Field Performance of an Asphalt Barrier Test Pad

A field study of asphalt concrete and fluid applied asphalt - geotextile (FAA/GT) was undertaken to evaluate their suitability as a barrier (liner/cover) material in waste containment applications. A test pad consisting of 2–3 mm thick FAA/GT and 10–15 cm thick asphalt cement concrete was designed, constructed using full-scale asphalt paving equipment and its performance monitored. The in situ hydraulic conductivity of the barrier was measured using sealed, double-ring infiltrometers. Core and large block samples were taken from the test pad and analyzed in the laboratory under several conditions including: immediately after compaction, after aging for up to three years and after deformation. The in situ hydraulic conductivity of the barrier was 1 x 10^–9 cm/s to 1 x 10^–10 cm/s. The conductivity range represents the lower limit of quantifiable conductivities with the in situ testing equipment. The laboratory-measured hydraulic conductivity of the specimens sampled immediately after compaction was 1 x 10^–10 cm to 1 x 10^–11 cm/s. The hydraulic conductivities of the same specimens were re-evaluated twice after exposing them to the ambient temperature in the laboratory for a period up to three years. No change in hydraulic conductivity was observed during this period. Beams of aged asphalt concrete were subjected to three point bending to impart distortions in the range from 1/500 to 1/25. Though observable cracks developed in the beam that underwent the maximum distortion of 1/25, there was no appreciable effect on the hydraulic conductivity. The hydraulic conductivity of the asphalt barrier design used in this test pad was uncompromised by aging of 3 years and distortions up to 1/25. Based on the results of the testing performed, asphalt concrete combined with fluid applied asphalt - geotextile proved to be an effective barrier when designed and constructed with low hydraulic conductivity as a goal.