chloride and urea.

[0019] In some preferred embodiments of the present invention, the molar ratio of choline chloride to urea is 1:0.5-2.

[0020] In some preferred embodiments of the present invention, the heating temperature is 70-90°C.

[0021] In some embodiments of the present invention, in step S1, the solid-liquid ratio of the rice straw fiber to the deep eutectic solvent is 1 g:6-12 mL, for example, 1 g:6-10 mL, 1 g:6-8 mL.

[0022] In some embodiments of the present invention, in step S1, the temperature of the ultrasound is 50-70°C, for example, 50-65°C, 55-65°C, 60-70°C, 60-65°C.

[0023] In some embodiments of the present invention, in step S1, the frequency of the ultrasound is 300-600W, for example, 300-500W, 400-600W, 400-500W, 500-600W.

[0024] The ultrasonic time is 2-5h, for example, 2-4h, 3-5h, 3-4h.

[0025] In some embodiments of the present invention, in step S1, after the ultrasonication is completed, water is added to the system and stirred for 20-60 minutes; wherein the volume of the added water is 1 / 4 to 1 / 2, for example, 1 / 3 of the volume of the deep eutectic solvent;

[0026] Preferably, after stirring, the system is filtered, and the filter residue is collected, washed with water, and freeze-dried to obtain the pretreated rice straw fiber.

[0027] In some embodiments of the present invention, in step S1, the pretreated rice straw fiber is placed in a dopamine hydrochloride solution and dispersed, and then a Tris-HCl buffer solution is added to adjust the pH value of the system to 8-8.5, and the soaking and stirring are continued, and the mixture is filtered and dried to obtain modified rice straw fiber.

[0028] In some embodiments of the present invention, the concentration of the dopamine hydrochloride solution is 1-4 g / L, for example, 1-3 g / L, 2 g / L.

[0029] In some embodiments of the present invention, the mass volume ratio of the pretreated rice straw fiber to the dopamine hydrochloride solution is 1-5 g:1 mL, for example, 1-4 g:1 mL, 1-3 g:1 mL, 1-2 g:1 mL, 2-3 g:1 mL, 2 g:1 mL.

[0030] In some embodiments of the present invention, the concentration of the Tris-HCl buffer solution is 0.5 to 2 mol / L, preferably 1 mol / L.

[0031] In some embodiments of the present invention, the soaking and stirring time is 12 to 48 hours.

[0032] In some embodiments of the present invention, the drying temperature is 50-70°C.

[0033] In some embodiments of the present invention, the raw materials for preparing the concrete further include 300-500 parts of micro-nano bubble water.

[0034] In some embodiments of the present invention, the raw materials for preparing the concrete include the following components in parts by mass:

[0035] 1000-1400 parts of coarse aggregate, 600-1000 parts of fine aggregate, 400-600 parts of Portland cement, 25-35 parts of modified rice straw fiber, 50-60 parts of admixture, 200-300 parts of polyurethane emulsion, 2-3 parts of water reducer, and 300-500 parts of micro-nano bubble water.

[0036] In some embodiments of the present invention, in step S2, the particle size of the coarse aggregate is in the range of 5-30 mm.

[0037] In some embodiments of the present invention, in step S2, the particle size of the fine aggregate is in the range of 0.1-3 mm.

[0038] In some embodiments of the present invention, in step S2, the fine aggregate is recycled aggregate of concrete.

[0039] In some embodiments of the present invention, in step S2, the admixture includes semi-densified silica fume and fly ash, and the mass ratio of the semi-densified silica fume to the fly ash is 1-3:1.

[0040] In some embodiments of the present invention, the water reducer is a polycarboxylate high-efficiency water reducer.

[0041] In some embodiments of the present invention, in step S2, the dry mixing time is 60-120s.

[0042] In some embodiments of the present invention, in step S3, the stirring time is 60-120 s.

[0043] The second aspect of the present invention provides a concrete prepared by the above production process.

