Solid waste admixture prepared based on microbiological treatment regenerated micro powder and preparation method

Abstract

The invention discloses a solid waste admixture prepared based on microbiological treatment of regenerated micro-powder and a preparation method, and aims to overcome the defect that the dilution effect is remarkable when regenerated micro-powder is directly used as an admixture in the prior art. The method comprises the following steps: treating waste concrete to obtain regenerated micro powder; culturing bacillus pasteurii, and preparing a bacterial solution with a target OD value; mixing the regenerated micro-powder and a bacterial solution according to a certain solid-to-liquid ratio, adding urea and biochar, and reacting in a magnetic stirrer for a set time to obtain modified regenerated micro-powder; and taking out the modified regenerated micro powder, filtering, drying to constant weight, and fully scattering to obtain the solid waste admixture. According to the present invention, the bacteria-containing culture solution is subjected to centrifugal treatment and the low concentration of the bacteria solution is adopted, such that the by-products generated by the metabolism of the bacillus pasteurii are reduced on the premise of ensuring the sufficient decomposition of the urea, and the prepared regenerated micro-powder contains rich ultrafine calcium carbonate on the surface, and can be adopted as the solid waste admixture to significantly enhance the compressive strength of the cement matrix.

Description

Technical Field

[0001] The present invention relates to the field of preparation methods of building materials, and particularly relates to a solid waste admixture prepared based on microbial treatment of recycled fine powder and a preparation method thereof. Background Art

[0002] With the expiration of the service life of some industrial and civil buildings built in the last century and the rapid progress of urbanization, a large number of buildings are facing demolition and renovation. The construction waste generated in this process has become an important factor affecting the ecological environment.

[0003] In the field of resource utilization of construction solid waste, the currently commonly used recycling methods mainly include means such as crushing and screening to prepare recycled aggregates, thermal activation, ultrafine grinding, alkali activation, and carbonation modification. The crushing and screening technology processes construction waste such as waste concrete into recycled aggregates through physical crushing and screening for use in backfilling the road base or sub-base; thermal activation enhances the activity of recycled fine powder with high temperature to better play the role of admixture in cement-based materials; ultrafine grinding grinds the recycled fine powder to an extremely fine state to increase the specific surface area and improve the reaction activity; alkali activation uses alkaline substances to activate the latent active components in the recycled fine powder; carbonation modification is to make the recycled fine powder react with carbon dioxide to improve its performance. These existing technologies have promoted the resource utilization of construction waste to a certain extent, but there are obvious deficiencies: the recycled aggregates prepared by crushing and screening have high water absorption and large crushing values, making it difficult to meet the specification requirements; thermal activation and ultrafine grinding have high energy consumption and rising costs; alkali activation increases the use cost; carbonation modification has harsh conditions, such as the need to increase the reaction pressure and carbon dioxide concentration, which requires high equipment requirements and high energy consumption. These deficiencies limit the application of recycled fine powder in cement-based materials, cannot effectively solve the dilution effect brought by recycled fine powder, resulting in difficult improvement of the compressive strength of the cement matrix, restricting the resource utilization efficiency of construction solid waste, and unable to fully meet the market and industry's demands for green building materials and reducing the carbon footprint of cement-based materials.

[0004] In summary, there is an urgent need for a new technical solution to solve the above problems to meet the urgent demands of the market and the industry for green building materials and reducing the carbon footprint of cement-based materials. Therefore, how to overcome the deficiency in the existing technology of resource utilization of construction solid waste that it is difficult to effectively improve the performance of recycled fine powder as a cement admixture has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a solid waste admixture prepared based on microbial treatment of recycled fine powder and a preparation method thereof to overcome the significant dilution effect caused by directly using recycled fine powder as an admixture in the existing technology.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention provides a method for preparing a solid waste admixture based on microbial treatment of recycled fine powder, including: Processing waste concrete to obtain recycled fine powder; Culturing Bacillus pasteurii to prepare a bacterial solution with a target OD value; Mixing the recycled fine powder and the bacterial solution at a certain solid-liquid ratio, adding urea and biochar, and reacting for a set time in a magnetic stirrer to obtain modified recycled fine powder; Taking out the modified recycled fine powder for filtration, drying to constant weight and then fully dispersing to obtain the solid waste admixture.

