A mortar material for reinforcing earthen sites based on hydraulic lime and MICP technology, as well as its preparation method and application

Abstract

The present invention belongs to the technical field of earthen ruins building material repair, and provides an earthen ruins reinforcement mortar material based on hydraulic lime and MICP technology, as well as its preparation method and application. The raw materials of the earthen ruins reinforcement mortar material of the present invention include modified soil and activated urea micrococcus bacterial solution; the modified soil includes a cementitious material, silt and water; the cementitious material includes natural hydraulic lime and slaked lime in a mass ratio of 2 to 4:2, the mass ratio of the cementitious material to silt is 23 to 27:100, and the mass ratio of silt to water is 22 to 26:100. The earthen ruins reinforcement mortar material of the present invention has excellent mechanical properties and good workability, meeting the normal construction requirements of earthen ruins; good anti-seepage and anti-expansion properties, with an expansion rate of <0.1%; no cracks or falling off problems occur within a short period of time after reinforcement; it can solidify and harden to produce strength in both dry and humid environments, meeting the construction needs of different seasons.

Description

Technical Field

[0001] The present invention relates to the technical field of earthen site building material repair, and in particular to an earthen site reinforcement mortar material based on hydraulic lime and MICP technology, and a preparation method and application thereof. Background Art

[0002] my country boasts numerous historic earthen ruins and architectural artifacts, with Pingyao Ancient City being the most famous. Over time, natural weathering and other erosion factors have damaged the original structures, causing them to fall apart and collapse. Furthermore, frequent human damage has left the structures in urgent need of reinforcement and repair. A wide variety of materials are available for restoring earthenware artifacts. Due to cost and construction constraints, lime-cement composite materials are often used. However, air-hardening lime suffers from several issues, including low early strength, slow setting and hardening, and poor durability. Its tendency to disintegrate upon contact with water and significant volume shrinkage limits its use alone in restoration projects. Cement, on the other hand, compromises mortar toughness, resulting in a decrease in flexural strength. When the two are combined, the damage to the original earthen ruins is exacerbated by the expansion stress generated by salt crystallization and the formation of ettringite within the crystal layers and pores.

[0003] Natural hydraulic lime (NHL), a hydraulic cementitious material, can be traced back to the masonry buildings of the Minoan civilization as early as 3100 BC. As a lime material, hydraulic lime possesses both air-hardening and water-hardening properties, characterized by rapid coagulation and hardening, good air permeability, and a low soluble salt content. It is not prone to causing damage to the original building and is a cementitious material that meets the needs of earthen site restoration. Microbial induced calcium carbonate precipitation (MICP) technology is environmentally friendly and sustainable, but its use alone may have certain limitations in terms of strength improvement. Natural hydraulic lime has good adhesion and durability, and its use alone is difficult to fully meet the needs of earthen site protection. Therefore, combining the two is expected to provide a more effective solution for earthen site protection.

[0004] In recent years, a growing number of researchers, both domestically and internationally, have conducted research on optimizing the performance of natural hydraulic lime and proposed feasible solutions. Qingwen Ma et al. replaced NHL with sodium methyl silicate. The results showed that 0.3% sodium methyl silicate enhanced NHL's compressive strength, reduced water absorption, and improved its resistance to wet-dry cycles. Kotteeswaran Santhanam et al. added carboxymethyl cellulose and alfalfa to replace NHL, finding improved early compressive strength and enhanced freeze-thaw resistance. M. MarBarbero-Barrera et al. replaced NHL5 with polypropylene fiber and found that 2% of the fiber increased the mortar's toughness and ductility. These research results are primarily focused on optimizing the performance of hydraulic lime mortars or mortars, focusing on improving early strength and durability. For the restoration of earthen sites, materials should meet the requirement of "repairing the old as it was" with similar physical and chemical properties. Compatibility is the most important goal of earthen site restoration.

