Low-carbon high-strength building material based on microbial confined mineralization and preparation method thereof

Abstract

The application belongs to the field of cement-free low-carbon high-strength building materials, and specifically comprises a low-carbon high-strength building material based on microbial confined mineralization and a preparation method thereof. The preparation method comprises the following steps: S1, dispersing microbial bacteria bodies with a mineralization liquid containing urea and mineral salt to obtain a dispersion liquid; S2, mixing starch and water, and heating to gelatinize to obtain starch gel; S3, mixing the starch gel, the dispersion liquid and solid particles in proportion, inducing starch gel to trigger gel-sol reversible conversion through stirring, making the microbial bacteria bodies uniformly confined in the gel network during the gel-sol reversible conversion, and then loading into a mold and placing for a period of time, demolding, and the low-carbon high-strength building material is obtained. The whole preparation process does not need to use traditional cement, reduces carbon emission and energy consumption, and the compressive strength of the prepared low-carbon high-strength building material can reach 10-27 MPa, meeting the strength requirements of MU10-MU25 in the strength grade of sintered common bricks in the national standard GB / T 5101-2017.

Description

Technical Field

[0001] This invention belongs to the field of cement-free, low-carbon, and high-strength building materials, specifically including a low-carbon, high-strength building material based on microbial confined mineralization and its preparation method. Background Technology

[0002] Since the beginning of the 21st century, the global urbanization process has continued to accelerate, leading to a rigid increase in market demand for building materials in the construction industry. While traditional cement-based building materials possess excellent mechanical properties, low production costs, and wide engineering adaptability, their large-scale application is accompanied by serious resource and environmental problems, becoming a core constraint on the construction industry's goals. Long-term over-exploitation has led to the rapid depletion of global natural river sand resources, causing a series of environmental problems such as river ecological damage and frequent geological disasters. Furthermore, large quantities of unconventional particulate materials globally, such as desert sand, sea sand, metallurgical slag, and recycled construction waste aggregates, cannot be utilized on a large scale and at high value in traditional cement-based building material systems due to their poor interfacial properties and difficulty in bonding. Their large-scale stockpiling not only occupies land resources but also causes serious secondary environmental pollution.

[0003] To reduce energy consumption and carbon emissions in the construction industry and promote the high-value utilization of unconventional particulate materials, microbial-induced calcium carbonate precipitation (MICP) mineralization technology under ambient temperature and pressure conditions has attracted widespread attention from researchers both domestically and internationally in the field of low-carbon building materials. This technology can generate a calcium carbonate mineral phase with cementing properties through the metabolic activities of functional microorganisms, achieving the consolidation and shaping of various particulate materials. The production process does not require high-temperature calcination, and carbon emissions are reduced by more than 80% compared to traditional cement-based building materials. It is also suitable for various unconventional aggregates that are difficult to utilize using traditional processes, such as desert sand and industrial solid waste, offering significant ecological and economic benefits. It is one of the most promising technological directions for industrialization in the current field of low-carbon building materials.

[0004] However, existing MIP mineralization technology still faces significant core technological bottlenecks in the large-scale preparation and engineering application of granular cemented building materials. In most existing technologies, the functional microorganisms are not effectively immobilized. The microorganisms are freely dispersed in the mineralization reaction system, migrating and diffusing freely with the liquid phase during mineralization liquid circulation and immersion. This prevents directional and localized enrichment and immobilization at the cementing interface between solid particles, resulting in uncontrollable calcium carbonate deposition sites, uneven deposition distribution, and the inability to form a continuous, dense, high-strength cemented structure between particles. Consequently, the mineralization reaction efficiency and cementing effect are significantly reduced, and the mechanical properties of the final building materials are far lower than traditional standard building materials, failing to meet the application requirements of construction engineering. Furthermore, due to the free diffusion of microorganisms and the uncontrollable mineralization reaction process, existing technologies must rely on a closed mold to constrain the reaction system and aggregate molding throughout the entire process to achieve granular material cementation. This makes it unsuitable for industrial continuous production processes, resulting in low production efficiency, poor molding flexibility, and high costs for large-scale production, severely hindering the industrialization and large-scale engineering application of this technology. In addition, although some existing technologies attempt to achieve cell fixation through adsorption on organic or inorganic carriers, they generally suffer from problems such as poor compatibility between the carrier and the aggregate interface, low cell loading rate, and easy detachment and loss, and still cannot fundamentally solve the above-mentioned core bottlenecks.

