The growingRed mud demandMortar for sustainable construction practices has led to increasing interest in self-sensing materials produced with recycled materialsRecycled materials. Therefore, this study investigated the effects of replacing natural sand with different contents of red mudRed mud (RM) on the rheological, mechanical, and self-sensing properties of cementitious sensorsCementitious sensors containing carbon black nanoparticles. Experimental tests were conducted to evaluate the workability, compressive strength, electrical resistivity, and piezoresistive behavior of mortarsMortar produced with replacement levels of 25, 50, 75 and 100% (by volume) of sand by RM. Increasing the replacement level resulted in an approximately 80% gain in the average compressive strength of the mortarsMortar but also reduced workability by about 60%. MortarsMortar with 25% replacement exhibited a typical insulating material behavior, while those with replacement levels higher than 50% showed high electrical conductivity. The mortarsMortar with 50, 75 and 100% replacement levels demonstrated consistent and reversible electrical resistivity variations under loading cycles, with a significant improvement in sensing ability as the RM content increased. Hence, the RM-based smart mortarsMortar produced in this study have a notable potential to contribute to the promotion of sustainabilitySustainability and structural integrity of buildings.