FACTORS AFFECTING SHRINKAGE OF PERIWINKLE SHELL POWDER (PSP) STABILIZED LATERISED CONCRETE SHORT COLUMN

Abstract

Shrinkage is a time-dependent reduction in the volume of concrete that may occur without externally applied loads. When shrinkage is restrained by reinforcement, foundations, adjacent structural members or differential moisture gradients, tensile stresses develop and may produce cracking. This paper reviews the principal factors affecting shrinkage in short columns made from laterised concrete stabilized with periwinkle shell powder (PSP). Laterised concrete contains lateritic soil as a partial or complete replacement for conventional fine aggregate, while PSP is produced by cleaning, drying, grinding and sieving periwinkle shells without calcination. The incorporation of these materials changes water demand, particle packing, paste volume, pore structure, stiffness and moisture transport. Consequently, the shrinkage of PSP-stabilized laterised concrete is governed by interacting factors, including laterite content and mineralogy, PSP replacement level and fineness, water-to-binder ratio, cement and paste contents, aggregate properties, workability, compaction, curing, relative humidity, temperature, column dimensions, reinforcement and age. This study evaluated the factors affecting shrinkage of periwinkle shell powder (PSP) stabilized laterized concrete short columns. This is with a view to determining the shrinkage characteristics of PSP-stabilized laterized concrete short columns and to determine the optimum replacement level of cement and sand with periwinkle shell powder and laterites in concrete short columns. Preliminary tests (moisture content, specific gravity, and Atterberg limit test) were carried out on sand, laterites, and PSP. Compressive strength test and shrinkage test were carried out to determine the strength and the rate of deformation. Four different percentages of replacement of periwinkle shell powder and lateritic soil (0%, 10%, 20%, and 30%) were used for the compressive strength test and shrinkage test. The results of the study show that the workability of concrete mix with or without periwinkle shell powder increases from 10 mm to 16 mm to 25 mm to 30mm at 0.5 water/cement ratio with 0%, 10%, 20%, and 30% replacement, respectively. Also, the compressive strength of all mixes continued to increase with an increase in curing age (5.70N/mm-12.00N/mm-12.67N/mm-16.60N/mm for 7days, 14 days, 21 days, and 28 days, respectively), and there is a decrease in strength with an increase in periwinkle shell powder and laterites. The shrinkage of all mixes continued to increase with an increase in the percentage of periwinkle shell powder and laterites. As the strength decreases with an increase in the percentage of periwinkle shell powder and laterites, the results of 10% replacement of periwinkle shell powder and laterites at a water/cement ratio of 0.60 are significant. The study concluded that 10% replacement of periwinkle shell powder and laterites in the form of cement and sand can be done on concrete.