Effects of expanded perlite aggregate and mineral admixtures on the compressive strength of low-density concretes

This article investigates the compressive strength of concretes made up of mixtures of expanded perlite (EPA) and pumice aggregates (PA). To determine the effects of silica fume (SF) and class C fly ash (FA) on the compressive strength of these lightweight aggregate concrete (LWAC), SF and FA were added as replacement for cement by decreasing the cement weights in the ratios of 10%, 20%, and 30% by weight. The binder dosage was kept constant at 200 kg/m(3) throughout this study. Superplasticizer was used 1.5% by weight of Portland cement (PC) to reduce w/c ratios. The obtained results showed that: Unit weights of all groups decreased from 1154 to 735 kg/m(3) with the increase of EPA in the mixtures. Both SF and FA decreased unit weight of samples. The compressive strengths increased by 52%, 85%, 55% for 7-day samples, and 80%, 84%, 108% for 28-day samples due to 20%, 40%, and 60% of EPA (used in place of PA) added into the mixtures, respectively. In general, FA decreased 7- and 28-day compressive strength of all groups for all percentage of FA replacement for PC. SF decreased 7-day compressive strength with increasing expanded perlite ratio in the mixtures. With the increasing curing period, the reductions in compressive strength due to SF and FA decreased drastically. (C) 2001 Elsevier Science Ltd. All rights reserved.