ABSTRACT
The study examined the partial replacement of Ordinary Portland Cement (OPC) with Periwinkle shell Ash (PSA) and Periwinkle Shell Dust which was obtained from burning 200kg of Periwinkle shell at 6000C and grinding 200kg with ball mill respectively. Concrete cubes were prepared from design mix with target strength of 20N/mm2, 25N/mm2, 30N/mm2 and 40N/mm2 and the replacement of the PSA and PSD were 0%, 5%, 10% and 20% respectively. The chemical analysis of both samples indicated that CaO content in PSA is higher than PSD leading to quick reaction with water. The presence of organic calcium in PSD was responsible for slowing setting of the concrete and subsequently leading to disintegration of the paste at 20% replacement when tested for soundness. The workability test indicated that as the percentage replacement of PSA and PSD increases the slump test value degreases, while compressive strength decrease with increasing replacement and increase with curing age. The design compressive strength was attained at 5% and 10% replacement for both PSA and PSD based on the 75% strength of OPC recommended by ASTM C618 for grades of concrete at 28days. The scanning electron microscopy (SEM) analysis of concrete showed an increase in pore space as the percentage replacement increases. However, at 20% PSA replacement the SEM result indicates as uneven distribution of Ca(OH) as a result of increase in lime (CaO). The One-way analysis of variance (ANOVA) on the laboratory test result shows a statistically significant effect of percentage replacement and workability on the compressive strength of concrete. The test concluded that 10% PSA and PSD content is enough for cement replacement at any strength grade.