Feasibility of kaolin tailing sand to be as an environmentally friendly alternative to river sand in construction applications

Kaolin tailing sand (KTS) generated as a by-product from kaolin mining sorting, is usually disposed of by delivering to landfills. Effective utilization of KTS in concrete could be an attractive solution for the waste disposal with the value-added advantage of conservation of natural resources and as an eco-friendly alternative for natural river sand (NRS). This paper explored the potential feasibility of recycling KTS, as a substitute for NRS as a fine aggregate in producing cement mortar and concrete. Material characterization tests revealed that KTS possessed a high content of quartz and comparable physical properties to NRS. The fresh and hardened properties of mortars and concretes with varying KTS replacement combinations were determined. The experimental results revealed that the introduction of KTS reduced workability of the resulting mortar, attributed to the high water absorption of KTS particles. However, the introduction of KTS led to a reduction of expansion induced by alkaline silicic acid reaction (ASR) as well as an improvement in flexural strength and compressive strength of the resulting mortar, closely relating to the rough texture and angular nature of KTS. In the case of concrete test, KTS was superior to NRS in enhancing the compressive strength and splitting tensile strength, while decreasing the chloride ion penetration of concrete regardless of whether fly ash or slag was incorporated as a mineral admixture. It is noteworthy that for both mortars and concretes, specimens with 60% of KTS replacement by mass exerted the best mechanical performance. Beyond this ratio led to a slight reduction in mechanical strength, but still acceptable, mainly due to the relatively low inherent strength and depressed packing induced by the flaky shape of KTS particles.