Influence of low-grade materials as clinker substitute on the rheological behavior, hydration and mechanical performance of ternary cements

Abstract

This study aims to evaluate the influence of low-grade local materials as clinker substitute in ternary cements, with calcined clay (30 wt%) and limestone (15 wt%), also known as LC³ cements. A coal mining waste (based on 35 wt% kaolinite content, AR) and a dolomitic limestone (LLS) were compared to more pure materials such as natural clay (constituted by 83% kaolinite content, NC) and high-grade limestone (HLS), respectively. LC³ cements were compared to reference system (45 wt% quartz filler instead of limestone and calcined clays), as well as a fly ash blended cement (40 wt% fly ash, 40FA). Hydration kinetics, water demand, plastic viscosity, and yield stress were evaluated in a fresh state. The fineness of the calcined clays and limestone had a greater impact on the water demand and thixotropy of the pastes than their mineralogical compositions. However, the higher kaolinite content of NC led to higher pozzolanic activity, greater formation of carboaluminate type phases, and compressive strength than LC3 cements with AR. The HLS and LLS had similar impact on the proprieties assessed despite their different mineralogical composition. Thus, both low-grade materials are feasible as raw materials for the production of LC³ type cements with similar performance when compared to conventional cements.