Abstract: The influence of the different densities (300-1200 kg/m3), water-binder ratio (0.3-0.6), the polypropylene fiber and the EPS particles were investigated .The microstructure of a variety of proportions was analyzed by SEM and then explain the change of the strength .The result shows that the density is the most important factors of foam concrete macroscopic and microscopic property .Through the density control ,the different needs of products can be obtained .The higher the density is ,the greater the strength will be.In addition, the polypropylene fiber mixed can increase the strength in a certain range .The addition of EPS particles can lower bulk density , but also can make strength decline .

Key words: foamed concrete;bulk density;compressive strength;microscopic mechanism