Twenty four mortar mixes have been tested to assess the effects mix design factors on complex electrical resistivity. Of these mixes, 6 were conventional and 18 were conductive mixes containing varying quantities of either graphite or carbon fibre powder additions, which have been shown in previous studies to reduce the resistivity of cementitous materials. Complex resistance measurements from 20Hz-10MHz taken between 7 and 35 days after casting were analysed. Comparisons were made between the effects on complex resistivity of varying quantities of additions, water/cement ratio, and grit/sand ratio. In conventional mixes w/c was found to have more significance for complex resistance than g/s. Conductive additions were found to reduce complex resistivity magnitude as well as the influence of other mix factors. This novel and comprehensive comparison of the effects of three elements of mix design on complex resistance will be of use to anyone wishing to produce mortars or concrete for use in self-heating, self-sensing, or electrical property imaging contexts.