Recycled concrete and preparation method thereof

Abstract

The invention relates to the field of building materials, in particular to recycled concrete and a preparation method thereof.The recycled concrete is prepared from, by weight, 3.52 parts of cement, 6.5 parts of sand, 0-12.08 parts of coarse aggregate, 0-12.08 parts of fine aggregate, 1.9-2.4 parts of water, 0.01-0.1 part of plant fiber and 0.011 part of water reducing agent, and the plant fiber is corn fiber or straw fiber. According to the scheme, a proper amount of plant fibers are mixed in the production of the recycled concrete, so that various properties of the recycled concrete are improved, the treatment mode of rural straw is expanded, and the resource utilization rate is increased.

Description

Technical Field

[0001] The invention relates to the field of building materials, and in particular to recycled concrete and a preparation method thereof. Background Art

[0002] Recycled concrete refers to a building material that uses discarded concrete materials as raw materials to produce new concrete after recycling, crushing, screening, washing, etc. The use of recycled concrete not only helps to reduce the accumulation of construction waste, but also reduces the consumption of natural resources. It is a green building material with good economic and environmental benefits.

[0003] For example, the prior art of CN106927756B discloses a recycled concrete, which is composed of cementitious material, coarse aggregate, fine aggregate, admixture, natural river sand and water. The weight proportions of the materials used in the recycled concrete are as follows: 300-470 parts of cementitious material, 900-1200 parts of coarse aggregate, 60-250 parts of fine aggregate, 125-375 parts of recycled modified PET plastic particles, 5-8 parts of admixture, 400-700 parts of natural river sand, water-cement ratio of 0.3-0.45, and air entraining agent of 0.01-0.03% of the mass of cementitious material.

[0004] Another typical prior art disclosed in CN113387668B is a recycled concrete, wherein the coarse aggregate is composed of gravel and recycled aggregate. The recycled aggregate is formed by curing concrete wet balls and accounts for 10wt%-100wt% of the total coarse aggregate.

[0005] Let's take a look at a recycled concrete disclosed in the prior art of CN106927756A, which is composed of cementitious materials, coarse aggregate, fine aggregate, admixture, natural river sand and water. The weight proportions of each material used in the recycled concrete are as follows: 300-470 parts of cementitious materials, 900-1200 parts of coarse aggregate, 60-250 parts of fine aggregate, 125-375 parts of recycled modified PET plastic particles, 5-8 parts of admixture, 400-700 parts of natural river sand, water-cement ratio of 0.3-0.45, and air entraining agent of 0.01-0.03% of the mass of cementitious materials added.

[0006] At present, the existing recycled concrete is relatively environmentally friendly and does not make full use of waste resources. In order to solve the common problems in this field, the present invention is made. Summary of the invention

[0007] The purpose of the present invention is to propose a recycled concrete and a preparation method thereof in view of the current deficiencies.

[0008] In order to overcome the shortcomings of the prior art, the present invention adopts the following technical solutions:

[0009] A recycled concrete and a preparation method thereof. The recycled concrete comprises, by weight, 3.52 parts of cement, 6.5 parts of sand, 0-12.08 parts of coarse aggregate, 0-12.08 parts of fine aggregate, 1.9-2.4 parts of water, 0.01-0.1 parts of plant fiber, and 0.011 parts of a water reducing agent, wherein the plant fiber is corn fiber or straw fiber.

[0010] Furthermore, the weight ratio of the coarse aggregate in the raw material is 6.04 parts, the weight ratio of the fine aggregate in the raw material is 6.04 parts, and the weight ratio of the plant fiber in the raw material is 0.01 parts.

[0011] Furthermore, the type of cement is P.O42.5 ordinary Portland cement, the fine aggregate is natural sand, and the apparent density of the natural sand is 2598 kg / m 3 , the soil content is 0.5%, the fineness modulus is 2.66, and the soil content is 2.2%; the coarse aggregate is a mixture of natural sand and gravel and recycled coarse aggregate, and the particle size of the coarse aggregate is 8 to 23 mm; the water reducer is a polycarboxylic acid water reducer, the solid content of the water reducer is 10%, and the water reduction rate is 30%.

