Researchers have used different micro fillers as a substitute for sand to understand their effects on the hydration behaviour of Portland cement-based materials (CBMs). Micro fillers can exhibit two effects, namely, physical effects attributed to particle fineness, surface energy, etc., and chemical effects if they are reactive, although the the effects of the latter have not been reported in most studies. Brick is one such material that contains significant silica and alumina contents and can be used in powder form to exhibit properties that a reactive micro fillers possess. Very few studies are currently available to understand the feasibility of using brick powders (BPs) as a sand substitute material, and hence, the main objective is to understand their effect on the hydration behaviour of CBMs. In this investigation, conventionally available burnt-clay bricks were crushed to sizes below 150 μm and used at 5% dosage in mixtures so that their water absorption effects after sand replacement were minimal. The hydration behaviour was assessed using Thermogravimetric Analysis (TGA), Electrical Impedance Spectroscopy (EIS) technique and compressive strength test at appropriate ages. Results indicated that the BP addition reduces the normalized Ca(OH)2 of pastes only after 7 days due to possible pozzolanic reaction. The high-frequency resistance (R1) and bulk resistivity (Rb) values obtained from EIS increased with BP addition at later ages, indicating the formation of more hydration products, refinement of pore structure, etc. The compressive strength trends also supported such behaviours for both mortar and concrete mixtures. At early ages, no significant improvement in properties was observed with BP addition, although improvements were substantial only at later ages. Overall, the positive effects of BP addition are evident although the study is limited only to the hydration and strength aspects. Since mixtures containing BP provided improved bulk resistivity, one can expect such mixtures to provide better durability also.