Abstract: Phosphoric acid-based geopolymer foams (PAGFs) were prepared from metakaolin with phosphoric acid as activator and hydrogen peroxide as foaming agent. The effects of liquid-solid ratio and manganese dioxide content on the physical properties, thermal conductivity and fire-resistance of PAGFs were studied. As liquid-solid ratio varies from 1.56 to 1.76, the PAGFs with uniform distribution pore and excellent pore structure can be prepared. As the liquid-solid ratio is 1.71, the sample presents maximum compressive strength (2.73 MPa) and minimum thermal conductivity (0.17 W/(m·K)). Furthermore, when the liquid-solid ratio is constant, the addition of manganese dioxide raises the decomposition efficiency and the rate of hydrogen peroxide, improves the pore structure of PAGFs.When the manganese dioxide mass content is 0.10%, the thermal conductivity of the sample decreases, the dry density and porosity increase, and the compressive strength remains at 2.09 MPa. After 3 h fire-resistance test, the backside temperature of the sample remains at about 262 ℃ under the condition of 1.71 liquid-solid ratio and 0.10% manganese dioxide content. The XRD and SEM indicate that lamellar tridymite and tridymite aluminum phosphate (T-AlPO₄) phase are detected in samples after fire-resistance test.

Key words: metakaolin, phosphoric acid, geopolymer, foams, fire-resistance