Mechanical properties of sustainable freshwater marine sand mortar

Marine sand has gained significant interest among researchers as a potential solution to the shortage of river sand for construction purposes. However, using marine sand as a fine aggregate in mortar has yielded contradictory results. To investigate the underlying reasons for this phenomenon, an experimental study was conducted to study the influence of marine sand with different characteristics on the mechanical performance of mortar. The shape and size of marine sand significantly impact its loose bulk density, voids and water absorption. The properties of marine sand mortar include workability, hardened density, flexural strength, and compressive strength. Beach marine sand, with its fine and uniform particles, requires higher water content, resulting in lower workability. This reduction in workability leads to decreased mechanical strength due to the increased voids within the mortar. However, marine sand's sub-angular to angular shape contributes to mechanical strength by bonding with the cement paste and through the interlocking action between sand particles. Despite this, it has been found that the presence of voids within the mortar is the dominant factor contributing to its low mechanical strength. The flexural strength of marine sand mortar was reduced by 16.9%-49.3% compared to river sand mortar, while the compressive strength decreased by 20.9%-64.9%. One important finding is that marine sand that contains impurities such as coral skeletons and seashell fragments significantly reduces the mechanical performance of marine sand mortar. Based on this observation, it is evident that not all marine sand is suitable for use as fine aggregate in mortar.