[0007] Among them, the step of processing waste concrete to obtain recycled fine powder includes: Crushing and screening waste cement slurry blocks to obtain initial particles; Ball-milling the initial particles to obtain recycled fine powder.

[0008] The step of culturing Bacillus pasteurii to prepare a bacterial solution with a target OD value includes: Preparing a culture solution of Bacillus pasteurii; Thawing Bacillus pasteurii and inoculating it into the culture solution, and placing it in a shaking incubator for shaking culture to obtain a bacterial-containing culture solution; Centrifuging the bacterial-containing culture solution to obtain bacterial precipitate; Adding deionized water to resuspend the bacterial precipitate and diluting to obtain a bacterial solution with a target OD value.

[0009] The step of preparing a culture solution of Bacillus pasteurii includes preparing a culture solution of Bacillus pasteurii using sodium chloride, soy peptone, beef extract and deionized water.

[0010] Among them, the concentration of sodium chloride is 3-8 g / L, the concentration of soy peptone is 5-15 g / L, and the concentration of beef extract is 1-5 g / L.

[0011] The step of thawing Bacillus pasteurii and inoculating it into the culture solution in a sterile environment and placing it in a shaking incubator for shaking culture to obtain a bacterial-containing culture solution includes thawing Bacillus pasteurii and inoculating it into the culture solution in a sterile environment and placing it in a shaking incubator for shaking culture for 18-24 hours to obtain a bacterial-containing culture solution.

[0012] The step of adding deionized water to resuspend the bacterial precipitate and diluting to obtain a bacterial solution with a target OD value, where the target OD value is OD0.05-OD0.25.

[0013] The step of centrifuging the bacterial-containing culture solution to obtain bacterial precipitate, where the centrifugation rate is 3000-6000 r / min and the centrifugation time is 8-16 min.

[0014] Mix the regenerated micropowder and the bacterial solution at a certain solid-liquid ratio, add urea and biochar, and react for a set time in an oscillating incubator to obtain the modified regenerated micropowder, including mixing the regenerated micropowder and the bacterial solution at a solid-liquid ratio of 1.0 - 3.0, adding urea with a concentration of 15 - 30 g / L and biochar with a concentration of 0.1 - 1.5 g / L, and reacting in a magnetic stirrer for three days.

[0015] The present invention also provides a solid waste admixture prepared by the preparation method described in the above technical solution, and concrete prepared using this solid waste admixture.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: A method for preparing a solid waste admixture based on microbial treatment of regenerated micropowder provided by the present invention promotes the hydrolysis of urea by using urease secreted by Bacillus pasteurii and generates carbonate ions in an alkaline environment. The surface of the microbial cell wall and the extracellular polymers secreted mainly consist of a variety of negatively charged groups, which attract surrounding calcium ions to aggregate, thereby generating supersaturation near the extracellular polymers and the cell wall and breaking through the nucleation barrier to promote calcium carbonate precipitation; biochar has a rich pore structure, which helps to maintain microbial activity and provide additional calcium carbonate nucleation sites; by centrifuging the bacterial culture solution and using a lower bacterial solution concentration in the present invention, while ensuring the full decomposition of urea, the by-products generated by the metabolism of Bacillus pasteurii are reduced. The surface of the prepared regenerated micropowder contains abundant ultrafine calcium carbonate, which can significantly enhance the compressive strength of the cement matrix as a solid waste admixture. Description of the Drawings

[0017] Figure 1 It is a schematic diagram of a method for preparing a solid waste admixture based on microbial treatment of regenerated micropowder in an embodiment of the present invention.

[0018] Figure 2 It is a schematic flow chart of preparing a solid waste admixture by microbial treatment of regenerated micropowder in an embodiment of the present invention.

[0019] Figure 3 It is a schematic diagram of the regenerated micropowder after microbial treatment in an embodiment of the present invention. Detailed Embodiments

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0022] In this document, among the technical features described in an open-ended manner, there are included closed technical solutions composed of the listed features, as well as open technical solutions containing the listed features.

[0023] The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0024] In this document, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0025] In this document, regarding the units of data ranges, if there is only a unit after the right endpoint, it means that the units of the left endpoint and the right endpoint are the same. For example, 720~750°C means that the units of the left endpoint "720" and the right endpoint "750" are both °C.

[0026] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recorded; and any lower limit can be combined with other lower limits to form a range not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or an upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recorded.

