Quartz Powder Valorisation in White Self-Compacting Concrete: Mortar Level Study

Abstract

Quartz powder (QP) from mining exploration has increased, and valorisation solutions are sought. QP incorporation in structural concrete is an exciting strategy for the growth and sustainable development of the concrete industry, waste management and environmental protection. This work addresses the valorisation of QP from a Portuguese company on powder-type self-compacting concrete for architectural and structural purposes, combining the light colour of quartz with white cement. As such, QP was used as a partial cement replacement, acting as a filler on self-compacting white mortars (SCWM) and pastes (SCWP). Firstly, the QP was characterised by chemical, physical and morphological properties. Afterwards, SCWM with 10% of the white Portland cement with QP were produced and, with 10% cement replacement by limestone fillers, commercially available, for comparison purposes. The following engineering properties were evaluated, flowability and viscosity, electrical resistivity, porosity and mechanical strength. In equivalent pastes samples, the heat of hydration was accessed. Finally, an architectonic element prototype was produced using SCWM-QP, and colour and aesthetics were evaluated. All SCWM reached adequate deformability and viscosity for self-compaction. In the hardened state, compressive strength, electrical resistivity and water-permeable porosity presented similar results for mortars incorporating quartz powder and limestone fillers. The isothermal calorimetry in equivalent pastes revealed a slight desacceleration of hydration for SCWP incorporating QP. The major findings of this study confirm the feasibility of SCWM with QP, meeting the required performance while reducing resource depletion in the concrete industry and adding value to a by-product.