Light-guiding fiber driven microbial mineralization enhanced 3D printed concrete and preparation method thereof

Abstract

This invention discloses a method for preparing 3D-printed concrete enhanced by microbial mineralization driven by optical fibers, belonging to the field of building materials technology. This invention solves the problems of the inability of internal light sources to penetrate 3D-printed concrete, the difficulty in achieving non-destructive repair of interlayer defects, and the anisotropic mechanical properties of the components. This invention prepares a photo-promoted synergistic mineralization microbial agent by adsorbing *Bacillus pseudosturcium* and *Spirulina platensis* into a porous carrier. This agent is then mixed with cement, fine aggregate, 3D printing rheology modifier, calcium lactate, and mixing water. The slurry is formed layer by layer using an extrusion 3D printing process, and optical fibers are embedded to obtain 3D-printed concrete. By transmitting light energy to the deep interface of the concrete through optical fibers, the photosynthesis of *Spirulina platensis* is activated, improving the metabolic environment of *Bacillus pseudosturcium*. Targeted deposition of mineralization products is achieved in interlayer pores, microcracks, and composite interfaces, improving the Z-axis compressive strength and interlayer bond strength of the concrete, and reducing mechanical anisotropy.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, and relates to 3D printed concrete enhanced by microbial mineralization driven by optical fibers and its preparation method. Background Technology

[0002] Extruded 3D printed concrete (3DPC) has become an important development direction in the field of intelligent construction due to its advantages such as no formwork required, high automation, and adaptability to complex geometries. However, its unique layer-by-layer stacking process inevitably introduces the problem of anisotropy in the formed structure. During continuous extrusion, due to the time interval between layer depositions, water migration at the interface, and incomplete fusion of new and old pastes, pore-rich areas and local weak bonding areas are easily formed between adjacent printed layers and adjacent strips within the same layer. These defect-rich interlayer networks not only significantly weaken the interlayer tensile and shear bearing capacity of 3DPC, but also provide preferential transport channels for water and corrosive ions, severely restricting the long-term service durability of 3DPC.

[0003] To address the issue of weak interlayer bonding in 3D PCs, existing technologies often employ physical or chemical modification methods, such as adding internal curing agents, spraying interfacial crosslinking solutions, or implanting micromesh and mechanical staples across layers. However, these methods are insufficient in improving interlayer and interstrip interface adhesion and generally face problems such as increased manufacturing costs, severe interference with automated continuous extrusion processes, or difficulty in seamless integration with existing 3D printing processes.

[0004] In recent years, microbial induced mineralization (MICP) technology has provided a novel approach for adaptive enhancement of 3D PC interfaces. This strategy utilizes microbial metabolism to induce targeted deposition of inorganic minerals such as calcium carbonate to fill defects. However, due to the extremely high opacity of traditional cement-based materials, external light energy has difficulty penetrating the matrix to reach deep interlayer interfaces. This fundamentally inhibits the metabolism and mineralization activity of aerobic mineralizing bacteria, making effective bioremediation of deep defects difficult to achieve.

[0005] In summary, how to break through the light transmission barrier inside 3D printed concrete and effectively introduce external light energy into deep defect areas without interfering with the continuous printing process, thereby achieving non-destructive strengthening and repair of interlayer defect networks, is a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In order to solve the above-mentioned problems in the prior art, the present invention provides 3D printed concrete with optical fiber-driven microbial mineralization enhancement and preparation method.

[0007] The technical solution of the present invention is as follows: One objective of this invention is to provide a method for preparing 3D-printed concrete enhanced by optical fiber-driven microbial mineralization, the method comprising the following steps: Step 1: Preparation of photo-promoting synergistic mineralization microbial preparation: Mix aerobic mineralizing bacteria solution with oxygen-producing photosynthetic microorganism solution to obtain a mixed solution. Soak porous coconut shell charcoal in the mixed solution for adsorption. The porous coconut shell charcoal after adsorption is completed is the photo-promoting synergistic mineralization microbial preparation. Step 2: Preparation of 3D Printed Concrete Fluid Slurry: Mix 950-1000 parts of cement, 950-1050 parts of fine aggregate, 1.1-2.5 parts of the dry powder component of 3D printing rheology modifier, and 8-15 parts of calcium lactate, and stir at low speed. Then add 15-30 parts of photo-promoting synergistic mineralization microbial agent and continue stirring. Next, add a liquid mixture consisting of 340-390 parts of mixing water and 1.0-1.5 parts of the liquid component of 3D printing rheology modifier, and wet mix to obtain 3D printed concrete fluid slurry. Step 3: Preparation of 3D-printed translucent concrete with composite interface: The concrete fluid slurry is extruded layer by layer using an extrusion 3D printing process. First, the first layer of slurry is printed, and then PMMA optical fibers are laid on the surface of the first layer of slurry. Then, the next layer of slurry is printed, and the optical fibers are wrapped between the upper and lower layers of slurry. The above cycle of printing one layer of slurry, laying one layer of optical fibers, and printing another layer of slurry is repeated until the predetermined component height is reached, thus obtaining 3D-printed translucent concrete with composite interface.

[0008] Preferably, in step one, 980 parts of cement, 1000 parts of fine aggregate, 1.8 parts of the dry powder component of 3D printing rheology modifier, and 10 parts of calcium lactate are mixed and stirred at low speed. Then, 20 parts of photo-promoting synergistic mineralization microbial preparation are added and stirring is continued. Finally, a liquid mixture consisting of 356 parts of mixing water and 1.3 parts of the liquid component of 3D printing rheology modifier is added and wet-mixed to obtain 3D printing concrete fluid slurry.

[0009] Preferably, the amount of photocatalytic synergistic mineralizing microbial agent added in step one is 1%-3% of the amount of cement replaced.

[0010] Preferably, in step one, the aerobic mineralizing bacteria is Bacillus pseudostrongylus, and the oxygen-producing photosynthetic microorganism is Spirulina platensis.

[0011] Preferably, the mass ratio of the aerobic mineralizing bacteria solution to the oxygen-producing photosynthetic microorganism solution in step one is (0.9-1.1):1, more preferably 1:1.

[0012] Preferably, the absorbance (OD) of the aerobic mineralizing bacteria solution in step one at a wavelength of 600 nm is... 600 The absorbance (OD) of the oxygen-producing photosynthetic microbial solution at a wavelength of 560 nm was 0.6. 560 The value is 0.8.

[0013] Preferably, the soaking time in step one is 20-24 h; the particle size of the porous coconut shell charcoal is 1 mm-2 mm, and the water absorption rate in the saturated surface-dry state is 120%.

[0014] Preferably, in step two, the dry powder component of the 3D printing rheology modifier includes 1.0-2.0 parts of thickener and 0.1-0.5 parts of retarder, and the liquid component of the 3D printing rheology modifier is polycarboxylate superplasticizer; the fine aggregate has a particle size ≤4.75mm and is natural river sand that has been dried to constant weight and sieved, more preferably, the dry powder component of the 3D printing rheology modifier includes 1.5 parts of thickener and 0.3 parts of retarder.

