Experimental and numerical study of the effect of PET and steel fibers on flexural strength and stress-strain curves of self-compacting concretes

The aim of this study is the experimental and numerical investigation of the simultaneous effect of PET and steel fibers on the rheological properties, flexural strength, and compressive stress-strain curve of self-compacting concrete. For this purpose, 30 mixing designs by response surface method (RSM) were designed by combining different percentages of PET, steel fibers, stone powder, and superplasticizer variables. The results demonstrate that with increasing the percentage of PET and steel fibers, the viscosity of concrete decreased. Also, the highest flexural strength was obtained from the combination of 0.4% fibers, 8% PET, and 1% superplasticizer. The stress-strain curves plotted for the mixtures showed that the steel fibers had little effect on the ascending part of the stress-strain curve and improved the stability on the descending part of the curve. PET particles also reduce the slope of the ascending part of the stress-strain curve. In general, Steel fibers and PET caused the soft failure of the samples so that PET increased the strain corresponding to the maximum compressive strength, and steel fibers increased the rupture strain of concrete.