Repair material and repair method for rammed earth ruin wind erosion disease

Abstract

The invention relates to the technical field of culture genetic protection, in particular to a repairing material and a repairing method for rammed earth ruin wind erosion diseases. The repairing material comprises a mineralized bacteria solution and a cementing nutrient solution, the mineralized bacterial liquid comprises a living bacillus pasteurii strain and a liquid culture medium, and the liquid culture medium comprises cane sugar serving as a carbon source and yeast powder serving as a nitrogen source; the cementation nutrient solution is an aqueous solution containing water-soluble calcium, wood calcium, corncob powder and urea; the corncob powder is corncob powder activated by potassium carbonate; the mineralized bacterial liquid and the cemented nutrient solution are independently stored, and are mixed and blended before being used, so that the rammed earth ruin wind erosion disease repairing material is obtained. After the repairing material is used for repairing the rammed earth ruins, further expansion and deterioration of diseases can be effectively prevented, the original appearance of the rammed earth ruins can be reserved, and the problem of historical aesthetic feeling loss caused by a traditional repairing method is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of cultural heritage protection, and particularly relates to a repair material and a repair method for wind erosion diseases of rammed earth sites based on microbial mineralization. Background Art

[0002] As a world cultural heritage, rammed earth sites are important historical symbols and precious cultural heritages of mankind. However, after centuries of wind and rain, the soil structure of their walls has been eroded by natural environmental factors for a long time, especially the influence of weathering and wind erosion, resulting in serious disease phenomena in the soil of the walls, including surface spalling, crack expansion, hole formation and aggravation, and even causing problems such as local collapse. These diseases not only reduce the structural stability of rammed earth sites, increase the risk of further damage, but also threaten their unique historical value and cultural significance.

[0003] When traditional repair methods solve these problems, they often adopt the method of filling or covering to fill the diseased parts to restore their surface integrity. Common repair materials are mainly some grouting materials with high viscosity and strength, including cement clinker, gypsum, lime, ultrafine slag, etc. Although this method can improve the appearance in the short term, due to the significant differences in the physical and chemical properties between the repair materials and the original soil, such repair methods usually damage the original texture and style of rammed earth sites, change the color and characteristics of the original soil cultural relics, and cannot reproduce their historical imprints. There is also the problem of water erosion caused by excessive repair solution for the repair of rammed earth sites. In addition, the practice of over-repairing or even filling all diseased parts is likely to damage their cultural authenticity and aesthetic value, and cannot achieve the effect of restoring the old as the old for raw soil cultural relics. Due to the poor compatibility between many existing repair materials and the original soil of rammed earth sites, their durability is not strong, and they are prone to falling off or deteriorating again under the long-term action of the natural environment, causing secondary damage. In addition, some repair materials also add rubber emulsions to increase toughness and viscosity, and their degradability is poor, causing certain pollution to the surrounding environment. Summary of the Invention

[0004] (I) Technical Problems to be Solved In view of the above-mentioned disadvantages and deficiencies of the prior art, the present invention provides a repair material and a repair method for wind erosion diseases of rammed earth sites; after repairing the diseased parts of rammed earth sites by the method of the present invention, a mineralized crust with air permeability, no color difference and wind erosion resistance can be formed, so as to effectively repair the diseases and prevent their continuous expansion. It can not only retain the original appearance of the soil sites, but also has good environmental protection and compatibility with the original soil, and solves the technical problems existing in the existing repair methods, such as loss of historical beauty, damage to the original texture and style of rammed earth sites, poor compatibility, weak durability and non-environmental protection.

[0005] (II) Technical Solutions In a first aspect, the present invention provides a repair material for wind erosion diseases of rammed earth sites, which comprises a mineralized bacterial liquid and a cementing nutrient solution; The mineralized bacterial liquid contains live Bacillus pasteurii strains and a liquid medium, and the liquid medium contains sucrose as a carbon source and yeast powder as a nitrogen source; the cementing nutrient solution is an aqueous solution containing water-soluble calcium, lignin calcium, corn cob powder and urea; the corn cob powder is corn cob powder activated by potassium carbonate; The mineralized bacterial liquid and the cementing nutrient solution are stored independently, and before use, the mineralized bacterial liquid and the cementing nutrient solution are mixed and formulated to obtain a repair material for wind erosion diseases of rammed earth sites.

