USE OF ASTM C1512 FOR EVALUATING FOAM BOARD INSULATION USED IN ROADWAY PROJECTS

Douglas Goering
Wed, 22 Apr 2026 17:11:06 PDT

This work focuses on the performance of Expanded Polystyrene and Extruded Polystyrene insulation used in roadway embankments. Insulated roadways have been used in Alaska since the 1960’s and have become ubiquitous in more recent roadway projects. These insulation layers are used to provide a thermal barrier that reduces frost heave and/or reduces permafrost thaw beneath the embankment. Both frost heave reduction and permafrost protection are dependent on an effective insulation layer that limits heat transfer into and out of the base layers of the embankment. It is well known that accumulated moisture in insulation layers can significantly reduce their thermal performance and, thus, reduce their ability to protect embankments. Existing Alaska Department of Transportation Standard Specifications for Highway Construction require that polystyrene insulation boards have a minimum thermal resistance (R-value) of 4.5 per inch thickness, and that they are able to withstand a 24-hr water immersion test with a limited amount of moisture ingress. However, short-term immersion tests are not well-suited to predict the long-term accumulation of moisture that occurs in insulation installed in embankments. A potentially better method for testing insulation moisture ingress under roadway embankment conditions consists of the use of ASTM C1512 which relies on moisture vapor diffusion rather than direct immersion to introduce water into the insulation. A modified version of ASTM C1512 is used in this study to better understand moisture ingress into polystyrene insulation samples and the implications for thermal performance of the products.