High-strength MICP reinforced SiO2 aerogel concrete composite material and preparation method thereof

Abstract

The invention relates to a high-strength MICP reinforced SiO2 aerogel concrete composite material and a preparation method thereof.The method comprises the steps that cement, river sand, pebbles, silicon dioxide aerogel particles and water are added into a stirrer according to the proportion and stirred for 2-3 min till even mixing is achieved, and aerogel concrete slurry is obtained; continuously adding water into the aerogel concrete slurry, stirring for 3-5 minutes until viscous slurry is formed, sequentially adding a bacterial liquid, a saturated urea solution and a saturated calcium chloride solution according to a ratio, and stirring for 2-3 minutes until microorganisms are uniformly distributed to obtain a uniform mixture with the fluidity reaching the standard; and pouring the mixture into a mold, vibrating until bubbles are discharged, transferring the mold into a constant-temperature and constant-humidity curing chamber, and curing to obtain the aerogel concrete composite material. The method is simple in process, the heat conductivity coefficient of the concrete material can be remarkably reduced, and the compressive strength is improved; the prepared concrete composite material has the characteristics of self-repairing and heat-insulating functions, high compressive strength and the like.

Description

Technical Field

[0001] This invention relates to the field of concrete-based composite materials and their preparation technology, specifically to a high-strength MICP-reinforced SiO2 aerogel concrete composite material and its preparation method. Background Technology

[0002] Most existing aerogel concretes focus on improving thermal insulation performance. The main methods for improvement are: (1) using SiO2 aerogel mixed with concrete to prepare thermal insulation materials; (2) using co-precipitation method to combine ultra-low thermal conductivity autoclaved aerated concrete aerogel composite insulation board with autoclaved aerated concrete; (3) using materials such as cement, silica fume, quartz sand, river sand, SiO2 aerogel, water-reducing agent, water and hydrophilic surfactants for 3D printed thermal insulation concrete containing SiO2 aerogel. However, these technologies have many problems: on the one hand, increasing the aerogel content will lead to a significant decrease in compressive strength. For example, when the content is 5%, the compressive strength is only 0.3 MPa, which is a contradiction between "thermal insulation and strength"; on the other hand, they lack self-healing ability, and the repair of concrete cracks depends on external intervention, which cannot cope with structural damage in long-term use. Summary of the Invention

[0003] The purpose of this invention is to provide a high-strength MIP-reinforced SiO2 aerogel concrete composite material and its preparation method. The method is simple and can significantly reduce the thermal conductivity of concrete materials and improve their compressive strength. The prepared concrete composite material has the characteristics of self-healing, heat insulation and high compressive strength.

[0004] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: a high-strength MICP-reinforced SiO2 aerogel concrete composite material, wherein the concrete composite material is composed of the following components in parts by mass: 20-26 parts cement, 40-48 parts river sand, 84-92 parts gravel, 2-10 parts silica aerogel particles, 40-42 parts water, 2-6 parts bacterial solution, 2-6 parts saturated urea solution, and 2-6 parts saturated calcium chloride solution; the mass ratio of the bacterial solution, saturated urea solution, and saturated calcium chloride solution is 1:1:1.

[0005] Preferably, the concrete composite material is composed of the following components in parts by weight: 23 parts cement, 44 parts river sand, 88 parts gravel, 2 parts silica aerogel particles, 41 parts water, 4 parts bacterial solution, 4 parts saturated urea solution, and 4 parts saturated calcium chloride solution.

[0006] Preferably, the cement is national standard 42.5 cement, the river sand has a particle size of 2 mm, and the silica aerogel particles have a particle size of 600-1500 μm.

[0007] To achieve the above-mentioned objective, the present invention also provides a method for preparing the above-mentioned high-strength MIP-reinforced SiO2 aerogel concrete composite material, comprising the following steps:

[0008] S1. Add cement, river sand, gravel, silica aerogel particles, and water to a mixer according to the proportion, and mix for 2-3 minutes until uniformly mixed to obtain aerogel concrete slurry.

