Experimental and numerical evaluation of rheological and mechanical properties of self-compacting concretes containing steel fibers and PET using response surface method (RSM)

In the modern characteristics of concrete design based on daily needs, the use of recycled materials is an important and basic principle. Therefore, in the present study, PET (Polyethylene Terephthalate) has been substituted for fine aggregates in self-compacting concrete. The aim of this study is to produce and optimize the mechanical and rheological properties of environmentally friendly self-compacting concretes. Input variables in the mixtures include (PET) as a substitute for a percentage of fine aggregates, steel fibers, powder stone as a substitute for a percentage of cement weight, and lubricant as a percentage of powder material weight. The studied responses are slump flow, L-box ratio (H2 / H1), compressive and tensile strengths. Mixing schemes were designed and studied using the Central Composite Design (CCD) method, which is one of the RSM (Response Surface Methodology) methods. The results demonstrated that with increasing PET, the rheological and mechanical properties of the mixtures decreased while the fibers effectively improved the reduction of strengths. Applying mathematical models provided by ANOVA, multi-objective optimizations were performed to maximize compressive strength by the RSM method and an optimal mixing scheme based on experimental results was proposed.