[0005] Similarly, the restoration design process for earthen sites largely relies on cement design as a reference, with mechanical properties being the primary focus. Unlike cement restoration materials, the primary objective for earthen site restoration materials is compatibility and durability with the site itself. The specific selection of restoration materials should be based on the actual conditions of the site's architecture and a thorough understanding of the materials used and their properties. Targeted evaluation and design based on the site's materials and their shortcomings is the prerequisite for achieving a highly compatible hydraulic lime restoration mortar. The properties of the restoration mortar, as well as its preparation, must be similar to those of the site being restored.

[0006] Based on an analysis of the soil used in earthen ruins and the mortar used for external restoration, it is clear that mortar materials for earthen ruins should possess the following basic properties: moderate mechanical properties (slightly higher than plain soil); excellent impermeability; low shrinkage and reduced cracking after hardening; and no negative impact on the original soil in the later stages of the product. Therefore, developing a mortar material and preparation method for earthen ruin reinforcement based on hydraulic lime and MICP technology is of great significance. Summary of the Invention

[0007] The purpose of the present invention is to provide a mortar material for reinforcing earthen ruins based on hydraulic lime and MICP technology, as well as a preparation method and application thereof, in response to the deficiencies of the prior art.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] The present invention provides a mortar material for reinforcing earthen ruins based on hydraulic lime and MICP technology. The raw materials of the mortar material for reinforcing earthen ruins include modified soil and activated urea micrococcus liquid.

[0010] The modified soil comprises a cementitious material, silt and water; the cementitious material comprises natural hydraulic lime and slaked lime, and the mass ratio of the natural hydraulic lime to the slaked lime is 2 to 4:2;

[0011] The mass ratio of the cementitious material to the silt is 23 to 27:100, and the mass ratio of the silt to water is 22 to 26:100;

[0012] The mass volume ratio of the activated urea micrococcus bacterial solution to the modified soil is 5-25g:1L; and the concentration of urea micrococcus in the activated urea micrococcus bacterial solution is 17-23g / L.

[0013] As a preference, the natural hydraulic lime has a 28d compressive strength of 2-7 MPa and an apparent density of 0.82-0.9 g / cm 3 .

[0014] Preferably, the average particle size of slaked lime is 4-4.2 μm, and the density of silt is 1.6-1.8 g / cm 3 , the maximum dry density is 1.65~1.85g / cm 3 , the moisture content is 24~25.5%.

[0015] Preferably, the preparation method of the activated urea micrococcus bacterial liquid is as follows: mixing urea micrococcus freeze-dried powder and bacterial culture solution and then curing to obtain the activated urea micrococcus bacterial liquid;

[0016] The curing is performed 2 to 3 times. After each curing is completed, the supernatant is removed by centrifugation, and then the bacterial culture solution is added for curing again. In each curing, the volume ratio of the urea micrococcus freeze-dried powder to the bacterial culture solution is 1:6 to 8.

[0017] Preferably, in each curing, the curing temperature is 27-33° C., the curing time is 45-52 h, and the curing is carried out at a rotation speed of 180-220 r / min.

[0018] Preferably, the culture medium comprises a buffered saline solution, yeast extract and ammonium sulfate, the mass volume ratio of yeast extract, ammonium sulfate and buffered saline solution is 18-22 g:9-11 g:1 L; the pH value of the buffered saline solution is 9-9.5, and the concentration of the buffered saline solution is 0.1-0.15 mol / L.

[0019] The present invention also provides a method for preparing the earthen ruins reinforcement mortar material based on hydraulic lime and MICP technology, comprising the following steps:

[0020] 1) performing a first mixing of silt, natural hydraulic lime, and slaked lime, and performing a second mixing of the mixture and water to obtain modified soil;

[0021] 2) The activated urea micrococcus liquid is sprayed onto the modified soil and mixed, and the mixed material is sequentially rammed, compacted, scraped, and cured to obtain the earthen site reinforcement mortar material.

