Hardened properties of mortar mixtures containing pre-treated waste oyster shells

Abstract Considering the environmental issue due to waste oyster shells (WOS) dumped randomly and over-exploitation of river sand resources, a drive toward utilization of crushed WOS as substitution materials for fine aggregates mixed in concrete has been initiated. Waste oyster shells have been proved to have the potential to be recycled for use as construction materials. However, applying fine WOS aggregates as substitute materials to produce concrete is likely to negatively affect the durability. This paper conducted a comparative study using two different surface treatment methods. Crushed WOS aggregates were modified by polyvinyl alcohol (PVA) and sodium silicate (SS). Both the mechanical properties and the durability-related transport properties of the WOS mortar were investigated with the pore size distribution, mineralogy and microstructure analysis. The results showed that the durability of the WOS mortar can be effectively improved through two treatment methods and mortar treated by SS performed better. Mortar treated by SS showed an improvement in mechanical properties while a slight decline was seen in the mortar treated by PVA, compared to the control mortar. By understanding the behavior of hardened mortar containing pre-treated WOS aggregates, a resource-friendly WOS mortar with better durable properties could be produced and used for the practical engineering application in future which will be beneficial to protecting the environment.