Understanding the utilization potential of lepidolite slag in cementitious materials: Composition characteristics, hydration properties, and high value-added cementitious system design

Abstract

Lepidolite slag (LES) is a kind of solid waste produced by extracting lithium from lepidolite, but researches focused on it are still limited. This paper works on understanding the utilization potential of LES in cementitious materials from its composition characteristics, hydration properties, and high value-added cementitious system design. Results show that the reactivity of LES is notably low in both water and alkaline solution. As a supplementary cementitious material (SCM), LES exhibits several drawbacks, including prolonging setting time, reducing compressive strength, and deteriorating pore structure. With addition of 30 % LES, the compressive strength at 28 d decreased by 63.3 %. Considering the high gypsum content within LES, an all-solid waste cementitious system was designed using high-volume LES combined with blast furnace slag (BS) and a small amount of lime. System with 40 % LES presents similar compressive strength with system composed entirely of BS at both 7 d and 28 d. The mechanism is that the excellent compound activation effect of gypsum in LES and lime on BS promoted the transformation of hydrotalcite to ettringite in the system. Even when LES content reached 70 %, compressive strength at 28 d surpassed 15 MPa. This study proposes a novel high value-added utilization way for LES in cementitious materials.