[0027] Referring to Figure 1 shown, a method for preparing a solid waste admixture based on microbial treatment of recycled fine powder provided by the present invention includes: Processing waste concrete to obtain recycled fine powder; Culturing Bacillus pasteurii to prepare a bacterial liquid with a target OD value; Mixing the recycled fine powder and the bacterial liquid at a certain solid-liquid ratio, adding urea and biochar, and reacting for a set time in a magnetic stirrer to obtain modified recycled fine powder; Taking out the modified recycled fine powder for filtration, drying to constant weight and then fully dispersing to obtain the solid waste admixture.

[0028] Specifically, regarding the step of processing waste concrete to obtain recycled fine powder, it includes the following steps: Crush and screen the waste cement slurry blocks to obtain initial particles; Ball mill the initial particles to obtain recycled fine powder.

[0029] Among them, the waste concrete used in the present invention is derived from construction waste after the demolition of old buildings, which has been completely hydrated inside. After crushing, initial cement mortar particles with a particle size < 2.36 mm are obtained through screening.

[0030] The ball milling time of the initial particles is 30 - 60 min, and the obtained recycled fine powder has a particle size < 150 μm.

[0031] Specifically, regarding the step of culturing Bacillus pasteurii to prepare a bacterial solution with a target OD value, it includes the following steps: Prepare a culture medium for Bacillus pasteurii; Thaw the Bacillus pasteurii and inoculate it into the culture medium, and place it in a shaking incubator for shaking culture to obtain a bacterial-containing culture medium; Centrifuge the bacterial-containing culture medium to obtain a bacterial precipitate; Add deionized water to resuspend the bacterial precipitate and dilute it to obtain a bacterial solution with a target OD value.

[0032] Among them, a culture medium for Bacillus pasteurii is prepared using sodium chloride, soy peptone, beef extract, and deionized water. The concentration of sodium chloride is 3 - 8 g / L, the concentration of soy peptone is 5 - 15 g / L, and the concentration of beef extract is 1 - 5 g / L.

[0033] The thawed Bacillus pasteurii is inoculated into the culture medium under a sterile environment throughout the process. After inoculation, it is placed in a shaking incubator for shaking culture for 18 - 24 hours, preferably 18 h, and the shaking culture temperature is 20°C - 35°C.

[0034] When centrifuging the bacterial-containing culture medium, the centrifugation rate is 3000 - 6000 r / min, preferably 4000 r / min, the centrifugation time is 8 - 16 min, preferably 12 min. After centrifugation, the supernatant is removed to remove metabolic wastes, residual culture medium components, or other impurities in the culture medium, and at the same time, the bacteria are enriched.

[0035] Then add deionized water to resuspend the bacterial precipitate and adjust the OD value to OD0.05 - OD0.25.

[0036] Specifically, regarding the step of mixing the regenerated micropowder and the bacterial solution at a certain solid-liquid ratio, adding urea and biochar, and reacting for a set time in a magnetic stirrer to obtain the modified regenerated micropowder, the ratio of the bacterial solution to the regenerated micropowder is 1.0 - 3.0, the concentrations of added urea and biochar are 15 - 30 g / L and 0.1 - 1.5 g / L respectively, and reacting in the magnetic stirrer for three days.

[0037] Among them, the preparation of biochar in this step is to pyrolyze the biomass raw material at a high temperature of 500 - 800 °C in a nitrogen environment, and the pyrolysis product is ground to obtain biochar powder with a particle size < 150 μm. The biomass raw material is preferably corn straw, and the biochar content required in the target bacterial solution is 0.1 - 1.5 g / L.

[0038] Specifically, regarding the step of taking out the modified regenerated micropowder for filtration, drying to constant weight and then fully dispersing it to obtain the solid waste admixture. Filter out the impurities or unreacted particles generated during the reaction process to ensure the purity of the modified regenerated micropowder. Put the filtered modified regenerated micropowder into an oven for drying, weigh it at regular intervals until the weight difference between two weighings is less than the specified value, which is considered to reach constant weight. Use a mortar, ball mill or screening equipment to disperse the dried micropowder. The dried modified regenerated micropowder may form lumps due to water evaporation, and dispersion is to redisperse the particles to ensure the uniformity of the material.

[0039] It should be noted that, as Figure 2 shown, in the method for preparing the solid waste admixture based on the microbial treatment of regenerated micropowder provided by the present invention, the preparation of the regenerated micropowder and the preparation of the bacterial solution can be carried out synchronously, and the preparation processes of the two do not affect each other, and they can be prepared separately and then mixed for the preparation of the solid waste admixture.

