Technological watch

This study examined the possibility of using PET aggregates as a partial substitute for natural fine-grained aggregates in RCCP mixtures. To enhance the performance of RCCP, the mixtures were also modified by using pozzolanic Metakaolin (MK) as a partial substitute for cement and adding steel fibers obtained from the recycling of worn vehicle tires. The response surface methodology (RSM), which is capable of predicting the variations of a response value in the variations range of independent variables, was used to cover all possible mix compositions. Using this method, 20 mix designs were prepared, which allowed for significant time and cost saving in experiments without sacrificing thoroughness. The behavior and characteristics of RCCP specimens in terms of specific gravity, ultrasonic pulse velocity, compressive strength, split tensile strength, and flexural strength at the age of 28?days were investigated. The obtained responses were used to develop statistical models, which were then utilized in the optimization of mix design with the help of analysis of variance. The results showed that the use of PET aggregates decreased the compressive, tensile, and flexural strength as well as specific gravity and ultrasonic pulse velocity of the RCCP specimens. Partial replacement of cement with MK generally improved the mechanical performance of the specimens. The effect of shredded recycled steel fibers (SRSF) was generally dependent on other components of the mixture. The optimal mix design obtained from the statistical models involves replacing 25?vol% of fine aggregate with PET, replacing 20?wt% of cement with MK powder, and adding 1.9?wt% SRSF to the mixture. The proposed mix design contributes to clean recycling of PET and conservation of natural resources and reduces the cost and carbon footprint of RCCP construction with considering the standard requirements for pavement structures.