Proper cement-sand ratio and water content can provide excellent consistency and stability for lightweight foamed concrete. The aims of this study are to investigate the comprehensive optimisation design mix of lightweight foamed concrete with different cement-sand ratio and the effect of sand size and admixture towards the consistency and stability of the design mix. Silica fume as admixture was used to verify the improvements in the strength of the foamed concrete. Two types of foamed concrete were prepared, namely SC with sieved sand and UC with unsieved sand used in foamed concrete. Three different cement-sand ratios with different water content were tested for the above two types of foamed concrete for their compressive strength, consistency and stability. The results indicate that foamed concrete using sieved sand gained better consistency and stability. In addition, using silica fume in foamed concrete significantly improved the compressive strength with the highest strength at 27.12 MPa with 1700 kg/m3 density
