Assessing graphite schist as a supplementary cementitious material in concrete for antifungal activity, strength, hydration, microstructure, and radiation shielding

Abstract

For the first time, this study explores the valorization of graphite schist (GS), a metamorphic rock, as a novel supplementary cementitious material (SCM) in concrete. Portland cement (PC) was partially replaced with GS at 0, 10, and 15% by mass to prepare CC (control), GC10, and GC15 mixes, respectively. Physical, mechanical, hydration, microstructural, and radiation shielding properties were investigated. GS showed superior particle fineness, higher surface area, notable antifungal activity, and remarkable thermal stability up to 800 °C, outperforming PC in several aspects. Unlike GC15, GC10 achieved sustained compressive strength, closely related to that of CC. Microstructural analysis revealed that GS functioned mainly as a filler with limited pozzolanic reactivity, contributing moderately to particle packing. However, unhydrated cement particles and weakened interfacial transition zones were more prevalent at 15% GS. The improved performance of GC10 over curing periods reflected the more favorable influence of 10% GS on hydration and microstructure. Moreover, GS incorporation slightly improved fast neutron attenuation but reduced gamma-ray shielding due to increased porosity and reduced density. Overall, GS can be a promising multifunctional SCM, offering antifungal potential, acceptable neutron shielding, balanced strength, and reduced PC usage at 10% replacement.