[0015] Preferably, in step two, the equal mass substitution method is used to replace part of the original cement with a photocatalytic microbial mineralization agent, so that the sand-to-binder ratio is always kept at 1 during the preparation of the 3D printed concrete fluid slurry.

[0016] Preferably, the total water-cement ratio of the 3D printed concrete fluid slurry in step two is 0.38, and the total water content in the water-cement ratio includes mixing water and the solution contained in the photo-promoting microbial mineralization agent.

[0017] Preferably, in step three, the diameter of the PMMA optical fiber is 0.8-1.2 mm, and the length is the same as the length of the printed slurry. Before use, the surface of the optical fiber is roughened with 60-grit sandpaper. The amount of PMMA optical fiber added is 3.8-4.2% of the volume of the preset concrete component. When laying each layer of optical fiber, the positioning spacing between the fibers is 8-10 mm. More preferably, the diameter is 1.0 mm, the volume fraction is 4%, and the positioning spacing is 10 mm.

[0018] Preferably, the 3D printing process parameters in step three are: nozzle diameter 18-22 mm, single-layer printing height 8-12 mm, printing speed 45-55 mm / s, material extrusion rate 1.5-2.3 L / min, and predetermined component height 10-15 cm. More preferably, the nozzle diameter is 20 mm, single-layer printing height is 10 mm, printing speed is 50 mm / s, material extrusion rate is 1.9 L / min, and predetermined component height is 12 cm.

[0019] Preferably, in step three, the nozzle diameter is 0.3 times the single-layer printing height and the single-layer printing height is 0.5 times the nozzle diameter, and the optical fiber diameter is 0.15 times the single-layer printing height.

[0020] Preferably, in step three, the 3D-printed translucent concrete contains a slurry-fiber-slurry composite interface, and the 3D-printed translucent concrete has an internal light transmission channel and a biomineralization reaction space.

[0021] A second objective of this invention is to provide 3D-printed concrete with optical fiber-driven microbial mineralization enhancement obtained by the above preparation method.

[0022] The beneficial effects of this invention are as follows: (1) This invention proposes a 3D printed concrete based on optical fiber-driven microbial mineralization. The photo-promoted synergistic mineralization microbial agent is a synergistic microbial system composed of Spirulina platensis and Bacillus pseudosturcium. The two are adsorbed in the pores inside the porous coconut shell carbon carrier. The optical fiber guides light to the deep composite interface of the concrete, activates oxygen-producing and aerobic microorganisms to synergistically form minerals in situ, fills the interlayer defects of the 3D printed concrete, and completes the interlayer structure reinforcement, thereby improving the overall isotropy of the concrete material.

[0023] (2) This invention utilizes optical fibers to drive the filling of internal defects in concrete. Addressing the interlayer defects in 3DPC caused by discontinuous deposition and incomplete fusion of strips, the optical fibers are reconstructed from passive light-transmitting components into active interface control units. Light energy is transmitted through the optical fibers to the deep interface of the concrete, targeting and activating pre-placed Spirulina platensis for photosynthesis. This improves the metabolic environment of Bacillus pseudosturcium in situ, thereby driving Bacillus pseudosturcium to continuously induce the deposition of minerals such as calcium carbonate in the deep concrete. The inorganic mineralization product calcium carbonate, synergistically induced by microorganisms, is then deposited in interlayer pores, microcracks, and the slurry-fiber-slurry composite interface. This invention achieves the filling of mineralized products into interlayer defects through a closed-loop mechanism of light energy conduction, in-situ oxygen production, and induced mineralization, thereby achieving closed-loop repair of deep interconnected pores, interfacial microcracks, and weakly bonded areas near fibers in 3DPC. This invention improves the Z-axis compressive strength, interlaminar bond strength and density of 3DPC, and effectively reduces the anisotropy of 3DPC in terms of mechanics, providing a new approach for the interfacial strengthening and intelligent construction of functional cement-based composite materials.

[0024] (3) This invention addresses the continuous defect network formed by interlayer stacking and strip overlap in extrusion 3D printing by constructing a slurry-light guiding fiber-slurry multiphase composite interface. The embedding of fibers effectively alters the spatial distribution morphology of this defect network. The micro-slits adjacent to the fibers, interlayer pores, and interconnected capillaries are reconstructed into effective targeted deposition spaces. At the same time, the establishment of light guiding channels breaks through the opaque barrier of traditional solid cement matrix, providing a continuous and precise photoexcitation microenvironment for the oxygen-producing photosynthetic microorganism Spirulina platensis in the deep composite interface, greatly improving the biological survival rate and metabolic activity of Bacillus pseudosturcium in the deep region of 3DPC.

[0025] (4) In the photo-promoted microbial mineralization system used in this invention, the mineralization induced by Bacillus pseudosturcium in the composite interface and deep microcracks inside 3DPC can form highly crystalline calcite directional deposition, thereby effectively dividing and sealing the interconnected pores and improving the density of the interlayer transition zone. Here, the division refers to the directional precipitation of highly crystalline calcite induced by Bacillus pseudosturcium in the interconnected pores. Multiple calcites bridge each other to form a mineral barrier, splitting and separating the continuous interconnected pore channels into several independent micropores. This process can effectively seal the internal seepage channels, reduce pore connectivity, improve the density of the interlayer area of ​​3D printed concrete, and promote the transformation of loose pores into a dense mineral network, thereby achieving interface defect repair and structural reinforcement. Meanwhile, Spirulina platensis performs photosynthesis by efficiently conducting external light energy, continuously releasing oxygen in situ and improving local microorganisms, breaking the hypoxic metabolic bottleneck for bacterial-induced calcium carbonate deposition and providing stable high-activity environmental conditions. The spatial coupling between Spirulina platensis and Bacillus pseudosturcium promotes the transformation of interfacial defects in 3DPC from loose pores to dense interconnected networks.

[0026] (5) The continuous hydration of traditional ordinary 3D printed cement matrix is ​​difficult to effectively fill interlayer cracks, resulting in mechanical anisotropy defects such as localized dense structure and overall weak interlayer structure. However, this invention utilizes the mechanism of internal light guide to drive deep mineralization, realizing the precise matching between microbial in-situ mineralization dynamics and the spatial distribution of interlayer defects. Test results show that under the symbiotic mineralization system assisted by light guide fiber, the Z-axis compressive strength of 3DPC controlled by interlayer can be increased by up to 72.7%, the interlayer bond strength can be increased by up to 59.3%, the proportion of macropores and capillaries in interlayers is significantly reduced, and cracks achieve 100% visible closure, which is significantly better than the internal repair effect under the traditional system without light channel assistance. This invention transforms the discrete and direction-dependent weak defect network in 3DPC into a highly continuous and dense homogeneous bearing network, effectively weakening the macroscopic mechanical anisotropy in 3DPC.

