To control the stability of air-voids during hardening process of foam concretes, foam stabilizing emulsion was added to accelerate the hydration of cement paste. Table 5 indicates that large amount of air-voids escaped during the hardening process of foam concrete without foam stabilizing emulsion, meanwhile significant collapse was also observed. When 1% foam stabilizing emulsion was added into foam concrete, slightly collapse and air-voids escape were observed, and the diameter of air-voids in foam concretes were emulsion. mainly laid in 2.0-4.0 mm as shown in Fig. 6, which can be attrib- uted to the slow hydration of cement paste. No collapse and air-voids escape were measured for foam concretes with 3% foam sta- bilizing emulsion, the apparent density of foam concrete was 268 kg/m3, which is close to the target density (250 kg/m3), and air-voids with size of 1.0-2.0 mm were uniformly distributed in foam concretes, indicating that the air-voids were much more sta- ble during the hardening process