Leached spodumene concentrate as SCM for cementitious applications

Abstract

Leached spodumene concentrate (LSC) was tested for cementitious applications as SCM. It was characterized by XRF, ICP‐OES and XRD. SEM was applied for microstructure analysis. Tests with prepared mixtures of LSC and OPC for cement applications considered the pozzolanic activity and the compressive strength. QPXRD was carried out to characterize the time dependence of hydration. Further tests determined grain size distribution, density, thermal properties and moisture. The chemical composition of LSC is comparable to fly ash. Sulfate content is low and poses hence not a critical issue. Mixtures with up to 20/80 ratio of LSC/Cement are pozzolanic and outperform the compressive strength after 28 days of the OPC. Despite its crystallinity this material is highly reactive. Due to processing issues hexagonal LSC still occurs in varying amounts along the tetragonal LSC. Samples with differing proportions of hexagonal (H‐LS) and tetragonal (T‐LS) leached spodumene were hence prepared with cement up to 30 wt.% LSC and hydrated up to 28 days to evaluate the impact of the H‐LS/T‐LS ratio. For comparison, synthetic references (α‐, β‐, and γ‐spodumene as well as H‐LS and T‐LS) were produced. Pozzolanic activity of both LS types is similar, particularly at replacement levels up to 20 wt.%.