[0005] Therefore, developing a low-carbon particulate cementitious building material preparation strategy that can achieve efficient confined mineralization by functional microorganisms while taking into account the excellent mechanical properties, significant ecological benefits, and feasibility of industrial-scale production is of vital theoretical significance and engineering application value for promoting the industrialization of microbial mineralized low-carbon building materials and helping the construction industry achieve its green and low-carbon transformation goals. Summary of the Invention

[0006] In view of the problems existing in the prior art, one object of the present invention is to provide a method for preparing a low-carbon, high-strength building material based on microbial confined mineralization. Utilizing the gel-sol transition characteristics of starch gel, a three-dimensional starch network confining system that can be precisely positioned between solid particles is constructed, and functional microbial cells are stably confined and fixed at the cementing interface between solid particles. This fundamentally solves the core bottleneck of uncontrolled microbial migration and mineralization sites, improving the cementing efficiency and bonding strength between solid particles. Furthermore, the preparation process does not require the use of traditional cement, reducing carbon emissions and energy consumption. Based on the above method, a cement-free building material with excellent mechanical properties, significant low-carbon and environmental benefits, and feasibility for industrial-scale production is obtained.

[0007] Another objective of this invention is to provide a low-carbon, high-strength building material based on microbial confined mineralization, prepared using the method described above. This low-carbon, high-strength building material exhibits a compressive strength of 10-27 MPa, meeting the strength requirements of MU10-MU25 in the national standard GB / T 5101-2017 for sintered common bricks.

[0008] To achieve the first objective mentioned above, the technical solution adopted by the present invention includes:

[0009] This invention discloses a method for preparing low-carbon, high-strength building materials based on microbial confined mineralization, comprising the following steps:

[0010] S1. Disperse the microbial cells with a mineralized solution containing urea and mineral salts to obtain a dispersion.

[0011] S2. Mix starch with water and heat to gelatinize to obtain starch gel;

[0012] S3. Mix starch gel, dispersion and solid particles in proportion. Induce the starch gel to trigger reversible gel-sol transition by stirring. The above operation makes the starch gel evenly distributed between the solid particles and acts as an adhesive. On the other hand, the microbial cells are uniformly confined in the starch gel network during the reversible gel-sol transition. After stirring is stopped, it will gradually return to the gel state. Then, put it into a mold and let it stand for a period of time. Demold it to obtain a low-carbon high-strength building material based on microbial confined mineralization.

[0013] To address the numerous problems existing in the preparation of low-carbon building materials using existing microbial induced calcium carbonate precipitation (MICP) mineralization technology, this invention provides a method for preparing cement-free, low-carbon, high-strength building materials based on microbial confined mineralization technology. The core of this method relies on the unique shear-induced gel-sol transition characteristics of starch gel to construct a three-dimensional starch network confined system. Upon introduction of shear force, the starch gel undergoes a transformation from a gel state to a sol state. This transformation enhances the uniformity of microbial cells within the system and causes a state change in the starch gel, further improving the uniformity of microbial cells within the starch network. After the shear force is removed, the system gradually returns to a gel state, and the microbial cells are now stably confined within the starch gel network, unable to migrate or diffuse freely. This precise positioning and control improves the controllability of mineralization sites. Simultaneously, utilizing the excellent anti-swelling properties of starch hydrogel, the microbial-loaded granular mixture can be stably molded without mold constraints. In-situ mineralization then forms continuous, dense, high-strength mineral bridges between solid particles, significantly improving the bonding efficiency and adhesion strength between particles.

[0014] Furthermore, the mineral salt is selected from one or more of calcium chloride, calcium nitrate, calcium lactate, magnesium chloride, and magnesium nitrate.

[0015] Furthermore, the starch is derived from one or more of corn starch, potato starch, tapioca starch, and wheat starch.

[0016] Furthermore, the microbial cells are all selected from microorganisms with urease-producing function, including but not limited to one or more of Bacillus pasteurellii, Bacillus spheroidae, Bacillus licheniformis, Bacillus cereus, Bacillus subtilis, and Bacillus megaterium.

[0017] Furthermore, the solid particles are selected from one or more of the following: quartz sand, sea sand, gold sand, pearl sand, desert sand, and industrial waste particles.

[0018] Furthermore, the molar ratio of urea to mineral salt is 1:2 to 2:1; for example, the molar ratio of urea to mineral salt can be 1:1, 1:1.5, 1:2, 1.5:1, 1.5:2, 2:1, 2:1.5, etc.

[0019] Furthermore, the concentration of microbial cells in the dispersion was 5 × 10⁻⁶. 7 ~5×10 8 CFU / mL.

[0020] Furthermore, the concentration of urea in the dispersion is 0.25~2.5 M; for example, the concentration of urea in the dispersion can be 0.25 M, 0.5 M, 0.75 M, 1 M, 1.25 M, 1.5 M, 1.75 M, 2 M, 2.25 M, 2.5 M, etc.

[0021] Furthermore, the concentration of mineral salts in the dispersion is 0.25~2.5 M; for example, the concentration of mineral salts in the dispersion can be 0.25 M, 0.5 M, 0.75 M, 1 M, 1.25 M, 1.5 M, 1.75 M, 2 M, 2.25 M, 2.5 M, etc.

