Pervious concrete reinforcing agent and preparation method thereof

Abstract

The invention belongs to the technical field of building materials. The invention relates to a reinforcing agent, in particular to a pervious concrete reinforcing agent and a preparation method thereof. The preparation method comprises the following specific preparation steps: cleaning rice hulls, drying, and performing oxygen-controlled calcination under the conditions that the temperature is 800-900 DEG C and the oxygen concentration is 3-5% to obtain calcined rice hull ash; the calcined rice hull ash is subjected to acid pickling and impurity removal and then dried, and acid-pickled rice hull ash is obtained; soaking the acid-washed rice hull ash in a sodium silicate solution, ultrasonically dispersing uniformly, adjusting the pH value to 4.8-5.0, carrying out heat preservation reaction at the temperature of 40-60 DEG C, filtering, washing and drying to obtain coated acid-washed rice hull ash; and placing the coated acid-washed rice hull ash in an inert atmosphere, heating to 1550-1700 DEG C, carrying out a high-temperature reaction for 8-12 h, cooling to 550-600 DEG C, carrying out oxygen-controlled calcination for 30-45 min under the condition that the oxygen concentration is 1.5-2.0%, cooling, and discharging to obtain the pervious concrete reinforcing agent.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and more specifically relates to a permeable concrete reinforcing agent and a preparation method thereof. Background Art

[0002] Permeable concrete enhancer is an admixture specifically used to improve the mechanical properties and durability of permeable concrete. It is mainly used to improve the strength, wear resistance and freeze-thaw resistance of permeable concrete while maintaining its good permeability.

[0003] At present, commonly used enhancers for permeable concrete include the following categories: polymers, such as acrylates, epoxy resins, etc., which enhance the toughness of cement paste through polymer film formation; silica fume / microsilica powder, which improves density and strength by filling micropores; nanomaterials, such as nano-silica, to optimize the structure of cement hydration products; organic-inorganic composites, which comprehensively improve strength and permeability.

[0004] Among them, nano-reinforcers are high-performance materials in the field of permeable concrete. They significantly improve the performance of concrete through the unique effects of nanomaterials (such as small size effect, high activity, etc.), but there are still some technical bottlenecks and limitations. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that existing nano-type reinforcing agents are prone to agglomeration when used as reinforcing agents for permeable concrete. In addition, during the mixing process, nano-silica reinforcing agents have a very strong volcanic ash effect, which consumes a large amount of calcium hydroxide in a short period of time and generates more CSH gel, which may block the interconnected pores between aggregates and cause a decrease in permeability. Furthermore, nano-silica easily absorbs free water and increases the viscosity of the slurry, resulting in local over-density and uneven permeable channels. In response to the above difficulties, the present invention provides a permeable concrete reinforcing agent and a preparation method thereof.

[0006] The purpose of the present invention is to provide a method for preparing a permeable concrete reinforcing agent.

[0007] Another object of the present invention is to provide a permeable concrete reinforcing agent.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] A method for preparing a permeable concrete reinforcing agent, the specific preparation steps comprising:

[0010] The rice husk is washed and dried, and then calcined at a temperature of 800-900°C and an oxygen concentration of 0.3-0.5% for 3-5 hours to obtain calcined rice husk ash;

[0011] The above technical solution uses biomass waste rice husk as the basic raw material to increase its added value and reduce environmental pollution;

[0012] On this basis, oxygen-controlled calcination is first carried out under low oxygen concentration. On the one hand, the silica in the rice husk is retained, making it an active ingredient in the preparation of permeable concrete. On the other hand, part of the organic matter in the rice husk forms an amorphous carbon coating on the surface of the amorphous silica under low oxygen content.

