Effect of Different Sulphate Types and Concentrations on Compressive Strength of Periwinkle Shell Ash Blended Cement Concrete

摘要

The study investigated the compressive strength performance of periwinkle shell ash (PSA) blended cement concrete exposed to sulphate environments. Periwinkle shells were obtained from Ikot Ekpene, Akwa Ibom state, Nigeria; and calcined in a furnace to temperature of 8000C at zero soaking time.udConcrete mix of design characteristic strength of 25N/mm2 was adopted as the control. The cement component replaced with PSA at five levels of 0%, 10%, 20%, 30% and 40% were cast, and on hardened exposed to varying concentration of sulphates of magnesium, sodium and calcium at four levels of 0%, 1%, 3% and 5% each for three exposure periods of 62, 92 and 152 days after complete immersion in water for 28 days. Using three replicates in all the tests, a total of 630 cubical (150mm) specimens were cast and tested.udThe results revealed that compressive strength increased with increase in curing age but decreased as the PSA contents increased. The design compressive strength was attained with 10% PSA content at the age of 28 days. The compressive strength reduction in sulphate solutions was noted to increase significantly (p = 0.005, R2 = 0.995) with increase exposure period and concentration, with the most severe caused by magnesium sulphate and the least by calcium sulphate. The least reduction in compressive strength was experienced with 10% PSA blended cement concrete.udBased on the test results the study concluded that 10% PSA content is adequate as supplementary cementitious material for structural concrete to be placed in an aggressive sulphate environment.