Value-added utilization of copper slag to enhance the performance of magnesium potassium phosphate cement

Copper slag, a byproduct of the production of copper metal, is difficult to be reused as supplementary cementitious material in the ordinary Portland cement due to the low content of active amorphous alumino-silicate and the high content of crystalline phases. This study proposes a high value-added utilization approach of copper slag to enhance the early performance of magnesium potassium phosphate cement (MPC). MPC is an expensive rapid repair material with excellent early mechanical property. The experimental results show that the addition of 40% copper slag lead to more than 30% growth of the 1 day's compressive strength of MPC mortar. The crystalline phases in copper slag, especially the fayalite (Fe2SiO4), could react and strongly increase the content of hydrates in MPC system. The reaction products of copper slag in MPC are mixtures of magnesium silicate hydrate (MSH), vivianite (Fe-3(PO4)(2)center dot 8H(2)O) and Fe-hydrotalcite (Mg4Fe2(OH)(14)center dot 3H(2)O). The novel approach proposed in this study to reuse copper slag as a reinforcing agent of MPC not only consumes solid waste but also improves the performance and reduces the cost of high-end rapid repair materials of concrete.