[0022] Furthermore, the mass ratio of starch to water is 5:95 to 25:75; for example, the mass ratio of starch to water can be 5:95, 7.5:92.5, 10:90, 12.5:87.5, 15:85, 17.5:82.5, 20:80, 22.5:77.5, 25:75, etc.

[0023] Furthermore, in step S2, the stirring time is 0.5~1 h, and the stirring temperature is 80~110 ℃.

[0024] Furthermore, the mass ratio of the starch gel to the dispersion is 1:2 to 2:1; for example, the mass ratio of the starch gel to the dispersion can be 1:1, 1:1.5, 1:2, 1.5:1, 1.5:2, 2:1, 2:1.5, etc.

[0025] Furthermore, the total mass ratio of the starch gel and dispersion to the solid particles is 1:2.5 to 3.5; for example, the total mass ratio of the starch gel and dispersion to the solid particles can be 1:2.5, 1:3, 1:3.5, etc.

[0026] Furthermore, in step S3, the stirring rate is 50~600 rpm and the stirring time is 1~20 min.

[0027] Furthermore, the placement time in the mold in step S3 is 12~24 hours. It should be noted that, in order to reduce moisture evaporation during placement in the mold, a thin film or other components can be placed over the mold opening to retain moisture.

[0028] Furthermore, the mold can be made of silicone, polytetrafluoroethylene, or any metal or non-metal material with an anti-stick coating sprayed on its surface; the mold must be detachable after the material is prepared so that the material can be completely removed.

[0029] After demolding, the preparation method further includes two post-treatment methods: direct drying or immersion in a mineralizing solution containing urea and mineral salts for a certain period of time followed by drying. Whether further immersion in the mineralizing solution is required is adjusted according to the actual situation. Choosing the second post-treatment method can achieve further orientation and efficient mineralization reaction between particles, which is conducive to the formation of denser mineral bridges, thereby further improving the compressive strength of the material. In one specific embodiment, the drying temperature is 50~80 ℃, and the drying time is 1~3 days. In addition, the immersion in the mineralizing solution for mineralization is 1~14 days.

[0030] Furthermore, step S1 also includes a process of pre-culturing the microbial cells:

[0031] The microbial cells are cultured, centrifuged, and the supernatant is discarded to obtain the product.

[0032] The centrifugation speed was 5000 rpm, the centrifugation time was 5~10 min, and the centrifugation temperature was 4~25 ℃.

[0033] To achieve the second objective mentioned above, the technical solution adopted by the present invention includes:

[0034] This invention discloses a low-carbon, high-strength building material based on microbial confined mineralization, prepared using the preparation method described above.

[0035] The compressive strength of the low-carbon, high-strength building material is 10~27 MPa.

[0036] Beneficial effects of this invention:

[0037] Compared with the closest existing microbial mineralization building material technology and traditional cement-based building materials, this invention has the following significant beneficial effects and technical advantages:

[0038] 1. The particle interface microbial confined mineralization system of the present invention fundamentally overcomes the core bottlenecks of low mineralization efficiency and poor mechanical properties in existing technologies, thereby achieving a leap in the strength of building materials:

[0039] This invention leverages the shear-induced gel-sol transition properties of starch gel to construct a confined mineralization system at the solid particle interface. During aggregate mixing, shearing causes the starch gel to transform into a sol state, enabling uniform dispersion of functional microorganisms within the aggregate system. After the shearing effect disappears, the starch system rapidly forms a three-dimensional network structure in situ, stably confining and fixing the functional microorganisms within the interfacial spaces between solid particles. This creates numerous localized, in-situ mineralization micro-reaction units, fundamentally preventing the migration and loss of microorganisms during mineralization. This confined system ensures that the mineralization reaction occurs precisely at the core cementation sites of the particles, directionally generating continuous, dense, and high-strength mineral bridges. This solves the industry pain points of uncontrollable mineralization sites and discontinuous cementation structures in existing technologies, significantly improving the cementation efficiency and bonding strength between particles. Experiments have verified that the compressive strength of the cement-free low-carbon building material prepared by this invention can reach up to 27 MPa, which is significantly higher than that of the existing mainstream cement-free microbial mineralized building materials. It meets the strength requirements of MU25 in GB / T 5101-2017 "Sintered Common Bricks" and can replace traditional sintered bricks and cement-based blocks for main building projects. This breaks through the long-standing industry deadlock of microbial mineralized building materials being low in carbon but lacking in strength and unable to be applied in engineering.

