Material propertiesConfidence intervals of long-term prediction and synthesis of creep compliance prediction estimates for expanded polystyrene (EPS) under permanent compressive stress

The results obtained in investigating creep behaviour of expanded polystyrene (EPS) with a density of 16.5-33 kg/m3, subjected to long-term compressive stress σc, making 0.25 and 0.35 of stress corresponding to 10% relative deformation of the test specimens, are presented. The overall period of the direct long-term experiment was 3-4 years. Confidence interval prediction of creep compliance for the period of 50 years in the future was based on extrapolation of creep formation approximated by power and exponential regression equations which were reduced to a linear form by taking logarithms. The consistency (agreement) of particular confidence interval predictions was demonstrated and the synthesis (integration) of these extrapolation-based predictions was made. The results of synthesized predictions are presented. The dependence of the prediction estimates of creep compliance (creep strains) of expanded polystyrene on its density, permanent compression stress and time of prediction was determined.