[0040] The fineness of the regenerated micropowder prepared by the method provided by the present invention meets the micropowder particle size under actual conditions. Abundant ultrafine calcium carbonate can be produced without increasing the fineness of the regenerated micropowder through long-term ball milling; the shaking culture time of 18 h can ensure the full reproduction of microorganisms without generating too many metabolites; the set centrifugation conditions can fully separate the bacteria from the culture solution; since the regenerated micropowder is strongly alkaline, maintaining an appropriate solid-liquid ratio can create good conditions for calcium carbonate nucleation, meeting the survival environment of microorganisms and the concentration of higher nucleating ions. Biochar has a rich pore structure, and maintaining an appropriate biochar content in the solution can provide additional nucleation sites for calcium carbonate nucleation, promoting the crystallization and growth of calcium carbonate.

[0041] As Figure 3Shown is the regenerated fine powder after microbial treatment in the present invention, that is, a solid waste admixture prepared by using the preparation method described in the above technical solution. The ultra-fine calcium carbonate enriched on the surface of the solid waste admixture can significantly enhance the compressive strength of the cement matrix. Its preparation process is based on the biomineralization of Bacillus pasteurii: under the optimized conditions of bacterial solution concentration and centrifugation treatment, the microorganism efficiently decomposes urea to generate carbonate ions, and calcium ions are directionally adsorbed through the negatively charged cell surface and extracellular polymers; combined with the maintenance effect of the porous matrix of biochar on the activity of the bacteria and the abundant nucleation sites provided by it, the directional crystallization of calcium carbonate is realized. By centrifuging the bacterial culture solution and using a relatively low bacterial solution concentration, under the premise of ensuring the full decomposition of urea, the by-products generated by the metabolism of Bacillus pasteurii are reduced.

[0042] The present invention also provides a concrete prepared by using the above solid waste admixture. The preparation process includes uniformly mixing the above solid waste admixture and PO42.5 cement according to a mass ratio of 5-30:95-70, adding water according to a water-cement ratio of 0.3-0.5, slowly stirring for 110-130 s, stopping for 10-30 s, and finally stirring for 110-130 s; after taking out, it is loaded into a mold with the inner surface coated with lubricating oil, the surface excess slurry is scraped flat after being fully vibrated and compacted, and it is placed in a curing box at a temperature of 20±2°C and a humidity of 90%-95%. After curing for 1 d, it is demolded, and taken out after curing for 3 d, 7 d, and 28 d respectively for testing the compressive strength of the composite cement specimens.

[0043] To further understand the present invention, the preferred implementation schemes of the present invention will be described below in conjunction with embodiments. However, it should be understood that these descriptions are only to further illustrate the features and advantages of the present invention, rather than a limitation on the claims of the present invention.

[0044] Example 1 A method for preparing a solid waste admixture based on regenerated fine powder by microbial treatment includes the following steps: S101, initially crush the waste cement slurry block with a jaw crusher, after screening through a 2.36 mm sieve, take the part on the sieve for re-crushing, take out the part under the sieve, grind it with a three-dimensional ball mill, and further screen the ground cement slurry to obtain a powder with a particle size of <150 μm, that is, the required regenerated fine powder.

[0045] S102, take out the Bacillus pasteurii strain and thaw it. Prepare a standard culture solution with 3 g / L of beef extract, 10 g / L of soy peptone, 5 g / L of sodium chloride and deionized water. After autoclaving and cooling, inoculate the thawed strain into the culture solution in a sterile operating table, and then place it in a shaking incubator at a temperature of 25°C and a rate of 180 rpm / min for 18 h. All the instruments involved are sterilized by high temperature and high pressure or ultraviolet rays.

[0046] S103. Place the cultured bacterial liquid in a sterile operating table and aliquot it into centrifuge tubes in equal volumes. Load them into the centrifuge in a symmetric form and centrifuge at a rate of 4000 r / min for 12 min. After removing the supernatant, add equal volumes of deionized water to resuspend it respectively. Centrifuge again and then resuspend. Dilute it with deionized water and prepare the Bacillus pasteurii bacterial liquid with an OD of 0.15 by means of an ultraviolet spectrophotometer.