[0009] S2. Continue to add water to the aerogel concrete slurry prepared in step S1, stir for 3-5 minutes until a viscous slurry is formed, then add bacterial solution, saturated urea solution and saturated calcium chloride solution in sequence according to the proportion, stir for 2-3 minutes until the microorganisms are evenly distributed to obtain a uniform and fluid mixture.

[0010] S3. Pour the mixture into the mold, vibrate it until the air bubbles are expelled, and then move the mold into a constant temperature and humidity curing room for curing to obtain aerogel concrete composite material.

[0011] Preferably, in step S3, the curing time is 7 hours.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0013] (1) Improved mechanical properties: This invention utilizes MICP technology to improve existing aerogel thermal insulation concrete, which significantly improves the compressive strength of the concrete compared to pure aerogel concrete. At the same time, the combination of mineralized bacterial metabolites and calcium sources makes the internal structure of the concrete more compact, greatly improving its impermeability and significantly reducing the permeability coefficient compared to before repair. This effectively inhibits the intrusion of moisture, gas and harmful ions, enhancing the durability and structural stability of the concrete.

[0014] (2) Functional Integration Advantages: This invention integrates the self-healing and high-efficiency thermal insulation functions of concrete composite materials; concrete can repair cracks up to a certain width without external intervention, making it particularly suitable for scenarios where manual maintenance is difficult, such as mine tunnels and underground engineering projects, thus extending the service life of the structure. In addition, the thermal conductivity of concrete is significantly reduced, which can effectively block heat transfer and meet the high requirements for thermal insulation performance in mine tunnels, building exterior walls, etc., providing a reliable solution for complex environments such as high temperature and high humidity.

[0015] In summary, this invention combines microbial induced calcium carbonate precipitation (MICP) technology with SiO2 aerogel to prepare a concrete material with both self-healing and heat insulation functions. When this concrete material is applied in deep mine tunnels, it can isolate the geothermal heat on the wall surface, thereby cooling the working environment of the mine. Attached Figure Description

[0016] Figure 1 SEM image of the concrete prepared in Comparative Example 1;

[0017] Figure 2 SEM images of the concrete prepared in Comparative Example 2: (a) observation diameter is 5 μm; (b) observation diameter is 20 μm.

[0018] Figure 3 SEM image of the concrete prepared in Example 1;

[0019] Figure 4 The figures show the uniaxial cyclic compression test results of the concrete prepared in Comparative Examples 1-2 and Example 1, respectively.

[0020] Figure 5 This is a schematic diagram of the structure of the heat-insulated tunnel;

[0021] Figure 6 This is a schematic diagram of spraying heat insulation material onto the tunnel wall. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments.

[0023] Comparative Example 1

[0024] A method for preparing ordinary cement mortar concrete involves mixing 230g of cement, 440g of river sand, 880g of gravel, and 330ml of water until uniform to obtain a mixture; pouring the mixture into a mold, vibrating it to remove air bubbles, and then transferring the mold into a constant temperature and humidity curing room for 7 days to obtain ordinary cement mortar concrete.

[0025] Comparative Example 2

[0026] A method for preparing silica aerogel concrete involves mixing 230g of cement, 440g of river sand, 880g of gravel, 20g of 600-1500μm silica aerogel particles, and 330ml of water until homogeneous to obtain a mixture; pouring the mixture into a mold, vibrating it to remove air bubbles, and then transferring the mold into a constant temperature and humidity curing room for 7 days to obtain 1.05% silica aerogel concrete.

[0027] Example 1

[0028] A high-strength MICP-reinforced SiO2 aerogel concrete composite material, wherein the concrete composite material is composed of the following components in parts by weight: 23 parts of national standard 42.5 cement, 44 parts of river sand with a particle size of 2 mm, 88 parts of gravel, 2 parts of silica aerogel particles with a particle size of 600-1500 μm, 41 parts of water, 4 parts of bacterial solution, 4 parts of saturated urea solution, and 4 parts of saturated calcium chloride solution.

