Eco-friendly ultra-high performance cement pastes produced with quarry wastes as alternative fillers

Abstract

About 35 billion tons of quarried material are produced annually throughout the world, generating large amounts of waste powders which are usually disposed of in landfills. This work investigated the feasibility of producing eco-friendly ultra-high performance cement pastes with diabase, granite and basalt quarry wastes as alternatives to quartz and limestone conventional fillers. The fresh properties (rheometry and mini slump), hydration (calorimetry, TGA and XRD), 3- and 28-day strength and microstructure (SEM-EDS) of the pastes were investigated. The results showed that granite and diabase fillers increased the yield stress of the pastes by about 1.6 times compared with quartz and limestone, while basalt increased it by 9 times. Only granite increased the apparent viscosity due to the irregular shape and rough texture of its particles. All the pastes presented self-levelling aspect. Calorimetry indicated equivalent hydration kinetics for quartz, granite and basalt, while limestone and diabase shortened the induction period and elevated the 72-h cumulative heat by 5%. XRD and TGA indicated similar compositions for all the pastes (calcium hydroxide and hydrates contents respectively of 6.8 ± 0.4% and 13.4 ± 0.4% at 28 days), and no evidence of pozzolanic activity by the fillers. All the mixes presented 3- and 28-day compressive strengths respectively of 71 ± 3 MPa and 132 ± 2 MPa, indicating that the incorporation of the quarry fillers did not lead to significant differences in strength. In line with that, SEM-EDS indicated similar microstructures. Overall, the alternative quarry powders can be used in the production of ultra-high performance cementitious composites with no impairments on its fresh, hardened and microstructural characteristics, contributing to the eco-efficiency of construction.