Binary blended cement pastes and concrete using gravel wash mud (GWM) powders

An alternative supplementary cementitious material (SCM) based on quarry waste sludge, namely gravel wash mud (GWM) powder, is investigated for its performance in blended cement pastes and concretes. Varying mix designs of blended cement pastes and concrete mixtures at Ordinary Portland cement (OPC) substitution degrees from 10 wt% up to 30 wt% by uncalcined and calcined GWM powders were examined at different curing ages using isothermal calorimetry, strength-based examinations, shrinkage test, carbonation test and scanning electron microscopy. The pozzolanic nature of the calcined GWM powder was confirmed, however, minor to no significant physiochemical contributions to the early hydration reactions were observed. The incorporation of calcined GWM powders up to OPC replacement levels of 20 wt% showed an enhancement of the long-term properties of the hardened specimens, namely less drying shrinkage and reduced progression of carbonation compared to the control mixtures. Beneficial strength-enhancing effects were observed for binary blended concrete mixes using calcined GWM powders at OPC replacement levels of 10 wt% and 20 wt% and classified them as viable proportions for alternative SCM-based concretes. The revalorisation of the GWM, a quarry waste product, as a novel and competitive raw material resource for cement production, would provide an environmental-friendly and alternative solution to the expensive and inefficient end-of-life scenario of GWM at the landfills.