[0012] Furthermore, the raw materials also include a sodium hydroxide solution with a concentration of 1% to 4% and a sodium metasilicate solution with a concentration of 1%, and the sodium hydroxide solution and the sodium metasilicate solution are used to modify the plant fibers.

[0013] Furthermore, the preparation method of the recycled concrete comprises the following steps:

[0014] S1, modifying the plant fiber by using a sodium hydroxide solution and a sodium metasilicate solution;

[0015] S2, pouring cement and sand into a container and stirring them evenly, and then pouring plant fiber into the container and stirring them evenly;

[0016] S3, adding water into the container and continuing to stir until uniform to obtain cement mortar, adding coarse aggregate and fine aggregate and allowing the cement mortar to fully wrap the coarse aggregate and fine aggregate, and then putting the mixture into a mold;

[0017] S4, vibrating the mold until cement slurry is precipitated on the surface of the mixture, and performing surface treatment;

[0018] S5, demoulding the mixture to obtain recycled concrete, placing the recycled concrete in a curing box, and curing it at 20 degrees Celsius;

[0019] S6, after curing for a specified number of days, the performance of the recycled concrete is tested;

[0020] S7, obtaining the performance index of the recycled concrete according to the test results, and judging whether the recycled concrete produced this time is qualified according to the performance index.

[0021] Furthermore, modifying the plant fiber comprises the following steps:

[0022] S11, soaking the plant fiber in a sodium hydroxide solution at 80 degrees Celsius for 1 to 2 hours;

[0023] S12, washing the plant fiber with water until the pH value detected on the surface of the plant fiber is 7;

[0024] S13, immersing the treated plant fiber in the sodium metasilicate solution, stirring evenly, and standing at 60 degrees Celsius for 30 to 60 minutes;

[0025] S14, filtering the reaction impurities and washing the plant fiber with water to obtain the modified plant fiber.

[0026] Furthermore, the performance testing of recycled concrete includes the following steps:

[0027] S61, taking a portion of the recycled concrete sample, applying uniform axial pressure to the surface directly above the sample using a pressure testing machine until the sample breaks, and obtaining the compressive strength of the sample;

[0028] S62, taking a portion of the recycled concrete sample and grinding it into a cylinder, placing the cylinder flat, applying downward pressure to the cylinder from the center until the sample breaks, and obtaining the splitting tensile strength of the sample;

[0029] S63, taking some recycled concrete samples, subjecting the samples to 10 freeze-thaw cycles in a freeze-thaw box at -25 degrees Celsius, and detecting the weight loss, volume change, surface area change, and surface cracking after each freeze-thaw cycle;

[0030] S64, taking part of the recycled concrete samples, subjecting them to 50 dry-wet cycles in an alternating dry and wet environment, and testing their weight loss, volume change, surface area change, and surface cracking after the cycles;

[0031] S65, take a part of the recycled concrete sample, then make one end of it exposed to the water surface and keep it dry, and the other end is underwater, apply a water pressure of 1.2MPa to the underwater end for 12 hours, and detect the water seepage condition of the end exposed to the water surface.

[0032] Furthermore, obtaining the performance index of recycled concrete and judging whether the produced recycled concrete is qualified includes the following steps:

[0033] S71, calculating the strength performance index according to the compressive strength and tensile strength of the sample;

[0034] S72, calculating the freeze-thaw resistance performance index according to the test data after freeze-thaw;

[0035] S73, calculating the durability performance index according to the test data after the dry-wet cycle;

[0036] S74, calculating a water resistance performance index according to the detected water immersion condition;

[0037] S75, calculating the comprehensive performance index of recycled concrete according to the strength performance index, freeze-thaw resistance performance index, durability performance index and water resistance performance index;

[0038] S76, judge whether the produced recycled concrete is qualified based on the comprehensive performance indicators.