[0047] S104. Add the regenerated micropowder prepared above, 20 g / L urea, and the biochar formed by pyrolysis at 800 °C at a solid-liquid ratio of 1:2, and place them in a magnetic stirrer to react for 72 h.

[0048] S105. Filter the regenerated micropowder after the above treatment and dry it at 60 °C to a constant weight. After fully dispersing it, the solid waste admixture is obtained.

[0049] The application of the solid waste admixture prepared in this example in the preparation of cement paste blocks includes the following steps: Mix the obtained solid waste admixture and PO42.5 cement evenly at a mass ratio of 5:95. Then add water at a water-cement ratio of 0.35, stir slowly for 120 s, stop for 15 s, and finally stir for 120 s. Take it out and load it into a mold with its inner surface coated with lubricating oil. After fully vibrating and compacting, scrape off the excess paste on the surface, place it in a curing box at a temperature of 20 °C and a humidity of 95%. After curing for 24 h, demold it and then place it in the curing box again to cure for 3 d, 7 d, and 28 d respectively, and take it out for testing the compressive strength of the composite paste block.

[0050] Example 2 In this example, the method for preparing the solid waste admixture by using microorganisms to treat the regenerated micropowder and the use as an admixture are the same as those in Example 1; in the preparation of the composite paste block, the solid waste admixture and PO42.5 cement are mixed evenly at a mass ratio of 10:90, and the remaining steps are the same as those in Example 1.

[0051] Example 3 In this example, the method for preparing the solid waste admixture by using microorganisms to treat the regenerated micropowder and the use as an admixture are the same as those in Example 1; in the preparation of the composite paste block, the solid waste admixture and PO42.5 cement are mixed evenly at a mass ratio of 15:85, and the remaining steps are the same as those in Example 1.

[0052] Example 4 In this example, the method for preparing the solid waste admixture by using microorganisms to treat the regenerated micropowder and the use as an admixture are the same as those in Example 1; in the preparation of the composite paste block, the solid waste admixture and PO42.5 cement are mixed evenly at a mass ratio of 20:80, and the remaining steps are the same as those in Example 1.

[0053] Example 5 In this embodiment, the method for preparing the solid waste admixture by using microorganisms to treat recycled fine powder is the same as that in Example 1; in the preparation of the composite paste block, the solid waste admixture and PO42.5 cement are mixed evenly at a mass ratio of 30:70, and the remaining steps are the same as those in Example 1.

[0054] Example 6 A method for preparing a solid waste admixture based on treating recycled fine powder with microorganisms, comprising the following steps: S601, initially crush the waste cement paste block with a jaw crusher, after screening through a 2.36 mm sieve, take the part on the sieve for re-crushing, take out the part under the sieve, grind it with a three-dimensional ball mill, further screen the ground cement paste to obtain powder with a particle size of <150 μm, that is, the required recycled fine powder.

[0055] S602, take out the Bacillus pasteurii strain and thaw it. Prepare a standard culture medium with 3 g / L beef extract, 10 g / L soy peptone, 5 g / L sodium chloride and deionized water. After autoclaving and cooling, inoculate the thawed strain into the culture medium in a sterile operating table, and then place it in a shaking incubator at a temperature of 30 °C and a rate of 180 rpm / min for 18 h. All the instruments involved are sterilized by high temperature and high pressure or ultraviolet rays.

[0056] S603, place the cultured bacterial liquid in a sterile operating table and aliquot it into centrifuge tubes in equal volume. Load it into the centrifuge in a symmetric form and centrifuge at a rate of 4000 r / min for 12 min. After removing the supernatant, add equal volume of deionized water to resuspend it respectively. After centrifuging again and resuspending, dilute it with deionized water, and prepare a Bacillus pasteurii bacterial liquid with an OD of 0.25 with the help of an ultraviolet spectrophotometer.

[0057] S604, add the recycled fine powder prepared above, 30 g / L urea, and 0.5 g / L biochar formed by pyrolysis at 800 °C according to a solid-liquid ratio of 1:2, and place it in a magnetic stirrer to react for 72 h.

[0058] S605, filter the recycled fine powder after the above treatment, dry it at 60 °C to constant weight, and obtain the solid waste admixture after sufficient dispersion.