[0040] 2. Break through the industry constraints of mold dependence and achieve compatibility between controllable mineralization processes and industrial-scale production:

[0041] This invention completely eliminates the reliance on molds through the synergistic effect of a starch gel confinement system and its anti-swelling properties. On the one hand, the aforementioned confinement system enables full control of the mineralization reaction, fundamentally solving the problem of microbial cell diffusion and loss. On the other hand, the starch gel endows the aggregate mixture with excellent shape retention and anti-swelling properties, allowing the mixture to stably maintain the preset component shape and structural integrity without any mold support, and can be directly immersed in the mineralization solution to complete the entire mineralization reaction process. This technical solution brings two core advantages: First, it eliminates the obstruction of mass transfer of the mineralization solution by the mold, significantly improving the uniformity and efficiency of the mineralization reaction and shortening the production cycle; second, it can be directly adapted to the existing industrial continuous production processes such as continuous extrusion and compression molding in the building materials industry, without the need for customized special molds and production lines, breaking through the core bottleneck of existing technologies that cannot be mass-produced, and laying a core foundation for the industrialization of microbial mineralized low-carbon building materials.

[0042] 3. The entire process is cement-free and low-carbon, combining extreme environmental benefits with resource recycling value:

[0043] This invention utilizes a low-temperature, atmospheric-pressure process throughout, completely eliminating the use of traditional high-carbon-emission cementitious materials such as cement and lime. This reduces carbon emissions by over 80% compared to traditional cement-based building material production, achieving low-carbon production of building materials from the source. Furthermore, the confined mineralization system of this invention has no strict limitations on aggregate types, perfectly adapting to various unconventional particulate materials that are difficult to utilize using traditional processes, such as desert sand, sea sand, metallurgical slag, and recycled aggregates from construction waste. This breaks through the high dependence of traditional building materials on natural river sand, realizing the large-scale, high-value utilization of industrial solid waste and unconventional resources. It possesses significant carbon reduction benefits, ecological protection benefits, and resource recycling value, perfectly aligning with national strategies and the policy orientation of resource recycling.

[0044] 4. Raw materials are widely available, the process is simple and controllable, it is highly compatible with existing building material production systems, and the cost of engineering promotion is low:

[0045] The starch gel system used in this invention uses natural, renewable starch as raw material, which is widely available, inexpensive, and biocompatible. It requires no complex chemical modification and achieves reversible gel-sol transformation simply through temperature control and physical shearing, without any negative impact on the mineralization activity of functional microorganisms. The entire preparation process is a continuous one-step molding process, which is simple to operate and has controllable parameters. It can be directly adapted to conventional production equipment in the existing building materials industry without the need for large-scale production line modification. The cost of engineering application and promotion is extremely low, and it can be quickly industrialized. It is suitable for various application scenarios such as civil buildings, municipal engineering, slope protection, and ecological restoration, and has strong market competitiveness and engineering practical value. Attached Figure Description

[0046] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0047] Figure 1 Electron micrographs of the state of bacteria in the conventional biomineralization system (a) of Comparative Example 1 and the starch-confined biomineralization system (b) of Example 1.

[0048] Figure 2 Fluorescence micrographs of the motility of bacteria in the conventional biomineralization system (a) of Comparative Example 1 and the starch-confined biomineralization system (b) of Example 1.

[0049] Figure 3 Electron micrographs showing the mineral distribution between sand grains in the conventional biomineralization system (a) of Comparative Example 1 and the starch-confined microbial mineralization system (b) of Example 1.

[0050] Figure 4 Stress-strain curves of the samples prepared in Examples 1-5.

[0051] Figure 5 The stress-strain curves of the samples prepared for comparative examples 1-5. Detailed Implementation

[0052] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further clarifies the invention. It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0053] Example 1

[0054] 1) Add the *Bacillus pasteurellii* strain to the culture medium and incubate at 30 °C and 200 rpm for 60 h to obtain a bacterial concentration of approximately 3.5 × 10⁻⁶. 8 CFU / mL bacterial culture medium;

[0055] 2) Prepare a mineralization solution with a urea molar concentration of 2 M by mixing urea and calcium chloride at a molar ratio of 1:1;

[0056] 3) Take an appropriate amount of bacterial culture medium into a centrifuge tube, centrifuge at 5000 rpm and 4 ℃ for 10 min, discard the supernatant, resuspend the bacteria with mineralizing solution to obtain 2×10⁻⁶ cells / mL. 8 A dispersion of CFU / mL;

[0057] 4) Mix starch granules with water, mechanically stir at 110 °C for 1 h and then cool to obtain starch gel, wherein the mass ratio of starch granules to water is 15:85.

[0058] 5) Mix starch gel with dispersion and quartz sand in a mass ratio of 1:1:6 and stir at 300 rpm for 5 min. Stirring induces the starch gel to transition from gel state to sol state. Then fill the well-stirred mixture into a double-hole polytetrafluoroethylene mold and cover the mold opening with sealing film for 24 h.