[0039] The beneficial effects achieved by the present invention are: 1. By mixing an appropriate amount of plant fiber into the production of recycled concrete, it is beneficial to improve the various properties of the recycled concrete, and it is beneficial to expand the treatment methods of rural straw and improve resource utilization.

[0040] 2. Calculating comprehensive performance indicators is helpful to comprehensively evaluate the various properties of recycled concrete and make a comprehensive judgment on its overall capabilities, thereby judging whether the produced recycled concrete is qualified. Judging the performance of recycled concrete with different proportions through comprehensive performance indicators is helpful to find the best proportion of different raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention can be further understood from the following description in conjunction with the accompanying drawings. The components in the figures are not necessarily drawn to scale, but the emphasis is placed on illustrating the principles of the embodiments. In different views, the same reference numerals designate the same parts.

[0042] Figure 1 The present invention is a flow chart of the preparation of recycled concrete.

[0043] Figure 2 The present invention is a flow chart of modifying plant fibers.

[0044] Figure 3 The present invention is a flow chart of the performance testing of recycled concrete.

[0045] Figure 4 It is a relationship diagram of the strength performance of the present invention with the compressive strength and the splitting tensile strength. DETAILED DESCRIPTION

[0046] The following is an explanation of the embodiments of the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. In addition, the drawings of the present invention are only simple schematic illustrations and are not depicted according to actual sizes. It is stated in advance. The following embodiments will further explain the relevant technical contents of the present invention in detail, but the disclosed contents are not intended to limit the scope of protection of the present invention.

[0047] Embodiment 1: According to Figure 1 , Figure 2 and Figure 3 The present embodiment provides a recycled concrete and a preparation method thereof. The recycled concrete includes 3.52 parts of cement, 6.5 parts of sand, 0 to 12.08 parts of coarse aggregate, 0 to 12.08 parts of fine aggregate, 1.9 to 2.4 parts of water, 0.01 to 0.1 parts of plant fiber, and 0.011 parts of a water reducing agent in a weight ratio. The plant fiber is corn fiber or straw fiber.

[0048] Furthermore, the weight ratio of the coarse aggregate in the raw material is 6.04 parts, the weight ratio of the fine aggregate in the raw material is 6.04 parts, and the weight ratio of the plant fiber in the raw material is 0.01 parts.

[0049] Furthermore, the type of cement is P.O42.5 ordinary Portland cement, the fine aggregate is natural sand, and the apparent density of the natural sand is 2598 kg / m 3 , the soil content is 0.5%, the fineness modulus is 2.66, and the soil content is 2.2%; the coarse aggregate is a mixture of natural sand and gravel and recycled coarse aggregate, and the particle size of the coarse aggregate is 8 to 23 mm; the water reducer is a polycarboxylic acid water reducer, the solid content of the water reducer is 10%, and the water reduction rate is 30%.

[0050] Specifically, the recycled coarse aggregate is formed by artificially processing waste concrete.

[0051] Furthermore, the raw materials also include a sodium hydroxide solution with a concentration of 1% to 4% and a sodium metasilicate solution with a concentration of 1%, and the sodium hydroxide solution and the sodium metasilicate solution are used to modify the plant fibers.

[0052] Furthermore, the preparation method of the recycled concrete comprises the following steps:

[0053] S1, modifying the plant fiber by using a sodium hydroxide solution and a sodium metasilicate solution;

[0054] S2, pouring cement and sand into a container and stirring them evenly, and then pouring plant fiber into the container and stirring them evenly;

[0055] S3, adding water into the container and continuing to stir until uniform to obtain cement mortar, adding coarse aggregate and fine aggregate and allowing the cement mortar to fully wrap the coarse aggregate and fine aggregate, and then putting the mixture into a mold;

[0056] S4, vibrating the mold until cement slurry is precipitated on the surface of the mixture, and performing surface treatment;

[0057] S5, demoulding the mixture to obtain recycled concrete, placing the recycled concrete in a curing box, and curing it at 20 degrees Celsius;

[0058] S6, after curing for a specified number of days, the performance of the recycled concrete is tested;

[0059] Specifically, the designated number of days is 20 days.