[0006] According to a preferred embodiment of the present invention, the Bacillus pasteurii strains in the mineralized bacterial liquid are in the logarithmic growth phase, and preferably the optical density OD600 is 1-2. The pH of the mineralized bacterial liquid is slightly acidic to slightly alkaline (i.e., pH is 6-8), preferably 6.5-7.5.

[0007] According to a preferred embodiment of the present invention, the sucrose concentration in the mineralized bacterial liquid is 10-15 g / L, and the yeast powder concentration is 15-20 g / L.

[0008] According to a preferred embodiment of the present invention, the molar concentration of urea in the cementing nutrient solution is 0.5-1 times the calcium ion concentration in the water-soluble calcium; the urea molar concentration is 0.05-1.0 mol / L; the lignin calcium content in the cementing nutrient solution is 0.5-3 wt%.

[0009] According to a preferred embodiment of the present invention, the water-soluble calcium in the cementing nutrient solution is at least one of calcium chloride, calcium nitrate, calcium acetate, and calcium lactate; preferably calcium chloride. The water-soluble calcium provides calcium ions required for mineralization, and the lignin calcium is used for color adjustment to make the repaired part closer to the original soil color of the rammed earth site, achieving the effect of restoring the old as the old.

[0010] Calcium chloride has a very high solubility, about 74 g / 100 mL of water at 20 °C, which can quickly provide free calcium ions. Moreover, its pH is neutral, and it has little interference with the activity of microorganisms (Bacillus pasteurii). However, chloride ions may corrode metal components (such as iron nails in the ruins). In addition, the solubility of calcium nitrate reaches about 121 g / 100 mL, which can quickly provide free calcium ions. And since it does not contain chloride ions, it is suitable for the restoration of ruins containing metal parts. However, its nitrate radical may become a nitrogen source for microorganisms and may promote the growth and attachment of algae in a humid environment, but it can take into account the nutrients required for the long-term calcification process of microorganisms. The solubility of calcium acetate is about 34 g / 100 mL. It is a mild organic water-soluble calcium, and its decomposition products are carbon dioxide and water, with excellent environmental compatibility. Calcium acetate is more suitable for use in restorations where the mineralization rate requirement is slow and it is suitable for pH-sensitive objects (such as murals). The solubility of calcium lactate is low (5 g / 100 mL), which cannot provide a large amount of free calcium ions, but it has good biodegradability and a slow mineralization rate. It needs to be used in combination with long-term biological activity and is suitable for areas with strict requirements for biological toxicity. In practical applications, one or several of the above four water-soluble calcium salts can be selected and combined in proportion according to the specific composition of the rammed earth ruins. For example, a combination of calcium chloride and calcium nitrate is used when high-efficiency mineralization is required. If the restoration object is sensitive and better ecological compatibility is needed, organic calcium salts are used. If calcium chloride and calcium lactate are combined, both the mineralization rate and ecological safety can be taken into account.

[0011] Preferably, the aqueous solution calcium is composite calcium, and the composite calcium is a combination of calcium chloride and calcium lactate. Calcium chloride can quickly release calcium ions to accelerate the initial mineralization rate, and calcium lactate slowly releases calcium ions, which can extend the mineralization cycle. Calcium lactate can also provide the carbon source required by microorganisms. In the composite calcium, the molar ratio of calcium chloride to calcium lactate is 2 - 3:2.

[0012] According to a preferred embodiment of the present invention, the concentration of corn cob powder in the cementing nutrient solution is 1 - 4 wt%, and the particle size of the corn cob powder is 0.05 - 0.25 mm; preferably, the corn cob powder is corn cob powder activated by potassium carbonate. By activating the corn cob powder with potassium carbonate, the porosity of the corn cob powder can be increased, thereby enhancing its loading speed and loading capacity for CaCO3.

[0013] According to a preferred embodiment of the present invention, 1-3 wt% of rice husk ash mesoporous (pore size 10-30 nm) silica with a specific surface area of 500-1000 m² / g and a particle size of 0.1–1 μm (obtained by directly calcining rice husk ash at high temperature) is further added to the cementitious nutrient solution. The main functions of the rice husk ash mesoporous silica are as follows: ① The rice husk ash mesoporous silica can load urea or calcium salts in the cementitious nutrient solution. Due to its chemical inertness, it is not likely to react with the components of rammed earth (such as clay minerals), and has an extremely low expansion coefficient, avoiding secondary damage to the structure of the site. ② The rice husk ash mesoporous silica can penetrate into the microcracks (0.1–10 μm) of rammed earth and cooperate with calcium carbonate precipitation to fill the pores, reducing the risk of wind erosion. ③ The rice husk ash mesoporous silica can adsorb SO2 and NO x in the air, slowing down the chemical weathering of the site. ④ Reducing the instantaneous release of ammonia and reducing the disturbance to the environment of the rammed earth site. ⑤ Using rice husk ash mesoporous silica with a pore size of 10-30 nm can make the repaired part have air permeability while blocking the microcracks.

