Ultra-Fine Treated and Untreated Walnut Shell Ash Incorporated Cement Mortar: Properties and Environmental Impact Assessments

The utilization of walnut shell (WS) as partial replacement of aggregates and cement is getting more attention in modern research on construction material. Though WS provides lightweight concrete, but less compressive strength and porous structure of concrete is still problematic for its utilization. Thus, this study is using untreated walnut shell powder (UWSP) and ultra-fine treated walnut shell ash (UFTWSA) as a substitute for cement. Different weight fractions of UWSP and UFTWSA (5, 10, 15 and 20%) were used to investigate the influence on fresh and hardened properties of cement mortar. Further, the durability of all mixes was evaluated by immersing them in different concentrations of MgSO4 (5, 10 and 20%). The experimental results revealed that the inclusion of UWSP and UFTWSA reduces the fresh and hardened properties of cement mortar. Moreover, UWSP addition has more negative impact on fresh and hardened properties of cement mortar as compared to UFTWSA. The hardened properties of mortar specimens remarkably decreased by immersing in MgSO4 solution. However, all mixes contained UWSP and UFTWSA and not exposed to acid attack achieved more than 30 MPa and can be classified as good type mortar depending on obtained ultra-sonic plus velocity values (UPV).