Effects of different control methods on the mechanical and thermal properties of ultra-light foamed concrete

Abstract

Porosity and pore structure are the critical factors affecting the properties of ultra-light foamed concrete. In this study, four different measures were adopted to control the performance of ultra-light foamed concrete. Specifically, by changing foam content, water-cement ratio (W/C), and hydroxypropyl methylcellulose ether content, different ultra-light foamed concrete specimens were prepared and their properties were studied. At the same time, hollow microspheres were incorporated into cement slurry to optimize the properties of the ultra-light foamed concrete further. The results reveal that when the foam content reached 30 wt% (by weight of cement), the dry density of foamed concrete was lower than 300 kg/m3. When the W/C reached 0.42, the volumetric water absorption, compressive strength and thermal conductivity of the foamed concrete were 31.9%, 0.499 MPa, 0.0857 W/(m·K), respectively. At W/C of 0.42, adding 1 wt% hydroxypropyl methylcellulose ether could lead to increase in compressive strength by about 24%. Hollow microspheres can effectively improve the pore structure of ultra-light foamed concrete and significantly reduce its thermal conductivity. With the addition of hollow microspheres at 6.5 wt%, the volumetric water absorption and thermal conductivity were 20.1% and 0.0456 W/(m·K), reduced by 37% and 95%, respectively.