[0022] Preferably, the first mixing time is 3 to 5 minutes, and the second mixing time is 6 to 10 minutes.

[0023] Preferably, the number of ramming and compacting layers is 2 to 4, the curing temperature is 28 to 32° C., the curing relative humidity is 67 to 73%, the curing pH value is 8.8 to 9.2, and the curing time is 26 to 30 days.

[0024] The present invention also provides the application of the earthen site reinforcement mortar material based on hydraulic lime and MICP technology in the restoration of earthen sites.

[0025] The beneficial effects of the present invention include the following:

[0026] 1) The present invention conducts a scientific analysis of the original mortar used in earthen sites and provides an earthen site reinforcement mortar material that is similar in composition to the mortar used in history and has good compatibility with earthen sites. The earthen site reinforcement mortar material is based on hydraulic lime and can be used for repair projects after MICP treatment. The bacteria in the MICP technology are used to solidify calcium ions, so that they produce better mechanical properties during the hardening process, achieving a reinforcement effect. The mortar material has the characteristics of fast coagulation and hardening, moderate strength, high water resistance and excellent working performance.

[0027] 2) The mechanical strength of the earthen ruins reinforcement mortar material based on hydraulic lime and MICP technology is significantly higher than that of the original earthen ruins soil block sample: the unconfined compressive strength of the original soil at 28 days is 0.7N / mm 2 The 28d flexural strength of the original soil is 0.2N / mm 2 The 28d unconfined compressive strength of the earthen ruins reinforcement mortar material of the present invention is higher than 2.7N / mm 2 , 28d flexural strength higher than 0.8N / mm 2 The earthen ruins reinforcement mortar material of the present invention has good workability and meets the normal construction requirements of earthen ruins; it has good anti-seepage and anti-expansion properties, with an expansion rate of <0.1%; no cracks or falling off problems occur within a short period of time after reinforcement; it can solidify and harden to produce strength (12h) in both dry and humid environments, meeting the construction needs of different seasons.

[0028] 3) The present invention has the characteristics of simple preparation process, wide material sources, similar color, moderate mechanical strength, excellent anti-seepage performance, and improved durability. Compared with cement materials, it does not cause damage to the original site structure, and meets the requirements of the dual carbon plan and the "sacrificial protection" principle required in site restoration projects. DETAILED DESCRIPTION

[0029] The present invention provides a mortar material for reinforcing earthen ruins based on hydraulic lime and MICP technology. The raw materials of the mortar material for reinforcing earthen ruins include modified soil and activated urea micrococcus liquid.

[0030] The modified soil comprises a cementitious material, silt and water; the cementitious material comprises natural hydraulic lime and slaked lime, and the mass ratio of the natural hydraulic lime to the slaked lime is 2 to 4:2;

[0031] The mass ratio of the cementitious material to the silt is 23 to 27:100, and the mass ratio of the silt to water is 22 to 26:100;

[0032] The mass volume ratio of the activated urea micrococcus bacterial solution to the modified soil is 5-25g:1L; and the concentration of urea micrococcus in the activated urea micrococcus bacterial solution is 17-23g / L.

[0033] In the present invention, the mass ratio of natural hydraulic lime to slaked lime is preferably 2.5-3.5:2, more preferably 3:2; the mass ratio of cementitious material to silt is preferably 24-26:100, more preferably 25:100; the mass ratio of silt to water is preferably 23-25:100, more preferably 23.5-24:100.

[0034] In the present invention, the mass volume ratio of the activated urea micrococcus bacterial solution to the modified soil is preferably 10-20 g:1L, more preferably 13-17 g:1L, and more preferably 15 g:1L; in the activated urea micrococcus bacterial solution, the concentration of urea micrococcus is preferably 19-21 g / L, more preferably 20 g / L.

[0035] In the present invention, the 28d compressive strength of natural hydraulic lime is preferably 2 to 7 MPa, more preferably 3 to 6 MPa, and more preferably 4 to 5 MPa, and the apparent density is preferably 0.82 to 0.9 g / cm 3 , more preferably 0.84 to 0.88 g / cm 3 , more preferably 0.86 g / cm 3 .