[0044] The concrete production process according to some embodiments of the present invention has at least the following beneficial effects:

[0045] The process of the present invention utilizes construction waste as recycled aggregate for concrete, thereby expanding the scope of reuse of construction waste and realizing resource utilization of construction waste, with economic, social and environmental benefits. The prepared concrete has excellent mechanical properties, high compressive strength, flexural strength and splitting tensile strength, and low water absorption and limited shrinkage. DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0047] Example

[0048] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0049] Specifically, in the specific implementation of the present invention:

[0050] Cement was purchased from Xinhua Conch Cement Co., Ltd. P·O42.5 cement, density 3.15g / cm 3 , specific surface area 348m 2 / kg, P·O42.5 cement;

[0051] Semi-densified silica fume was purchased from Sichuan Langtian Resources Comprehensive Utilization Co., Ltd., with a SiO2 content of 95%, a loss on ignition of 42%, and a bulk density of 415 kg / m 3 , water requirement ratio 110%, 3d activity index 95%, 7d activity index 112%, 28d activity index 125%;

[0052] Fly ash (FA) was purchased from Yiyang Power Plant, grade II, with a fineness of 20%, loss on ignition of 6.5%, moisture content of 0.23%, water requirement ratio of 90%, f-CaO content of 0.45%, 7d activity index of 60%, and 28d activity index of 74%;

[0053] The polyurethane emulsion is a conventional water-based polyurethane product with a particle size of 0.5 to 1 μm and a solid content of 25%;

[0054] The water reducer (AR) was a polycarboxylate high-efficiency water reducer purchased from Runyue Chemical;

[0055] The water is micro-nano bubble water, and NBW is prepared by a bulk NBW generator and put into use after standing.

[0056] Example 1

[0057] This embodiment provides a production process for concrete. Specifically, the raw materials for preparing the concrete include the components shown in Table 1 below. The preparation process for the concrete includes the following steps:

[0058] (1) Preparation of modified rice straw fiber

[0059] Accurately weigh a certain amount of choline chloride and urea in a molar ratio of 2:1 into a flask, then heat and stir at 80°C until a transparent homogeneous liquid forms to obtain a deep eutectic solvent. Thoroughly mix the pre-crushed rice straw fiber with 8 times the amount of the obtained deep eutectic solvent (i.e., the ratio of rice straw fiber mass to deep eutectic solvent volume is 1g:8mL). Ultrasonicate (ultrasonic frequency: 500W) at 60°C for 3 hours, let it cool, and simultaneously add 1 / 3 of the deep eutectic solvent in water. Continue stirring for 30 minutes. Filter, remove the filter residue, wash it with water two to three times, and freeze-dry it to obtain the rice straw fiber pretreated with the low-melting-point solvent, which is stored for later use.

[0060] Dopamine hydrochloride was dissolved in deionized water in a beaker to prepare a dopamine solution with a concentration of 2 g / L. Tris(hydroxymethyl)aminomethane hydrochloride was dissolved in deionized water to prepare a 1 mol / L solution (tris buffer solution). At room temperature, the rice straw fiber pretreated with a low melting point solvent was mixed with the dopamine solution in a mass volume ratio of 2 g:1 mL. Tris buffer was then added to adjust the pH of the solution to 8.5. After stirring at room temperature for 24 hours, the solution was taken out, rinsed with deionized water until neutral, and dried in an oven at 60°C to obtain dopamine-modified rice straw fiber.

[0061] (2) Dry mixing concrete preparation

[0062] According to the amount of each component in Table 1, coarse aggregate (crushed stone) with a particle size range of 5-30 mm, fine aggregate with a particle size range of 0.1-3 mm (obtained by screening after crushing waste concrete), P·O42.5 grade ordinary Portland cement, modified rice straw fiber and admixture (specifically a mixture of fly ash and semi-densified silica fume) were placed in a concrete mixer and dry mixed for 90 seconds.

[0063] Mix the polyurethane emulsion, water reducer and micro-nano bubble water evenly, pour the resulting mixture into a cement mixer, and continue stirring until it is evenly mixed. The stirring time is 90 seconds;

[0064] The mixture was poured into a steel mold in two batches, and demolded after curing for 24 hours under natural conditions (27°C). After demolding, it was cured at room temperature (25±1°C, humidity 90%), with curing ages of 7 days and 28 days respectively.

