Mechanical and Physical Performance of Mortars Incorporating Crushed Hazelnut Shells as Partial Fine Aggregate Replacement

This study investigates the mechanical and physical properties of mortars incorporating crushed hazelnut shell (HS) as a partial replacement for fine aggregates. Mortar mixtures were prepared with varying water‐to‐cement (w/c) ratios ranging from 0.35 to 0.50 and HS dosages of 2.5%, 5%, and 7.5% by weight, along with reference mixtures without HS. The mechanical performance, abrasion resistance, water absorption, and setting times of the mixtures were evaluated. Results showed that incorporating 2.5%–7.5% of crushed HS increased water absorption by up to 60% and reduced compressive and flexural strengths by 35% and 25%, respectively. However, the addition of HS attenuated autogenous and drying shrinkage by up to 45% and delayed the setting time by approximately 40%, indicating beneficial internal curing effects. Although the inclusion of HS leads to a decrease in strength, it contributes to improved dimensional stability and sustainability. Therefore, crushed HS can be considered a viable material for nonstructural, eco‐friendly mortar applications where moderate strength reduction is acceptable.