In this research work, experiments were conducted followed by collection of materials and the data required for mix design obtained by sieve analysis and specific gravity test. Sieve analysis was carried out from various fine aggregates (FA) and coarse aggregates (CA) samples and the sample which suits the requirement was selected. Specific gravity tests were carried out for various samples of fine and coarse aggregate. The different materials used were tested as per Indian standard specification. Based on the experimental studies carried out on M30 grade concrete as partial replacement of coarse aggregates with sea shells and coconut shells, the following conclusions were drawn.Comparing to traditional concrete, compressive strength of 10% (5% + 5%) of coconut shells (5%) and sea shells (5%) was found to be increased wherein the compressive strength of the concrete cubes gradually decreased from addition of 10% (5% + 5%) of coconut shells and sea shells. 10% mix was considered to be the most preferable, so as to achieve both economic viability and optimum compressive strength. Thus, 10% replacement of coconut shells and sea shells were recommended for both heavy weight and light weight concrete production