Consideration of a Tack Coat Bond Strength Test to Minimize the Potential for Slippage Failures on Flexible Airfield Pavements

Abstract

Slippage failures on flexible pavements are a potential problem for airports given the large wheel loads and high tire pressures of modern aircraft. While not common, when slippage failures do occur the impact can be significant on flexible pavement performance. This paper has three components: (1) case studies of slippage failures that have occurred on airfield pavements; (2) a literature review of relevant interlayer bond strength test procedures; and (3) the results of an analytical, field, and laboratory research investigation. Component (3) was conducted to assess the suitability of interface bond strength tests to evaluate the sufficiency of interlayer bond strength between lifts of asphalt pavement, either new construction or an overlay of existing pavement. The analytical study found that for a fully bonded pavement (no-slip condition), subgrade strength was the primary factor affecting horizontal stress at the interface followed by wheel load. Field cores were obtained from recently constructed asphalt pavements and brought to the laboratory for monotonic direct shear testing to determine bond strength as well as monotonic indirect tensile testing to determine mixture strength. Testing was conducted at 77°F (25°C) and 136°F (58°C). Results showed better repeatability at room temperature with similar relative performance ranking to the critical case high temperature test. Bond strength was influenced by in-place mixture density. Overall, the bond strength test method was practicable for use in field laboratories for acceptance testing.