Influence of macadamia nutshell particles on the apparent density and mechanical behavior of cement-based mortars

The production of cement mortar has resulted in significant environmental issues. Many scientists have attempted to reduce environmental pollution by using agricultural waste as a substitute for mortar raw materials. This study creatively investigated the physical and mechanical properties of the new green cement mortar made from macadamia nutshell(MN), including compressive strength, flexural strength, and apparent density of 7d, 14d, and 28d. The effects of cement-sand ratio (c/s), nutshell particle size, and MN substitution rate on cement mortar's physical properties were studied using three-factor and three-level orthogonal test design methods. The digital image correlation (DIC) technique was used to analyze the crack development of macadamia nutshell cement mortar (MNM) at different loading stages. The analysis of variance (ANOVA) showed that the cement-sand ratio was the most significant factor affecting the strength of MNM. In addition, adding MN can increase the compressive strength of the mortar compared to the control group. The apparent density of the mortar decreases with the increase of MN addition. •The influence of adding varying particle sizes of the nutshell on the strength of mortar was studied.•The density and flexural strength of mortar decreased with the increase of macadamia nutshell addition.•Macadamia nutshell could be used as an eco-friendly supplementary natural aggregate material.