[0060] S7, obtaining the performance index of the recycled concrete according to the test results, and judging whether the recycled concrete produced this time is qualified according to the performance index.

[0061] Furthermore, modifying the plant fiber comprises the following steps:

[0062] S11, soaking the plant fiber in a sodium hydroxide solution at 80 degrees Celsius for 1 to 2 hours;

[0063] S12, washing the plant fiber with water until the pH value detected on the surface of the plant fiber is 7;

[0064] S13, immersing the treated plant fiber in the sodium metasilicate solution, stirring evenly, and standing at 60 degrees Celsius for 30 to 60 minutes;

[0065] S14, filtering the reaction impurities and washing the plant fiber with water to obtain the modified plant fiber.

[0066] Furthermore, the performance testing of recycled concrete includes the following steps:

[0067] S61, taking a portion of the recycled concrete sample, applying uniform axial pressure to the surface directly above the sample using a pressure testing machine until the sample breaks, and obtaining the compressive strength of the sample;

[0068] Specifically, the compressive strength of the sample can be obtained according to S61 and the existing formula;

[0069] S62, taking a portion of the recycled concrete sample and grinding it into a cylinder, placing the cylinder flat, applying downward pressure to the cylinder from the center until the sample breaks, and obtaining the splitting tensile strength of the sample;

[0070] Specifically, the splitting tensile strength of the sample can be obtained according to S62 and the existing formula;

[0071] S63, taking some recycled concrete samples, subjecting the samples to 10 freeze-thaw cycles in a freeze-thaw box at -25 degrees Celsius, and detecting the weight loss, volume change, surface area change, and surface cracking after each freeze-thaw cycle;

[0072] Specifically, each freeze-thaw cycle consisted of a 6-hour freezing phase and a 6-hour thawing phase;

[0073] S64, taking part of the recycled concrete samples, subjecting them to 50 dry-wet cycles in an alternating dry and wet environment, and testing their weight loss, volume change, surface area change, and surface cracking after the cycles;

[0074] Specifically, in S64, an upper limit and a lower limit of humidity are set, and the staff continuously adjusts the ambient humidity through a humidifier and a dryer so that the environment alternates between dryness and wetness. Whenever the ambient humidity reaches the upper limit of humidity, the dryer works but the humidifier does not work, and whenever the ambient humidity reaches the lower limit of humidity, the dryer does not work but the humidifier works. The upper limit and the lower limit of humidity are set by technicians in this field according to possible application scenarios of recycled concrete.

[0075] S65, take a part of the recycled concrete sample, then make one end of it exposed to the water surface and keep it dry, and the other end is underwater, apply a water pressure of 1.2MPa to the underwater end for 12 hours, and detect the water seepage condition of the end exposed to the water surface.

[0076] Specifically, except for S62, S61 to S65 all use 10cm*10cm*20cm rectangular parallelepiped samples. In S61, the surface on which pressure is applied is a 10cm*20cm surface. In S65, the underwater ground and the top surface above water are both 10cm*10cm surfaces.

[0077] Furthermore, obtaining the performance index of recycled concrete and judging whether the produced recycled concrete is qualified includes the following steps:

[0078] S71, calculating the strength performance index according to the compressive strength and tensile strength of the sample;

[0079] Specifically, the comprehensive strength index can be calculated according to the following formula:

[0080]

[0081] Among them, QDZB is a strength performance index used to characterize the strength of recycled concrete. The larger the index, the higher the strength of the recycled concrete. FC is compressive strength, FT is splitting tensile strength, A is the compressive strength coefficient, and B is the splitting tensile strength coefficient. The compressive strength coefficient and the splitting tensile strength coefficient are set by the possible application scenarios of the recycled concrete. When the possible application scenarios are uncertain, A=B=1. When the possible application scenarios are small buildings, A=1 and B=1.5. When the possible application scenarios are medium-sized buildings, A=1.2 and B=1.3. When the possible application scenarios are large buildings, A=1.4 and B=1. When the possible application scenarios are special environments (alpine areas or high humidity environments or highly corrosive environments), A=1.1 and B=1.4.

