Compressibility of Recycled Materials for Use As Highway Embankment Fill

Compressibility of recycled materials including bottom ash (BA), foundry slag (FSG), foundry sand (FSD), recycled asphalt pavement (RAP), recycled pavement material (RPM), recycled concrete aggregate (RCA), and recycled asphalt shingle (RAS) mixed with glacial outwash sand (GOS) was evaluated using one-dimensional (1D) compression tests. Results showed that except RCA, compressibility of all the compacted recycled materials is higher than that of the compacted GOS. Different compression mechanisms were attributed to each recycled material depending on the type, composition, and morphological characteristics of the particles. Bituminous recycled materials including RAP, RPM, and RAS-GOS mixtures exhibited relatively higher compressibility compared with nonbituminous recycled materials. At a constant vertical effective stress (sigma(v)'), compression of the recycled materials increased over time with strain rates that are higher for bituminous recycled materials compared to nonbituminous recycled materials. The vertical strain rates ((epsilon) over dotv) of all the recycled materials log-linearly increased with increasing sigma(v)'. The slope of the log (epsilon) over dotv - log sigma(v)' curves, termed stress coefficient of compression, is independent of the elapsed time after loading. The stress coefficient of compression indicates degree of stress dependency for compression and is different for each recycled material. Secondary compression ratio is a power function of sigma(v)' indicating that an embankment constructed with recycled materials settles at different rates along the embankment height. Temperature rises increased compressibility of the compacted RAP and RAS-GOS mixtures. On the other hand, thermal preloading significantly reduced the compressibility of the compacted RAP and RAS-GOS mixtures. Construction of embankments containing bituminous materials such as RAP, RPM, or RAS is recommended during summer to induce thermal preloading and reduce long-term settlement. Long-term settlements of typical highway embankments constructed with the recycled materials used in this study were below the allowable limit. (C) 2015 American Society of Civil Engineers.