The present work is aimed to utilize slag as the primary source of binder (aluminosilicate) in alkali activated concrete so that CO₂ emissions can be reduced. Also, sand is partially replaced 20% by volume (constant) with Used Foundry Sand. Minitab’s response surface method is applied to optimize the mixing proportions and also to study the effect of independent variables (Slag, Alkali/Binder and Fine aggregate/Coarse aggregate) on the dependent variables (compressive strength at 3, 7 and 28 days of curing). The experimentalcompressive strength of the studied concrete is measured and compared with the predicted results of the response surface method and the predictions are in good agreement. The optimized independent variables, S = 416.418 kg/m³, A/B = 0.488 and F/C = 0.554 are also validated with another set of experiments and it is found that error is <10%. It can be concluded that Response Surface Method can be efficiently used in optimization.