[0013] After acid washing and impurity removal of calcined rice husk ash, the ash is dried to obtain acid washed rice husk ash;

[0014] By using acid washing, impurity components such as K2O or Na2O remaining in the rice husk ash after calcination are removed, thereby preventing these components from reacting with silicon dioxide to form highly active silicates under the high temperature conditions of 1550-1700°C in the next stage. Although the formation of such silicates can directly release silicate ions during the cement hydration process and thus directly participate in the cement hydration reaction, the reaction can proceed at the early stage of cement hydration and the reaction rate is high. In this case, it is easy to cause uneven distribution of pores in the permeable concrete, affecting the product's reinforcement effect on the permeable concrete;

[0015] Specifically, the oxygen concentration can be adjusted at room temperature and pressure by regulating the volume ratio of oxygen to nitrogen so that the volume ratio of oxygen to the total gas is within the above range, that is, a mixed gas with an oxygen concentration within a suitable range is obtained;

[0016] The acid-washed rice husk ash is heated to 1550-1700°C in an inert atmosphere, reacted at high temperature for 8-12 hours, cooled to 550-600°C, and then calcined under oxygen control at an oxygen concentration of 1.5-2.0% for 30-45 minutes, cooled, and discharged to obtain a permeable concrete reinforcing agent.

[0017] The oxygen concentration is the volume fraction of oxygen.

[0018] The above technical solution reacts the residual amorphous carbon on the surface of rice husk ash with silica at high temperatures of 1550-1700°C, transforming the adsorption between the two from simple van der Waals forces to Si-C chemical bonds, thereby forming a strong bond between the surface amorphous carbon and silica, preventing the coating from falling off during the concrete mixing process; the hydrophobicity of amorphous carbon can reduce the hydrogen bonding of hydroxyl (-OH) groups on the surface of nanoparticles and reduce the tendency to agglomerate; at the same time, the steric hindrance effect of the carbon layer can prevent direct contact between particles, thereby improving the uniformity of silica distribution in the cement paste and enhancing its pore refinement effect; and the heat generated by cement hydration, thanks to the support of the Si-C chemical bonds between silica and amorphous carbon, can also prevent the refined pores from collapsing under thermal stress, maintaining a good water permeability effect;

[0019] Finally, through secondary oxygen-controlled calcination, the degree of surface oxidation is further regulated, so that a portion of oxygen-containing functional groups such as hydroxyl groups exist on the surface, making the reinforcing agent well compatible with the concrete system.

[0020] Furthermore, the specific preparation steps also include:

[0021] The pickled rice husk ash is immersed in a sodium silicate solution with a mass fraction of 3-5%, and after ultrasonic dispersion, the pH is adjusted to 4.8-5.0, and the reaction is carried out at a temperature of 40-60°C for 80-120 minutes, and then filtered, washed and dried to obtain coated pickled rice husk ash;

[0022] Wherein, the mass ratio of the pickled rice husk ash to the sodium silicate solution is 1:8-10;

[0023] The coated acid-washed rice husk ash is heated to 1550-1700° C. in an inert atmosphere, reacted at high temperature for 8-12 hours, cooled to 550-600° C., and then calcined under controlled oxygen at an oxygen concentration of 1.5-2.0% for 30-45 minutes, cooled, and discharged to obtain a permeable concrete reinforcer.

[0024] The beneficial effects of the above technical solution are:

[0025] The above technical solution further coats the surface of the pickled rice husk ash. During this process, silicate combines with ions and hydrogen ions to form orthosilicic acid colloidal particles. Once the particles are formed, they can be adsorbed by the amorphous carbon coating layer on the surface of the pickled rice husk ash, thereby embedding into the pores of the amorphous carbon coating layer. In the subsequent high-temperature reaction process, the amorphous carbon coating layer on the surface is made into a composite coating layer of amorphous carbon and silica, thereby forming a core-shell structure with silica in the rice husk as the core and the composite coating layer as the surface layer; due to the presence of the surface coating layer, the physical properties of the surface coating layer can be effectively stabilized to avoid falling off during the concrete mixing process, thereby causing the protective effect of the coating layer to fail.

[0026] Furthermore, the ultrasonic dispersion comprises: continuously performing ultrasonic dispersion for 30-45 minutes at an ultrasonic frequency of 100-120 kHz.

[0027] Furthermore, the specific preparation steps also include:

[0028] The coated acid-washed rice husk ash is slowly heated to 1550-1700°C at a rate of 1.5-3.0°C / min in an inert atmosphere, reacted at high temperature for 8-12 hours, cooled to 550-600°C, and then calcined under controlled oxygen at an oxygen concentration of 1.5-2.0% for 30-45 minutes. The mixture is cooled and discharged to obtain a permeable concrete reinforcer.

