This paper focuses on the electrical, physical and mechanical characterization of the ancient mortar (khorasan mortar) materials of precious structures, the Ali Pasa bathhouse, Candarli Ibrahim Pasa bathhouse, Hasan Pasa bathhouse, Iznik Castle and Tophane rampart historical constructions located in the West of Turkey, in Bursa. An exhaustive description of the materials has been obtained to enriching the knowledge on historical construction materials. The definition of the physical and mechanical properties of the materials, sophisticated laboratory tests were performed such as compressive strength, point loading, weight loss in acid, specific porosity, density and water absorption tests. Microstructure investigations and electrical resistivity measurements were also performed on the ancient mortars. The good correlations were obtained between electrical resistivity and mechanical properties of historical mortars as result of relations between them. The experimental investigation has allowed a better understanding of the remote origin of these structures.