[0059] 6) Demolding, removing the mixture, immersing it in the mineralization solution in step 2) for mineralization for 14 days, and then removing it. The mixture can maintain a stable shape without mold support after mineralization in the mineralization solution. After drying at 60 ℃ for 2 days, a low-carbon high-strength building material prepared based on microbial confined mineralization is obtained.

[0060] In this invention, solid particles are mixed with bacterial dispersion and starch gel. The shear-induced gel-sol transition property of the starch gel is utilized to apply shear force, causing the microbial cells to uniformly integrate into the starch sol. After the shear force is removed, the mixture gradually returns to a gel state, at which point the microbial cells are stably confined within the starch gel network (see [link to invention]). Figure 1 (b) can no longer undergo free migration and diffusion (see also b) Figure 2 (b) Simultaneously, utilizing the excellent anti-swelling properties of starch hydrogel, the granular mixture loaded with microbial cells can be immersed in the mineralization solution for a full biomineralization reaction without relying on mold constraints. Through this precise positioning control, minerals are generated around the bacteria and adhere to the starch network, forming continuous, dense, and high-strength mineral bridges between solid particles, significantly improving the bonding efficiency and adhesion strength between particles (see [reference]). Figure 3 (b)

[0061] The obtained low-carbon, high-strength building material was subjected to compression testing, and the resulting stress-strain curves are shown below. Figure 4 The compressive strength is 19.4 MPa, and the elastic modulus is 978.1 MPa. If it is dried directly without immersion in the mineralizing solution, the compressive strength will be slightly lower, with a tested compressive strength of 12.2 MPa and an elastic modulus of 520.2 MPa. It meets the application requirements in certain fields (such as load-bearing walls of 1-3 story low-rise civil buildings, masonry mortar for various walls, and sidewalk paving in urban roads without parking needs). Technicians can choose the post-treatment method according to the actual situation.

[0062] Example 2

[0063] 1) Add the *Bacillus pasteurellii* strain to the culture medium and incubate at 30 °C and 200 rpm for 60 h to obtain a bacterial concentration of approximately 3.5 × 10⁻⁶. 8 CFU / mL bacterial culture medium;

[0064] 2) Prepare a mineralization solution with a urea molar concentration of 1.5 M by mixing urea and calcium chloride at a molar ratio of 1:1;

[0065] 3) Take an appropriate amount of bacterial culture medium into a centrifuge tube, centrifuge at 5000 rpm and 4 ℃ for 10 min, discard the supernatant, resuspend the bacteria with mineralizing solution to obtain 2×10⁻⁶ cells / mL. 8 A dispersion of CFU / mL;

[0066] 4) Mix starch granules with water, mechanically stir at 110 °C for 1 h, and then cool to obtain starch gel, wherein the mass ratio of starch granules to water is 15:85.

[0067] 5) Mix starch gel with dispersion and quartz sand in a mass ratio of 1:1:6 and stir at 300 rpm for 5 min. Stirring induces the starch gel to transition from gel state to sol state. Then fill the well-stirred mixture into a double-hole polytetrafluoroethylene mold and cover the mold opening with sealing film for 24 h.

[0068] 6) Demold the mixture, remove it, and immerse it in the mineralization solution from step 2) for 14 days. The mixture retains a stable shape even without mold support during mineralization in the solution. After drying at 60°C for 2 days, a low-carbon, high-strength building material prepared based on microbial confined mineralization is obtained. Compression testing is performed, and the stress-strain curves are shown below. Figure 4 The compressive strength is 15.2 MPa and the elastic modulus is 1004.7 MPa. If it is dried directly without immersion in the mineralizing solution, the compressive strength will be slightly lower, at 12.2 MPa and the elastic modulus will be 653.91 MPa.

[0069] Example 3

[0070] 1) Add the *Bacillus pasteurellii* strain to the culture medium and incubate at 30 °C and 200 rpm for 60 h to obtain a bacterial concentration of approximately 3.5 × 10⁻⁶. 8 CFU / mL bacterial culture medium;

[0071] 2) Prepare a mineralization solution with a urea molar concentration of 0.5 M by mixing urea and calcium chloride at a molar ratio of 1:1;

[0072] 3) Take an appropriate amount of bacterial culture medium into a centrifuge tube, centrifuge at 5000 rpm and 4 ℃ for 10 min, discard the supernatant, resuspend the bacteria in mineralizing solution, and obtain 5×10⁶ cells / mL. 7 A dispersion of CFU / mL;

[0073] 4) Mix starch granules with water and mechanically stir at 110 °C for 1 h to obtain starch gel, wherein the mass ratio of starch granules to water is 22.5:77.5;

[0074] 5) Mix starch gel with dispersion and quartz sand in a mass ratio of 1:1:6 and stir at 300 rpm for 5 min. Stirring induces the starch gel to transition from gel state to sol state. Then fill the well-stirred mixture into a double-hole polytetrafluoroethylene mold and cover the mold opening with sealing film for 24 h.