[0029] By further controlling the heating rate in an inert atmosphere, under the aforementioned lower heating rate conditions, cracks at the interface between the coating layer and the core due to inconsistent thermal expansion coefficients between the two can be avoided, thereby further improving the coating effect.

[0030] Furthermore, the specific preparation steps also include:

[0031] The rice husk is washed and dried, and then crushed and passed through an 80-mesh sieve to obtain the rice husk fine material below the sieve. Subsequently, the rice husk is calcined under oxygen control for 3-5 hours at a temperature of 800-900°C and an oxygen concentration of 3-5% to obtain calcined rice husk ash.

[0032] Furthermore, the pickling and impurity removal includes:

[0033] The calcined rice husk ash and hydrochloric acid with a mass fraction of 8-10% are mixed in a mass ratio of 1:8-10, and the mixture is stirred at a stirring rate of 300-400 r / min and a temperature of 40-50°C. After acid washing for 30-60 minutes, the mixture is filtered, the filter cake is collected, and the filter cake is washed with deionized water until the washing liquid is neutral. The washed filter cake is then transferred to an oven and dried to constant weight at a temperature of 100°C to obtain the acid-washed rice husk ash.

[0034] A permeable concrete reinforcing agent is prepared by the above preparation method. DETAILED DESCRIPTION

[0035] The present invention is further described below with reference to specific examples, which, however, are not intended to limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0036] Unless otherwise specified, the reagents and materials used in the following examples were commercially available.

[0037] Example 1

[0038] The rice husks were soaked in clean water, ultrasonically cleaned at 40°C and 80kHz for 2 hours, filtered, and dried. The dried rice husks were crushed and passed through an 80-mesh sieve to obtain the rice husk fines below the sieve. The rice husks were then transferred to a carbonization furnace and heated to 800°C at a rate of 6°C / min. The husks were calcined under oxygen control for 3 hours at an oxygen concentration of 3% to obtain calcined rice husk ash.

[0039] Specifically, the oxygen concentration can be adjusted at room temperature and pressure by regulating the volume ratio of oxygen to nitrogen so that the volume ratio of oxygen to the total gas is within the above range, that is, a mixed gas with an oxygen concentration within a suitable range is obtained; the oxygen concentration in this embodiment is regulated by referring to the following method;

[0040] The calcined rice husk ash and 8% hydrochloric acid were mixed in a mass ratio of 1:8, and the mixture was stirred at a stirring rate of 300 r / min and a temperature of 40°C for 30 minutes under heat preservation and stirring. The filter cake was collected by filtration and washed with deionized water until the washing liquid was neutral. The washed filter cake was then transferred to an oven and dried at a temperature of 100°C to constant weight to obtain the acid-washed rice husk ash.

[0041] The pickled rice husk ash was immersed in a sodium silicate solution with a mass fraction of 3%, and ultrasonic dispersion was continued for 30 minutes at an ultrasonic frequency of 100 kHz. The pH was adjusted to 4.8, and the mixture was kept at 40°C for 80 minutes. The mixture was filtered, washed and dried to obtain coated pickled rice husk ash.

[0042] Wherein, the mass ratio of the pickled rice husk ash to the sodium silicate solution is 1:8;

[0043] The coated acid-washed rice husk ash is placed in an inert atmosphere, in this embodiment, the inert atmosphere is argon, and is slowly heated to 1550°C at a rate of 1.5°C / min. After high-temperature reaction for 8 hours, it is cooled to 550°C and then calcined under oxygen control at an oxygen concentration of 1.5% for 30 minutes. After cooling and discharging, a permeable concrete reinforcer is obtained.

[0044] Example 2

[0045] The rice husks were soaked in clean water, ultrasonically cleaned at 45°C and 85kHz for 3 hours, filtered, and dried. The dried rice husks were crushed and passed through an 80-mesh sieve to obtain the rice husk fines below the sieve. The rice husks were then transferred to a carbonization furnace and heated to 860°C at a rate of 7°C / min. The husks were calcined under oxygen control for 4 hours at an oxygen concentration of 4% to obtain calcined rice husk ash.

