The pore structure of the foamed concrete is crucial to its
mechanical properties, thermal insulation and hygroscopic property.
Optical micrographs of the pores distributed in the soil-based
foamed concrete are presented in Fig. 15, wherein (a)–(d) are the
optical micrographs of the pores for soil-based foamed concrete
containing 20%, 40%, 60% and 75% foam, respectively. The foam formation
in foamed concrete is clearly better with increasing foam
contents. As the aperture grows, it become more uniform as the
groove becomes increasingly circular. Compared with the other
three mixtures, there are more interconnected pores in the mixture
with 75% foam added. A high foam and micropore content greatly
improves the thermal insulation and hygroscopic property of soilbased
foamed concrete. We know that the strength of soil-based
foamed concrete depends mainly on the matrix pore structure
and bonding interface. Although the foam formation improves,
the changes in the foam volume enlarged the inner pores, significantly
reducing the compressive strength of concrete.