The Behaviour of Concrete Made with Nanosized Periwinkle Shell Ash as Partial Replacement of Cement Under Varying Curing Conditions with Emphasis on Its Compressive Strength

Abstract

The need to optimize the outcome of concrete casting, to curb excessive shrinkage and cracking in concrete, promotes the attention on concrete curing as durability, and strength, especially compressive strength of concrete depends largely on it. In this paper, the compressive strength of concrete containing nanosized periwinkle shell ash (NPSA) as a partial replacement of cement, was investigated using different curing techniques. The study applied three methods of curing: sprinkling, immersion and plastic wrapping. A concrete mix ratio of 1:1.5:3 and a water-cement ratio of 0.6 was employed to produce a total of 144 concrete cubes, with 48 cubes used for each of the curing methods. Curing periods of 14, 28, 56 and 90 days were considered with NPSA replacements at 5%, 10%, 15% and 20%. At 15% cement replacement with NPSA, immersion, sprinkling and plastic wrapping method produced optimum compressive of strengths of 24.76N/mm2, 23.28N/mm2, 21.25N/mm2; 31.54N/mm2, 29.24N/mm2, 27.85N/mm2; 37.44N/mm2, 34.12N/mm2, 31.53N/mm2; and 43.73N/mm2, 40.27N/mm2, 37.16N/mm2, at 14, 28, 56 and 90 days respectively. Immersion and sprinkling methods produced concrete with greater compressive strengths due to adequate moisture and vapour pressure sustained for continued cement hydration. The reduction in strength encountered in the plastic sheeting technique was due to early blockage of the pores by sufficient calcium silicate hydrate which stopped the cement hydration. The compressive strength of the concrete increases with age in all the curing methods with immersion curing producing the highest strength at all ages. The adoption of immersion curing is reliable for the optimization of concrete strength. However, sprinkling can be applied in case of water dearth