[0046] Specifically, the oxygen concentration can be adjusted at room temperature and pressure by regulating the volume ratio of oxygen to nitrogen so that the volume ratio of oxygen to the total gas is within the above range, that is, a mixed gas with an oxygen concentration within a suitable range is obtained; the oxygen concentration in this embodiment is regulated by referring to the following method;

[0047] The calcined rice husk ash and 9% hydrochloric acid were mixed in a mass ratio of 1:9, stirred at a stirring rate of 360 r / min and a temperature of 45°C, and acid washed for 50 minutes. The mixture was filtered, the filter cake was collected, and the filter cake was washed with deionized water until the washing liquid was neutral. The washed filter cake was then transferred to an oven and dried at a temperature of 100°C to constant weight to obtain the acid-washed rice husk ash.

[0048] The pickled rice husk ash was immersed in a sodium silicate solution with a mass fraction of 4%, and ultrasonic dispersion was continued for 35 minutes at an ultrasonic frequency of 110 kHz. The pH was adjusted to 4.9, and the mixture was kept at 50°C for 100 minutes. The mixture was then filtered, washed and dried to obtain coated pickled rice husk ash.

[0049] Wherein, the mass ratio of the pickled rice husk ash to the sodium silicate solution is 1:9;

[0050] The coated acid-washed rice husk ash is placed in an inert atmosphere, in this embodiment, the inert atmosphere is argon, and is slowly heated to 1600°C at a rate of 2.0°C / min. After high-temperature reaction for 10 hours, it is cooled to 580°C and then calcined under oxygen control for 35 minutes at an oxygen concentration of 1.8%. After cooling and discharging, a permeable concrete reinforcer is obtained.

[0051] Example 3

[0052] The rice husks were soaked in clean water, ultrasonically cleaned at 50°C and 90kHz for 4 hours, filtered, and dried. The dried rice husks were crushed and passed through an 80-mesh sieve to obtain the rice husk fines below the sieve. The rice husks were then transferred to a carbonization furnace and heated to 900°C at a rate of 8°C / min. The husks were calcined under oxygen control for 5 hours at an oxygen concentration of 5% to obtain calcined rice husk ash.

[0053] Specifically, the oxygen concentration can be adjusted at room temperature and pressure by regulating the volume ratio of oxygen to nitrogen so that the volume ratio of oxygen to the total gas is within the above range, that is, a mixed gas with an oxygen concentration within a suitable range is obtained; the oxygen concentration in this embodiment is regulated by referring to the following method;

[0054] The calcined rice husk ash and 10% hydrochloric acid were mixed in a mass ratio of 1:10, stirred at a stirring rate of 400 r / min and a temperature of 50°C, and acid washed for 60 minutes. The mixture was filtered, the filter cake was collected, and the filter cake was washed with deionized water until the washing liquid was neutral. The washed filter cake was then transferred to an oven and dried at a temperature of 100°C to constant weight to obtain acid-washed rice husk ash.

[0055] The pickled rice husk ash was immersed in a sodium silicate solution with a mass fraction of 5%, and ultrasonic dispersion was continued for 45 minutes at an ultrasonic frequency of 120 kHz. The pH was adjusted to 5.0, and the reaction was kept at 60°C for 120 minutes. The mixture was filtered, washed and dried to obtain coated pickled rice husk ash.

[0056] Wherein, the mass ratio of the pickled rice husk ash to the sodium silicate solution is 1:10;

[0057] The coated acid-washed rice husk ash is placed in an inert atmosphere, in this embodiment, the inert atmosphere is argon, and is slowly heated to 1700°C at a rate of 3.0°C / min. After high-temperature reaction for 12 hours, it is cooled to 600°C and then calcined under oxygen control for 45 minutes at an oxygen concentration of 2.0%. After cooling and discharging, a permeable concrete reinforcer is obtained.

[0058] Example 4

[0059] Compared with Example 1, this embodiment differs in that:

[0060] The sodium silicate solution was replaced by deionized water of equal mass, and the other conditions remained unchanged.

[0061] It can be foreseen that due to the lack of the presence of sodium silicate solution, the amorphous carbon coating lacks further introduction of silicon dioxide. Therefore, compared with Example 1, the stability of the amorphous carbon coating is weakened, especially during the concrete mixing process, part of the amorphous carbon may fall off, causing part of the silicon dioxide to begin to agglomerate.

