Utilization of coal gangue as coarse aggregates in structural concrete

In this paper, coal gangue is utilized as a replacement of coarse aggregate in structural concrete. The effects of coal gangue on the mechanical properties of concrete material, circular reinforced concrete column and concrete-filled steel tubular column are experimentally studied and discussed in detail. The mechanical behavior of coal gangue concrete is reduced by increasing the coal gangue replacement ratio. A model is proposed for predicting the compressive strength of coal gangue concrete. Some constants are proposed based on test results to predict the splitting tensile strength and elastic modulus of coal gangue concrete. The increase of coal gangue replacement ratio decreases the axial compressive strength and elastic modulus of reinforced coal gangue concrete stubs and coal gangue concrete-filled steel tubular stubs linearly. The enhancement factor and the confinement factor both approximately increase with the increase of coal gangue replacement ratio which indicates that concrete-filled steel tube is a more preferable product than reinforced concrete for the usage of coal gangue as coarse aggregates. A modified design method for reinforced concrete and concrete-filled steel tube towards cleaner products is proposed by considering the coal gangue replacement ratio. The full-range prediction analysis for the strength degradation of coal gangue concrete-filled steel tube implies that relative higher steel strength and lower concrete strength should be used in the preparation of concrete-filled steel tube using coal gangue as coarse aggregates in structural stubs.