Importance of pumice amount in the design of self-compacting lightweight concrete

Although concrete has high compressive strength values, it has a heavy unit volume and low tensile strength. In this study, the normal-weight aggregate, which takes up the most space in concrete by volume and mass, was partially replaced with pumice aggregate, and macro steel fiber (30 mm) was also added to the mixtures. This experimental work aims to investigate the effect of pumice aggregate amount on the fresh and hardened properties, as well as the flexural performance of the self-compacting lightweight concrete (SCLC). The replacement proportions of pumice aggregate with crushed sand were arranged as 45%, 50%, and 55% of the entire aggregate by weight. Three mixtures, each with 1% macro steel fiber reinforcement and without fiber, were prepared for each mixture scenario. The mix design of these six mixtures was arranged to achieve the self-compacting ability and the workability tests recommended by EFNARC (slump-flow, T50, J-ring) were taken into account. To investigate the mechanical properties (compressive, splitting tensile, and flexural strengths) and flexural toughness of the samples, the specimens were cured in water at 23±2 °C for 28 days. As a result, the unit volume weights of the specimens produced from pumice-substituted mixtures decreased with the increase in the pumice dosage, while the compressive, splitting tensile, and flexural strengths decreased. However, it has been determined that all SCLC mixtures including pumice aggregate provided workability properties in general and had enough compressive strength to be used in the production of structural bearing elements, regardless of fiber content. As a result, the optimum pumice aggregate replacement percentage with crushed sand was found to be 45% and the best flexural performance values of the specimens having macro steel fiber were observed in the ones having 45% pumice aggregate substitution.