[0062] Example 5

[0063] Compared with Example 1, this embodiment differs in that:

[0064] The coated acid-washed rice husk ash is placed in an inert atmosphere, in this embodiment, the inert atmosphere is argon, and is slowly heated to 1550°C at a rate of 8°C / min. After high-temperature reaction for 8 hours, it is cooled to 550°C, and then calcined under oxygen control at an oxygen concentration of 1.5% for 30 minutes. After cooling and discharging, a permeable concrete reinforcer is obtained.

[0065] Since a high heating rate is used during the high-temperature heating process, a small number of microcracks appear at the interface between amorphous carbon and silica due to the inconsistency of thermal expansion coefficients, thereby affecting the direct bonding strength between the coating layer and the core silica.

[0066] Comparative Example 1

[0067] Compared with Example 1, this comparative example has the following differences:

[0068] The rice husks were soaked in clean water, ultrasonically cleaned at 40°C and 80kHz for 2 hours, filtered, and dried. The dried rice husks were crushed and passed through an 80-mesh sieve to obtain the rice husk fines below the sieve. The rice husks were then transferred to a carbonization furnace and heated to 800°C at a rate of 6°C / min. The husks were calcined under oxygen control for 3 hours at an oxygen concentration of 3% to obtain calcined rice husk ash.

[0069] Specifically, the oxygen concentration can be adjusted at room temperature and pressure by regulating the volume ratio of oxygen to nitrogen so that the volume ratio of oxygen to the total gas is within the above range, that is, a mixed gas with an oxygen concentration within a suitable range is obtained; the oxygen concentration in this embodiment is regulated by referring to the following method;

[0070] The calcined rice husk ash and 8% hydrochloric acid were mixed in a mass ratio of 1:8, and the mixture was stirred at a stirring rate of 300 r / min and a temperature of 40°C for 30 minutes under heat preservation and stirring. The filter cake was collected by filtration and washed with deionized water until the washing liquid was neutral. The washed filter cake was then transferred to an oven and dried at a temperature of 100°C to constant weight to obtain the acid-washed rice husk ash.

[0071] The pickled rice husk ash was immersed in a sodium silicate solution with a mass fraction of 3%, and ultrasonic dispersion was continued for 30 minutes at an ultrasonic frequency of 100 kHz. The pH was adjusted to 4.8, and the mixture was kept at 40°C for 80 minutes. The mixture was filtered, washed and dried to obtain coated pickled rice husk ash.

[0072] Wherein, the mass ratio of the pickled rice husk ash to the sodium silicate solution is 1:8;

[0073] The coated acid-washed rice husk ash is placed in an inert atmosphere, in this embodiment, the inert atmosphere is argon, and is slowly heated to 550°C at a rate of 1.5°C / min. It is first calcined in an inert atmosphere for 8 hours, and then calcined for 30 minutes under oxygen control at an oxygen concentration of 1.5%. After cooling and discharging, a permeable concrete reinforcer is obtained.

[0074] Since a high-temperature reaction of 1550°C or higher is not performed in the final stage, Si-C chemical bonding is not formed between silicon dioxide and amorphous carbon.

[0075] The performance tests of the products obtained in the above examples and comparative examples were carried out, and the specific test methods and test results are as follows:

[0076] Preparation of permeable concrete samples:

[0077] Refer to the following recipe:

[0078] Calculated by weight, 300 parts of 42.5# Portland cement, 1400 parts of coarse aggregate with an average particle size of 5 mm, 3 parts of polypropylene fiber with an average length of 5 mm, 1 part of polycarboxylate water reducer, and 30 parts of the permeable concrete reinforcing agent prepared in the above embodiment or comparative example were weighed, and water was added at a water-binder ratio of 0.35;

[0079] After mixing for 20 minutes at a stirring speed of 80 r / min and a temperature below 50°C, the concrete was poured into a 150 mm × 150 mm × 150 mm cubic standard specimen. After curing for 28 days at a temperature of 20°C and a relative humidity of 90%, the compressive strength of the concrete was tested with reference to GB / T 50081-2019. The relevant test results are shown in Table 1.