[0027] (6) The OD of the aerobic mineralizing bacteria solution of the present invention 600 The absorbance was set at 0.6, and the measurement was performed at a wavelength of 600 nm. This effectively avoided the strong absorption peaks of proteins and nucleic acids within bacterial cells, ensuring that the absorbance accurately reflected the turbidity and biomass of the system. The concentration, i.e., OD... 600 The concentration was set at 0.6, at which point the *Bacillus pseudosturcium* population was in the late logarithmic growth phase, exhibiting peak cellular metabolism and exhibiting peak activity of key enzymes inducing calcium carbonate precipitation, such as urease or carbonic anhydrase. This concentration ensured sufficient mineral-producing activity after immobilization while avoiding metabolic decline and pore aggregation and blockage caused by excessively high concentrations (e.g., greater than 1.0). For *Spirulina platensis* solutions, this invention used a 560 nm wavelength and calibrated the concentration as OD. 560=0.8, because Spirulina platensis is rich in photosynthetic pigments such as chlorophyll a and phycocyanin, and its absorption peaks are mainly concentrated around 430 nm, 620 nm and 680 nm. The 560 nm wavelength measurement is exactly at the trough of the photosynthetic pigment absorption peak, which fundamentally eliminates the interference of pigment content fluctuations on biomass concentration measurement. The concentration is limited to 0.8 in order to construct a mature suspension with high density and extremely strong photosynthetic activity. This concentration ensures that there are enough photosynthetic cells per unit volume to continuously produce oxygen, while effectively avoiding the serious self-shading effect caused by excessively high Spirulina platensis concentration, thereby maximizing the oxygen production efficiency between deep layers of 3D printed concrete.

[0028] (7) In this invention, the amount of photocatalytic synergistic mineralization microbial agent added to the 3DPC slurry is strictly controlled to 1%-3% of the total mass of the cementitious material. This addition range not only ensures sufficient biomineralization cores, but also prevents the thixotropic properties and yield stress unique to 3DPC from being damaged by the strong water absorption of porous coconut shell carbon. In terms of the type of optical fiber, this invention uses PMMA optical fiber instead of traditional quartz glass optical fiber or ordinary polymer mechanical fiber. PMMA optical fiber has extremely high visible light transmittance (especially with extremely low attenuation near 560 nm wavelength) and excellent alkali resistance, and can maintain its optical performance without degradation in strongly alkaline (pH>12) concrete pore liquid for a long time; at the same time, its good flexibility meets the process characteristics of continuous extrusion and deformation between 3DPC layers, avoiding the risk of brittle fracture of rigid glass optical fiber during the printing and compaction process.

[0029] (8) The setting of the printing parameters of this invention determines the geometry of the initial interlayer defects and the interface encapsulation quality of the optical fiber. The nozzle diameter of this invention is 18-22 mm, the single-layer printing height is 8-12 mm, and the optical fiber diameter is 0.8-1.2 mm. The three satisfy the following relationship: 0.3 times the nozzle diameter ≤ single-layer printing height ≤ 0.5 times the nozzle diameter, and the optical fiber diameter ≤ 0.15 times the single-layer printing height. If the single-layer printing height is too high, such as h>0.5D, the extrusion and interlocking force between the upper and lower slurry strips will be insufficient, which will lead to excessively large initial interlayer macroscopic pores, exceeding the maximum healing threshold of Bacillus pseudostrongylus-induced mineralization (usually 500 μm); if the single-layer printing height is too small, it will cause excessive overflow of slurry.

[0030] (9) As can be seen from Comparative Example 1, which lacks optical fibers, due to the lack of deep light energy input, Spirulina platensis is in a dark-phase dormant or dead state in the deep concrete layer and cannot release oxygen. The deep concrete environment quickly turns into an anaerobic state, resulting in the stagnation of Bacillus pseudosturcium's metabolism. The Z-axis compressive strength and interlayer bond strength of the concrete specimen increased by less than 10%, indicating that the deep interlayer microcracks could not be filled by minerals. As can be seen from Comparative Examples 2 and 3, in the photo-promoted synergistic mineralization microbial preparation, when only Bacillus pseudosturcium or only Spirulina platensis is immobilized, even with the introduction of optical fibers, due to the lack of in-situ oxygen production by photosynthetic microalgae, simple light cannot change the hypoxic background environment of the deep concrete. Calcium carbonate precipitation is limited to the oxygen-rich area of ​​2-3 mm on the surface of the specimen. The interconnected pores in the deep interlayer still exist, and the overall isotropic strengthening of the concrete cannot be achieved. Attached Figure Description

[0031] Figure 1 The process flow diagram for preparing 3D-printed translucent concrete in Example 1 is shown. Figure 2 The graph shows the variation of the fluidity of the slurry and the width of the extruded strip in Example 1 with the settling time within 5-100 min. Figure 3 Survival rate of Bacillus pseudostrongylus in concrete samples of Example 1 and Comparative Examples 1-2 after 28 days of curing: (a) results of plate coating at different dilutions, (b) viable bacterial count based on colony count. Figure 4 The failure morphology of concrete in Example 1 and Comparative Examples 1-5 after 28 days of curing under different loading directions is shown. Figure 5 The surface crack propagation characteristics of concrete in Example 1 and Comparative Examples 1-5 after 28 days of curing are visible. (a) Bending failure morphology and observable crack propagation traces under different loading directions, (b) Measured length of main surface crack after bending test of fiber-reinforced specimens. Figure 6 The interlayer and interstrip bond strength of the concrete in Example 1 and Comparative Examples 1-5 after 28 days of curing; Figure 7 The interface crack morphology of concrete at different healing ages in Example 1 and Comparative Examples 1-5; Figure 8 The images show the pore structure characteristics of the interface region near the optical fiber after 28 days of concrete curing in Examples 1 and Comparative Examples 1-3, obtained by mercury intrusion porosimetry (MIP). Among them, (a) pore size distribution curve, (b) pore volume ratio of different pore size ranges. Figure 9The images show SEM, TEM, HRTEM and FFT images of the mineralized products at a distance of 0-1 mm from the optical fiber in the concrete of Example 1 after 28 days of curing. (a) is the SEM image, (b) is the TEM image, and (c) is the HRTEM and FFT image. Figure 10 The images shown are SEM, TEM, HRTEM and FFT images of mineralized products at a distance of 1-3 mm from the optical fiber in the concrete of Example 1 after 28 days of curing. (a) is the SEM image, (b) is the TEM image, and (c) is the HRTEM and FFT image. Figure 11 The images show SEM, TEM, HRTEM and FFT images of the mineralized products at a distance of 3-5 mm from the optical fiber in the concrete of Example 1 after 28 days of curing. (a) is the SEM image, (b) is the TEM image, and (c) is the HRTEM and FFT image. Figure 12 The images are SEM, TEM, HRTEM and FFT images of mineralized products at a distance of 0-1 mm from the optical fiber in the concrete of Comparative Example 2 after 28 days of curing. (a) is the SEM image, (b) is the TEM image, and (c) is the HRTEM and FFT image. Figure 13 The images are SEM, TEM, HRTEM and FFT images of mineralized products at a distance of 1-3 mm from the optical fiber in the concrete of Comparative Example 2 after 28 days of curing. (a) is the SEM image, (b) is the TEM image, and (c) is the HRTEM and FFT image. Figure 14 The images are SEM, TEM, HRTEM and FFT images of mineralized products at a distance of 3-5 mm from the optical fiber in the concrete of Comparative Example 2 after 28 days of curing. (a) is the SEM image, (b) is the TEM image, and (c) is the HRTEM and FFT image. Figure 15 The images are SEM, TEM, HRTEM and FFT images of mineralized products at a distance of 0-1 mm from the optical fiber in the concrete of Comparative Example 3 after 28 days of curing. (a) is the SEM image, (b) is the TEM image, and (c) is the HRTEM and FFT image. Figure 16 The images are SEM, TEM, HRTEM and FFT images of mineralized products at a distance of 1-3 mm from the optical fiber in the concrete of Comparative Example 3 after 28 days of curing. (a) is the SEM image, (b) is the TEM image, and (c) is the HRTEM and FFT image. Figure 17 The images are SEM, TEM, HRTEM and FFT images of mineralized products at a distance of 3-5 mm from the optical fiber in the concrete of Comparative Example 3 after 28 days of curing. (a) is the SEM image, (b) is the TEM image, and (c) is the HRTEM and FFT image. Figure 18The TG-DTG curves of mineralized products after 28 days of concrete curing in Example 1 and Comparative Examples 1-3 are shown. Figure 19 The X-ray diffraction analysis results are for concrete in Example 1 and Comparative Examples 1-3. Detailed Implementation

