The present study valorizes cashew nutshell ash (CNA) and uses it at 5–20 wt. % of cement for concrete production. The concrete grades of 25–40 MPa were used as mix design proportions. The thermal and mechanical properties of the concrete samples were determined on day 28 of curing. Regression models were used to predict the thermophysical properties of the concrete specimens. Also, the concrete's sustainability was estimated via the inventory of carbon and energy (ICE). The results revealed that CNA enhanced the thermal insulating characteristics of the concrete produced. Maximum compressive strength was obtained at 15 wt. % of CNA content, while the developed models yielded high precision. Compared with the control concrete, the sustainability index decreased as CNA content in the mix increased, indicating that incorporating CNA in concrete production improves the sustainability of such concrete. Therefore, the outcome of this work can be beneficial, especially in hot or arid climate regions, and at the same time, achieve a cleaner environment.

Strength failure persists both in structural and mechanical analysis. One of its prominent characteristics is the adequate provision for parameters that minimise or maximise strength objectives while satisfying boundary conditions. The previous optimisation of concrete strength usually neglects mix design mechanisms induced by optimisation. Recent efforts to accurately optimise the concrete compressive strength have factored in some of these mechanisms. However, optimising concrete strength modified with high silica and alumina precursors, and crucial mix design factors are rare. Consequently, this paper optimised the concrete workability and strength, incorporating binding, water/binder ratio, binder/aggregate ratio, and curing mechanisms using the Box–Behnken design approach (BBDA). A waste material, anacardium occidentale (cashew) nutshell ash, was valorised and used at 5, 10, and 15 wt.% of cement. The composites were made, cured and tested at 14–90 d. The results revealed a high precision between the experimental slump and the optimisation slump at 97% R². In addition, a 5% increase in compressive strength was obtained compared with the target compressive strength. Besides, the correlation between the model equation obtained from this study and predictions of previous studies via BBDA yielded a strong relationship.