[0080] The water permeability of concrete was tested with reference to ASTM C1701. Using the sample preparation method described above, concrete was poured into 1500 mm × 150 mm × 150 mm specimens, which were then cut into 150 mm × 150 mm × 150 mm cubic standard specimens. These specimens were used as 10 sets of parallel samples. The maximum and minimum permeability values of the 10 sets of parallel samples were statistically analyzed to evaluate the uniformity of the permeability rates in different areas. The greater the deviation between the two, the poorer the uniformity. The detailed test results are shown in Table 1.

[0081] Table 1: Product performance test results

[0082]

[0083] It can be seen from the test results in Table 1 that the product obtained by the present invention has better mechanical properties than that of Comparative Example 1, and at the same time, it has high water permeability and better uniformity of water permeability between different regions.

[0084] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a permeable concrete reinforcing agent, characterized in that: The specific preparation steps include: The rice husk is washed and dried, and then calcined at a temperature of 800-900°C and an oxygen concentration of 3-5% for 3-5 hours to obtain calcined rice husk ash; After acid washing and impurity removal of calcined rice husk ash, the ash is dried to obtain acid washed rice husk ash; The acid-washed rice husk ash is heated to 1550-1700°C in an inert atmosphere, reacted at high temperature for 8-12 hours, cooled to 550-600°C, and then calcined under oxygen control at an oxygen concentration of 1.5-2.0% for 30-45 minutes, cooled, and discharged to obtain a permeable concrete reinforcing agent. The oxygen concentration is the volume fraction of oxygen.

2. The method for preparing a permeable concrete reinforcing agent according to claim 1, wherein: The specific preparation steps also include: The pickled rice husk ash is immersed in a sodium silicate solution with a mass fraction of 3-5%, and after ultrasonic dispersion, the pH is adjusted to 4.8-5.0, and the reaction is carried out at a temperature of 40-60°C for 80-120 minutes, and then filtered, washed and dried to obtain coated pickled rice husk ash; Wherein, the mass ratio of the pickled rice husk ash to the sodium silicate solution is 1:8-10; The coated acid-washed rice husk ash is heated to 1550-1700° C. in an inert atmosphere, reacted at high temperature for 8-12 hours, cooled to 550-600° C., and then calcined under controlled oxygen at an oxygen concentration of 1.5-2.0% for 30-45 minutes, cooled, and discharged to obtain a permeable concrete reinforcer.

3. The method for preparing a permeable concrete reinforcing agent according to claim 2, wherein: The ultrasonic dispersion comprises: continuously dispersing the mixture for 30-45 minutes at an ultrasonic frequency of 100-120 kHz.

4. The method for preparing a permeable concrete reinforcing agent according to claim 2, wherein: The specific preparation steps also include: The coated acid-washed rice husk ash is slowly heated to 1550-1700°C at a rate of 1.5-3.0°C / min in an inert atmosphere, reacted at high temperature for 8-12 hours, cooled to 550-600°C, and then calcined under controlled oxygen at an oxygen concentration of 1.5-2.0% for 30-45 minutes. The mixture is cooled and discharged to obtain a permeable concrete reinforcer.

5. The method for preparing a permeable concrete reinforcing agent according to any one of claims 1 to 4, characterized in that: The specific preparation steps also include: The rice husk is washed and dried, and then crushed and passed through an 80-mesh sieve to obtain the rice husk fine material below the sieve. Subsequently, the rice husk is calcined under oxygen control for 3-5 hours at a temperature of 800-900°C and an oxygen concentration of 3-5% to obtain calcined rice husk ash.

6. The method for preparing a permeable concrete reinforcing agent according to any one of claims 1 to 4, characterized in that: The pickling and impurity removal comprises: The calcined rice husk ash and hydrochloric acid with a mass fraction of 8-10% are mixed in a mass ratio of 1:8-10, and the mixture is stirred at a stirring rate of 300-400 r / min and a temperature of 40-50°C. After acid washing for 30-60 minutes, the mixture is filtered, the filter cake is collected, and the filter cake is washed with deionized water until the washing liquid is neutral. The washed filter cake is then transferred to an oven and dried to constant weight at a temperature of 100°C to obtain the acid-washed rice husk ash.

7. A permeable concrete reinforcing agent, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 6.

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