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0033] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0034] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0035] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0036] The ordinary silicate cement used in the following examples was PO 42.5 cement; Spirulina platensis was purchased from the Freshwater Algae Culture Collection of the Chinese Academy of Sciences, with accession number FACHB-314; Bacillus pseudosturcium was purchased from the China Industrial Microbial Culture Collection Center (CICC), with accession number CICC10722; the extrusion 3D printing process was carried out by the HC-3DPRT / L type printing system provided by Hangzhou Guanli Co., Ltd.; the fine aggregate particle size was ≤4.75mm, which was natural river sand that had been dried to constant weight and sieved; the water-reducing agent was a polycarboxylate slump-retaining water-reducing agent, purchased from Sichuan Dongrun Baisheng New Materials Co., Ltd.

[0037] Example 1 Step 1: Preparation of photo-promoting synergistic mineralizing microbial agents: Preparation of *Bacillus pseudostrongylus* solution: The liquid culture medium for aerobic mineralizing bacteria was prepared by adding 5.0 g / L peptone, 3.0 g / L beef extract, 5.0 g / L sodium chloride, 0.0015 g / L manganese sulfate, and 1 L distilled water. After autoclaving at 121°C for 20 min, the medium was cooled to room temperature. *Bacillus pseudostrongylus* was inoculated at 1% of the total liquid culture volume in a laminar flow hood. The inoculated culture was then placed in a shaker and cultured at 25°C and 120 rpm for 24 h. After incubation, the bacterial solution was centrifuged at 6000 rpm for 5 min and washed with phosphate-buffered saline (PBS) at pH 8.0-8.1 to adjust the OD of the bacterial solution. 600 To a concentration of 0.6, an aerobic mineralizing bacteria solution, namely Bacillus pseudostrongylus solution, was obtained; Preparation of *Spirulina platensis* solution: The culture medium for *Spirulina platensis* consisted of 13.61 g / L NaHCO3, 4.03 g / L Na2CO3, 0.5 g / L K2HPO4, 2.5 g / L NaNO3, 1 g / L K2SO4, 1 g / L NaCl, 0.2 g / L MgSO4·7H2O, 0.04 g / L CaCl2·2H2O, 0.01 g / L FeSO4·7H2O, and 1 L of water. *Spirulina platensis*, an oxygen-producing photosynthetic microorganism with in-situ continuous oxygen production activity, was inoculated into the culture medium at a ratio of 1:2, i.e., 500 mL of a solution with a concentration greater than 1×10⁻⁶ was used. -6 CFU / mL of algal solution was added to the culture medium, and after inoculation, it was placed in an incubator for expansion. The expansion environment conditions were: ambient temperature 25 ± 2 ℃, continuous artificial light, and light intensity controlled at 1500 lux. After continuous culture for 15 days, the optical density OD of the culture medium was measured. 560 The OD value increased from an initial 0.067 to 1.823. Subsequently, the oxygen-producing photosynthetic microbial culture medium was diluted with deionized water to adjust its OD value. 560 Adjust the concentration to 0.8 to obtain an oxygen-producing photosynthetic microorganism solution, namely Spirulina platensis solution; A solution of *Bacillus pseudosternae* and a solution of *Spirulina platensis* were mixed at a mass ratio of 1:1 to obtain 24 g of mixed solution. Then, 20 g of porous coconut shell charcoal with a particle size range of 1 mm-2 mm was soaked in the mixed solution for 24 h for adsorption. The adsorption was carried out by capillary action and pore adsorption, and the adsorbed porous coconut shell charcoal was fully absorbed into the internal pore structure of the coconut shell charcoal. Finally, the adsorbed porous coconut shell charcoal was obtained, which is a photocatalytic synergistic mineralization microbial preparation. In this step, the water absorption rate of the porous coconut shell charcoal in the saturated surface-dry state was 120%, that is, the liquid adsorption capacity of 20 g of porous coconut shell charcoal was the mixed solution of 12 g of *Bacillus pseudosternae* solution and 12 g of *Spirulina platensis* solution. Step 2: Preparation of 3D Printed Concrete Slurry: First, 980 parts of dry cement, 1000 parts of fine aggregate, 10 parts of calcium lactate, 1.5 parts of hydroxypropyl methylcellulose as a thickener, and 0.3 parts of sodium gluconate as a retarder are added to a mortar mixer. The mixing blades are stirred clockwise at 80 r / min for 3 minutes, while the mixing drum is stirred counterclockwise at 60 r / min. Then, 20 parts of photo-promoting synergistic mineralization microbial agent are added, and the mixture is stirred at low speed for another 3 minutes to ensure initial dispersion in the dry materials, resulting in a dry mixture. To ensure a constant mortar-to-cement ratio of 1.0 during slurry preparation, an equal-mass substitution method is used in this step: 1 part of material equals 1 g, and the substitution amount is 2% of the original total cement mass. Therefore, the original total cement mass is 1000 g. After replacing it with 20 g of photo-promoting synergistic mineralization microbial agent, the material usage in the above process is calculated as follows: cement is 980 g (980 parts), photo-promoting synergistic mineralization microbial agent is 20 g (20 parts), and fine aggregate is 1000 g. g (parts), the photocatalytic synergistic mineralizing microbial preparation in this step is 20 g. This mass refers to the mass of porous coconut shell charcoal soaked in the mixed solution in step (1); Then, 356 parts of mixing water and 1.3 parts of polycarboxylate superplasticizer were premixed to obtain a liquid phase mixture. Then, 2 / 3 of the volume of the liquid phase mixture was added to the dry mixture and wet-mixed for 4 min. During the wet mixing process, the stirring blade was stirred at a low speed of 80 r / min clockwise, while the mixing tank was stirred at a low speed of 60 r / min counterclockwise. After 4 min, the stirring was stopped, and the material on the inner wall of the mixing tank and the blade was manually scraped and turned over with a scraper to reduce local agglomeration and improve the mixing uniformity of the system. Finally, add the remaining 1 / 3 volume of liquid phase mixture and continue wet mixing for 4 min to obtain a printing concrete fluid slurry with stable rheological properties, uniform component distribution, and that meets the requirements of no breakage, blockage, segregation or obvious collapse during the extrusion 3D printing process. Step 3: Preparation of 3D-printed translucent concrete with composite interfaces: The aforementioned 3D printed concrete slurry was transferred to the pumping device of the printing system and delivered to the printing nozzle through a conveying pipe. The process parameters were set as follows: nozzle diameter of 20 mm, single-layer printing height of 10 mm, printing speed of 50 mm / s, and material extrusion rate of 1.9 L / min. First, the nozzle was used to print the first layer of slurry. Then, 1.0 mm diameter PMMA optical fibers were laid on the surface of the first layer of slurry. The fiber length was the same as the length of the printed slurry, and the positioning spacing between the fibers was 10 mm. After laying, the next layer of slurry was printed. The PMMA optical fibers were covered between the upper and lower layers of slurry by the covering effect of the subsequent slurry. The above cycle of printing one layer of slurry, laying one layer of optical fibers, and printing another layer of slurry was repeated until the predetermined component height of 12 cm was reached, thereby obtaining 3D printed translucent concrete with internal light transmission channels and biomineralization reaction space. The volume fraction of PMMA optical fibers incorporated was 4%.

