Fresh, mechanical and impact properties of self-compacting lightweight concrete containing waste PET fibers

The aim of this study is to evaluate fresh, mechanical, and impact resistance of structural lightweight self-compacting concrete with good thermal insulation and incorporating waste PET fibers with different volume fractions and aspect ratios. Integration of the characteristics of self-compacting concrete, which are followability, good strength and sustainability with the characteristics of lightweight concrete, represented in reducing the loads of the structure and thermal insulation, in addition and with reducing the environmental damage represented by plastic by utilizing a fiber is the goal of this research. As a first stage of this study, lightweight Ponza aggregate was used as a coarse aggregate, as four reference mixtures were produced with volume replacement ratios of coarse aggregate volume ranging from 20 to 100%, and a reference mixture was produced for the purpose of comparison. In the second stage of this study, the performance of self-compacting lightweight concrete SCLC reinforced with waste PET fibers were analyzed in terms of fresh, physical, mechanical, and thermal properties as well as its flexural toughness and impact behavior. Nine different fiber reinforced self-compacting lightweight concrete were designed using waste plastic fibers WPF at three different volume fraction (0.5%, 0.75%, and 1%) and three different aspect ratio (15, 30, and 45). After design process, similar properties in the first stage in addition to toughness and impact test were performed. The results of second stage verified that the adding WPF to SCLC leads to reduction in dry density, ultrasonic pulse velocity, and thermal conductivity around 9%, 14%, 19%, respectively, with increase in PET fibers ratio from 0 to 1% at aspect ratio of 45. Further, the result of flexural toughness test showed that the use of WPF in SCLC leads to an interesting improvement in the post-cracking performance and enhanced ductility of concrete. Furthermore, there is substantial improvement in impact resistance of all WPF-reinforced SCLC mixes over control mix. Results clarified that WPF concrete mix of volume fraction 1% and aspect ratio 45 gave the best impact resistance, the improvement of its impact resistance at ultimate failure over control mix was 373.3%.