[0065] Example 2

[0066] This embodiment provides a production process for concrete. Specifically, the raw materials for preparing the concrete include the components shown in Table 1 below. The preparation process for the concrete includes the following steps:

[0067] (1) Preparation of modified rice straw fiber

[0068] Accurately weigh a certain amount of choline chloride and urea in a molar ratio of 1:2 into a flask, then heat and stir at 80°C until a transparent homogeneous liquid forms to obtain a deep eutectic solvent. Thoroughly mix the pre-crushed rice straw fiber with 6 times the amount of the obtained deep eutectic solvent (i.e., the ratio of rice straw fiber mass to deep eutectic solvent volume is 1g:6mL). Ultrasonicate (ultrasonic frequency: 500W) at 60°C for 4 hours, let it cool, and simultaneously add 1 / 3 of the deep eutectic solvent in water. Continue stirring for 40 minutes. Filter, remove the filter residue, wash it with water two to three times, and freeze-dry it to obtain the rice straw fiber pretreated with the low-melting-point solvent, which is stored for later use.

[0069] Dopamine hydrochloride was dissolved in deionized water in a beaker to prepare a dopamine solution with a concentration of 2 g / L. Tris(hydroxymethyl)aminomethane hydrochloride was dissolved in deionized water to prepare a 1 mol / L solution (tris buffer solution). At room temperature, the rice straw fiber pretreated with a low melting point solvent was mixed with the dopamine solution in a mass volume ratio of 2 g:1 mL. Tris buffer was then added to adjust the pH of the solution to 8.5. After stirring at room temperature for 24 hours, the solution was taken out, rinsed with deionized water until neutral, and dried in an oven at 60°C to obtain dopamine-modified rice straw fiber.

[0070] (2) Dry mixing concrete preparation

[0071] According to the amount of each component in Table 1, coarse aggregate (crushed stone) with a particle size range of 5-30 mm, fine aggregate with a particle size range of 0.1-3 mm (obtained by screening after crushing waste concrete), P·O42.5 grade ordinary Portland cement, modified rice straw fiber and admixture (specifically a mixture of fly ash and semi-densified silica fume) were placed in a concrete mixer and dry mixed for 90 seconds.

[0072] Mix the polyurethane emulsion and micro-nano bubble water evenly, pour the resulting mixture into a cement mixer, and continue stirring until it is evenly mixed. The stirring time is 90 seconds;

[0073] The mixture was poured into a steel mold in two batches, and demolded after curing for 24 hours under natural conditions (27°C). After demolding, it was cured at room temperature (25±1°C, humidity 90%), with curing ages of 7 days and 28 days respectively.

[0074] Example 3

[0075] This embodiment provides a production process for concrete. Specifically, the raw materials for preparing the concrete include the components shown in Table 1 below. The preparation process for the concrete includes the following steps:

[0076] (1) Preparation of modified rice straw fiber

[0077] Accurately weigh a certain amount of choline chloride and urea in a 1:1 molar ratio into a flask, then heat and stir at 80°C until a transparent homogeneous liquid forms to obtain a deep eutectic solvent. Thoroughly mix the pre-crushed rice straw fiber with 8 times the amount of the obtained deep eutectic solvent (i.e., the ratio of rice straw fiber mass to deep eutectic solvent volume is 1g:8mL). Ultrasonicate (ultrasonic frequency: 500W) at 60°C for 4 hours, let it cool, and simultaneously add 1 / 3 of the deep eutectic solvent in water. Continue stirring for 30 minutes. Filter, remove the filter residue, wash it with water two to three times, and freeze-dry it to obtain the rice straw fiber pretreated with the low-melting-point solvent, which is stored for later use.

