Nowadays, the sustainable development of the construction industry has become a focus of attention. Crushing and grinding waste seashells originating from the fishery industry, such as oyster shells, cockle shells, mussel shells, and scallop shells, into different particle sizes for usage as aggregate and cement in concrete or mortar provides an effective and sustainable solution to environmental problems by reducing natural resource dependence. Numerous studies have attempted to analyze the suitability of waste seashell as a possible alternative to natural aggregates and cement in concrete or mortar. This paper presents an up-to-date review of the characteristics of different types of waste seashell, as well as the physical, mechanical, durability, and other notable functional properties of seashell concrete or mortar. From the outcome of the research, waste seashell could be an inert material, and it is important to conduct a series of proper treatment for a better-quality material. It is also seen from the results that although the mechanical properties of seashell concrete have been reduced, they all meet the required criteria set by various international standards and codes. Therefore, it is recommended that the replacement of seashells as aggregate and cement should not exceed 20% and 5%, respectively. Seashell concrete or mortar would then have sufficient workability and strength for non-structural purposes. However, there is still a lack of investigation concerning the different properties of reinforced concrete members using seashells as the replacement of aggregate or cement. Further innovative research can solidify its utilization towards sustainable development.

Considering the environmental problems arising from random disposal of waste shells and the overexploitation of river sand, crushed waste shells (CWS) can be recycled and used as fine aggregates in eco-friendly concrete production. Nevertheless, existing studies on CWS concrete still present notable limitations, including a low optimal replacement level and poor workability caused by the high water absorption of CWS. This study primarily explored the feasibility of 100% CWS replacement of fine aggregates for producing eco-friendly concrete with different strength grades and satisfactory workability. With pre-absorption treatment applied to CWS aggregates, three groups of eco-friendly CWS concrete (C30, C40 and C50) were made instead of direct sand replacement based on ordinary river sand concrete. The hardened properties of CWS concrete, including mechanical strength, durability-related transport characteristics, pore structure, mineral composition and microstructure, were systematically investigated and compared with those of ordinary river sand concrete. This study provides a technical basis for the efficient recycling of waste shell resources and the practical engineering application of eco-friendly CWS concrete.