Application potentials of decomposed granite from Benggang area in South China as fine aggregates in cement-based materials

Abstract This study evaluates the sustainability of using Benggang sand as an aggregate in cement-based materials (mortar and concrete). The sand is essentially a kind of decomposed granite that is widely distributed in the Benggang erosion area in southern China; the erosion generally causes great damage to the ecological environment unless cost-effective management strategies are implemented. A systematic study was performed on the different gradations of mortar and concrete (ordinary concrete and ultra-high performance concrete, UHPC) made with Benggang sand (BS) by substituting different percentages of standard quartz sand (SS), including 0% (SS-only), 20%, 50%, 80% and 100% (BS-only). The workability index and mechanical performance for each mixture were assessed by slump and flowability tests and compressive and flexibility tests. The results show that BS replacement exhibits a negligible effect on the workability of mortar and ordinary concrete, but obviously improved UHPC; the compressive strength of ordinary concrete increases linearly as the BS proportion increases, while the potential benefits for mortar and UHPC are only indicated when the mortar gradation reaches 40 MPa and more than 50% of SS is replaced by BS. The microstructure and mineralogical composition analysis for UHPC indicates that UHPC with BS alone possesses fewer voids, a thinner interface transition zone (ITZ) thickness and a greater microcline phase content. This research highlights the potential sustainability credentials of using waste sediments distributed in bulk in Benggang erosion area in South China.