Effect of Pumice Stone Aggregate on the Fresh and Hardened
Properties of Self-Compacting Concrete

Abstract

Self-compacting concrete is a concrete which has the flowing ability, filling ability, passing ability and self-compacting nature without any need of external vibrator or compacting devices and without exhibiting defects due to segregation and bleeding. Reduction in weight of concrete improves fresh properties of SCC whereas it affects to the hardened mechanical property of SCC. The density of SCC can be reduced by partially replacing normal aggregate by lightweight aggregate. The combination of these types of aggregates again poses some problem like a heterogeneous aggregate mix which may further affect the fresh and hardened properties of SCC. The heterogeneity of combined aggregate can be measured by a factor called packing density. Pumice stone is a natural lightweight aggregate which is formed by the rapid cooling of the molten lava of the volcanic origin. Due to the sudden cooling millions of tiny air bubbles are trapped inside it making it lightweight sponge-like material with very low specific gravity. Concrete using PSLWA has several advantages over normal concrete.The present work was to study the effect of pumice stone aggregate on fresh and hardened properties of self-compacting concrete. For this purpose, seven mixes were prepared with 0%, 5%, 10%, 15%, 20%,25%, and 100% replacement of coarse aggregate with PSLWA.Since by replacing fractions of normal aggregate by pumice aggregate the grading of combined aggregate was changed. Hence, to observe the effect of grading, packing density of the aggregate was determined for each mix.For each mix, slump-flow, L-box, V-funnel,compressive strength, ultrasonic pulse velocity and split tensile strength tests were conducted. To check the homogeneity in the hardened state, two empirical factors mass and strength segregation factor Sm and Sσ were calculated.The test results revealed that the pumice stone lightweight aggregate up to 15 % can be used successfully in self-compacting concrete as a partial replacement of coarse aggregate without much compromising the strength and with enhanced fresh properties.