An experimental investigation and response surface methodology-based modeling for predicting and optimizing the rheological and mechanical properties of self-compacting concrete containing steel fiber and PET

Abstract

In this study, rheological and mechanical properties of self-compacting concrete containing polyethylene terephthalate (PET) and steel fibers have been investigated experimentally and numerically. A total of 30 mixing schemes are investigated using a response surface (RSM) method. Input variables in the mixtures include PET as a substitute for part of the fine aggregates, steel fibers, stone powder as a substitute for a percentage of cement and superplasticizer. The PET, steel fibers and stone powder quantity in the concrete were in the range of 0–16% of the fine aggregates, 0–0.4% of the concrete volume, and 0–16% of cement weight, respectively. The superplasticizer quantity was 0.5–1.5% of the weight of powder materials. An optimum mixture was determined using RSM optimization technique.To evaluate the rheological specifications, slump flow, T50, V funnel, and l-box tests were used in the experiments. For the mechanical specifications, compressive strength, tensile strength, flexural strength, and stress–strain curve were used. Experimental results show that steel fibers reduce rheological properties while improve mechanical properties, especially ductility. Additionally, PET increases the corresponding strain of maximum compressive strength of concrete (ε0) and ductile fracture. The optimization results indicate that with 4% PET, 0.23% fiber, 6.47% stone powder, and 1.132% superplasticizer, the maximum 28-day compressive strength is obtained, while meeting EFNARC workability indicators.