Utilizing lithium slag to improve the physical-chemical properties of alkali-activated metakaolin-slag pastes: Cost and energy analysis

The utilization of lithium slag (LS) poses an imminent challenge in the solid waste disposal industry. In this work, ternary alkali-activated materials (AAM) were synthesized for the first time using a combination of LS, metakaolin (MK) and granulated blast furnace slag. The roles of LS replacing MK ratio (LRMR) on rheology, initial fluidity, setting time, compressive strength, heat release, phase composition, microstructure, cost and energy consumption were investigated. The results show that the substitution of LS leads to a reduction in the yield stress of the paste and an increase in its initial fluidity, which can be attributed to the comparatively lower specific surface area of LS compared to MK. Additionally, incorporating LS deepens the early reaction degree of the paste, so the setting time is shortened. Moreover, the incorporation of LS improves the compressive strength of the samples by promoting increased calcium (aluminate) silicate hydrate gel formation and refining pore structure. In terms of cost and energy consumption, the samples with LRMR of 25 % and 50 % exhibit a cost index that is respectively 37.2 % and 48.7 % lower than that of the control sample without LS, resulting in corresponding decreases in energy indexes by 24.1 % and 21.4 %. The findings may shed valuable light for the rational utilization of natural mineral resource (MK) and industrial by-product (LS).