Study on the durability of Bayer red mud solidified by microorganisms

CHEN Long;LIU Peng;HU Wenlu;XU Cheng;College of Civil Engineering, Nanjing Forestry University;Jiangsu Province Key Laboratory of Soil and Water Conservation and Ecological Restoration;

Bayer red mud;;microbial reinforcement;;compressive strength;;dry-wet cycle;;freeze-thaw cycle

Bayer red mud is a solid waste generated by the process of extracting alumina from bauxite, and the use of microbial reinforcement technology for the resource utilization of Bayer red mud resources is an effective approach to solve the large-scale piling issue of red mud. In this study, the durability characteristics of Bayer red mud reinforced by microbial grouting were studied, and the reinforcement effect of Bayer red mud reinforced by microorganisms was evaluated by studying the changes of mass loss rate and unconfined compressive strength of samples after water stability test, dry-wet cycle and freeze-thaw cycle test. The results showed that the microbial curing technology has a good reinforcement effect on Bayer red mud, as well as the strength and durability of the sample are further improved by adding calcium hydroxide. In the water stability test for up to 14 d, the maximum mass loss rate of microbial solidified red mud sample was only 2.29%. The mass loss rate of microbial red mud sample containing 10% calcium hydroxide was only 1.16%, which solves the Bayer method issue of the collapse characteristics of red mud when exposed to water. In the dry-wet cycle test, the mass loss of microbial red mud sample after 16 dry-wet cycles was 3.25%, and the unconfined compressive strength was decreased by 41.4%. The largest mass loss rate of microbial red mud samples containing 10% calcium hydroxide was 1.49%, and the unconfined compressive strength was only reduced by 14.5%. In the freeze-thaw cycle test, the unconfined compressive strength of the specimen decreased to varying degrees after two freeze-thaw cycles, and the compressive strength of microbial red mud sample did not changed significantly when the further freeze-thaw cycle was eight times. The effect of dry-wet cycle on the unconfined compressive strength of microbial red mud sample was higher than that of freeze-thaw cycle. The test results showed that microbial reinforcement can significantly improve the mechanical properties and durability of Bayer red mud and solve its easy disintegration characteristics in water, which is of great significance for the use of microorganisms to control Bayer red mud.