Influence of volcanic originated natural materials as additives on the setting time and some mechanical properties of concrete

The natural materials provide a way for an economic production of concrete in hot weather conditions without using high cost chemical retarders. Effects of a natural additive on the properties of concrete vary with the additive type and volume. In this study, the effect of two natural materials as additives on the properties of concrete was investigated. Nine concrete mixtures were produced in three series with control mixes having 300 kg cement content. These control mixes were modified to have 1%, 2%, and 4% pumice or diatomite ill place of cement. As the diatomite or pumice ratio increases, the initial setting and setting duration of concrete increase. The effect of the additive ratio on the compressive strength and the modulus of elasticity were varied. The additive ratio increase in concrete resulted a sudden decrease at first and an increase than, of the compressive strength and of the modulus of elasticity. The variation of the compressive strength and of the modulus of elasticity along the time is similar to the conventional concrete and confirmed some of the existing empiric formulas. (c) 2006 Elsevier Ltd. All rights reserved.