[0036] In the present invention, the natural hydraulic lime is preferably natural hydraulic lime NHL2.

[0037] In the present invention, the average particle size of slaked lime is preferably 4 to 4.2 μm, more preferably 4.05 to 4.15 μm, and even more preferably 4.096 to 4.12 μm; the density of silt is preferably 1.6 to 1.8 g / cm 3 , more preferably 1.63 to 1.76 g / cm 3The maximum dry density is preferably 1.65 to 1.85 g / cm 3 , more preferably 1.67 to 1.83 g / cm 3 The moisture content is preferably 24 to 25.5%, more preferably 24.21 to 25.31%.

[0038] In the present invention, the cementitious material is selected from a high dosage of natural hydraulic lime NHL2, which has the characteristics of air hardening and water hardening, so that the mortar can solidify and harden in dry or humid environments, thereby generating mechanical strength. In order to avoid the damage to the earthen ruins caused by excessively rapid early strength development during the repair process, slaked lime is used to partially replace the natural hydraulic lime NHL2. This avoids the problem of excessively rapid early strength development while allowing the mortar to have a certain toughness. The slaked lime can also serve as a bacterial carbon source.

[0039] The urea-producing micrococcus used in the present invention has a strong decomposition ability and can quickly produce urease to catalyze the hydrolysis of urea. It combines with calcium ions and the like in the modified soil material to rapidly increase the mechanical properties in the early stage. The urea-producing micrococcus can survive in a variety of environments and can still maintain a stable population size under fluctuations in temperature, humidity, and pH value.

[0040] In the present invention, the method for preparing the activated urea micrococcus bacterial liquid is preferably as follows: mixing urea micrococcus freeze-dried powder and bacterial culture solution and then curing to obtain the activated urea micrococcus bacterial liquid;

[0041] The curing is performed 2 to 3 times. After each curing is completed, the supernatant is removed by centrifugation, and then the bacterial culture solution is added for curing again. In each curing, the volume ratio of the urea micrococcus freeze-dried powder to the bacterial culture solution is 1:6 to 8.

[0042] In the present invention, the volume ratio of the urea Micrococcus freeze-dried powder to the bacterial culture solution is preferably 1:6.5-7.5, more preferably 1:7.

[0043] In the present invention, it is preferred that the bacterial culture solution be placed on a sterile bench to cool after steam sterilization on a sterile bench. The steam sterilization temperature is preferably 120-130°C, more preferably 122-128°C, and more preferably 124-125°C. The steam sterilization time is preferably 18-22 minutes, more preferably 19-21 minutes, and more preferably 20 minutes.

[0044] In the present invention, in each curing, the curing temperature is preferably 27 to 33°C, more preferably 28 to 32°C, more preferably 30°C, the curing time is preferably 45 to 52 hours, more preferably 46 to 50 hours, more preferably 48 hours, and the curing is preferably carried out at a rotation speed of 180 to 220 r / min, more preferably 190 to 210 r / min, more preferably 200 r / min.

[0045] In the present invention, the urea micrococcus is cured until white colonies appear, indicating that the bacteria are successfully activated.

[0046] In the present invention, the culture medium preferably comprises a buffered saline solution, yeast extract and ammonium sulfate. The mass-to-volume ratio of yeast extract, ammonium sulfate and buffered saline solution is preferably 18-22 g:9-11 g:1 L, more preferably 19-21 g:9.5-10.5 g:1 L, and more preferably 20 g:10 g:1 L. The pH value of the buffered saline solution is preferably 9-9.5, more preferably 9.2-9.3, and more preferably 9.25. The concentration of the buffered saline solution is preferably 0.1-0.15 mol / L, more preferably 0.12-0.14 mol / L, and more preferably 0.13 mol / L.