[0078] Dopamine hydrochloride was dissolved in deionized water in a beaker to prepare a dopamine solution with a concentration of 2 g / L. Tris(hydroxymethyl)aminomethane hydrochloride was dissolved in deionized water to prepare a 1 mol / L solution (tris buffer solution). At room temperature, the rice straw fiber pretreated with a low melting point solvent was mixed with the dopamine solution in a mass volume ratio of 2 g:1 mL. Tris buffer was then added to adjust the pH of the solution to 8.5. After stirring at room temperature for 24 hours, the solution was taken out, rinsed with deionized water until neutral, and dried in an oven at 60°C to obtain dopamine-modified rice straw fiber.

[0079] (2) Dry mixing concrete preparation

[0080] According to the amount of each component in Table 1, coarse aggregate (crushed stone) with a particle size range of 5-30 mm, fine aggregate with a particle size range of 0.1-3 mm (obtained by screening after crushing waste concrete), P·O42.5 grade ordinary Portland cement, modified rice straw fiber and admixture (specifically a mixture of fly ash and semi-densified silica fume) were placed in a concrete mixer and dry mixed for 90 seconds.

[0081] Mix the polyurethane emulsion, water reducer and micro-nano bubble water evenly, pour the resulting mixture into a cement mixer, and continue stirring until it is evenly mixed. The stirring time is 90 seconds;

[0082] The mixture was poured into a steel mold in two batches, and demolded after curing for 24 hours under natural conditions (27°C). After demolding, it was cured at room temperature (25±1°C, humidity 90%), with curing ages of 7 days and 28 days respectively.

[0083] Example 4

[0084] This embodiment provides a production process for concrete. Specifically, the raw materials for preparing the concrete include the components shown in Table 1 below. The preparation process for the concrete includes the following steps:

[0085] (1) Preparation of modified rice straw fiber

[0086] Accurately weigh a certain amount of choline chloride and urea in a molar ratio of 2:1 into a flask, then heat and stir at 80°C until a transparent homogeneous liquid forms to obtain a deep eutectic solvent. Thoroughly mix the pre-crushed rice straw fiber with 12 times the amount of the obtained deep eutectic solvent (i.e., the ratio of rice straw fiber mass to deep eutectic solvent volume is 1g:12mL). Ultrasonicate at 65°C (ultrasonic frequency of 500W) for 2 hours, let it cool, and simultaneously add 1 / 3 of the deep eutectic solvent in water. Continue stirring for 30 minutes. Filter, collect the filter residue, wash it with water two to three times, and freeze-dry it to obtain the rice straw fiber pretreated with the low-melting-point solvent, which is stored for later use.

[0087] Dopamine hydrochloride was dissolved in deionized water in a beaker to prepare a dopamine solution with a concentration of 2 g / L. Tris(hydroxymethyl)aminomethane hydrochloride was dissolved in deionized water to prepare a 1 mol / L solution (tris buffer solution). At room temperature, the rice straw fiber pretreated with a low melting point solvent was mixed with the dopamine solution in a mass volume ratio of 2 g:1 mL. Tris buffer was then added to adjust the pH of the solution to 8.5. After stirring at room temperature for 24 hours, the solution was taken out, rinsed with deionized water until neutral, and dried in an oven at 60°C to obtain dopamine-modified rice straw fiber.

[0088] (2) Dry mixing concrete preparation

[0089] According to the amount of each component in Table 1, coarse aggregate (crushed stone) with a particle size range of 5-30 mm, fine aggregate with a particle size range of 0.1-3 mm (obtained by screening after crushing waste concrete), P·O42.5 grade ordinary Portland cement, modified rice straw fiber and admixture (specifically a mixture of fly ash and semi-densified silica fume) were placed in a concrete mixer and dry mixed for 90 seconds.

[0090] Mix the polyurethane emulsion, water reducer and micro-nano bubble water evenly, pour the resulting mixture into a cement mixer, and continue stirring until it is evenly mixed. The stirring time is 90 seconds;

[0091] The mixture was poured into a steel mold in two batches, and demolded after curing for 24 hours under natural conditions (27°C). After demolding, it was cured at room temperature (25±1°C, humidity 90%), with curing ages of 7 days and 28 days respectively.

