Utilization of Waste Oyster Shell in Concrete: Effect of Conplast Sp430 on Compressive Strength

The depletion of natural sand and the accumulation of oyster shell [OS] waste in coastal regions have necessitated the search for sustainable alternatives in concrete production. This study investigates the effect of partial replacement of fine aggregate with OS and the addition of Conplast SP430 superplasticizer [SP] on the workability and compressive strength of concrete. Fine aggregate was replaced with OS at 0%, 5%, 10%, 15%, and 20%, while SP was added at 0%, 0.5%, and 1.0% by weight of cement. A total of 13 mix combinations were prepared using a 1:2:4 mix ratio and 0.6 water-cement ratio. Slump and compressive strength tests were conducted at 7, 14, and 28 days of curing. Results showed that the inclusion of SP significantly improved workability, with the highest slump of 500 mm recorded at 20% OS + 0.5% SP. Compressive strength increased with curing age for all mixes. The optimum performance was achieved at 5% OS + 0.5% SP, which recorded the highest 28-day compressive strength of 31.63 N/mm², representing a 57.8% increase over the control. The study concludes that the combined use of OS and SP is effective for producing sustainable concrete with enhanced mechanical properties.

Oyster shell; Superplasticizer; Compressive strength; Workability; Sustainable concrete

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