[0014] Preferably, a silane coupling agent can be grafted on the surface of the rice husk ash mesoporous silica to enhance the bonding force with the rammed earth matrix.

[0015] Preferably, corn cob powder can also be added to the mineralized bacterial solution as a negative carrier and nutrient for the bacteria.

[0016] In a second aspect, the present invention provides a method for repairing wind erosion diseases of rammed earth sites, which includes the following steps: Using the repair material described in any of the above embodiments for repair construction, mixing the mineralized bacterial solution and the cementitious nutrient solution in a volume ratio of 1:1 - 1:2 to form a bio-mineralization precursor solution; performing repair construction within 5-40 minutes after obtaining the bio-mineralization precursor solution; applying the bio-mineralization precursor solution to the diseased parts of the rammed earth site, applying it 3 times a day, with an interval of at least 3 hours between adjacent applications. Each day of application is regarded as one round. After continuously treating for 3-6 days in the foregoing manner, natural curing is carried out. Preferably, the diseased parts of the rammed earth site include hole diseases and crack diseases.

[0017] (III) Beneficial effects 1. The present invention provides a repair material for wind erosion diseases of rammed earth sites, which can be used to repair rammed earth sites vulnerable to wind erosion and water erosion. By combining a bacterial solution with mineralization ability and a cementitious nutrient solution with specific components, a bio-mineralization precursor solution is obtained. Applying this bio-mineralization precursor solution to the diseased parts, the flocculates generated by rapid induction can be well adsorbed on the diseased parts, forming a mineralized crust with good air permeability, no color difference, and wind erosion resistance, thereby effectively repairing the diseases and preventing their further expansion. After the repair material of the present invention is used to repair the rammed earth site, not only can the original appearance of the rammed earth site be retained, avoiding the problem of loss of historical aesthetic feeling caused by traditional repair methods, but also after repairing local hole diseases and crack diseases, it can effectively prevent the further expansion and deterioration of the diseases. The repaired parts do not change the original soil color and maintain the original historical aesthetic feeling.

[0018] 2. Adding corn cob powder to the cementitious nutrient solution can increase the mineralization reaction rate by 5 - 20%, and can quickly form a protective mineralized crust. Through potassium carbonate activation treatment, the porosity of corn cob powder can be increased, thereby enhancing its loading speed and loading capacity for CaCO3. The proportion of lignocellulose is adjusted according to the color of the original soil of the rammed earth site until it is similar to the color of the original soil body to ensure color consistency after repair (color difference ΔE < 5); in actual use, a composite calcium of organic calcium and inorganic calcium is adopted, which can adjust the release speed of free calcium ions, and then adjust the mineralization speed and ecological safety according to the repair object; rice husk ash mesoporous silica and calcium carbonate precipitation cooperate to fill pores, reduce the risk of wind erosion, and slow down the chemical weathering of the site, which is suitable for fine repair of high-value sites such as reinforcement of micro-cracks in mural layers and carving details; after graft modification with a coupling agent, the binding force with the rammed earth matrix is enhanced, preventing particle migration or aggregation. Rice husk ash mesoporous silica is grayish-white or light gray, and cooperates with lignocellulose to adjust the color during use.

[0019] The components of the repair material of the present invention are environmentally friendly and contain no chemical synthetic materials, and can be well compatible with the original soil body, ensuring the air permeability and environmental adaptability of the rammed earth site during the repair process, achieving the dual goals of cultural heritage protection and environmentally friendly repair, and are particularly suitable for the control and repair of hole diseases and crack diseases of rammed earth sites, having the advantages of environmental protection, durability, and avoiding secondary damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the repair flow chart of the wind erosion disease of the rammed earth site of the present invention.

[0021] Figure 2 It is a picture of an indoor specimen of the rammed earth site selected for the experiment.

[0022] Figure 3 It is a data graph of the mineralization rate of the repair material for the wind erosion disease of the rammed earth site of the present invention.