[0082] Specifically, Figure 4 As shown, Figure 4 When A=1.1 and B=1.4, the relationship diagram between the comprehensive strength index, the compressive strength and the splitting tensile strength.

[0083] S72, calculating the freeze-thaw resistance performance index according to the test data after freeze-thaw;

[0084] Specifically, the freeze-thaw resistance index is calculated according to the following formula:

[0085]

[0086] Among them, KDRZB is the freeze-thaw resistance index, which is used to characterize the freeze-thaw resistance of recycled concrete. The larger the index, the higher the freeze-thaw resistance. i is the surface area of ​​the sample after the i-th freeze-thaw, SS i is the surface area of ​​the cracked part of the sample after the i-th freeze-thaw, e is a natural constant, G i-1 is the weight of the sample after the i-1th freeze-thaw, G i is the weight of the sample after the i-th freeze-thaw cycle, S i-1 is the surface area of ​​the sample after the i-1th freeze-thaw, V i-1 is the volume of the sample after the i-1th freeze-thaw cycle, V i is the volume of the sample after the i-th freeze-thaw treatment, G0 is the weight of the sample before freeze-thaw treatment, S0 is the surface area of ​​the sample before freeze-thaw treatment, and V0 is the volume of the sample before freeze-thaw treatment.

[0087] S73, calculating the durability performance index according to the test data after the dry-wet cycle;

[0088] Specifically, the durability performance index is calculated according to the following formula:

[0089]

[0090] Among them, NJZB is the durability index. The larger the index is, the stronger the durability of the recycled concrete is. max The maximum humidity value set during the dry-wet cycle, RH min is the minimum humidity value set during the dry-wet cycle, e is a natural constant, s i is the surface area of ​​the sample after the i-th dry-wet cycle, ss i is the surface area of ​​the cracked part of the sample after the i-th dry-wet cycle, e is a natural constant, g i-2 The weight of the sample after the g-2nd dry-wet cycle is g i-1 is the weight of the sample after the g-1th dry-wet cycle, g i is the weight of the sample after the i-th dry-wet cycle, s i-1 is the surface area of ​​the sample after the i-1th dry-wet cycle, v i-1 is the volume of the sample after the i-1th dry-wet cycle, v i is the volume of the sample after the i-th dry-wet cycle, g0 is the weight of the sample before the dry-wet cycle, s0 is the surface area of ​​the sample before the dry-wet cycle, and v0 is the volume of the sample before the dry-wet cycle.

[0091] S74, calculating a water resistance performance index according to the detected water immersion condition;

[0092] Specifically, the water resistance index is calculated according to the following formula:

[0093]

[0094] Among them, NSZB is the water resistance index. The larger the index is, the stronger the water resistance of the recycled concrete is. 水 is the surface area of ​​the sample immersed in water, S 面 is the surface area of ​​the sample above water, S j It is the surface area of ​​the part immersed in water in the part of the j-th side of the sample above the water.

[0095] S75, calculating the comprehensive performance index of recycled concrete according to the strength performance index, freeze-thaw resistance performance index, durability performance index and water resistance performance index;

[0096] Specifically, the comprehensive performance index can be calculated according to the following formula:

[0097]

[0098] Specifically, ZHZB is a comprehensive performance indicator.

