Mechanochemical activation of granite powder waste surface with carbon dioxide for cementitious composites

Abstract

The inherent lack of reactivity of typical quarry wastes significantly limits their potential application in cementitious composites. In this study, two-steps mechanochemical activation of granite powder waste (GP) combined with CO2 mineralisation was employed to prepare mineralised granite powder (MGP). In addition to standard tests (slump spread, setting time, volume density, specific surface area (SSA) compressive and flexural strength, sulphate attack, and freeze-thaw resistance), the study also used X-ray diffraction (XRD), thermogravimetry (TGA), microcalorimetry, reactivity test (R3) and micro-computed tomography (µCT). It was observed that MGP had a rougher surface, and its SSA increased by 30.4% compared to GP. The relative strength of MGP increased by 10% compared to GP (R3 test). MGP caused a change in the hydration kinetics of cement, accelerating the setting time (by up to 26.9% initial and 32.4% final) and released more heat (by 6.7%) than GP-modified pastes. TGA indicated more bound water in MGP-modified pastes (approx. 3%) compared to GP, and µCT revealed that the microstructure of MGP-modified pastes was less porous and more homogeneous compared to GP-modified pastes. The paper presents a sustainable way of changing the inert mineral waste (GP) into a multi-functional additive for modern cementitious systems, which will improve its properties, increase durability and reduce the environmental footprint. The limitation of the work is the observed effect of a more than 10% reduction in the slump spread of fresh paste, which may require a higher content of plasticizer.