The effect of surfactant is just to stabilize the air pores formed by the foaming agent in concrete/mortar before stiffening so as to stabilize the density of lightweight concrete. As long as the air pores exist, compressive strength, tensile strength, modulus of elasticity and density will be reduced. Purpose of surfactant is to prevent excessive bursting out of air pores formed so as to ensure the resulted concrete has the density close to the target value.