Investigation of the properties of high-porosity cement foams based on ternary Portland cement–metakaolin–silica fume blends

• The pre-foaming method was successfully used to prepare high-porosity cement foams.
• The addition of metakaolin and silica fume hinders the collapse of fresh high-porosity cement foam.
• The air-void structure of high-porosity cement foam can be stabilized by the addition of metakaolin and silica fume.
• Cement foam with a compressive strength of 0.74 MPa and thermal conductivity of 0.054 W/m K at 91.6% was achieved.

High-porosity cement foams based on ternary blends of Portland cement, metakaolin and silica fume were prepared by the pre-foaming method. The effects of ternary blends on the early-age properties, air-void structure and hardened state properties of cement foams were investigated. The effect of metakaolin and silica fume on stabilizing air-voids was observed, and the collapse of cement foams during the hardening process was avoided by addition of metakaolin. Moreover, the compressive strength of the prepared 91% high-porosity cement foams was enhanced by addition of metakaolin and silica fume. The compressive strength and thermal conductivity reached 0.74 MPa and 0.054 W/m K, respectively. However, metakaolin and silica fume had a negative impact on the workability of the cement foam.