Study on Restoration Materials for Historical Silty Earthen Sites Based on Lime and Starch Ether

Advances in Materials Science and Engineering

et al. 2021

The silty clay in the lower reaches of the Yellow River is characterized by loose structure, low strength, and strong capillary effect. Based on the technology of ancient glutinous rice mortar and microbial-induced calcium carbonate precipitation (MICP), experiments on optimal mass ratio of cementitious liquid to bacterial liquid and optimal concentration of cementitious liquid for MICP and improved MICP technology were carried out by measuring the production of CaCO3, and direct shear test and unconfined compressive strength test of plain silt, glutinous mixing silt, and improved silt with MICP and modified MICP were conducted. The microstructure of the reaction products of MICP and improved MICP technology were also evaluated based on scanning electron microscopy (SEM). Research results showed that the mechanical properties of silt with glutinous rice slurry were effectively improved. With the increase in the concentration of glutinous rice slurry, the strength and internal friction angle of soil samples first increased and then decreased, and the cohesion presented a linear increasing trend. When the concentration of cementitious liquid was 0.5 M and the mass ratio of cementitious liquid to bacterial liquid was 2 : 1, the amount of CaCO3 formed was the most, and the conversion rate of Ca2+ was more than 80%. The improved MICP could increase the conversion rate of Ca2+ (93.44%). An improved MICP showed that glutinous rice slurry could improve bacterial activity, increase the urease content in the bacterial solution, and promote the production of CaCO3. Silt cohesion and internal friction angle of the silt were improved by the improved MICP technology, and the strengthening effect of mechanical properties of modified MICP-reinforced soil is better than that of the MICP-reinforced soil; conventional MICP technology could also improve the soil cohesion, but the improvement in the internal friction angle was not obvious. The SEM results indicated that compared with the reaction product of MICP technology, the structure of the product of improved MICP technology is more compact, resulting in a marked reinforcement of MICP performance with glutinous rice slurry. This study provides new insights into enhancing the mechanical behaviour of MICP-treated silt in the Yellow River Basin with glutinous rice slurry.

Section: Mechanical Properties Of Improved Siltmentioning

confidence: 84%

Effect of Glutinous Rice Slurry on the Reinforcement of Silt in the Yellow River Basin by Microbially Induced Carbonate Precipitation (MICP): Mechanical Property and Microcosmic Structure

Yue

Zhao

Advances in Materials Science and Engineering

et al. 2021

“…According to the principle of minimum intervention in the protection of cultural relics, traditional restoration materials should be used as far as possible. At present, the materials applied to the restoration of soil sites mainly include inorganic materials such as lime [3], cement [4], and hydraulic lime [5]. Lime is an air-hardening material whose mechanical properties are unstable in water environments, which leads to the adverse situation of repeated repair and destruction of soil sites [6].…”

Section: Introductionmentioning

confidence: 99%

Effect of Dry‐Wet Cycles on Strength Properties and Microstructure of Lime‐Metakaolin‐Modified Soil

Advances in Civil Engineering

Guo

et al. 2022

To explore the feasibility of replacing natural hydraulic lime (NHL) with lime-metakaolin (L-MK) in the restoration of soil sites, the samples of L-MK-modified silty sand (hereinafter L-MK-modified soil) underwent 0, 5, 10, and 15 dry-wet cycles and were then tested for mass loss, unconfined compressive strength, and splitting tensile strength. Some samples were tested using XRD, TG and SEM microscopic tests to study the strength mechanism for L-MK- and NHL-modified soil. The results showed that the mass loss ratios of the L-MK- and NHL-modified soils after 15 dry-wet cycles were within 2%. The compressive and tensile strengths of the L-MK-modified soil decreased with more dry-wet cycles, but the tensile strength decreased sharply initially and then to be stable after five dry-wet cycles. The attenuation characteristics were different obviously for the failure mode of compressive and tensile strength and the unevenness of the specimen caused by dry-wet cycles. The compressive and tensile strengths of L-MK-modified soil were significantly higher than those of NHL-modified soil after the same dry-wet cycle, and the decreased range of compressive and tensile strength was smaller than that of NHL-modified soil. The strength formation and attenuation characteristics of L-MK-modified soil are closely related to the influence of dry-wet cycles on the hydration products (e.g., CSH and C4AH13) generated by hydration reaction. The mix proportion of 6% L + 4% MK can effectively replace 8% and 10% NHL to protect soil sites.

“…Niu et al [ 10 ] improved the disintegration characteristics of soil sites in Northwestern China with a glutinous rice slurry, which provided a theoretical basis for the application of glutinous rice solution in the protection of soil sites. Kong et al [ 11 ] improved the shear strength and compressive strength of the site soil by adding lime and starch ether to the silt. Qian et al [ 12 ] conducted a study on the use of desulfurization waste to modify raw soil materials, and the results showed that the calcined desulfurization gypsum and the content of solid sulfur significantly improved the compressive strength of raw soil materials.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Mix Ratio of Restored Heritage Building Adobe

Yue

et al. 2022

Materials

The reciprocating action of the external environment gradually reduces the mechanical properties and water stability of original heritage buildings, resulting in the gradual loss of their cultural value. In this paper, the adobe for the construction of raw soil and cultural relics in western Henan is taken as the research object. The local plain soil is used as the raw material, and the adobe samples are prepared with modified materials such as quicklime and sodium methyl silicate, in order to improve its mechanical properties and water stability. The degree of correlation between the compressive strength, capillary water absorption, pH value, particle size distribution, and the electrical conductivity of modified raw adobe, as well as the modification mechanism of the microstructure, was studied. The results show that the addition of quicklime and sodium methyl silicate can enhance the compressive strength and water resistance of the modified raw adobe, and the optimum dosage is 1.5% sodium methyl silicate; with the increase of the curing age, the compressive strength of the single-mixed quicklime sample, the single mixed sodium methyl silicate samples, and the composite sample were increased by 1.94 times, 12.6 times and 2.61 times, respectively, compared with the plain soil samples, and with the increase of compressive strength, the pH, conductivity and capillary water absorption of the samples decreased continuously. It is evident from the particle gradation test and SEM images that the internal pores of the samples in the modified group become smaller, and the particle structure of the sample doped with sodium methyl silicate is the densest. The results of the study provide support for the restoration of the soil and cultural-relic buildings.