[0038] The preparation process in this embodiment is as follows: Figure 1 As shown. After the concrete printing and molding is completed, the outer surface of the concrete is covered and sealed with a water-retaining polyethylene film. Then, the concrete is placed in a standard curing environment with a temperature of 20 ± 2 ℃ and a relative humidity of not less than 95% for early pre-curing, with a pre-curing period of 3 days. After reaching the pre-curing age, the concrete was marked with orientation. Then, according to the test specifications, it was cut into test specimens of corresponding sizes along the three specific directions of X, Y, and Z. The specimens with dimensions of 40 mm × 40 mm × 40 mm were used for compressive strength testing, 40 mm × 40 mm × 160 mm were used for flexural strength testing, and 40 mm × 40 mm × 20 mm were used for interlaminar bond strength testing. Both compressive and flexural strength tests were conducted in the three directions of X, Y, and Z. After cutting, all test specimens were continued to be cured under the curing conditions of step (2) until the target age. The compressive strength test was conducted according to "ASTM C109 / C109M-21 Standard Test Method for Compressive Strength of Hydraulic Cement Mortar", the flexural strength test was conducted according to "ASTM C293 / C293M-16 Standard Test Method for Bending Strength of Concrete", and the ultrasonic pulse velocity (UPV) test was conducted according to "ASTM C597-22". The test was conducted according to the "Standard Test Method for Ultrasonic Pulse Velocity of Concrete" and the interlayer bond strength test was conducted according to "T / CBMF 183-2022 Test Method for Basic Mechanical Properties of 3D Printed Concrete".

[0039] To verify the continuous forming and extrusion stability of the 3D printed translucent concrete of Example 1 of the present invention, Figure 2The fluidity and extruded strip width of the slurry from step (2) change with the settling time over a period of 5 to 100 minutes. It can be seen that the fluidity of the slurry reaches 185.8 mm 5 minutes after mixing. As the settling time increases to 60 minutes, the fluidity of the slurry only decreases gradually to 165.7 mm, a decrease of approximately 10.8%, while the extruded strip width slowly decreases from 34.7 mm to approximately 30.0 mm. During this stage, although the system gradually establishes its internal structure through early cement hydration and particle flocculation, it still maintains excellent flowability and operational stability. The extruded strip morphology is continuous and uniform, without breakage or blockage. When the settling time exceeds 60 minutes, the early hydration of cement continuously consumes free water, and the thickening effect of hydroxypropyl methylcellulose causes a rapid increase in slurry stiffness. Furthermore, the coconut shell charcoal, acting as a porous carrier, adsorbs some of the mixing water, *Bacillus pseudosturcium* solution, and *Spirulina platensis* solution, leading to a reduction in the effective free water in the system. The mortar rapidly transitions from a plastic state to a semi-solid state, resulting in an accelerated decrease in fluidity and strip width. Considering both conveying efficiency and extrusion continuity, this invention defines 5-60 minutes as the optimal 3D printing time window. This range provides sufficient flexibility for construction operations while ensuring the printing accuracy and density of the formed components.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that no optical fiber is laid in step three, while the remaining process operations and parameter settings are the same as in Example 1.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that: no Spirulina platensis solution was prepared; in step one, 20 g of porous coconut shell charcoal was only soaked in 12 g of Bacillus pseudostrongylus solution in order to encapsulate Bacillus pseudostrongylus in porous coconut shell charcoal; in step two, the mixing water was 368 parts; and the remaining process operations and parameter settings were the same as in Example 1.

[0042] Comparative Example 3 The difference between this comparative example and Example 1 is that: no *Bacillus pseudostrongylus* solution was prepared; in step one, 20 g of porous coconut shell charcoal was only soaked in 12 g of *Spirulina platensis* solution to encapsulate *Spirulina platensis* in porous coconut shell charcoal; in step two, the mixing water was 368 parts; and the remaining process operations and parameter settings were the same as in Example 1.

[0043] Comparative Example 4 The difference between this comparative example and Example 1 is that step one was not performed, i.e., Bacillus pseudostrongylus and Spirulina platensis were not added to the 3D printed concrete fluid slurry. In step two, 20 parts of photocatalytic synergistic mineralization microbial preparation were replaced with 20 parts of dried porous coconut shell charcoal, and the mixing water was 380 parts. The remaining process operations and parameter settings are the same as in Example 1.

[0044] Comparative Example 5 The difference between this comparative example and Example 1 is that step one was not performed, i.e., Bacillus pseudostrongylus and Spirulina platensis were not added to the 3D printed concrete fluid slurry, and optical fibers were not laid in step three. The remaining process operations and parameter settings are the same as in Example 1.