[0047] The present invention also provides a method for preparing the earthen ruins reinforcement mortar material based on hydraulic lime and MICP technology, comprising the following steps:

[0048] 1) performing a first mixing of silt, natural hydraulic lime, and slaked lime, and performing a second mixing of the mixture and water to obtain modified soil;

[0049] 2) The activated urea micrococcus liquid is sprayed onto the modified soil and mixed, and the mixed material is sequentially rammed, compacted, scraped, and cured to obtain the earthen site reinforcement mortar material.

[0050] In the present invention, the first mixing time is preferably 3 to 5 minutes, more preferably 3.5 to 4.5 minutes, more preferably 4 minutes, and the second mixing time is preferably 6 to 10 minutes, more preferably 7 to 9 minutes, more preferably 8 minutes.

[0051] In the present invention, the number of ramming and compacting layers is preferably 2 to 4 layers, more preferably 3 layers, the curing temperature is preferably 28 to 32°C, more preferably 29 to 31°C, more preferably 30°C, the curing relative humidity is preferably 67 to 73%, more preferably 68 to 72%, more preferably 70%, the curing pH value is preferably 8.8 to 9.2, more preferably 8.9 to 9.1, more preferably 9.0, and the curing time is preferably 26 to 30 days, more preferably 27 to 29 days, more preferably 28 days.

[0052] The present invention also provides the application of the earthen site reinforcement mortar material based on hydraulic lime and MICP technology in the restoration of earthen sites.

[0053] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0054] In the embodiment, the natural hydraulic lime is NHL2 produced by StAstier Company of France, and the apparent density of the natural hydraulic lime is 0.86 g / cm 3 The compressive strength after 28 days is 5MPa. The chemical composition of natural hydraulic lime is: SiO215.20%, CaO 74.39%, Fe2O34.73%, SO32.34%, K2O2.27%, Al2O31.07%.

[0055] Hydrated lime is industrial calcium hydroxide produced by Shanghai Jianghu Industrial Co., Ltd. It has the appearance of a white powdery solid with an average particle size of 4.096 μm. The chemical composition of hydrated lime is: Ca(OH)2 93.61%, CaCO3 4.39%, SiO2 1.03%, MgO 0.62%, and Na2O 0.35%.

[0056] The lyophilized powder of Micrococcus urea was purchased from the American Type Culture Collection (ATCC 700405) and stored in ampoules.

[0057] The bacterial culture medium was purchased from the American Type Culture Collection as NH4-YE culture medium (deposit number ATCC 1376). 1 L of bacterial culture medium consisted of 1 L of buffered salt solution (NH4Cl solution, concentration of 0.13 mol / L) with a pH value of 9.25, 10 g of ammonium sulfate, and 20 g of yeast extract.

[0058] The silt was taken from the collapsed part of Pingyao Ancient City in Shanxi Province (original soil) and the Pingyao soil yard (new soil). The mass ratio of original soil to new soil was 1:1. The physical indicators of the silt are shown in Table 1.

[0059] Table 1 Physical indicators of silt

[0060]

[0061] Example 1

[0062] The preparation process for the activated urea micrococcus culture is as follows: sterilize the culture at 125°C for 20 minutes on a sterile bench, then cool the culture on a sterile bench until ready for use. Use a sterile pipette to draw 1.5 mL of culture into an ampoule and dissolve 0.5 g of urea micrococcus freeze-dried powder. Pour the dissolved urea micrococcus into a 9 mL culture tube, mix thoroughly, score the tube, and inoculate into a flask containing fresh culture medium. Cured at 30°C and 200 rpm for 48 hours. The activated culture was centrifuged at 8000 rpm for 20 minutes. Remove the supernatant, add fresh culture medium, and shake thoroughly. Cured again at 30°C and 200 rpm for 48 hours (the volume ratio of urea micrococcus freeze-dried powder to culture medium was 1:7 for each curing). The activated urea micrococcus bacterial solution (concentration of 20 g / L) was placed in a 4°C refrigerator for later use.

