Mechanical and hydraulic compatibility of RAP with geosynthetics used in MSE walls

Mechanical and hydraulic properties of recycled asphalt pavement (RAP) as backfill in mechanically stabilized earth (MSE) walls were evaluated. Woven and nonwoven geotextiles and uniaxial and biaxial geogrids were used as reinforcements. Results of interface direct shear tests showed that the interface friction angle (δ) of RAP-geogrid was higher than that of RAP-geotextile. On average, the δ for RAP-biaxial geogrid was 15% higher than δ for RAP-uniaxial geogrid. For geotextile reinforcement, the δ for RAP-woven geotextile was 20% higher than δ for RAP-nonwoven geotextile. Compaction of RAP at elevated temperatures only slightly affected δ. Pullout capacities of RAP-uniaxial geogrid and RAP-woven geotextile are comparable to those of sand-uniaxial geogrid at different overburden pressures. The compacted RAP reinforced with uniaxial geogrid, however, exhibited significant creep strains at a range of sustained pullout forces that led to failure of the RAP-uniaxial geogrid. Reducing the pullout capacity by 40% is recommended for design to reduce the potential of creep failure. Long-term filtration tests showed that in all cases RAP-geosynthetic systems were able to drain freely and this behavior could be predicted with the existing clogging criteria that have been previously developed for sands and gravels.