The Effect of Using a High Proportion of Waste Bottom Ash Instead of Sand on the Mechanical Properties of Mortars

Waste bottom ash (WBA) disposal requires large landfill areas and poses significant environmental risks due to possible leaching. Therefore, using WBA as sand replacement in mortar production is a sustainable alternative to reduce these environmental concerns. This study investigated the effects of high WBA substitution rates on the mechanical properties of mortars, including ultrasonic pulse velocity (V), flexural strength (ff), and compressive strength (fc), at different substitution levels (0%, 15%, 25%, 35%, 50%, 70%, and 100%) and specimen ages (28, 60 and 90 days). The study results showed that V, ff, and fc values decreased as the WBA substitution rate increased. However, up to a substitution level of 35%, the decrease in mechanical properties remained minimal, and this substitution level was considered applicable to the practices. Moreover, 30-35 MPa strength was obtained at 70% and 100% WBA replacement ratios. Therefore, these strength values are very close to the strength level expected from normal concrete. This study highlights that despite the variation in mortar strength, WBA can serve as an economical and environmentally friendly alternative to sand and reduce the environmental impacts of natural sand mining and landfilling.