Evaluation of chloride transport in blended cement mortars containing coal mining waste

In this study, the effect of the addition of a thermally activated coal mining waste (CMW) on the chloride permeability of blended cements in amounts from 10 to 50% was assessed by salt ponding test. The parameters involved in the infiltration of chloride have been evaluated by XRD, TG and MIP techniques, as well as by electric resistivity measurements. A remarkable improvement in chloride diffusion was found as the CMW content increased, which has resulted in a decrease of one order of magnitude in the chloride diffusion coefficients of specimens containing 50% of CMW (2.7·10−12 m2/s) with respect to OPC samples (20·10−12 m2/s). The chemical analyses have shown that immobilization of chloride ions as Friedel's salt takes place as a result of their reaction with the abundant hydrated aluminate phases formed as a consequence of the high alumina content in CMW. Moreover, it has been observed a refinement of the capillary network with the addition of CMW that has been manifested through a decrease in pore size and a subsequent increase in electrical resistivity.