[0045] The survival ability of *Bacillus pseudostrongylus* inside the concrete of Example 1 and Comparative Examples 1-2 at 28 days of age was tested, and the method is as follows: Bacterial concentration testing method: First, the nutrient culture medium (with the same composition as the culture medium used in the preparation of *Bacillus pseudostrongylus* solution in Example 1) was mixed with agar, with the amount of agar being 1.5 wt% of the total components in the culture medium. After sterilization, the mixture was poured into sterile petri dishes and allowed to cool and solidify to prepare a solid culture medium. Subsequently, 1 g of concrete material debris sample was taken and 9 g of sterile physiological saline was added to prepare an initial bacterial suspension. The bacteria in the sample were fully released into the solution by shaking. The resulting suspension was diluted using a 10-fold serial dilution method, with a dilution range of 10... -1 Up to 10 -8 ; Take 100 μL of suspension at different dilutions and spread it evenly on the surface of solid culture medium, and incubate at a constant temperature of 23 ℃ for 48 h. After the incubation, select plates with colony counts between 30 and 300 for counting, and calculate the colony concentration according to formula (1): (1) In the formula, N is the colony concentration in the diluted suspension; n1 represents the total number of colonies on all valid counting plates; n2 represents the number of valid plates for the first dilution; n3 represents the number of valid plates for the second dilution; d represents the dilution factor corresponding to the first dilution; and V represents the plating volume of each plate.

[0046] Figure 3 The survival ability of *Bacillus pseudostrongylus* obtained by plate counting at 28 days in concrete samples from Examples 1 and Comparative Examples 1-2 is demonstrated within 3D-printed concrete. The results show that the concentration of *Bacillus pseudostrongylus* culturable in the 28-day specimen of Example 1 reached 16.3 × 10⁻⁶. 5 CFU / mL, compared to 8.4 × 10⁻⁶ in Comparative Example 1. 5The CFU / mL increased by 94.0%, demonstrating excellent bioactivity. This enhancement stems from a synergistic mechanism involving optical fibers, *Bacillus pseudosturcium*, and *Spirulina platensis*: the optical fibers act as energy channels, introducing external light into the deep, opaque concrete matrix, driving *Spirulina platensis* to release oxygen in situ. This fundamentally solves the problem of hypoxic metabolism at the deep interface of 3D-printed concrete, thereby significantly improving the survival rate of *Bacillus pseudosturcium* at the interlayer composite interface. This sustained and high level of bioactivity provides impetus for subsequent targeted repair of interlayer defects through microbial-induced mineralization and the homogenization of concrete performance.

[0047] The compressive and flexural strengths of the concrete in all embodiments and comparative examples were tested after 28 days of curing, and the results are detailed in Table 1.

[0048] Table 1. Compressive and flexural strengths of 3D-printed concrete specimens after 28 days of curing.

[0049] As can be seen from the data in Table 1, Comparative Example 4, which did not use *Bacillus pseudostrongylus* and *Spirulina platensis*, still significantly reduced the mechanical properties of the concrete in all directions and exacerbated the anisotropy of the concrete structure by simply embedding PMMA optical fibers in the concrete. This is because the surface of the optical fibers lacks hydration activity. Their introduction introduces a large number of heterogeneous interfaces into the extruded 3D-printed matrix, which already has interlayer overlap defects, increasing local porosity and weak bonding areas. This blocks stress transmission, weakens the overall compactness and load transfer efficiency of the specimen, and the lack of *Bacillus pseudostrongylus* and *Spirulina platensis* prevents subsequent healing of the resulting cracks, thus failing to improve the overall mechanical properties of the concrete specimen.

[0050] In contrast, Example 1, employing a strategy combining optical fibers with photocatalytic synergistic mineralizing microbial agents, significantly enhances the anisotropic load-bearing capacity of the specimen and mitigates the mechanical anisotropy caused by the 3D-printed structure. This is because the optical fibers overcome the physical barrier of opacity in solid concrete, efficiently transmitting external light energy to the deep interface and targeting and activating the in-situ oxygen release process of the oxygen-producing photosynthetic microorganism *Spirulina platensis*. The oxygen-rich microenvironment then greatly enhances the metabolic activity of *Bacillus pseudosturcium*, inducing the directional deposition of calcium carbonate in interlayer pores and micro-cracks near the fibers. The mineralized product, calcium carbonate, not only plays a role in physical filling and crack bridging but also promotes the densification of the multiphase composite interface, transforming the originally discrete interlayer weak defect network into a continuous homogeneous load-bearing network. Therefore, Example 1, with its internal optical fiber transmission channels and pre-filled *Spirulina platensis* and *Bacillus pseudosturcium*, exhibits optimal triaxial mechanical homogeneity and overall load-bearing performance after 28 days of curing, demonstrating not only effective bridging of interlayer defects but also superior triaxial mechanical homogeneity.

[0051] Figure 4 The images show the failure morphology of concrete from Examples 1 and Comparative Examples 1-5 after 28 days of curing under different loading directions. Figure 4 It can be seen that under compressive loading, the concrete specimens of Comparative Example 1 and Comparative Example 5 are prone to overall brittle peeling along the continuous defect network between layers and strips; while the main cracks of Example 1 of the present invention are significantly reduced after being subjected to compression, and the structural integrity is greatly improved. Figure 5 The images show the surface crack propagation characteristics of concrete from Examples 1 and Comparative Examples 1-5 after 28 days of curing. (a) shows the flexural failure morphology and observable crack propagation traces under different loading directions, and (b) shows the measured length of the main surface crack after bending tests on the fiber-reinforced specimens. Figure 5 (a) It can be seen that in the flexural strength test, Comparative Example 1 and Comparative Example 5 exhibited straight, brittle, through-fracture fractures along the interlayer weak zones. Example 1 of this invention benefits from the dual fracturing effect of the physical interlayer bridging of the optical fiber and the deep interfacial mineral deposition; the crack is significantly deflected and passivated when traversing the multiphase composite interface. From Figure 5 (b) It can be seen that the Z-axis surface fracture path length controlled by the interlayer weak zone was reduced from 2.88 cm in Comparative Example 4 to 0.96 cm in Example 1, a reduction of 66.7%. The shortening of the fracture path indicates that the optical fiber targeted and activated the synergistic mineralization of Spirulina platensis and Bacillus pseudosturcium in the deep concrete, effectively reconstructing the interface porosity and cutting off the interlayer instability propagation channel. This invention successfully transformed the rapid brittle penetration failure of cracks along the printing interface into a controlled propagation mode of crack propagation obstruction, deflection, and local termination, fundamentally improving the overall crack resistance stability of 3D printed translucent concrete.

