Shear and Hydraulic Behavior of Compacted Foamed Glass Aggregates for Transportation Earthworks

Recycled foamed glass aggregate (FGA) is an emerging material in the USA for use as a lightweight structural backfill. FGA is considered a sustainable solution, with advantageous engineering properties noted throughout the literature, but since the FGA market in the USA began less than 10 yr ago, independently assessing the behavior of the FGAs available for highway transportation agencies became necessary. The Federal Highway Administration (FHWA) has therefore made a concerted effort to evaluate the physical, mechanical, and hydraulic properties of US-manufactured, recycled FGAs under varying compaction efforts and loading conditions. This paper presents some initial findings from large-scale laboratory testing performed to evaluate shear strength and permeability of FGA under different compaction ratios and applied normal stresses. The overall results demonstrate that the breakage of FGAs due to compaction can have advantageous impacts, such as an increase in density and shear strength. While compaction does reduce permeability, FGA is still a free-draining material. The findings suggest that FGA is a viable substitute for sustainable, niche geotechnical applications; however, understanding the in-place FGA engineering properties is needed to develop better construction specifications and design guidance to ensure serviceability in transportation earthwork projects.