Non Destructive Testing for EPS Geofoam Quality Assurance

Abstract

Expanded Polystyrene (EPS) geofoam is a compressible lightweight fill material. The quality of the EPS geofoam supplied must be inspected thoroughly before its placement in a project site. A review of the quality assurance measures put forward by different construction authorities around the globe was performed. It was found that the quality measures cited by these authorities are not representative of actual full sized EPS geofoam block properties.Hence, these measures have room for more revision and improvement for an effective and efficient quality assurance measure both at the EPS geofoam production plant and on the project site. Moreover, a comparison of case studies showed that in the absence of a strict quality assurance measure, uneven settlements had occurred in road way constructed over EPS geofoam which eventually led to the removal and replacement of the entire EPS geofoam fill.Non Destructive Testing, specifically P waves, were used to check the mechanical properties of EPS geofoam blocks of different densities which were produced at four different EPS production plants. The relationship between P wave velocities were checked against the different EPS densities tested. Additional relationships were examined between P wave velocities through a virgin EPS geofoam block (without any regrind/recycled content) and another EPS block of the same density which had a specific percentage of regrind/recycled content. The effect of using a signal amplifier on EPS virgin blocks and blocks containing regrind was studied. Excessively high P wave velocity variations within an EPS geofoam block was tied to the use of EPS resin beads that were not recommended for that density of geofoam. Pentane loss and the use of a resin bead type with non-uniform sizes are also believed to have caused additional variations in the P wave velocity of the blocks. EPS geofoam blocks with regrind content transmitted slower velocity and lower amplitude P waves than their virgin counterparts for the same density. Furthermore, information provided from prior large scale tests performed on EPS geofoam were found to agree with the Young's modulus values obtained by using the P wave velocities. Finally, the use of P wave velocity as a quality assurance measure on an EPS geofoam block is found to be effective and practical and is recommended to be incorporated in the various construction quality standards that pertain to EPS geofoam blocks.