[0075] 6) Demold the mixture, remove it, and immerse it in the mineralization solution from step 2) for 14 days. The mixture retains a stable shape even without mold support during mineralization in the solution. After drying at 60°C for 2 days, a low-carbon, high-strength building material prepared based on microbial confined mineralization is obtained. Compression testing is performed, and the stress-strain curves are shown below. Figure 4 The compressive strength is 16.0 MPa and the elastic modulus is 653.9 MPa. If it is dried directly without immersion in the mineralizing solution, the compressive strength will be slightly lower, at 10.8 MPa and the elastic modulus will be 406.2 MPa.

[0076] Example 4

[0077] 1) Add the *Bacillus pasteurellii* strain to the culture medium and incubate at 30 °C and 200 rpm for 60 h to obtain a bacterial concentration of approximately 3.5 × 10⁻⁶. 8 CFU / mL bacterial culture medium;

[0078] 2) Prepare a mineralization solution with a urea molar concentration of 2 M by mixing urea and calcium chloride at a molar ratio of 1:1;

[0079] 3) Take an appropriate amount of bacterial culture medium into a centrifuge tube, centrifuge at 5000 rpm and 4 ℃ for 10 min, discard the supernatant, resuspend the bacteria with mineralizing solution to obtain 2×10⁻⁶ cells / mL. 8 A dispersion of CFU / mL;

[0080] 4) Mix starch granules with water and mechanically stir at 110 °C for 1 h to obtain starch gel, wherein the mass ratio of starch granules to water is 15:85.

[0081] 5) Mix starch gel with dispersion and desert sand in a mass ratio of 1:1:6 and stir at 300 rpm for 5 min. Stirring induces the starch gel to transition from gel state to sol state. Then fill the well-stirred mixture into a double-hole polytetrafluoroethylene mold and cover the mold opening with sealing film for 24 h.

[0082] 6) Demold the mixture, remove it, and immerse it in the mineralization solution from step 2) for 14 days. The mixture retains a stable shape even without mold support during mineralization in the solution. After drying at 60°C for 2 days, a low-carbon, high-strength building material prepared based on microbial confined mineralization is obtained. Compression testing is performed, and the stress-strain curves are shown below. Figure 4 It has a compressive strength of 26.7 MPa and an elastic modulus of 1412.3 MPa.

[0083] Example 5

[0084] 1) Add the *Bacillus pasteurellii* strain to the culture medium and incubate at 30 °C and 200 rpm for 60 h to obtain a bacterial concentration of approximately 3.5 × 10⁻⁶. 8 CFU / mL bacterial culture medium;

[0085] 2) Prepare an aqueous solution with a urea molar concentration of 1.75 M by mixing urea and calcium chloride at a molar ratio of 1:1;

[0086] 3) Take an appropriate amount of bacterial culture medium into a centrifuge tube, centrifuge at 5000 rpm and 4 ℃ for 10 min, discard the supernatant, resuspend the bacteria with mineralizing solution to obtain 2×10⁻⁶ cells / mL. 8 A dispersion of CFU / mL;

[0087] 4) Mix starch granules with water, mechanically stir at 110 °C for 1 h, and then cool to obtain starch gel, wherein the mass ratio of starch granules to water is 17.5:82.5;

[0088] 5) Mix the starch gel with the dispersion and the coal slag in a mass ratio of 2:1:7.5 and stir at 300 rpm for 5 min. Stirring induces the starch gel to transition from gel state to sol state. Then fill the well-stirred mixture into a double-hole polytetrafluoroethylene mold and cover the mold opening with a sealing film for 24 h.

[0089] 6) Demold the mixture, remove it, and dry it at 60 ℃ for 1 day to obtain low-carbon, high-strength building materials prepared based on microbial confined mineralization. Perform compression tests and obtain the stress-strain curves under compression. Figure 4 It has a compressive strength of 13.4 MPa and an elastic modulus of 452.9 MPa.

[0090] Comparative Example 1

[0091] 1) Add the *Bacillus pasteurellii* strain to the culture medium and incubate at 30 °C and 200 rpm for 60 h to obtain a bacterial concentration of approximately 3.5 × 10⁻⁶. 8 CFU / mL bacterial culture medium;

[0092] 2) Prepare a mineralization solution with a urea molar concentration of 2 M by mixing urea and calcium chloride at a molar ratio of 1:1;

[0093] 3) Take an appropriate amount of bacterial culture medium into a centrifuge tube, centrifuge at 5000 rpm and 4 ℃ for 10 min, discard the supernatant, resuspend the bacteria with mineralizing solution to obtain 2×10⁻⁶ cells / mL. 8 A dispersion of CFU / mL;

[0094] 4) Mix the dispersion and quartz sand at a mass ratio of 1:6, stir at 300 rpm for 5 min, then fill the well-stirred mixture into a double-ended polytetrafluoroethylene mold, cover the mold opening with sealing film and let it stand for 24 h.

