The axial behavior of the low and extremely low strength concrete confined with large-rupture-strain PET-FRPs made of production wastes

Based on the fact that there are many substandard reinforced concrete (RC) buildings in developing countries built with low or extremely low strength concrete (LSC or ELSC) and the urgent need of improving the structural performance of such buildings, this study aims to examine the axial behavior of LSC and ELSC externally confined with fiber reinforced polymers (FRPs) having large rupture strain capacity. In order to achieve this aim, as a preliminary study, twelve standard cylinder specimens are produced with ready-mix concrete of 28 days compression strength of 3 and 7 MPa to be tested under monotonic compression with and without external confinement through large-rupture-strain FRPs. For strengthening, nowadays, when it is an inevitable need to protect the environment, it is a proper choice to use polyethylene terephthalate (PET) sheets with high deformation capacity produced through recycling. The PET sheets used in this study are waste PET sheets formed during the tire production process. In this preliminary study, axial compressive strength, axial and lateral deformation capacities of the specimens have been obtained under monotonic axial compression loading. While four specimens are left unconfined to be tested as reference specimens, the others are confined externally with 1-ply and 2-ply large-rupture-strain PET-FRPs by wet lay-up jacketing technique. The monotonic compression test results show that the axial compressive strength and axial strain capacity of LSC and ELSC increase significantly through external confinement with PET-FRPs and the strength enhancement ratios obtained for ELSC are higher than those for LSC whereas the axial strain enhancement ratio of ELSC specimens is smaller than that of LSC.