Fibre-reinforced polymer confined-coal rejects concrete: Compressive behaviour

Coal rejects concrete (CRC) made of the industry by-product generated during the mining preparation and washing procedure is usually regarded as the alternative to natural aggregate concrete (NAC). To improve the low strength and brittleness of CRC, this paper presents a new structural form, termed fibre-reinforced polymer (FRP)-confined CRC (FCCR) column. The most attractive feature of the FCCR column is its cost-effectiveness and environmental-friendly, because that the aggregates of infilled CRC are all from sieved coal rejects without any more artificial crushing process. To obtain the further understanding on the behaviour of FCCR column, a total of 10 hybrid columns, consisting of 6 FCCR and 4 FRP-confined NAC (FCNA) columns with a diameter of 200 mm and a height of 450 mm, have been prepared and tested. The main variables tested in the present study covered the FRP thickness and the concrete strength. Test results showed that FCCR columns obtained the similar mechanical performance of FCNA under the uniaxial compression. Particularly, these FCCR columns exhibited superior axial deformation ability compared with their counterparts, when the low strength CRC is infilled. Compared to the concrete strength, the effect of FRP thickness in enhancing both the strength and ductility of FCCR columns is much more significant. In addition to their superior mechanical performance, the environmental benefits and reduced carbon emission by add-value use of mine wastes make the FCCR column to be an ideal option for infrastructure or underground spaces where the large deformation ability of structural form is the most important concern.