Multivariable optimization of mechanical and physical properties of hybrid alkali-activated cement mortars

In this research, it was determined that the optimum values of variables significantly affect the mechanical and physical properties of hybrid alkali-activated cement mortars by multi-response optimization. Fly ash, blast furnace slag, Portland cement, sodium hydroxide, sodium metasilicate, standard sand, distilled water, and liquid superplasticizer were used. In the experimental study, the effect levels of the controllable variables (Portland cement ratio, fly ash + blast furnace slag ratio, and specimen age) on the response variables (unit weight, water absorption, void ratio, ultrasonic pulse velocity, flexural strength, and compressive strength) were determined using an Optimal (Combined) Custom Design. The run points that provided the optimum mechanical, physical, and mechanical/physical properties were determined by using the desirability function. The optimization method used in this study and the selected effect and response variables have not been found in previous studies. The desirability of the optimum run points for mechanical, physical, and mechanical/physical properties was 1.00, 0.97, and 0.67, respectively. Low desirability for mechanical/physical properties (0.67) indicates that the desired target values could not succeed. Thus, not only the mechanical but also the physical properties should be considered in application to obtain optimum values.