Dynamic properties of mortar with oyster shell sand replacement

With the rapid expansion of construction engineering, the demand for traditional materials, particularly natural river sand, has surged, resulting in excessive resource exploitation and significant ecological damage. In response, the use of waste oyster shells as a sustainable alternative for fine aggregates has gained attention. However, limited research has been conducted on the dynamic properties of mortar with this substitution. This study explores the potential of using crushed oyster shell sand (OSS) as fine aggregates in mortar. A series of Split Hopkinson Pressure Bar (SHPB) tests under different gas pressures (p_g) (0.2, 0.3, and 0.4 MPa) were carried out on mortar samples with five OSS replacement ratios (R_r) (0%, 20%, 50%, 80%, and 100%), using a water-to-cement ratio of 0.55. The results showed that when the OSS replacement rate (R_r) increased from 0 to 20%, there was a significant increase in peak stress (σ_max) and elastic modulus (E), attributed to the filling effect of OSS, which enhanced the absorbed energy (E_ab) and strength contribution rate (SCR). However, at R_r above 20%, a sharp decline in σ_max and E was observed, primarily due to porous characteristics of OSS. Correspondingly, E_ab decreased, reducing the impact resistance of mortar. Moreover, the negative SCR suggests detrimental effects on mortar integrity at higher OSS R_r levels. Predictive relationships for peak stress and elastic modulus across different replacement ratios were established in this study, providing a foundational reference for the design and assessment of the dynamic mechanical response of structures incorporating OSS.