[0052] Figure 6 The interfacial bond strength of concrete specimens from Examples 1 and Comparative Examples 1-5 after 28 days of curing is shown. It can be seen that the present invention eliminates the anisotropy of concrete materials, resulting in the highest interfacial bond strength for both interlayer and interstrip bonding. Traditional 3D printing, affected by deposition time differences, exhibits significantly lower interlayer strength compared to interstrip bonding. Introducing only optical fibers has limited effect on improving interfacial bond strength and can easily introduce local interfacial defects. The interfacial and interstrip bond strengths of Example 1 of the present invention are 1.88 MPa and 1.93 MPa, respectively, with an interfacial increase of 59.3% compared to Comparative Example 4. The mechanism lies in the following: the optical fibers guide light deep into the concrete, targeting and activating *Spirulina platensis*, promoting continuous calcium carbonate deposition of *Bacillus pseudosturcium* in the interlayer; simultaneously, the surface of the optical fibers provides heterogeneous nucleation sites for mineral crystals, forming a strong mechanical interlocking and mineral bridging. Ultimately, the interlayer / strip bond strength ratio of Example 1 increased from 0.84 in Comparative Example 5 to 0.97, indicating that the above-mentioned synergistic mechanism repaired the slurry-fiber-slurry multiphase interface network in the 3D printed structure and achieved homogenization and strengthening of the internal load-bearing interface.

[0053] Table 2 shows the test results of interface crack filling rate and UPV growth rate of concrete specimens at different healing ages for Examples 1 and Comparative Examples 1-5. Figure 7 The interface crack morphology of concrete specimens from Examples 1 and Comparative Examples 1-5 at different healing ages is also shown.

[0054] Table 2. Interfacial filling test results of samples from Example 1 and Comparative Examples 1-5

[0055] As can be seen from Table 2, the interfacial crack filling rate of concrete in Comparative Example 4 and Comparative Example 5 was less than 16% at 28 days, indicating that the hydration effect of the cement matrix itself is insufficient to bridge the inherent interlayer continuity defects in 3D printing.

[0056] Example 1 of this invention exhibits a unique deep-filling capability with excellent performance and accelerated growth in the later stages. Its crack filling rate develops slowly in the early stages (7-14 days), but jumps to 100% complete closure at 28 days. This late-stage acceleration reveals the deep response mechanism of this invention: the establishment of internal light transmission channels, targeted activation and oxygen release by deep-seated Spirulina platensis, and synergistic metabolism with Bacillus pseudostrongylus require a certain microbial construction cycle; once this symbiotic system is established at a deep depth, inorganic mineralization deposition is significantly enhanced, thereby filling and reconstructing the interlayer defect spaces formed during 3D printing. Furthermore, Example 1 shows a UPV growth rate as high as 41.2%, significantly higher than the comparative example, indicating that the synergistic system of this invention improves the overall density and structural integrity of the 3D printed components.

[0057] Figure 8 The pore structure characteristics of the interface region near the optical fiber in the concrete after 28 days of curing in Examples 1 and Comparative Examples 1-3 were obtained using the mercury intrusion porosimetry (MIP). The results showed that in Example 1, the total proportion of macropores and capillaries, which are detrimental to mechanical and durability properties, decreased to 26.93%, while the proportion of gel pores and transition pores increased to 73.07%. This shift in pore structure from coarse to fine in Example 1 is due to the targeted activation of *Spirulina platensis* and the strong promotion of *Bacillus pseudosturcium* by deep light transmission within the concrete, resulting in the continuous and deep crystallization and deposition of the generated calcium carbonate mineral product at the layer-optical fiber-layer composite interface. In contrast, the comparative examples showed limited ability to suppress larger pores, such as macropores and capillaries, making it difficult to completely eliminate defects at the multiphase interface.

[0058] Figure 9-17The images show SEM, TEM, HRTEM, and FFT characterization images of mineralization products near the optical fiber in specimens of Example 1, Comparative Example 2, and Comparative Example 3 at 28 days of age. To reveal the in-situ targeted mineralization mechanism of the optical fiber-microbial synergistic system at the interlayer multiphase composite interface, this invention performed multi-scale microscopic characterization of mineralization products in different mineralization systems within 0-1 mm, 1-3 mm, and 3-5 mm of the optical fiber. Figures 15-17 As can be seen from Comparative Example 3, the mineralization products exhibit a spatial gradient decrease with increasing distance from the fiber. In the near-end region at a distance of 0-1 mm from the fiber, due to the local illumination provided by the optical fiber, Spirulina platensis efficiently secretes carbonic anhydrase, catalyzing the formation of large-sized, polyhedral calcium carbonate crystals with clear crystal boundaries, ranging from 10-15 μm in size. Figure 15 (b) The TEM bright-field image shows that the product in this region is generally dense. Figure 15 (c) Continuous and clear parallel lattice fringes are visible in the HRTEM image. FFT analysis shows that the lattice spacing is approximately 0.30 nm, corresponding to the (104) crystal plane of calcite. However, from... Figure 16 , Figure 17 It was found that as the distance increased to 1-3 mm or even 3-5 mm, the photosynthesis at the far end was limited due to the sharp decrease in light flux inside the cement matrix, and the mineralization products rapidly degenerated into plate-like or flower-like aggregates with uneven morphology. Although lattice fringes related to the (104) crystal plane could still be captured locally in HRTEM, TEM images confirmed that the overall density of the structure had decreased significantly, making it difficult to form dense filling in deep defects.

[0059] In contrast, the induced mineralization process in Comparative Example 2 mainly relies on the adsorption of calcium ions by the negatively charged cell walls of *Bacillus pseudostrongylus*, and does not directly depend on light. Therefore, its mineralization products exhibit better spatial distribution consistency across different depth regions. However, the metabolic activity of *Bacillus pseudostrongylus* is limited by the oxygen scarcity in the deep, enclosed environment. Figure 12 (b) Figure 13 (b) and Figure 14 (b) The TEM image shows obvious flocculent or cloud-like features at the edges, indicating relatively low crystallinity. However, HRTEM and FFT results show that a lattice spacing of approximately 0.30 nm can be stably identified in different spatial regions at different distances from the optical fiber, confirming the high stability of calcite in this system.

[0060] Embodiment 1 of the present invention overcomes the above-mentioned dual limitations, from Figures 9-11As can be seen, in the region 0-1 mm from the optical fiber, polyhedral calcite crystals with a size of 12-18 μm, smooth crystal faces, and extremely sharp edges were formed, exhibiting highly ordered lattice fringes. More importantly, in the deep region 3-5 mm from the fiber, the system still maintained a high mineralization capacity. At the same time, TEM images showed that the deep sediments still exhibited extremely high crystallinity, and ordered lattice fringes could still be clearly observed in HRTEM, indicating that this invention broke through the mineralization stagnation caused by the attenuation of light in the deep part of 3D printed concrete.

[0061] Figure 18 Table 3 shows the TG-DTG test results of specimens from Example 1 and Comparative Examples 1-3 after 28 days of curing. The test results can measure the mass loss in the temperature range of 500-800 ℃ at the internal cracks of the specimens, i.e., the mass loss of calcium carbonate.

