Behavior of Actively Confined Rubberized Concrete under Cyclic Axial Compression

The results of the first experimental study on the behavior of axial cyclically loaded rubberized concrete under active confinement are presented. Four different mixes of concrete with rubber replacement ratios of 0%-18% were considered to investigate the influence of the rubber content on the cyclic compressive behavior of concrete under different levels of lateral confining pressure ranging from 5 to 25 MPa. The results show that trends of the axial stress-axial strain and lateral strain-axial strain relationships of rubberized concrete under cyclic loading closely follow those of the corresponding monotonically loaded concrete. At a given confining pressure and rubber content, concrete exhibits a higher ductility under cyclic loading than under monotonic loading. Furthermore, cyclically loaded rubberized concrete specimens exhibit higher peak and residual stress ratios, but slightly lower peak and residual strain ratios compared with those of their monotonically loaded counterparts. Results also show that the unloading and reloading tangent modulus of rubberized concrete increase but axial plastic strain of rubberized concrete decreases with an increase in the confining pressure, following a trend similar to that of natural aggregate concrete. Owing to the lower unloading tangent modulus of the concrete with a higher rubber content, for a given confining pressure, the axial plastic strain of cyclically loaded rubberized concrete slightly decreases with increasing rubber replacement ratio. Based on the test results, simple model expressions were developed to predict the axial stress-strain relationship of actively confined rubberized concrete under cyclic axial compression. Promising findings of this study suggest that confined rubberized concrete can be used in column applications to reduce the environmental impact of waste tires and conserve nonrenewable natural resources.