Image-aided physical and compression characterisation of expanded polystyrene geofoam

The present study focuses on an advanced and accurate characterisation of the compressive behaviour of expanded polystyrene (EPS) geofoam with the aid of imaging techniques. To this end, four types of EPS geofoam with nominal densities varying from 15 kg/m³ to 30 kg/m³ are used. Initially, a detailed physical characterisation is carried out including image-based microstructural quantification (cell size, void fraction, population density), homogeneity using ultrasonic pulse velocity and apparent density. Insights into the compression behaviour of the geofoams, including true strains and failure patterns, are further gathered through full-field strain behaviour in the block using two-dimensional image correlation analysis. For the first time, the effect of nominal densities on the Poisson's ratio of geofoam is also studied through image analysis. The study reveals that compressive response is significantly influenced by homogeneity, which is manifested by the changes in microstructure and apparent density of the geofoam. Furthermore, the image analysis provides insights into the development of failure patterns and strain localisation and their dependency on density, comprehending the geofoam's complex behaviour. Predictions of compressive response based on apparent density and non-destructive tests are developed. The study further recommends safety factors for determining permissible and yield stresses based on statistical analysis.