[0059] The application of the solid waste admixture prepared in this embodiment in the preparation of cement paste blocks, comprising the following steps: Mix the obtained solid waste admixture with PO42.5 cement evenly at a mass ratio of 5:95, then add water at a water-cement ratio of 0.35, stir slowly for 120 s, stop for 15 s, and finally stir for 120 s. After taking out, put it into a mold with lubricating oil coated on the inner surface. After sufficient vibration compaction, scrape off the excess slurry blocks on the surface, place it in a curing box at a temperature of 20 °C and a humidity of 95%. After curing for 24 h, demold it, and then place it in the curing box again for curing for 3 d, 7 d, and 28 d respectively, and take it out for testing the compressive strength of the composite slurry block.

[0060] Example 7 A method for preparing solid waste admixture based on microbial treatment of recycled fine powder, comprising the following steps: S701, Use a jaw crusher to preliminarily crush the waste cement slurry block. After screening through a 2.36 mm sieve, take the part on the sieve for re-crushing, take out the part under the sieve, use a vertical ball mill for grinding, and further screen the ground cement slurry to obtain powders with a particle size of <150 μm, that is, the required recycled fine powder.

[0061] S702, Take out the Bacillus pasteurii strain and thaw it. Prepare a standard culture medium with 3 g / L of beef extract, 10 g / L of soy peptone, 5 g / L of sodium chloride and deionized water. After autoclaving and cooling, inoculate the thawed strain into the culture medium in a sterile operating table, and then place it in a shaking incubator at a temperature of 35 °C and a rate of 180 rpm / min for 24 h. All the instruments involved are sterilized by high temperature and high pressure or ultraviolet rays.

[0062] S703, Place the cultured bacterial liquid in a sterile operating table and equally divide it into centrifuge tubes, load it into the centrifuge in a symmetric form, centrifuge at a rate of 4000 r / min for 8 min. After removing the supernatant, add an equal volume of deionized water to resuspend it respectively, centrifuge again and then resuspend it, dilute it with deionized water, and prepare a Bacillus pasteurii bacterial liquid with an OD of 0.25 with the help of an ultraviolet spectrophotometer.

[0063] S704, Add the recycled fine powder prepared above, 20 g / L of urea, and 1.0 g / L of biochar formed by pyrolysis at 800 °C according to a solid-liquid ratio of 1:3, and place it in a magnetic stirrer to react for 48 h.

[0064] S705, Filter the recycled fine powder after the above treatment, dry it at 60 °C to constant weight, and obtain the solid waste admixture after sufficient dispersion.

[0065] The application of the solid waste admixture prepared in this example in the preparation of cement slurry blocks, comprising the following steps: Mix the obtained solid waste admixture and PO42.5 cement evenly at a mass ratio of 5:95. Then, add water at a water-cement ratio of 0.35, stir slowly for 120 s, stop for 15 s, and finally stir for 120 s. After taking out, put it into a mold with its inner surface coated with lubricating oil. After full compaction, scrape off the excess slurry on the surface, place it in a curing box at a temperature of 20 °C and a humidity of 95%. After curing for 24 h, demold it, and then place it in the curing box again for curing for 3 d, 7 d, and 28 d respectively, and take it out for testing the compressive strength of the composite slurry block.

[0066] Comparative Example 1 Add water to PO42.5 cement at a water-cement ratio of 0.35, stir slowly for 120 s, stop for 15 s, and finally stir for 120 s. After taking out, put it into a 20 mm×20 mm×20 mm mold with its inner surface coated with lubricating oil. After full compaction, scrape off the excess slurry on the surface, place it in a curing box at a temperature of 20 °C and a humidity of 95%. After curing for 24 h, demold it, and then place it in the curing box again for curing for 3 d, 7 d, and 28 d respectively, and take it out for testing the compressive strength of the pure cement paste.

[0067] Comparative Example 2 Mix the recycled fine powder and PO42.5 cement evenly at a mass ratio of 5:95. Then, add water at a water-cement ratio of 0.35, stir slowly for 120 s, stop for 15 s, and finally stir for 120 s. After taking out, put it into a 20 mm×20 mm×20 mm mold with its inner surface coated with lubricating oil. After full compaction, scrape off the excess slurry on the surface, place it in a curing box at a temperature of 20 °C and a humidity of 99%. After curing for 24 h, demold it, and then place it in the curing box again for curing for 3 d, 7 d, and 28 d respectively, and take it out for testing the compressive strength of the composite cement slurry block.