[0063] Add silt, natural hydraulic lime NHL2, and slaked lime into a mortar mixer and continue stirring for 4 minutes until the color is uniform. Then slowly add water and continue stirring for 8 minutes to obtain a uniform modified soil. The mass ratio of natural hydraulic lime NHL2 to slaked lime is 3:2, the mass ratio of the total mass of natural hydraulic lime NHL2 and slaked lime to silt is 25:100, and the mass ratio of silt to water is 24.21:100.

[0064] The activated urea micrococcus liquid was sprayed onto the surface of the modified soil (the mass volume ratio of the activated urea micrococcus liquid to the modified soil was 20 g:1 L), and the mixture was evenly mixed at the same time. The mixture was poured into a mold with an open top and compacted by tamping and scraping in three layers. After that, it was cured for 28 days under the curing conditions of 30°C, 70% relative humidity and pH 9.0 to obtain the earthen site reinforcement mortar material.

[0065] The permeability coefficient of the earthen ruins reinforcement mortar material obtained in this example is 1.3×10 -5 cm·s -1 , showing good anti-seepage performance, with a 28d compressive strength of 3.6N / mm 2 , 28d flexural strength is 1.1N / mm 2 The expansion rate is less than 0.1%. The performance of the mortar is similar to that used in earthen ruins, and it has good compatibility with the original earthen ruins and city walls. No cracks or falling off occurred within one year after reinforcement. It meets the requirements of hydraulic lime and MICP technology composite mortar for earthen ruins restoration.

[0066] Example 2

[0067] The mass ratio of silt and water in Example 1 was changed to 23.38:100, the mass volume ratio of the activated urea micrococcus liquid to the modified soil was changed to 15 g:1 L, and the other conditions were the same as in Example 1.

[0068] The permeability coefficient of the earthen ruins reinforcement mortar material obtained in this example is 1.8×10 -5 cm·s -1 , showing good anti-seepage performance, with a 28d compressive strength of 3.1N / mm 2 , 28d flexural strength is 1.0N / mm 2 The expansion rate is less than 0.1%. The performance of the mortar is similar to that used in earthen ruins, and it has good compatibility with the original earthen ruins and city walls. No cracks or falling off occurred within one year after reinforcement. It meets the requirements of hydraulic lime and MICP technology composite mortar for earthen ruins restoration.

[0069] Example 3

[0070] The mass volume ratio of the activated Micrococcus urea bacteria solution to the modified soil in Example 1 was changed to 10 g:1 L, and other conditions were the same as in Example 1.

[0071] The permeability coefficient of the earthen ruins reinforcement mortar material obtained in this example is 2.7×10 -5 cm·s -1 , showing good anti-seepage performance, with a 28d compressive strength of 2.7N / mm 2 , 28d flexural strength is 0.8N / mm 2 The expansion rate is less than 0.1%. The performance of the mortar is similar to that used in earthen ruins, and it has good compatibility with the original earthen ruins and city walls. No cracks or falling off occurred within one year after reinforcement. It meets the requirements of hydraulic lime and MICP technology composite mortar for earthen ruins restoration.

[0072] Example 4

[0073] The preparation process for the activated urea micrococcus culture is as follows: sterilize the culture at 122°C for 22 minutes on a sterile bench. Cool the culture on a sterile bench until ready for use. Use a sterile pipette to draw 1.5 mL of culture medium into an ampoule and dissolve 0.5 g of urea micrococcus lyophilized powder. Pour the dissolved urea micrococcus into a 9 mL culture medium tube, mix thoroughly, score the tube, and inoculate into a flask containing fresh culture medium. Cured at 28°C and 190 rpm for 50 hours. The activated culture was centrifuged at 8000 rpm for 20 minutes. Remove the supernatant, add fresh culture medium, and shake well. Cured again at 28°C and 190 rpm for 50 hours (the volume ratio of urea micrococcus lyophilized powder to culture medium was 1:6.5 for each curing). The activated urea micrococcus bacterial solution (concentration of 19 g / L) was placed in a 4°C refrigerator for later use.