[0095] 5) Since the mixture in step 4) will disintegrate when placed in water, the mixture, along with the mold, was immersed in the mineralization solution in step 2) for 14 days. After removal, it was dried at 60 ℃ for 3 days to obtain building materials prepared by ordinary microbial mineralization. Compression tests were then performed, and the stress-strain curves under compression are shown in the figure. Figure 5 It has a compressive strength of 4.3 MPa and an elastic modulus of 162.5 MPa.

[0096] Because no starch gel is introduced into the system, it is impossible to control the stable confinement domain of microbial cells (see [link]). Figure 1 (a) is highly susceptible to free migration and diffusion (see [reference]). Figure 2 (a), and fewer mineral bridges are formed (see also) Figure 3 (a) affects the bonding strength between particles.

[0097] Comparative Example 2

[0098] 1) Mix starch granules with water and mechanically stir at 110 °C for 1 h to obtain starch gel, wherein the mass ratio of starch granules to water is 15:85.

[0099] 2) Mix starch gel and quartz sand at a mass ratio of 1:6 and stir at 300 rpm for 5 min. Stirring induces the starch to transition from gel state to sol state. Then fill the well-stirred mixture into a double-hole polytetrafluoroethylene mold and cover the mold opening with sealing film for 24 h.

[0100] 3) Demold the mixture, remove it, and dry it at 60 ℃ for 1 day to obtain a starch-based adhesive building material. Perform a compression test and obtain the stress-strain curve under compression. Figure 5 It has a compressive strength of 5.4 MPa and an elastic modulus of 280.6 MPa.

[0101] Comparative Example 3

[0102] 1) Add the *Bacillus pasteurellii* strain to the culture medium and incubate at 30 °C and 200 rpm for 60 h to obtain a bacterial concentration of approximately 3.5 × 10⁻⁶. 8 CFU / mL bacterial culture medium;

[0103] 2) Prepare a mineralization solution with a urea molar concentration of 2 M by mixing urea and calcium chloride at a molar ratio of 1:1;

[0104] 3) Take an appropriate amount of bacterial culture medium into a centrifuge tube, centrifuge at 5000 rpm and 4 ℃ for 10 min, discard the supernatant, resuspend the bacteria with mineralizing solution to obtain 2×10⁻⁶ cells / mL. 8 A dispersion of CFU / mL;

[0105] 4) Mix starch granules with water and mechanically stir at room temperature for 1 hour to obtain a starch suspension (because the granules did not dissolve into starch gel), wherein the mass ratio of starch granules to water is 15:85.

[0106] 5) Mix the starch suspension, dispersion and quartz sand in a mass ratio of 1:1:6, stir at 300 rpm for 5 min, then fill the well-stirred mixture into a double-hole polytetrafluoroethylene mold, cover the mold opening with sealing film and let it stand for 24 h.

[0107] 6) Since the starch granules did not gelatinize and transform into a gel state, the interaction force between them and the solid particles was poor. Therefore, the mixture, along with the mold, needed to be immersed in the mineralization solution in step 2) for mineralization for 14 days. After removal, it was dried at 60 ℃ for 2 days to obtain building materials prepared based on starch granule-assisted microbial mineralization. Compression tests were performed, and the stress-strain curves under compression are shown in the figure. Figure 5 It has a compressive strength of 6.2 MPa and an elastic modulus of 241.8 MPa.

[0108] Comparative Example 4

[0109] 1) Add the *Bacillus pasteurellii* strain to the culture medium and incubate at 30 °C and 200 rpm for 60 h to obtain a bacterial concentration of approximately 3.5 × 10⁻⁶. 8 CFU / mL bacterial culture medium;

[0110] 2) Prepare a mineralization solution with a urea molar concentration of 2 M by mixing urea and calcium chloride at a molar ratio of 1:1;

[0111] 3) Take an appropriate amount of bacterial culture medium into a centrifuge tube, centrifuge at 5000 rpm and 4 ℃ for 10 min, discard the supernatant, resuspend the bacteria with mineralizing solution to obtain 2×10⁻⁶ cells / mL. 8 A dispersion of CFU / mL;

[0112] 4) Mix sodium alginate particles with water and mechanically stir at room temperature for 1 hour to obtain sodium alginate solution, wherein the mass ratio of sodium alginate particles to water is 10:90.

[0113] 5) Mix sodium alginate solution, dispersion and quartz sand in a mass ratio of 1:1:6, stir at 300 rpm for 5 min, then fill the well-stirred mixture into a double-ended polytetrafluoroethylene mold, cover the mold opening with sealing film and leave for 24 h.