[0068] Comparative Example 3 In this comparative example, the preparation method of the recycled fine powder used and its use as an admixture are the same as those in Comparative Example 2; in the preparation of the composite slurry block, the recycled fine powder and PO42.5 cement are mixed evenly at a mass ratio of 10:90, and the remaining steps are the same as those in Example 2.

[0069] Comparative Example 4 In this comparative example, the preparation method of the recycled fine powder used and its use as an admixture are the same as those in Comparative Example 2; in the preparation of the composite slurry block, the recycled fine powder and PO42.5 cement are mixed evenly at a mass ratio of 15:85, and the remaining steps are the same as those in Example 2.

[0070] Comparative Example 5 In this comparative example, the preparation method of the recycled fine powder used and its use as an admixture are the same as those in Comparative Example 2; in the preparation of the composite slurry block, the recycled fine powder and PO42.5 cement are mixed evenly at a mass ratio of 20:80, and the remaining steps are the same as those in Example 2.

[0071] Comparative Example 6 The preparation method of recycled fine powder used in this comparative example and its use as a blending material are the same as those in Comparative Example 2; in the preparation of the composite paste block, the recycled fine powder and PO42.5 cement are mixed evenly at a mass ratio of 30:70, and the remaining steps are the same as those in Example 2.

[0072] Compressive strength tests were carried out on the cement paste specimens prepared in Examples 1 to 5 and Comparative Examples 1 to 6 at 3 days, 7 days, and 28 days during the second curing. The compressive strength tests were carried out in accordance with the cement paste strength inspection method GB / T 17671-2021 (ISO method), and the results are shown in Table 1.

[0073] Table 1: Compressive strength of cement paste specimens at each age in Examples and Comparative Examples

[0074] Comparing Examples 1 to 5 and Comparative Examples 2 to 6, the recycled fine powder treated by microorganisms as a blending material has higher compressive strength at each blending amount and each age than the recycled fine powder blending material without microorganism treatment, and the strength increase is obvious at 7 days and 28 days. Taking Example 4 as an example, that is, the ratio of cement to solid waste blending material is 80:20. Compared with Comparative Example 4, that is, the blending amount of recycled fine powder is 20%, the strength increase at 7 days reaches 13.14%, and the strength increase at 28 days reaches 11.46%.

[0075] Among Comparative Examples 1 to 6, compared with pure cement paste blocks, since the recycled fine powder has been completely hydrated and hardly participates in the hydration reaction during the cement curing process, the dilution effect brought by the introduction of recycled fine powder reduces the compressive strength of the cement paste block. Due to the stable calcium hydroxide and calcium silicate hydrate components in the recycled fine powder, it is not conducive to the later strength development of the cement paste block, and the strength decreases significantly at a large blending amount. Taking Comparative Example 6 as an example, that is, the ratio of cement to recycled fine powder is 70:30, the 3-day compressive strength decreases by 37.96%, the 7-day compressive strength decreases by 32.63%, and the 28-day strength decreases by 24.30%.

[0076] Comparing Example 1 and Example 6, it can be seen that when the urea concentration reaches 30 g / L, the compressive strength of the composite cement block at each age decreases slightly. An appropriate urea concentration is beneficial to ensuring the microbial activity and the decomposition ability of urea, and has high potential for the formation of bio-calcium carbonate in recycled fine powder by microorganisms.

[0077] Comparing Example 1 and Example 7, it can be seen that when the biochar content reaches 1.0 g / L, the strength of the composite cement block at each age decreases. Due to the release of toxic substances from biochar during high-temperature calcination, adding a higher content of biochar has a negative impact on microbial activity. Adding 0.5 g / L of biochar is more conducive to promoting the increase of calcium carbonate content in recycled fine powder, so that the solid waste blending material has excellent application performance.

[0078] Microorganisms contribute to the modification of recycled fine powder through the mechanism of catalyzing urea hydrolysis and inducing carbonate precipitation. From Figure 1 It can be seen that abundant calcium carbonate is generated on the surface of the recycled fine powder after microbial treatment, and the roughness of the recycled fine powder increases significantly. The general size of these calcium carbonate crystals is in the nanometer or micrometer range (<5μm), which can effectively fill pores, refine pore sizes, and contribute to enhancing the hydration of silicate minerals in cement. At the same time, micrometer- and nanometer-sized calcium carbonate can react with aluminate in cement to form calcium carboaluminate, thereby increasing the volume of hydration products and optimizing the pore structure of the paste block, and further improving the mechanical properties of the cement-based material. The compressive strength is significantly higher than that of the comparative example. Taking Example 2 as an example, that is, the ratio of cement to solid waste admixture is 90:10, the 3d compressive strength is 33.58 MPa, the 7d compressive strength is 62.12 MPa, and the 28d compressive strength is 79.88 MPa, which is much higher than that of Comparative Example 3, and the 7d and 28d compressive strengths are close to those of Comparative Example 1, that is, adding 10% solid waste admixture can reach the same strength as the reference cement paste in the later stage of curing.

