The effect of lithium silicate impregnation on the compressive strength and pore structure of foam concrete

Foam concrete (FC) has been widely used to make slab structures, retaining walls, and backfill materials for highways, railways, plazas and other projects due to its high flowability, low cement content, cost reduction, and thermal insulation. However, the low compressive strength and durability of FC limit its further application in structural materials. This paper focuses on improving the compressive strength and freeze-thaw cycle (FTC) resistance by adjusting the pore structure. The method proposed in this paper utilizes calcium silicate hydrate gel (C-S-H) formed by the rehydration reaction between lithium silicate (LS) and calcium hydroxide (CH). In this paper, the FC samples were treated by LS solution impregnation for 6 h. LS's effects on the dry density, 7- and 28-day compressive strength, strength-to-weight ratio (S/W ratio), and FTC resistance were studied. The results show that LS enhances the properties of FC, including the S/W ratio, compressive strength, and FTC resistance. In particular, the growth rate of the sample's compressive strength varies between 4.8% and 59.5%. The growth rate of the compressive S/W ratio was between 27.0% and 52.0%. The FTC resistance is improved. Thermogravimetric (TG) analysis and pore structure analysis results show that a rehydration process to generate C-S-H was observed between CH and LS, which can optimize FC's pore structure.