[0092] Comparative Example 1

[0093] This comparative example provides a concrete production process. Specifically, the process is carried out in accordance with Example 1, except that "(2) preparing concrete by dry mixing" is replaced by "(2) preparing concrete by wet mixing". The specific steps include:

[0094] According to the amount of each component in Table 1, coarse aggregate (crushed stone) with a particle size range of 5-30 mm, fine aggregate with a particle size range of 0.1-3 mm (obtained by screening after crushing waste concrete), and half of the micro-nano bubble water were poured into the concrete mixer in sequence, and the mixer was turned on and stirred for 1 minute. Then, P·O42.5 grade ordinary Portland cement, modified rice straw fiber, and admixture (specifically a mixture of fly ash and semi-densified silica fume) were placed in the concrete mixer and stirred for 1 minute;

[0095] Mix the polyurethane emulsion, water reducer and the remaining half of the micro-nano bubble water evenly, pour the resulting mixture into a cement mixer, and continue stirring to mix evenly for 1 minute;

[0096] The mixture was poured into a steel mold in two batches, and demolded after curing for 24 hours under natural conditions (27°C). After demolding, it was cured at room temperature (25±1°C, humidity 90%), with curing ages of 7 days and 28 days respectively.

[0097] Comparative Example 2

[0098] This comparative example provides a concrete production process, which is specifically carried out with reference to Example 1, except that "(1) Preparation of modified rice straw fiber" is the following steps:

[0099] Accurately weigh a certain amount of choline chloride and urea in a molar ratio of 2:1 into a flask, then heat and stir at 80°C until a transparent homogeneous liquid forms to obtain a deep eutectic solvent. Thoroughly mix the pre-crushed rice straw fiber with 8 times the amount of the obtained deep eutectic solvent (i.e., the ratio of rice straw fiber mass to deep eutectic solvent volume is 1g:8mL). Ultrasonicate (ultrasonic frequency: 500W) at 60°C for 3 hours, let it cool, and simultaneously add 1 / 3 of the deep eutectic solvent in water. Continue stirring for 30 minutes. Filter, remove the filter residue, wash it with water two to three times, and freeze-dry it to obtain the rice straw fiber pretreated with the low-melting-point solvent, which is stored for later use.

[0100] Omit the dopamine modification step.

[0101] In addition, in step (2), the modified rice straw fiber is replaced by the pretreated rice straw fiber in this comparative example.

[0102] Comparative Example 3

[0103] This comparative example provides a concrete production process, which is specifically carried out with reference to Example 1, except that "(1) Preparation of modified rice straw fiber" is the following steps:

[0104] Omit the pretreatment step for low melting point solvents.

[0105] Dopamine hydrochloride was dissolved in deionized water in a beaker to prepare a solution with a concentration of 2 g / L. Tris(hydroxymethyl)aminomethane hydrochloride was dissolved in deionized water to prepare a 1 mol / L solution (tris buffer solution). At room temperature, the preliminarily crushed rice straw fiber was mixed with the dopamine solution in a mass volume ratio of 2 g:1 mL. Tris buffer was then added to adjust the pH of the solution to 8.5. After stirring at room temperature for 24 hours, the solution was taken out, rinsed with deionized water until neutral, and dried in an oven at 60°C to obtain dopamine-modified rice straw fiber.

[0106] In addition, the modified rice straw fiber of this comparative example is used in step (2).

[0107] Comparative Example 4

[0108] This comparative example provides a production process of concrete, which is specifically carried out with reference to Example 1, except that the components are changed. Specifically, the polyurethane emulsion is omitted in step (2).

[0109] Comparative Example 5

[0110] This comparative example provides a production process of concrete, which is specifically carried out with reference to Example 1, except that the components are changed. Specifically, the amount of modified rice straw fiber added in step (2) is 100 g.

[0111] Comparative Example 6

[0112] This comparative example provides a concrete production process, which is specifically carried out with reference to Example 1, except that the components are changed. Specifically, only the micro-nano bubble water in step (2) is replaced with ordinary deionized water.

