Full-Scale Evaluation of Concrete-Asphalt Interphase in Thin Bonded Concrete Overlay on Asphalt Pavements

Abstract

Thin bonded concrete overlay on asphalt (BCOA) pavements rely on concrete-asphalt bonding to resist traffic loading. To investigate variables affecting bonding, experimental data were used from 15 instrumented thin BCOA sections, with 11 tested with heavy vehicle simulators (HVS). Sections included three slab sizes, four rapid-strength concrete mixes, new and old asphalt bases, and three asphalt surface texturing techniques. Analysis of strain data from HVS testing served to determine the concrete-asphalt bonding condition. Laboratory testing and forensic data from the sections were also evaluated. Overall, the performance of concrete-asphalt bonding in the sections with 1.8 × 1.8 m (6 × 6 ft) slabs was excellent. In these sections, concrete-asphalt bonding remained intact throughout the HVS testing despite the unfavorable testing conditions, which included flooding of the section, channelized traffic at the slab edge, and HVS wheel (half axle) loading of up to 100 kN (22.5 kips). The sections with 3.6 × 3.6 m (12 × 12 ft) slabs presented a delamination band between the asphalt and concrete along the perimeter of the slabs. This delamination was a tensile break occurring in the asphalt around 5–10 mm (0.2–0.4 in.) below the concrete-asphalt interphase caused by the large vertical hygrothermal deformations in the slabs. Because of this asphalt failure, the concrete and asphalt worked as two independent layers near the transverse joints. Based on laboratory procedures, it was observed that cement paste penetration into the asphalt layer caused a reinforcing effect in the concrete-asphalt interphase. It was also observed that milling and micromilling did not improve the concrete-asphalt bonding.