Structure and properties of expanding polyurethane foam in the context of foundation remediation in expansive soil

Polyurethane foams have many applications and their fundamental properties have been widely investigated, mostly in relation to specific applications. In manufacturing, the need to produce homogeneous materials has led to the optimization of the formation processes and the understanding of the foam behaviour actually applies to homogeneous material. When applied to foundation remediation, expanding polyurethane foam is formed in the ground under conditions which are less controlled than in manufacturing processes or in the laboratory. Consequently, macrovoids and interfaces are created which result in a heterogeneous foam material. This paper investigates the microstructure and physical properties of expanded polyurethane foam injected in the ground using Scanning Electron Microscopy and physical testing. It is shown that the compressive strength is reduced by the resulting structural heterogeneity and the hydraulic conductivity is increased, but only to a value equivalent to that of a typical clay soil.