[0079] In this article, specific examples are used to elaborate on the principle and implementation mode of the present invention. The description of the above examples is only used to help understand the method and its core idea of the present invention, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in the technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements approximately the same as the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for preparing solid waste admixture based on microbial treatment of regenerated micropowder, characterized in that: include: Process waste concrete to obtain recycled micro powder; Cultivate Bacillus pasteurianus and prepare bacterial solution with target OD value; The regenerated micropowder and bacterial solution are mixed at a certain solid-liquid ratio, urea and biochar are added, and the mixture is reacted in a magnetic stirrer for a set time to obtain modified regenerated micropowder; The modified regenerated micro powder is taken out for filtration, dried to constant weight and then fully dispersed to obtain a solid waste admixture.

2. The method for preparing solid waste admixture based on microbial treatment of regenerated micropowder according to claim 1, characterized in that: The method of treating waste concrete to obtain recycled micro powder comprises: Crushing and screening the waste cement slurry blocks to obtain initial particles; The initial particles are ball milled to obtain regenerated micro powder.

3. The method for preparing solid waste admixture based on microbial treatment of regenerated micropowder according to claim 1, characterized in that: The method of culturing Bacillus pasteurianus and preparing a bacterial solution with a target OD value comprises: Prepare Bacillus pasteurianus culture solution; Thawing Bacillus pasteurianus and inoculating it into the culture solution, and placing it in a shaking incubator for shaking culture to obtain the culture solution containing bacteria; Centrifuge the bacterial culture solution to obtain bacterial precipitate; Deionized water was added to resuspend the bacterial pellet and the bacterial solution with the target OD value was diluted.

4. The method for preparing solid waste admixture based on microbial treatment of regenerated micropowder according to claim 3, characterized in that: The preparation of the Bacillus pasteurianus culture solution comprises the steps of using sodium chloride, soy peptone, beef extract and deionized water to prepare the Bacillus pasteurianus culture solution.

5. The method for preparing solid waste admixture based on microbial treatment of regenerated micropowder according to claim 4, characterized in that: The sodium chloride concentration is 3-8 g / L, the soy peptone concentration is 5-15 g / L, and the beef extract concentration is 1-5 g / L.

6. The method for preparing solid waste admixture based on microbial treatment of regenerated micropowder according to claim 3, characterized in that: The method comprises the steps of thawing the Bacillus pasteurianus, inoculating the culture solution in a sterile environment, and placing the culture solution in a shaking incubator for shaking culture for 18 to 24 hours to obtain the culture solution containing bacteria.

7. The method for preparing solid waste admixture based on microbial treatment of regenerated micropowder according to claim 3, characterized in that: Deionized water is added to resuspend the bacterial precipitate, and the bacterial solution is diluted to obtain a target OD value, wherein the target OD value is OD0.05-OD0.

25.

8. The method for preparing solid waste admixture based on microbial treatment of regenerated micropowder according to claim 3, characterized in that: The bacterial culture solution is centrifuged to obtain a bacterial precipitate, wherein the centrifugal speed is 3000-6000 r / min and the centrifugal time is 8-16 min.

9. The method for preparing solid waste admixture based on microbial treatment of regenerated micropowder according to claim 1, characterized in that: The regenerated micropowder and the bacterial solution are mixed at a certain solid-liquid ratio, urea and biochar are added, and the reaction is performed in a shaking incubator for a set time to obtain the modified regenerated micropowder, including mixing the regenerated micropowder and the bacterial solution at a solid-liquid ratio of 1.0-3.0, adding urea with a concentration of 15-30 g / L and biochar with a concentration of 0.1-1.5 g / L, and reacting in a magnetic stirrer for three days.

10. The solid waste admixture prepared by the preparation method according to any one of claims 1 to 9, and the concrete prepared using the solid waste admixture.

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