[0113] Table 1

[0114]

[0115] Performance test case

[0116] Test pieces with a size of 100 mm × 100 mm × 100 mm were prepared using the production processes of Examples 1-4 and Comparative Examples 1-6. After curing for 7 and 28 days, the surfaces were cleaned and dried, and performance tests were performed. The test standards are as follows:

[0117] (1) Compressive strength

[0118] The compressive strength of the specimens was tested with reference to GB / T 50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete".

[0119] (2) Durability

[0120] The durability performance of concrete specimens was tested with reference to GB / T 50082-2009 "Standard for test methods of long-term performance and durability of ordinary concrete".

[0121] (3) Water absorption test

[0122] The water absorption of the specimens was tested with reference to GB / T 50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete".

[0123] (4) Flexural strength

[0124] The flexural strength of the specimens was tested with reference to GB / T 50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete".

[0125] (5) Splitting tensile strength performance test

[0126] Referring to GB / T50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete", the splitting tensile strength performance of the specimens was tested.

[0127] (6) Limiting shrinkage test

[0128] The restricted shrinkage test of concrete specimens was carried out with reference to GB / T 50082-2009 "Standard for test methods of long-term performance and durability of ordinary concrete".

[0129] The test results are shown in Table 2 below.

[0130] Table 2

[0131]

[0132]

[0133] As can be seen from the above table, the concrete prepared by the method of the present invention has excellent mechanical properties, high compressive strength, flexural strength and splitting tensile strength, low water absorption and limited shrinkage. In addition, the use of construction waste as recycled aggregate for concrete expands the scope of reuse of construction waste, realizes the resource utilization of construction waste, and has economic, social and environmental benefits.

[0134] Comparison of Example 1 and Comparative Example 1 shows that dry-process concrete produces better overall performance, which is related to the dispersion of the modified fibers within the concrete. This may be due to the fact that, when dry-process concrete is prepared, cement particles can propel the agglomerated modified fibers apart, thereby promoting their dispersion. However, when wet-process concrete is prepared, cement particles and water easily form a viscous cement slurry. This viscous cement slurry adheres to the surface of the modified fibers, promoting their aggregation and hindering their effective dispersion.

[0135] A comparison of Example 1 and Comparative Example 2 shows that the lack of dopamine modification leads to a decrease in the overall performance of the concrete. This may be due to the following reasons: firstly, dopamine coating the fiber surface further enhances the dispersion of the modified fiber, and the protective effect of the dopamine layer also helps the modified fiber maintain high mechanical properties in various environments; secondly, the hydrogen bonding interactions between the hydroxyl and amino groups of the dopamine molecules and the modified fiber help improve the surface activity of the modified fiber and its adhesion to the substrate.

[0136] A comparison of Example 1 and Comparative Example 3 shows that the lack of prior treatment of rice straw fiber with a low-melting-point solvent results in a decrease in the overall performance of the concrete. This may be due to the fact that low-melting-point solvents can damage plant fiber cell walls, and lignin is more susceptible to hydrolysis in solution than cellulose, causing fiber degradation. Treatment with a low-melting-point solvent effectively reduces lignin while preserving the properties of cellulose.

[0137] Furthermore, whether or not the low-melting-point solvent is used, as well as the type of hydrogen bond donors and acceptors in the low-melting-point solvent, have a certain impact on the length of the final treated fiber. Because the modified fiber acts as a bridge internally, when cracks appear in the concrete due to external forces, the fiber bridges the concrete pores, bonding the two ends of the matrix and improving the concrete's flexural strength. Therefore, when the fiber length is short, the bridging effect is not significant; while when the fiber length is long, the fibers agglomerate within the concrete, reducing the concrete's flexural strength.

[0138] From the comparison between Example 1 and Comparative Example 4, it can be seen that the addition of polyurethane emulsion can improve the comprehensive performance of concrete. The reason may be that the polyurethane emulsion can fill the microcracks generated during the crushing process of waste concrete, which helps to increase the crack resistance of concrete; in addition, the polyurethane emulsion can also reduce the water absorption of concrete materials.

