In the process of microbial curing of desert aeolian sandy soil, we thought of the water-holding properties of straw flour in view of the high proportion of fine particles and poor water retention of desert aeolian sandy soil, and therefore designed an experiment to add straw flour to enhance the effect of microbial curing of desert aeolian sandy soil. The sand columns prepared under different curing stages were analysed by low-field NMR techniques. The test results show that: (1) the curing product calcium carbonate can effectively fill the pores of the sand and reduce the total porosity, and the addition of straw powder increases the total porosity of the sand column, especially the number of large pores (5–60µm) increases significantly; (2) The addition of straw powder increased the original sand column pore volume and pore size, significantly increasing the water holding capacity of the cured sand column, and the free water content of the sand column was significantly greater than that of the original sand column;(3) The pore filling rate of the sand column decreased after mixing with straw powder, which improved the uniformity of calcium carbonate precipitation within the sand column, but the shear strength was lower than that of the original sand column. The results of the study provide a theoretical basis and data support for optimising the curing effect of desert aeolian sandy soil and its water-holding capacity.
In this study, steel slag powder and fly ash were used as reinforcement and modification materials, and their effects on the growth, survival, and nucleation of mineral admixtures on bacteria were analyzed. Electrical conductivity, urease activity, and zeta potential tests were conducted, and the results showed that: (1) different mineral environments had different effects on the urease activity of Sporosarcina pasteurii. The steel slag powder solution inhibited urease activity, while the fly ash solution promoted urease activity. (2) S. pasteurii showed different growth characteristics in different mineral environments, especially in the fly ash solution, which showed higher hydrolysis efficiency, urease activity, and calcium carbonate yield. (3) The zeta potential test results showed that the nucleation of mineral admixtures on bacteria started to occur when the calcium ion concentration in the mineral filtrate was higher than 15 mmol/L. Different calcium ion concentrations showed greater impacts on the nucleation rate of mineral admixtures. The results of this study indicated the adaptability of microorganisms in the steel slag powder and fly ash solutions and the nucleation characteristics of calcium carbonate on the microbial surface, providing a theoretical and experimental basis for the subsequent development of new sand-fixing materials.
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