[0114] 6) Demold the mixture, remove it, and dry it directly at 60 ℃ for 1 day to obtain building materials prepared based on sodium alginate-assisted microbial mineralization. Perform compression tests and obtain the stress-strain curves under compression. Figure 5 The compressive strength is 4.0 MPa and the elastic modulus is 201.5 MPa. If the operation of first immersing in the mineralizing solution and then drying is used to improve the compressive strength, it will be found that the mixture after demolding cannot be stably maintained in the mineralizing solution and its shape will be scattered. Therefore, the strength cannot be further improved, and its use is relatively limited.

[0115] Comparative Example 5

[0116] 1) Add the *Bacillus pasteurellii* strain to the culture medium and incubate at 30 °C and 200 rpm for 60 h to obtain a bacterial concentration of approximately 3.5 × 10⁻⁶. 8 CFU / mL bacterial culture medium;

[0117] 2) Prepare a mineralization solution with a urea molar concentration of 2 M by mixing urea and calcium chloride at a molar ratio of 1:1;

[0118] 3) Take an appropriate amount of bacterial culture medium into a centrifuge tube, centrifuge at 5000 rpm and 4 ℃ for 10 min, discard the supernatant, resuspend the bacteria with mineralizing solution to obtain 2×10⁻⁶ cells / mL. 8 A dispersion of CFU / mL;

[0119] 4) Mix gelatin particles with water and mechanically stir at room temperature for 1 h to obtain a gelatin solution, wherein the mass ratio of gelatin particles to water is 10:90;

[0120] 5) Mix the gelatin solution, dispersion and quartz sand in a mass ratio of 1:1:6, stir at 300 rpm for 5 min, then fill the well-stirred mixture into a double-hole polytetrafluoroethylene mold, cover the mold opening with sealing film and let it stand for 24 h.

[0121] 6) Demold the mixture, remove it, and dry it at 60 ℃ for 1 day to obtain the building material prepared based on gelatin-assisted microbial mineralization. Perform compression tests and obtain the stress-strain curves under compression. Figure 5The compressive strength is 6.3 MPa and the elastic modulus is 121.3 MPa. If the operation of first immersing in the mineralizing solution and then drying is used to improve the compressive strength, it will be found that the mixture after demolding cannot be stably maintained in the mineralizing solution and its shape will be scattered. Therefore, the strength cannot be further improved, and its use is relatively limited.

[0122] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All embodiments falling under the scope of the present invention...

[0123] Obvious variations or modifications derived from the technical solution are still within the scope of protection of this invention.

Claims

1. A method for preparing low-carbon, high-strength building materials based on microbial confined mineralization, characterized in that, Includes the following steps: S1. Disperse the microbial cells with a mineralized solution containing urea and mineral salts to obtain a dispersion. S2. Mix starch with water and heat to gelatinize to obtain starch gel; S3. Mix starch gel, dispersion and solid particles in proportion. Stirring induces starch gel to trigger gel-sol reversible transformation, so that microbial cells are uniformly confined in the gel network during the gel-sol reversible transformation. Then, put it into a mold and let it stand for a period of time before demolding to obtain a low-carbon high-strength building material based on microbial confined mineralization. The molar ratio of urea to mineral salt is 1:2 to 2:1; The concentration of urea in the dispersion is 0.25~2.5 M; The mass ratio of starch to water is 5:95 to 25:75; The mass ratio of the starch gel to the dispersion is 1:2 to 2:1; The total mass ratio of the starch gel and dispersion to the solid particles is 1:2.5~3.

5.

2. The preparation method according to claim 1, characterized in that, The mineral salt is selected from one or more of calcium chloride, calcium nitrate, calcium lactate, magnesium chloride, and magnesium nitrate. The microbial cells are selected from one or more of Bacillus pasteurellii, Bacillus spheroidae, Bacillus licheniformis, Bacillus cereus, Bacillus subtilis, and Bacillus megaterium. The solid particles are selected from one or more of the following: quartz sand, sea sand, gold sand, pearl sand, desert sand, and industrial waste particles.

3. The preparation method according to claim 1, characterized in that, The concentration of microbial cells in the dispersion was 5 × 10⁻⁶. 7 ~5×10 8 CFU / mL.

4. The preparation method according to claim 1, characterized in that, In step S3, the stirring speed is 50~600 rpm and the stirring time is 1~20 min; The placement time in the mold in step S3 is 12~24 h.

5. The preparation method according to claim 1, characterized in that, Step S1 also includes the process of pre-culturing the microbial cells: The microbial cells are cultured, centrifuged, and the supernatant is discarded to obtain the product. The centrifugation speed was 5000 rpm, the centrifugation time was 5~10 min, and the centrifugation temperature was 4~25 ℃.

6. A low-carbon, high-strength building material based on microbial confined mineralization, characterized in that, It was prepared by the preparation method according to any one of claims 1-5; The compressive strength of the low-carbon, high-strength building material is 10~27 MPa.

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