[0029] The preparation method of the above-mentioned aerogel concrete composite material includes the following steps:

[0030] S1. Add 230g cement, 440g river sand, 880g gravel, 20g silica aerogel particles, and 330ml water to a mixer according to the proportion, and mix for 2-3 minutes until the mixture is uniform to obtain aerogel concrete paste.

[0031] S2. Continue to add 80ml of water to the aerogel concrete slurry prepared in step S1, stir for 3-5 minutes until a viscous slurry is formed, then add 40g of bacterial solution, 40g of saturated urea solution and 40g of saturated calcium chloride solution in sequence according to the proportion, stir for 2-3 minutes until the microorganisms are evenly distributed and a uniform and fluid mixture is obtained.

[0032] S3. Pour the mixture into the mold, vibrate it until the air bubbles are expelled, and then move the mold into a constant temperature and humidity curing room for 7 days to obtain a high-strength MICP-reinforced SiO2 aerogel concrete composite material.

[0033] The samples prepared in Comparative Examples 1-2 and Example 1 were subjected to SEM scanning, pore analysis, thermal conductivity detection, and uniaxial compression tests to determine the microstructure, pore characteristics, thermal insulation performance, and mechanical properties of the samples.

[0034] The samples prepared by Comparative Examples 1-2 and Example 1 were scanned by SEM, and the scanning analysis results are as follows:

[0035] Figure 1 The image shows the diameter of ordinary concrete measured at 5 μm using SEM without the addition of SiO2 aerogel. The image shows that the ordinary concrete structure is relatively dense before the addition of SiO2 aerogel.

[0036] Figure 2 Images of ordinary concrete after SiO2 aerogel was incorporated, taken under SEM at diameters of 5 μm and 20 μm. The images show that the mixture has a more porous structure after the incorporation of SiO2 aerogel.

[0037] observe Figure 3 It is known that due to the presence of silica aerogel particles, the surface structure of concrete is more porous than that of unmixed concrete. Due to the action of mineralizing bacteria MIP, calcite crystals appear on its surface, thereby improving the strength of the material.

[0038] The porosity of concrete before and after modification was tested and analyzed. The results are shown in Table 1 below. The test results show that the specific surface area of ​​the concrete after incorporating SiO2 aerogel and undergoing the urease-bacterial MIP process is significantly increased compared with that before incorporation.

[0039] Table 1 Calculation results of adsorption volume at 77k

[0040]

[0041] The thermal conductivity of the samples prepared in Comparative Examples 1-2 and Example 1 was tested, and the results are shown in Table 2 below:

[0042] Table 2. Thermal conductivity of concrete mixed with different mass fractions of SiO2

[0043] Serial Number Test temperature unit Test Results Example 1 25.16℃ W / m·K 0.52369 Comparative Example 1 25.36℃ W / m·K 0.59771 Comparative Example 2 25.44℃ W / m·K 0.52674

[0044] In the thermal conductivity tests shown in Table 2, the measurements were conducted according to the relevant standard of ISO 22007-2:2015, using the protective hot plate method and a professional thermal constant analyzer. The test results show that the thermal conductivity of the normal concrete sample in Comparative Example 1 differs significantly from that of the concrete materials in Example 1 and Comparative Example 2 with added SiO2 aerogel. The latter two exhibit significantly lower thermal conductivity with no significant difference between them, demonstrating good thermal insulation performance. This performance improvement is mainly due to the SiO2 aerogel altering the microstructure of the concrete, increasing internal porosity and specific surface area, and forming more air barrier layers. Simultaneously, the urease-producing bacteria in the system generate calcium carbonate precipitate through metabolic activity, effectively filling the micro-cracks inside the concrete, improving the material's density and self-healing ability, and achieving synergistic optimization of thermal insulation and mechanical properties.