[0074] Add silt, natural hydraulic lime NHL2, and slaked lime into a mortar mixer and continue stirring for 3 minutes until the color is uniform. Then slowly add water and continue stirring for 7 minutes to obtain uniform modified soil. The mass ratio of natural hydraulic lime NHL2 to slaked lime is 2.5:2, the mass ratio of the total mass of natural hydraulic lime NHL2 and slaked lime to silt is 24:100, and the mass ratio of silt to water is 23.5:100.

[0075] The activated urea micrococcus liquid was sprayed onto the surface of the modified soil (the mass volume ratio of the activated urea micrococcus liquid to the modified soil was 13g:1L), and the mixture was evenly mixed at the same time. The mixture was poured into a mold with an open top and compacted by tamping and scraping in three layers. After that, it was cured for 28 days under the curing conditions of 28°C, relative humidity 68%, and pH 9.1 to obtain the earthen site reinforcement mortar material.

[0076] The permeability coefficient of the earthen ruins reinforcement mortar material obtained in this example is 1.5×10 -5 cm·s -1 , showing good anti-seepage performance, with a 28d compressive strength of 3.3N / mm 2 , 28d flexural strength is 1.05N / mm 2 The expansion rate is less than 0.1%. The performance of the mortar is similar to that used in earthen ruins, and it has good compatibility with the original earthen ruins and city walls. No cracks or falling off occurred within one year after reinforcement. It meets the requirements of hydraulic lime and MICP technology composite mortar for earthen ruins restoration.

[0077] Example 5

[0078] The activated urea micrococcus culture was prepared as follows: sterilize the culture at 128°C for 18 minutes on a sterile bench. The culture was then placed on a sterile bench to cool until ready for use. Using a sterile pipette, 1.5 mL of culture was pipetted into an ampoule and dissolved with 0.5 g of urea micrococcus lyophilized powder. The dissolved urea micrococcus was then transferred to a 9 mL culture tube, mixed thoroughly, streaked, and inoculated into a flask containing fresh culture medium. The tube was then incubated at 32°C and 210 rpm for 46 hours. The activated culture was centrifuged at 8000 rpm for 20 minutes. The supernatant was removed, and fresh culture medium was added and shaken thoroughly. The tube was then incubated again at 32°C and 210 rpm for 46 hours (the volume ratio of urea micrococcus lyophilized powder to culture medium was 1:7.5 for each incubation). The activated urea micrococcus bacterial solution (concentration of 21 g / L) was placed in a 4°C refrigerator for later use.

[0079] Add silt, natural hydraulic lime NHL2, and slaked lime into a mortar mixer and continue stirring for 5 minutes until the color is uniform. Then slowly add water and continue stirring for 9 minutes to obtain uniform modified soil. The mass ratio of natural hydraulic lime NHL2 to slaked lime is 3.5:2, the mass ratio of the total mass of natural hydraulic lime NHL2 and slaked lime to silt is 26:100, and the mass ratio of silt to water is 25:100.

[0080] The activated urea micrococcus liquid was sprayed onto the surface of the modified soil (the mass volume ratio of the activated urea micrococcus liquid to the modified soil was 17g:1L), and the mixture was evenly mixed at the same time. The mixture was poured into a mold with an open top and compacted by tamping and scraping in three layers. After that, it was cured for 28 days under the curing conditions of 32°C, relative humidity 72%, and pH 8.9 to obtain the earthen site reinforcement mortar material.

