Effects of bentonite slurry on air-void structure and properties of foamed concrete

The increase of nano-scaled pores may further improve the thermal insulation properties of foamed concrete. However, air voids in foamed concrete prepared by pre-fabricated foams through surfactant or hydrolyzed protein solutions are commonly above micron level. It becomes a key issue to decrease the air-void sizes and increase the nano-scaled pores in foamed concrete by the modification of pore-forming methods. In this study, gel-like bentonite slurry with solid content of 9.1% was used to replace some of cement and pre-fabricated foams to prepare foamed concrete with dry bulk density of 300 and 600 kg/m3, respectively. Apparent viscosity of the fresh pastes decreased with the increase of bentonite slurry, and the fluidity firstly decreased and then increased. Compressive strength decreased with the increase of bentonite slurry, specially the as-prepared foamed concrete with dry bulk density of 300 kg/m3. Much better thermal insulation properties of the foamed concrete with bentonite slurry could be obtained. Thermal conductivity of the foamed concrete with 50% of bentonite slurry decreased by 29.8% and 15.3% for dry bulk density of 300 kg/m3 and 600 kg/m3, respectively. It is found that the increased pores with nano-scaled sizes in foamed concrete with bentonite slurry could be responsible for the lower thermal conductivity.