[0045] Uniaxial compression tests were conducted on the samples prepared in Comparative Examples 1-2 and Example 1, respectively. The test results are as follows: Figure 4 As shown. Under standard experimental conditions, in accordance with GB / T 50081-2019 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", three uniaxial compression tests were conducted on prism specimens of specified dimensions using a universal testing machine. The test results show that SiO2 aerogel concrete reinforced by microbial induced calcium carbonate precipitation (MICP) technology exhibits a fuller and more complete hysteresis loop morphology in the stress-strain curve. Compared with concrete specimens with only added SiO2 aerogel, its load-bearing capacity and ductility are significantly improved. This phenomenon is attributed to the filling and strengthening effect of calcium carbonate crystals induced in the pores inside the concrete by MIP technology on the microstructure.

[0046] exist Figure 5 In this scenario, the tunnel walls are sprayed with insulating material. The tunnel cross-section is actually rectangular. It is assumed that the original rock integrity is good after excavation, the sprayed layer and the original rock strata are structurally stable, and the coupling effect is good, forming a tunnel surrounding rock structure with an insulating layer. Therefore, if... Figure 6 The tunnel walls are sprayed with heat insulation material, which can be simplified into a flat-wall heat conduction model.

[0047] Calculations show that, under actual working conditions at a horizontal elevation of -1000m and a rock temperature of 40.6℃, when the high-strength MICP-reinforced SiO2 aerogel concrete prepared according to Example 1 is used as the insulation material, the wall temperature is significantly reduced, thereby lowering the ambient temperature to below 26℃.

Claims

1. A high-strength MIP-reinforced SiO2 aerogel concrete composite material, characterized in that, The concrete composite material is composed of the following components in parts by weight: 20-26 parts cement, 40-48 parts river sand, 84-92 parts gravel, 2-10 parts silica aerogel particles, 40-42 parts water, 2-6 parts bacterial solution, 2-6 parts saturated urea solution, and 2-6 parts saturated calcium chloride solution; the mass ratio of the bacterial solution, saturated urea solution, and saturated calcium chloride solution is 1:1:

1.

2. The high-strength MICP-reinforced SiO2 aerogel concrete composite material according to claim 1, characterized in that, The concrete composite material is composed of the following components in parts by weight: 23 parts cement, 44 parts river sand, 88 parts gravel, 2 parts silica aerogel particles, 41 parts water, 4 parts bacterial solution, 4 parts saturated urea solution, and 4 parts saturated calcium chloride solution.

3. A high-strength MICP-reinforced SiO2 aerogel concrete composite material according to claim 1 or 2, characterized in that, The cement is national standard 42.5 cement, the river sand has a particle size of 2mm, and the silica aerogel particles have a particle size of 600-1500μm.

4. A method for preparing high-strength MICP-reinforced SiO2 aerogel concrete composite material as described in claims 1-3, characterized in that, Includes the following steps: S1. Add cement, river sand, gravel, silica aerogel particles, and water to a mixer according to the proportion, and mix for 2-3 minutes until uniformly mixed to obtain aerogel concrete slurry. S2. Continue to add water to the aerogel concrete slurry prepared in step S1, stir for 3-5 minutes until a viscous slurry is formed, then add bacterial solution, saturated urea solution and saturated calcium chloride solution in sequence according to the proportion, stir for 2-3 minutes until the microorganisms are evenly distributed to obtain a uniform and fluid mixture. S3. Pour the mixture into the mold, vibrate it until the air bubbles are expelled, and then move the mold into a constant temperature and humidity curing room for curing to obtain aerogel concrete composite material.

5. The method for preparing a high-strength MICP-reinforced SiO2 aerogel concrete composite material according to claim 4, characterized in that, In step S3, the curing time is 7 hours.

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