[0081] The permeability coefficient of the earthen ruins reinforcement mortar material obtained in this example is 1.28×10 -5 cm·s -1 , showing good anti-seepage performance, with a 28d compressive strength of 3.7N / mm 2 , 28d flexural strength is 1.15N / mm 2 The expansion rate is less than 0.1%. The performance of the mortar is similar to that used in earthen ruins, and it has good compatibility with the original earthen ruins and city walls. No cracks or falling off occurred within one year after reinforcement. It meets the requirements of hydraulic lime and MICP technology composite mortar for earthen ruins restoration.

[0082] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A mortar material for reinforcing earthen ruins based on hydraulic lime and MICP technology, characterized in that: The raw materials of earthen ruins reinforcement mortar materials include modified soil and activated urea micrococcus liquid; The modified soil comprises a cementitious material, silt and water; the cementitious material comprises natural hydraulic lime and slaked lime, the mass ratio of natural hydraulic lime to slaked lime being 2 to 3.5:2; the silt is taken from the collapsed part of Pingyao Ancient City in Shanxi Province and the Pingyao soil yard; The mass ratio of the cementitious material to the silt is 23-27:100, and the mass ratio of the silt to water is 22-26:100; The mass volume ratio of the activated urea micrococcus bacterial solution to the modified soil is 5-25 g:1 L; and the concentration of urea micrococcus in the activated urea micrococcus bacterial solution is 17-23 g / L.

2. The earthen ruins reinforcement mortar material according to claim 1, characterized in that: The 28d compressive strength of natural hydraulic lime is 2~7MPa, and the apparent density is 0.82~0.9g / cm 3 .

3. The earthen ruins reinforcement mortar material according to claim 1 or 2, characterized in that: The average particle size of slaked lime is 4~4.2μm, and the density of silt is 1.6~1.8g / cm 3 , the maximum dry density is 1.65~1.85g / cm 3 , the moisture content is 24~25.5%.

4. The earthen ruins reinforcement mortar material according to claim 1, characterized in that: The preparation method of the activated urea micrococcus bacterial liquid is as follows: urea micrococcus freeze-dried powder and bacterial culture solution are mixed and then maintained to obtain the activated urea micrococcus bacterial liquid; The curing is performed 2 to 3 times. After each curing, the supernatant is removed by centrifugation, and then the bacterial culture solution is added for curing again. In each curing, the volume ratio of the urea micrococcus freeze-dried powder to the bacterial culture solution is 1:6 to 8.

5. The earthen ruins reinforcement mortar material according to claim 4, characterized in that: During each curing, the curing temperature is 27~33℃, the curing time is 45~52h, and the curing is carried out at a speed of 180~220r / min.

6. The earthen ruins reinforcement mortar material according to claim 4 or 5, characterized in that: The culture medium comprises a buffered salt solution, yeast extract and ammonium sulfate, wherein the mass volume ratio of the yeast extract, ammonium sulfate and buffered salt solution is 18-22 g:9-11 g:1 L; the pH value of the buffered salt solution is 9-9.5, and the concentration of the buffered salt solution is 0.1-0.15 mol / L.

7. The method for preparing a mortar material for reinforcing earthen ruins based on hydraulic lime and MICP technology according to any one of claims 1 to 6, characterized in that: The following steps are included: 1) performing a first mixing of silt, natural hydraulic lime, and slaked lime, and performing a second mixing of the mixture and water to obtain modified soil; 2) The activated urea-containing micrococcus liquid is sprayed onto the modified soil and mixed. The mixed material is then compacted, scraped, and cured to obtain a mortar material for earthen site reinforcement.

8. The preparation method according to claim 7, characterized in that The first mixing time is 3 to 5 minutes, and the second mixing time is 6 to 10 minutes.

9. The preparation method according to claim 7 or 8, characterized in that The number of tamping and compaction layers is 2 to 4, the curing temperature is 28 to 32°C, the curing relative humidity is 67 to 73%, the curing pH value is 8.8 to 9.2, and the curing time is 26 to 30 days.

10. Use of the earthen site reinforcement mortar material based on hydraulic lime and MICP technology according to any one of claims 1 to 6 in earthen site restoration.

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