Post-fire behavior of unconfined and steel tube confined rubberized concrete under axial compression

Employing steel as a confining material for concrete has gradually been gaining popularity over the last decades. The literature demonstrates strength improvement, concrete stiffness, damage reduction, and delayed failure of steel-confined concrete after exposure to fire. Concrete columns confined by steel tubes, referred to as the steel tube-confined concrete (STCC) columns, have enhanced performance in terms of axial loading. Moreover, the presence of tire rubber aggregate in concrete mix has been shown to improve the plasticity and energy absorption, particularly in seismic areas. Even so, this method may decrease concrete strength in case of exposure to fire. In the present work, the compressive behavior of rubberized concretes confined by steel tubes was investigated where the replacement percentages of fine aggregates with rubber were 0, 7.5, and 15%. Thirty specimens were tested mechanically after thermal loading at 200, 400, 600, and 800 degrees C. The post-fire physicomechanical properties involving the failure modes, compressive stress-strain relationships, compressive strengths, elastic moduli, stiffness, and peak strain were experimentally investigated, together with visual observations. The experimental results demonstrate that an increase in the exposed temperature up to 400 degrees C does not have a significant effect on the compressive strength of rubberized STCC, whilst an increased temperature to 800 degrees C results in a significant decrease in the compression of the specimens. It is also indicated increasing the exposure temperature and crumb rubber replacement ratio leads to lead to an increase in the strain at peak stress of steel tube confined rubberized concrete.