[0139] A comparison of Example 1 and Comparative Example 5 shows that when the modified fiber content is too high, the greater the amount distributed per unit volume of concrete, the more severe the agglomeration. This causes the modified fiber to occupy a larger space within the concrete, affecting the bonding of aggregates and reducing the concrete's compressive strength. Furthermore, the agglomeration of the modified fiber can lead to cracking in the concrete.

[0140] From the comparison of Example 1 and Comparative Example 6, it can be seen that micro-nano bubble water can improve the compressive strength and flexural strength of concrete to a certain extent. This may be due to the increase in crystallization nuclei and hydration products, the denser internal structure of the concrete, and thus the improved mechanical properties of the concrete.

[0141] The above content describes the embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments. Various modifications can be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. In addition, the embodiments of the present invention and the features thereof can be combined with each other unless there is a conflict.

Claims

1. A concrete production process, characterized in that: The following steps are involved: S1. Mixing rice straw fiber with a deep eutectic solvent and sonicating to obtain pretreated rice straw fiber, then placing the pretreated rice straw fiber in a dopamine hydrochloride solution to disperse it, then adding a Tris-HCl buffer solution to adjust the pH value of the system to 8-8.5, continuing to soak and stir for 12-48 hours, filtering, and drying to obtain modified rice straw fiber; S2, dry-mixing the coarse aggregate, fine aggregate, Portland cement, the modified rice straw fiber, and an admixture to obtain a dry mix; S3, adding polyurethane emulsion, water reducing agent and micro-nano bubble water to the dry mix, stirring, and obtaining; The raw materials for preparing the concrete include the following components in parts by mass: 1000-1600 parts of coarse aggregate, 400-1000 parts of fine aggregate, 400-600 parts of Portland cement, 20-50 parts of modified rice straw fiber, 20-80 parts of admixture, 100-400 parts of polyurethane emulsion, 1-5 parts of water reducer; Wherein, in step S1, the deep eutectic solvent is prepared by heating choline chloride and urea; In step S2, the fine aggregate is recycled aggregate of concrete.

2. The production process according to claim 1, characterized in that The molar ratio of choline chloride to urea is 1:0.5~2.

3. The production process according to claim 1, characterized in that In step S1, the solid-liquid ratio of the rice straw fiber to the deep eutectic solvent is 1 g: 6-12 mL.

4. The production process according to claim 1, characterized in that In step S1, the ultrasonic temperature is 50-70°C, the ultrasonic frequency is 300-600W, and the ultrasonic time is 2-5h.

5. The production process according to claim 1, wherein: In step S1, after the ultrasonic treatment is completed, water is added to the system and stirred for 20-60 min; The volume of the added water is 1 / 4 to 1 / 2 of the volume of the deep eutectic solvent.

6. The production process according to claim 1, characterized in that: In step S1, the concentration of the dopamine hydrochloride solution is 1-4 g / L; The mass volume ratio of the pretreated rice straw fiber to the dopamine hydrochloride solution is 1-5 g:1 mL.

7. The production process according to claim 1, characterized in that: The raw materials for preparing the concrete include the following components in parts by mass: 1000-1400 parts of coarse aggregate, 600-1000 parts of fine aggregate, 400-600 parts of Portland cement, 20-40 parts of modified rice straw fiber, 30-70 parts of admixture, 200-400 parts of polyurethane emulsion, 2-4 parts of water reducer, and 300-500 parts of micro-nano bubble water.

8. The production process according to claim 1, characterized in that: In step S2, the particle size of the coarse aggregate is in the range of 5-30 mm, and the particle size of the fine aggregate is in the range of 0.1-3 mm.

9. The production process according to claim 1, characterized in that: In step S2, the admixture includes semi-densified silica fume and fly ash, wherein the mass ratio of the semi-densified silica fume to the fly ash is 1-3:

1.

10. A concrete, characterized in that: The method is prepared by the production process according to any one of claims 1 to 9.

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