Optimization and modeling the impact of a green cementless binder and biogenic nanosilica on cement setting time

Abstract

This work deals with the possible use of a renewable resource; the ash of walnut shell as partial replacement for cement to produce an economical and ecologically friendly cementinous binding material for cement, mortar and concrete. The agricultural waste; the walnut shell was processed and converted to ash in order to increase its pozzzolanic properties. The green ash is characterized and converted chemically to nanosilica to be incorporated later into cement contain the optimum content of the green pozzolanic admixture. A statistical method is used to narrow the number of experiments, followed by computational optimization to identify the optimal balance of the cementless additive and water/cement ratio on initial and final setting time, as well as modeling the influence of the variables on setting time. Reference samples of cement samples are prepared and evaluated for the purpose of comparison. The results obtained revealed that walnut shell ash act as green binder for partial replacement of cement, and the optimum content of walnut shell ash in cement which can retain the cement setting time is 22% wt. Also, the incorporation of nanosilica resulted in decrease of the setting time of (cement-walnut shell ash) fresh paste.