Experimental research on the preparation and properties of foamed concrete using recycled waste concrete powder

Foamed concrete was prepared mainly by recycled waste concrete powder (RP) using wet foam mixing method. By measuring the stability time of preformed foam and setting process of paste, as well as the compressive strength, dry density, porosity and thermal conductivity of specimen, the effects of water to solid ratio (W/S), RP content and foam dosage on the properties of foamed concrete were discussed. The pore structure and reaction mechanism were analyzed by means of image analysis and X-ray diffraction. The results indicate that with the increase of W/S, the viscosity of paste decreased and the setting time increased gradually. The paste and preformed foam achieved a good matching state when W/S was 0.8. Thus the specimen had a largest porosity. With the increase of RP content, the compressive strength decreased obviously. The maximum amount of RP can reach up to 70%. Foamed concrete with different density grades can be prepared by changing preformed foam content. With the increase of foam content, compressive strength and thermal inertia were obviously decreased, and the pore distribution was gradually coarsening. Due to its inert properties, RP mainly played a filling role in the foamed concrete, but it can still have a significant effect on the setting process of paste, as well as the compressive strength and thermal conductivity of specimen.