[0023] Figure 4 The contrast diagram of color difference for specimens repaired by different repair methods.

[0024] Figure 5 The wind erosion test results of the specimens repaired with the repair material of the present invention.

[0025] Figure 6 The anti-chemical + wind erosion test results of the specimens repaired with the repair material of the present invention. Specific embodiments

[0026] For better explaining the present invention for easy understanding, the present invention will be described in detail below in conjunction with the accompanying drawings through specific embodiments.

[0027] Example 1 As Figure 1 shown, it is the preparation flow chart of the repair material for the wind erosion disease of rammed earth sites of the present invention. It includes: S1. First, prepare the mineralized bacterial liquid The mineralized bacterial liquid contains living Bacillus pasteurii strains and a liquid medium. The liquid medium contains sucrose as a carbon source and yeast powder as a nitrogen source. The sucrose concentration in the mineralized bacterial liquid is 10 - 15 g / L, and the yeast powder concentration is 15 - 20 g / L. Among them, the Bacillus pasteurii strains are in the logarithmic growth phase. Preferably, its optical density OD600 is 1 - 2, preferably 1.2. A urease inducer of 0.01 - 0.1 mM can be added to the mineralized bacterial liquid. The urease inducer contains nickel metalloenzyme and can catalyze the hydrolysis of urea into ammonia and carbon dioxide.

[0028] When preparing the bacterial liquid, take the Bacillus pasteurii strains, inoculate them into the liquid medium, and under the conditions of a culture temperature of 30 °C and shaking culture, culture for 24 - 48 h to make the OD600 value of the bacterial liquid reach 1 - 2, obtaining a bacterial liquid with higher activity. The Bacillus pasteurii ( Bacillus pasteurii ) strains can be used, for example, ATCC 11859, DSM 33 or KCTC 3558. The pH of the mineralized bacterial liquid is 6 - 8.

[0029] S2. Prepare the cementing nutrient solution Dissolve water-soluble calcium, lignin calcium, corn cob powder and urea in water to obtain the cementing nutrient solution. The water required for the cementing nutrient solution can be natural rainfall, river water, well water, tap water, deionized water, etc. The corn cob powder in the cementing nutrient solution is the corn cob powder activated by potassium carbonate, and the addition amount is 1 - 4 wt%, and the particle size is 0.05 - 0.25 mm, preferably 0.1 mm. Activating the corn cob powder with potassium carbonate can increase the porosity of the corn cob powder, thereby improving its loading speed and loading capacity for CaCO3.

[0030] The water-soluble calcium is at least one of calcium chloride, calcium nitrate, calcium acetate, and calcium lactate, and preferably calcium chloride. The water-soluble calcium can quickly provide calcium ions required for mineralization. The total molar concentration of the water-soluble calcium is 0.1 - 2.0 mol / L. In some cases, the aqueous solution calcium is a composite calcium. For example, the composite calcium is a combination of calcium chloride and calcium lactate. Calcium chloride can quickly release calcium ions to accelerate the initial mineralization rate, and calcium lactate slowly releases calcium ions, which can extend the mineralization period. Calcium lactate can also provide the carbon source required by microorganisms. The molar ratio of calcium chloride to calcium lactate in the composite calcium is 2 - 3:2. The molar concentration of urea is 0.5 - 1 times the concentration of calcium ions in the water-soluble calcium, preferably 0.6 - 0.7 times; the urea concentration is preferably 0.05 - 1.0 mol / L.

[0031] Wood calcium is used for color adjustment to make the repaired part closer to the original soil color of the rammed earth site, achieving the effect of restoring the old as the old. The dosage is 0.5 - 3 wt%. The addition of wood calcium can meet the color difference requirements of the rammed earth site, making the color difference ΔE between the repaired part and the original soil less than 5.

[0032] S3. After the above-mentioned mineralization bacterial solution and cementing nutrient solution are prepared, they need to be stored separately and independently. Before use, the mineralization bacterial solution and the cementing nutrient solution are mixed and prepared according to a volume ratio of 1:1 to 1:2 to obtain a biological mineralization precursor solution with flocculants, and it is ensured that it is used for construction within 5 - 40 minutes. The biological mineralization precursor solution is applied to the damaged parts of the rammed earth site, three times a day, with an interval of at least 3 hours between adjacent applications. Each day of application is regarded as one round. After continuously treating for 3 - 6 days in the aforementioned manner, natural curing is carried out. Preferably, the damaged parts of the rammed earth site include hole diseases and crack diseases.

