Evaluation of post-fire pull-out behavior of steel rebars in high-strength concrete containing waste PET and steel fibers: Experimental and theoretical study

Abstract

The present research addressed the post-fire bond performance between high-strength concrete incorporating waste polyethylene terephthalate (WPET) and steel reinforcement; a subject that had not been previously addressed. Further, the impact of incorporating steel fiber, as a commonly used material, into the mixture on the bond improvement was assessed. To this end, the content of WPET substituting for the fine aggregate by volume (0, 5, and 10%), volume fraction of steel fibers (0, 0.5, and 1%), applied temperature (25, 200, 400, and 600 °C) were considered as variables in a total of 108 samples that were produced. Afterward, the samples were subjected to the pullout test to examine different parameters. These parameters included the bond behavior, failure mode, bond stress-slip response, and bond strength-compressive strength behavior. Based on the results, with the incorporation of 5 and 10% volume content of WPET replacing fine particles, the bond strength declined by 4 and 26%, respectively, and as the temperature was raised, this reducing effect increased. Furthermore, the presence of steel fiber had a positive impact in the samples with the splitting failure mode, while it had a negligible or sometimes even negative impact in the samples with the pull-out failing mode. Lastly, multivariate prediction models were proposed for the bond behavior and bond-slip response as a function of the concrete compressive strength, WPET content, content of steel fiber, and the target temperature. Afterward, a comparison was made between the empirical results and the predictions of models developed by other researchers and the fib Model Code 2010 and ACI 408-12 codes.