[0099] S76, judging whether the produced recycled concrete is qualified according to the comprehensive performance index;

[0100] Specifically, whether the produced recycled concrete is qualified can be judged by setting a comprehensive performance index threshold. When the obtained comprehensive performance index is greater than the comprehensive performance index threshold, the produced recycled concrete is considered qualified. The comprehensive performance index threshold is set by technical personnel in this field according to the required recycled concrete standard. One feasible setting method is that technical personnel in this field refer to other types of high-quality concrete (determine whether it is high quality by existing methods), repeat the above experiment on these high-quality concretes and obtain corresponding comprehensive performance indicators, and weight the corresponding comprehensive performance indicators obtained according to the formula similarity between other types of high-quality concrete and the recycled concrete produced this time, so as to obtain the comprehensive performance index threshold.

[0101] The beneficial effects of this scheme are as follows: 1. By mixing an appropriate amount of plant fiber into the production of recycled concrete, it is beneficial to improve the various properties of recycled concrete, and it is beneficial to expand the treatment methods of rural straw and improve resource utilization.

[0102] 2. Calculating comprehensive performance indicators is helpful to comprehensively evaluate the various properties of recycled concrete and make a comprehensive judgment on its overall capabilities, thereby judging whether the produced recycled concrete is qualified. Judging the performance of recycled concrete with different proportions through comprehensive performance indicators is helpful to find the best proportion of different raw materials.

[0103] Embodiment 2: This embodiment should be understood to include all the features of any of the above embodiments, and further improves on the basis thereof, and also includes a method for obtaining an optimal curing time, the method comprising the following steps:

[0104] Get the minimum value of the curing days that satisfies the following formula, and use the minimum value as the optimal curing days:

[0105]

[0106] Among them, C day+1 is the daily economic benefit index when the maintenance days are day+1 day, C day is the daily economic benefit index when the number of maintenance days is day. The larger the daily economic benefit index is, the greater the economic benefits that can be obtained every day. day+1 It is the comprehensive performance index that can be obtained by testing the recycled concrete sample when the curing days are day+1 day. day is the comprehensive performance index that can be obtained by testing the recycled concrete samples when the curing days are day days, MONEY is the selling price of each batch of recycled concrete produced, day is the curing days, COST1 is the daily salary of the staff who maintain the recycled concrete, and COST2 is the daily electricity cost of the equipment used to maintain the recycled concrete.

[0107] Beneficial effects of this embodiment: Generally speaking, the longer the curing time, the better the performance of the produced recycled concrete. However, blindly extending the curing cycle will lead to an extension of the production cycle, thereby reducing economic benefits. This embodiment obtains the optimal curing time, which is beneficial to reducing the curing time while improving the quality of the recycled concrete as much as possible, thereby improving economic benefits.

[0108] The above disclosed contents are only preferred feasible embodiments of the present invention, and do not limit the protection scope of the present invention. Therefore, all equivalent technical changes made by using the contents of the present invention specification and drawings are included in the protection scope of the present invention. In addition, the elements therein can be updated with the development of technology. The above units are only examples. Those skilled in the art can use corresponding units according to different designs according to actual needs when implementing this solution.

Claims

1. A recycled concrete and a preparation method thereof, characterized in that: The recycled concrete comprises, by weight, 3.52 parts of cement, 6.5 parts of sand, 0-12.08 parts of coarse aggregate, 0-12.08 parts of fine aggregate, 1.9-2.4 parts of water, 0.01-0.1 parts of plant fiber, and 0.011 parts of water reducing agent, wherein the plant fiber is corn fiber or straw fiber.

2. A recycled concrete and a preparation method thereof according to claim 1, characterized in that: The weight ratio of the coarse aggregate in the raw material is 6.04 parts, the weight ratio of the fine aggregate in the raw material is 6.04 parts, and the weight ratio of the plant fiber in the raw material is 0.01 parts.

3. A recycled concrete and a preparation method thereof according to claim 2, characterized in that: The type of cement is P.O42.5 ordinary Portland cement, the fine aggregate is natural sand, and the apparent density of the natural sand is 2598kg / m 3 , the soil content is 0.5%, the fineness modulus is 2.66, and the soil content is 2.2%; the coarse aggregate is a mixture of natural sand and gravel and recycled coarse aggregate, and the particle size of the coarse aggregate is 8 to 23 mm; the water reducer is a polycarboxylic acid water reducer, the solid content of the water reducer is 10%, and the water reduction rate is 30%.