[0062] Table 3. Mass loss at the crack in the specimen within the temperature range of 500-800 ℃

[0063] Depend on Figure 18 It can be seen that all groups of specimens exhibited significant weight loss peaks in the 500-800 ℃ range. The mass loss in this temperature range is mainly related to the high-temperature decarburization process of calcium carbonate, and therefore can be used as an important indicator for comparing the relative deposition of calcium carbonate in the interlayer repair area. The results in Table 3 show that Example 1 exhibited a significant mass loss, which was higher than that of Comparative Example 1 (25.4%). This indicates that, with the assistance of internal light energy conduction, the spatial coupling between Spirulina platensis and Bacillus pseudosturcium exerted the best mineralization kinetic advantage, forming the highest calcium carbonate deposition network after 28 days of curing.

[0064] Figure 18 The DTG curves in the figure reveal the fundamental differences in the thermal decomposition behavior and crystal quality of calcium carbonate under different systems. Generally, the thermal decomposition peak temperature of calcium carbonate is positively correlated with its crystallinity and lattice integrity. As can be seen from the figure, the main decomposition peak temperatures of Comparative Examples 2 and 3 are only 725.4℃ and 703.2℃, respectively; the peak temperature of Comparative Example 1 is 727.9℃; while Example 1 of the present invention further increases the decomposition peak temperature to 738.2℃. This significant shift of the decomposition peak temperature to the high-temperature region, combined with the low deposition amounts in Comparative Examples 2 and 3, indicates that in systems lacking deep light-driven processes or with a single microbial component, the mineralization ability of *Bacillus pseudosternae* is significantly limited, making it difficult to increase the deposition amount and crystal quality of calcium carbonate. Example 1 of the present invention not only increases the relative deposition amount of calcium carbonate but also endows the mineralized product with higher crystallinity and a more complete lattice structure.

[0065] Figure 19The X-ray diffraction analysis results of the concrete in Example 1 and Comparative Examples 1-3 show that calcite characteristic peaks were detected in both examples at 2θ≈29.4° and 39.5°, indicating that the system of Spirulina platensis, Bacillus pseudosturcium, and optical fiber coexistence can stably induce calcium carbonate deposition. Compared with systems using only Spirulina platensis, only Bacillus pseudosturcium, or without optical fiber, the calcite (104) crystal plane diffraction peak of the optical fiber-assisted microbial synergistic system in Example 1 is the strongest and sharpest, fully demonstrating that the optical fiber successfully broke through the light transmission barrier inside the concrete matrix, targeted and activated the synergistic mineralization efficiency of deep microorganisms, and promoted the large-scale generation and perfect crystallization of calcite. In addition, the calcium hydroxide characteristic peak at 2θ≈18.1° in Example 1 was significantly weakened, revealing that the system can consume the weak free phase generated by cement hydration in situ, promoting its transformation into a dense and stable calcium carbonate phase, thereby realizing the adaptive filling of interlayer defects and non-destructive strengthening of the microstructure in 3D printed concrete.

[0066] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing 3D printed concrete enhanced by microbial mineralization driven by optical fibers, characterized in that, The preparation method includes the following steps: Step 1: Preparation of photo-promoting microbial mineralization agent: Mix aerobic mineralizing bacteria solution with oxygen-producing photosynthetic microorganism solution to obtain a mixed solution. Soak porous coconut shell charcoal in the mixed solution for adsorption. The porous coconut shell charcoal after adsorption is the photo-promoting synergistic mineralization microbial agent. Step 2: Preparation of 3D Printed Concrete Fluid Slurry: Mix 950-1000 parts of cement, 950-1050 parts of fine aggregate, 1.1-2.5 parts of the dry powder component of 3D printing rheology modifier, and 8-15 parts of calcium lactate, and stir at low speed. Then add 15-30 parts of photo-promoting synergistic mineralization microbial agent and continue stirring. Next, add a liquid mixture consisting of 340-390 parts of mixing water and 1.0-1.5 parts of the liquid component of 3D printing rheology modifier, and wet mix to obtain 3D printed concrete fluid slurry. Step 3: Preparation of 3D-printed translucent concrete with composite interface: The concrete fluid slurry is extruded layer by layer using an extrusion 3D printing process. First, the first layer of slurry is printed, and then PMMA optical fibers are laid on the surface of the first layer of slurry. Then, the next layer of slurry is printed, and the optical fibers are wrapped between the upper and lower layers of slurry. The above cycle of printing one layer of slurry, laying one layer of optical fibers, and printing another layer of slurry is repeated until the predetermined component height is reached, thus obtaining 3D-printed translucent concrete with composite interface.

2. The preparation method according to claim 1, characterized in that, In step one, the aerobic mineralizing bacteria is Bacillus pseudosturcium, and the oxygen-producing photosynthetic microorganism is Spirulina platensis. The mass ratio of the aerobic mineralizing bacteria solution to the oxygen-producing photosynthetic microorganism solution is (0.9-1.1):

1.

3. The preparation method according to claim 1, characterized in that, In step one, the absorbance of the aerobic mineralizing bacteria solution at a wavelength of 600 nm was 0.6, and the absorbance of the oxygen-producing photosynthetic microorganism solution at a wavelength of 560 nm was 0.

8.

4. The preparation method according to claim 1, characterized in that, The soaking time in step one is 20-24 hours; the particle size of the porous coconut shell charcoal is 1 mm-2 mm, and the water absorption rate in the saturated surface-dry state is 120%.

5. The preparation method according to claim 1, characterized in that, In step two, the dry powder component of the 3D printing rheology modifier includes a thickener and a retarder, while the liquid component of the 3D printing rheology modifier is a polycarboxylate superplasticizer; the fine aggregate particle size is ≤4.75mm, and it is natural river sand that has been dried to constant weight and sieved.

6. The preparation method according to claim 1, characterized in that, In step two, the equal mass substitution method is used to replace part of the original cement with a photocatalytic microbial mineralization agent, so that the sand-to-binder ratio is always kept at 1 during the preparation of 3D printed concrete fluid slurry.

7. The preparation method according to claim 1, characterized in that, In step two, the total water-cement ratio of the 3D printed concrete fluid slurry is 0.

38. The total water content in the total water-cement ratio includes mixing water and the solution contained in the photo-promoting microbial mineralization agent.

8. The preparation method according to claim 1, characterized in that, In step three, the diameter of the PMMA optical fiber is 0.8-1.2 mm, and the length is the same as the length of the printed slurry. The amount of PMMA optical fiber added is 3.8-4.2% of the volume of the pre-set concrete component. The positioning spacing between the fibers is 8-10 mm when laying each layer of optical fiber.

9. The preparation method according to claim 1, characterized in that, The 3D printing process parameters in step three are as follows: nozzle diameter 18-22 mm, single-layer printing height 8-12 mm, printing speed 45-55 mm / s, material extrusion rate 1.5-2.3 L / min, and predetermined component height 10-15 cm.

10. 3D printed concrete with optical fiber driven microbial mineralization enhancement obtained by the preparation method according to any one of claims 1-9.

Images