[0033] Example 2 In this example, the repair material for the wind erosion disease of the rammed earth site was prepared according to the method of Example 1, and its composition is as follows: Composition of the mineralization bacterial solution: Bacillus pasteurii (OD600 = 1.5), sucrose 12 g / L, yeast powder 18 g / L. The Bacillus pasteurii strain is ATCC 11859. The pH of the mineralization bacterial solution is 6 - 7.

[0034] Composition of the cementing nutrient solution: 0.5 M urea, 1.2 wt% wood calcium, 0.72 M CaCl2, 2 wt% potassium carbonate-activated corn cob powder (particle size 0.1 - 0.2 mm), deionized water. Among them, the addition amount of wood calcium is determined according to Figure 2 the color difference detection results of the middle test pieces.

[0035] The mineralization bacterial solution and the cementing nutrient solution are mixed according to a volume ratio of 1:1, and flocculants gradually form in the mineralization solution to obtain a biological mineralization precursor solution.

[0036] Select as Figure 2Pictures of indoor specimens of rammed earth sites shown Figure 2 In Figure 2 , a is a test piece for color difference detection of rammed earth sites to determine the most suitable addition amount of wood calcium. b is a test piece for simulating hole diseases, and c is a test piece for simulating crack diseases.

[0037] The repair method is as follows: The mineralized bacterial liquid and the cementing nutrient solution are used within 25 minutes after mixing. First, use a brush to apply the biological mineralization precursor solution on the surface of the earth site specimen. After each application, cure it under natural conditions for 3 hours to ensure that the flocs are fully adsorbed on the soil surface, reducing water erosion and solution loss. Apply it 3 times a day, each time under the same conditions. Before each application, prepare the repair material on-site. Perform the above operations for 6 days. After completion, cure it under natural conditions for one week to form a mineralized crust structure with wind erosion resistance. The repair process of the present invention adopts a local treatment method, only applying to the disease areas such as cracks and holes, without filling the diseases to retain their historical traces and beauty. The application method can reduce the usage amount and ensure that the material is firmly adsorbed on the disease surface, forming a uniform and firm mineralized crust, avoiding water erosion or damage to non-disease parts caused by spraying.

[0038] Examples 3 - 4 In Example 3, the repair material was prepared according to the method of Example 2, with the only difference being that 2wt% of corn cob powder in the cementing nutrient solution was adjusted to 4wt% and 6wt% respectively. For other preparation conditions and usage methods of the repair material, refer to Example 2.

[0039] Comparative Example 1 In Comparative Example 1, the repair material was prepared according to the method of Example 2, with the only difference being that 2wt% of corn cob powder in the cementing nutrient solution was removed, that is, the addition amount of corn cob powder was adjusted to zero. For other preparation conditions and usage methods of the repair material, refer to Example 2.

[0040] Test the change curves of calcium ion conversion rates of the three repair materials in Examples 2 - 4 and Comparative Example 1 over time. The experimental results are as Figure 3 shown; where "2%" represents Example 2, "4%" represents Example 3, "6%" represents Example 4, and "0%" represents Comparative Example 1.

[0041] As Figure 3As shown, within 0 - 2 h, compared with the repair materials prepared in Comparative Example 1 without corncob powder, the repair materials of Examples 2 - 4 had significantly faster calcium ion conversion rates. And when the corncob powder content in the cementitious nutrient solution was 2 wt%, 4 wt%, and 6 wt%, there were certain differences in the calcium ion conversion rates of the three repair materials before 2 h, but they almost coincided at 2 h. Therefore, in order to balance costs, it is appropriate to determine the addition amount of corncob powder as 1 - 4 wt%, preferably 2 - 4 wt%. Corncob powder is a natural polysaccharide substance, which not only provides a slow-release carbon source and nitrogen source for bacteria, but also, due to its porous structure and adsorption capacity, can promote the attachment of microorganisms and the formation of biofilms, accelerating the reaction rate of microbial mineralization. The potassium carbonate activation treatment further increases the porosity and hydrophilic groups of corncob powder, further promoting the attachment of microorganisms, all of which are beneficial to improving the mineralization rate.

[0042] Comparative Example 2 The repair material in Comparative Example 1 was prepared according to the method of Example 2, with the only difference being that 1.2 wt% of lignocellulose in the cementitious nutrient solution was removed, that is, the lignocellulose content was adjusted to zero. For other preparation conditions and usage methods of the repair material, refer to Example 2.

