The effects of pumice aggregate/cement ratios on the low-strength concrete properties

Lightweight concretes can be produced by using processed natural material, processed by-product or unprocessed porous materials, depending upon the requirements of density and strength levels. The present study covers the use of pumice lightweight aggregate (PLA) to produce the lightweight concrete (LWC) for use in construction of load-bearing or non-load bearing elements. In this study, pumice aggregate lightweight concrete (PALWC) blocks were produced with different sizes of 8-16 mm as coarse pumice aggregate (CPA), of 48 mm as medium pumice aggregate (MPA) and 0-4 mm as fine pumice aggregate (FPA). According to the preliminary trial batch results, the optimum grade of aggregates was determined as 25% FPA, 25% MPA and 50% CPA by weight for the mixture compositions. The pumice aggregates were obtained from a pumice quarry in Isparta region, Turkey. To analyse the effects of CPA, MPA and FPA/cement ratios on the non-structural concrete engineering properties, the range of different pumice aggregate/cement (A/C) ratios of 6:1, 8: 1, 10: 1, 15:1, 20:1, 25:1 and 30:1 by weight and cement contents of 180, 137, 110, 72, 52, 40 and 32 kg/m(3) were used to make PALWC mixture testing samples with a slump of from 2 to 4 cm. The properties of PALWC with the range of different pumice aggregate/cement ratios were evaluated by conducting comprehensive series of tests on workability, compressive strength, elasticity modulus, bulk density, wetting expansion, drying shrinkage, water absorption and thermal conductivity. Experimental test results showed the PALWC up to 25:1 A/C ratios has sufficient strength and adequate density to be accepted as load-bearing block applications. Further, higher than 25:1 A/C ratio has sufficient strength, adequate density and the thermal conductivity to be accepted as non-load bearing infill blocks for insulation purposes. PALWC showed the design flexibility and substantial cost savings by providing less dead load due to its lower density values. The properties, which increase in value and indicate the increasing quality with lower A/C ratios (high cement contents), are compressive strength, modulus of elasticity and density. Properties, which decrease in value, with higher A/C ratios are water absorption, wetting expansion, drying shrinkage and thermal conductivity. It was experienced that lowering the A/C ratios increases strength quality of PALWC. But, increase of the A/C ratio increases the thermal insulation property. Basically, the research showed that non-structural lightweight concrete can be produced by the use of fine, medium and coarse pumice aggregates mixes without using any additions or admixtures. (C) 2007 Elsevier Ltd. All rights reserved.