Engineering properties of soil-based controlled low-strength materials made from local red mud and silty soil.

• CLSM made using silty soil as only aggregate is feasible for structural fills. • The flowability of CLSM decreases with the increasing RM content. • The optimal mass ratio of RM/cement is 0.5 for engineering properties of CLSM. The aim of this paper is to investigate the feasibility of controlled low-strength materials (CLSM) made from silty soil as the only aggregate, together with local red mud (RM) and portland cement as binder on structural fills. The results indicate that water to solid ratio of 0.46 satisfies the flowability and initial setting time demand, and the RM content less than 7.5% satisfies the strength and impermeability demand. RM has a significant influence on the engineering properties of CLSMs. At 3 d, the properties containing unconfined compressive strength, direct shear strength, and impermeability decrease with the increase of RM content. However, these properties initially increase and then decrease with the increase of RM content from 7 to 28 d, the optimum mass ratio of RM to cement is 0.5. The mechanism is summarized as a filler effect, an alkali environment effect, and a pozzolanic effect. [ABSTRACT FROM AUTHOR]