[0043] As Figure 4 shown, the color difference after repairing the rammed earth site specimens with the repair material of Example 2 and the repair material of Comparative Example 2 was further compared. As shown in the figure, after the specimen repair and curing were completed, it could be seen that there was a whitening phenomenon on the surface of the specimen repaired with the repair material of Comparative Example 2, and several white spots appeared, damaging the overall aesthetics. While for the specimen repaired with the repair material of Example 2 of the present invention, the color distribution was very uniform, the repaired part presented the color of the normal soil body, no color difference could be observed with the naked eye, and the repaired part was almost integrated with its surroundings.

[0044] This is because the active bacteria provided by the mineralization bacterial liquid will produce urease during metabolism. When there is a certain concentration of calcium ions in the solution, the calcium ions will be adsorbed by the bacterial strain, and CaCO3 crystals with gelling effects will form around the bacterial cells, thereby forming a calcium carbonate protective layer on the soil layer surface to achieve the effect of repairing holes and microcracks. However, at the same time, it will present the white color of the CaCO3 crystals, while lignocellulose is brownish - black. The introduction of lignocellulose neutralizes the white color of the calcium carbonate precipitate, achieving the effect of reducing the color difference. Lignocellulose (Calcium Lignosulfonate) is a kind of lignosulfonate, a by - product of the paper industry, with a chemical structure containing sulfonic acid groups and calcium ions, and appears as a yellow - brown powder or liquid, which is easily soluble in water. In the present invention, it is used as a color toner for the repair agent, not only realizing resource utilization, but also enabling the repaired part to maintain the lasting original soil color, presenting the effect of restoring the old as the old and preventing whitening.

[0045] Further, the rammed earth specimens repaired with the repair material of Example 2 and the rammed earth specimens without any repair treatment were placed under the condition of sand-carrying wind with a wind speed of 20 m / s (equivalent to a strong wind of Grade 8), a sand-carrying amount of 200 g / m³, and sand grains of 0.1 - 0.5 mm for a 20-minute wind erosion test. Twenty minutes after the end of the test, the erosion rate of each specimen was measured as Figure 5 shown.

[0046] It can be seen from Figure 5 that for the specimens with hole and crack diseases without repair treatment, the erosion amounts are 2.33 times and 2.25 times respectively of those of the specimens repaired with the repair material of the present invention. Thus, it can be seen that the repair material provided by the present invention can significantly inhibit the erosion process of the diseases of the rammed earth site, effectively improve its wind erosion resistance, and achieve the repair and protection of the diseases.

[0047] Example 5 Based on Example 2, in this example, 1.6 wt% of rice husk ash mesoporous (pore size of 10 - 30 nm) silica with a specific surface area of 500 - 1000 m² / g and a particle size of 0.1 - 1 μm is further added to the cementitious nutrient solution. The rice husk ash mesoporous silica is obtained by directly calcining rice husk ash at a high temperature of >600 °C and is light gray in color. The rice husk ash mesoporous silica is spray-treated with a 1.5 wt% ethanol solution of silane coupling agent and then dried. For other preparation conditions and usage methods of the repair material, refer to Example 2. The pore size and dosage of the rice husk ash mesopores take into account the air permeability of the repaired part, the strength and weather resistance after repair, while the particle size mainly considers the repair and reinforcement effect of microcracks.

[0048] The rammed earth specimens repaired with the repair materials of Example 2 and Example 5 were placed in a closed test chamber, and SO2 and NOx acidic gases were filled into the closed test chamber to make the SO2 concentration in the closed test chamber reach 50 ppm and the NOx concentration reach 50 ppm. The test temperature was set at 25 ± 2 °C, and the water vapor: RH was 75 ± 5%. After 48 hours of closed treatment, the specimens were taken out and placed under the condition of sand-carrying wind with a wind speed of 20 m / s (refer to the test conditions in Figure 5 ) for a 20-minute wind erosion test. Twenty minutes after the end of the test, the erosion rate of each specimen was measured as Figure 6 shown. As Figure 6 shown, the mass loss of the rammed earth specimens repaired with the repair material of Example 5 is less than that of the rammed earth specimens repaired with the repair material of Example 2, and the former is only about 50% of the mass loss of the latter specimens. Thus, it can be seen that adding a small amount of rice husk ash mesoporous silica to the cementitious nutrient solution helps to significantly reduce the total erosion rate of the specimens and makes the repaired specimens have better weather resistance.

