Pumice powder as filler of self-compacting concrete

An experimental study on the rheological and mechanical properties of self-compacting concrete with pumice powder used as filler additive is presented. Self-compacting concrete (SCC) shows its peculiar characteristics in the fresh state and many researches have been developed with reference to its rheological characteristics paying attention to the techniques of self-compacting properties assessment. One of the most important aspect in concrete mix-design is the type and the amount of fillers with respect to water and cement: this amount has great influence not only on self-compacting properties (fluidity, segregation, etc.), but also on the mechanical properties of the mixture. Volcanic materials like white pumice have pozzolanic properties, so that it is possible to use powdered pumice in SCC manufacturing with a double effect: on one hand as filler and on another hand as a pozzolanic element in the mixture. The experimental campaign investigates SCC properties when white pumice powder is used as filler with or instead of silica fumes or flying ashes. From the rheological model of the paste, varying the components of the mixture, the determination of pumice powder amount and the consequences on the rheological properties of SCC are investigated. SCC with pumice powder is compared to other mixtures with silica fume and marble powder as filler, through tests on fresh and hardened concrete. Compressive and tensile strength tests were carried out together with the evaluation of fracture energy with the aim of characterizing the constitutive law of SCC with pumice powder. Results from shrinkage tests in the first days of curing are reported and comparisons with ordinary concrete manufactured with the same basic components are shown in order to evaluate the suitability and effectiveness of pumice powder added as filler to self-compacting concrete mix-design. Pozzolanicity of pumice strictly influences the mechanical properties with a significant increase of compressive strength after 28 days of curing.