The paper presents the use of blast furnace slag as a fine aggregate in foam concrete. Besides, the paper also presents the research results of the effect of the water-cement ratio and Silica fume on the mechanical properties of foam concrete. The absolute volume method was used to calculate the ratio of foam concrete mixture. Besides, the mechanical properties of foam concrete were determined at the age of 28 days. The method of Box-Wilson central composite design for two factors was used to predict the effect of the water-cement ratio and Silica fume on foam concrete properties. The results showed that the proposed regression equations of this mathematical model achieved an adequate prediction accuracy. Using computer programs obtained surface images of equations (10) and (12). Besides, the maximum value of the objective function was determined with compressive strength = 8.52 MPa and flexural strength = 1.21 MPa. This research result is a premise for studying foam concrete bricks to replace clay bricks in construction works.