4. A recycled concrete and a preparation method thereof according to claim 3, characterized in that: The raw materials also include a sodium hydroxide solution with a concentration of 1% to 4% and a sodium metasilicate solution with a concentration of 1%. The sodium hydroxide solution and the sodium metasilicate solution are used to modify the plant fibers.

5. A recycled concrete and a preparation method thereof according to claim 4, characterized in that: The method for preparing the recycled concrete comprises the following steps: S1, modifying the plant fiber by using a sodium hydroxide solution and a sodium metasilicate solution; S2, pouring cement and sand into a container and stirring them evenly, and then pouring plant fiber into the container and stirring them evenly; S3, adding water into the container and continuing to stir until uniform to obtain cement mortar, adding coarse aggregate and fine aggregate and allowing the cement mortar to fully wrap the coarse aggregate and fine aggregate, and then putting the mixture into a mold; S4, vibrating the mold until cement slurry is precipitated on the surface of the mixture, and performing surface treatment; S5, demoulding the mixture to obtain recycled concrete, placing the recycled concrete in a curing box, and curing it at 20 degrees Celsius; S6, after curing for a specified number of days, the performance of the recycled concrete is tested; S7, obtaining the performance index of the recycled concrete according to the test results, and judging whether the recycled concrete produced this time is qualified according to the performance index.

6. A recycled concrete and a preparation method thereof according to claim 5, characterized in that: Modification of plant fibers includes the following steps: S11, soaking the plant fiber in a sodium hydroxide solution at 80 degrees Celsius for 1 to 2 hours; S12, washing the plant fiber with water until the pH value detected on the surface of the plant fiber is 7; S13, immersing the treated plant fiber in the sodium metasilicate solution, stirring evenly, and standing at 60 degrees Celsius for 30 to 60 minutes; S14, filtering the reaction impurities and washing the plant fiber with water to obtain the modified plant fiber.

7. A recycled concrete and a preparation method thereof according to claim 6, characterized in that: The performance testing of recycled concrete includes the following steps: S61, taking a portion of the recycled concrete sample, applying uniform axial pressure to the surface directly above the sample using a pressure testing machine until the sample breaks, and obtaining the compressive strength of the sample; S62, taking a portion of the recycled concrete sample and grinding it into a cylinder, placing the cylinder flat, applying downward pressure to the cylinder from the center until the sample breaks, and obtaining the splitting tensile strength of the sample; S63, taking some recycled concrete samples, subjecting the samples to 10 freeze-thaw cycles in a freeze-thaw box at -25 degrees Celsius, and detecting the weight loss, volume change, surface area change, and surface cracking after each freeze-thaw cycle; S64, taking part of the recycled concrete samples, subjecting them to 50 dry-wet cycles in an alternating dry and wet environment, and testing their weight loss, volume change, surface area change, and surface cracking after the cycles; S65, take a part of the recycled concrete sample, then make one end of it exposed to the water surface and keep it dry, and the other end is underwater, apply a water pressure of 1.2MPa to the underwater end for 12 hours, and detect the water seepage condition of the end exposed to the water surface.

8. The recycled concrete and preparation method thereof according to claim 7, characterized in that: Obtaining the performance indicators of recycled concrete and judging whether the produced recycled concrete is qualified includes the following steps: S71, calculating the strength performance index according to the compressive strength and tensile strength of the sample; S72, calculating the freeze-thaw resistance performance index according to the test data after freeze-thaw; S73, calculating the durability performance index according to the test data after the dry-wet cycle; S74, calculating a water resistance performance index according to the detected water immersion condition; S75, calculating the comprehensive performance index of recycled concrete according to the strength performance index, freeze-thaw resistance performance index, durability performance index and water resistance performance index; S76, judge whether the produced recycled concrete is qualified based on the comprehensive performance indicators.

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