[0049] As can be seen from the above embodiments, the repair material for wind erosion diseases of rammed earth sites based on microbial mineralization of the present invention is an efficient repair agent that combines rapid mineralization and meets the color difference requirements. During the repair process, Bacillus pasteurii produces urease through metabolism, decomposes urea to generate ammonium ions and carbonate ions, and forms calcium carbonate crystals with adhesive effects between particles. As a natural polysaccharide substance, corn cob powder not only provides nitrogen source and energy for the bacterial solution, but also due to its porous structure, increases the reaction surface area, promotes microbial attachment, and thus accelerates the mineralization reaction (increases the conversion rate of calcium ions). By adding lignin calcium, its brown color effectively neutralizes the white color of calcium carbonate precipitation, significantly reducing the color difference problem. After applying the repair material, a firm crust layer can be quickly formed on the surface of the diseases of the rammed earth site, effectively inhibiting the further deterioration of the diseases. The method of the present invention has the advantages of environmental protection, simple operation, and long-lasting repair effect, is suitable for the repair of wind erosion diseases of rammed earth sites, and shows important research and application prospects.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or equivalently replace some or all of the technical features; and these modifications or replacements, or when the technical features in the above embodiments do not conflict with each other, can be combined in the manner recorded in the embodiments, and these modifications, replacements or combinations do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A repair material for wind erosion damage in rammed earth ruins, characterized in that: Including mineralizing bacterial solution and cementing nutrient solution; The mineralized bacterial liquid contains a living Bacillus pasteurianus strain and a liquid culture medium, wherein the liquid culture medium contains sucrose as a carbon source and yeast powder as a nitrogen source; the cementing nutrient solution is an aqueous solution containing water-soluble calcium, wood calcium, corn cob powder and urea; the corn cob powder is corn cob powder activated by potassium carbonate; The mineralizing bacterial solution and the cementing nutrient solution are stored separately and independently, and are mixed and prepared before use to obtain the rammed earth site wind erosion disease repair material.

2. The repair material according to claim 1, characterized in that The Bacillus pasteurianus strain in the mineralized bacterial liquid is in a logarithmic growth phase, and its optical density OD600 is 1-2.

3. The repair material according to claim 1, characterized in that The sucrose concentration in the mineralized bacterial liquid is 10-15 g / L, and the yeast powder concentration is 15-20 g / L.

4. The repair material according to claim 1, characterized in that The molar concentration of urea in the cementing nutrient solution is 0.5-1 times the concentration of calcium ions in water-soluble calcium; the molar concentration of urea is 0.05-1.0 mol / L; and the amount of wood calcium added in the cementing nutrient solution is 0.5-3wt%.

5. The repair material according to claim 1, characterized in that The water-soluble calcium in the cementing nutrient solution is at least one of calcium chloride, calcium nitrate, calcium acetate and calcium lactate.

6. The repair material according to claim 5, characterized in that The aqueous calcium solution is composite calcium, which is a combination of calcium chloride and calcium lactate; in the composite calcium, the molar ratio of calcium chloride to calcium lactate is 2-3:

2.

7. The repair material according to claim 1, characterized in that The concentration of corn cob powder in the cementing nutrient solution is 1-4wt%, and the particle size of the corn cob powder is 0.05-0.25mm.

8. The repair material according to claim 1, characterized in that The cementing nutrient solution is also added with 1-3wt% rice husk ash mesoporous silica with a pore size of 10-30nm and a particle size of 0.1-1μm.

9. The repair material according to claim 1, characterized in that: Silane coupling agent grafted onto the surface of mesoporous silica from rice husk ash.

10. A method for repairing wind erosion damage in rammed earth ruins, characterized in that: The steps include: Using the repair material described in any one of claims 1 to 9 to carry out repair construction, the mineralizing bacterial solution and the cementing nutrient solution are mixed in a volume ratio of 1:1-1:2 to form a biomineralization precursor solution; and the repair construction is carried out within 5-40 minutes after the biomineralization precursor solution is obtained by mixing; The biomineralization precursor solution is applied to the diseased parts of the rammed earth ruins three times a day, with an interval of at least 3 hours between two adjacent applications, and each day of application is considered a round. After continuous treatment for 3-6 days, natural curing is carried out; the diseased parts of the rammed earth ruins include hole diseases and crack diseases.

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