A study of asphalt aging using Indirect Tensile Strength test

• One-day laboratory long-term aging is close to one-year of field aging.
• ITS of laboratory long-term and field aged samples increase with aging period.
• ITS of short-term oven aged loose sample is concave down with aging period.
• Brittleness increases with conditioning period under all aging modes.

While dynamic modulus, diametrical resilient modulus, and loss of ductility are the most common parameters to study aging, this study determines laboratory equivalence of field aging using an Indirect Tensile Strength (ITS) test for its simplicity and wide usages in Asphalt Concrete (AC) performance evaluation. Cylindrical samples were compacted in the laboratory, aged in the laboratory and field, and then loaded diametrically to determine ITS value and flow number. The ITS tests were conducted on six sets of compacted samples after subjecting them to 1, 5, 10, 15, 20, and 25 days of oven aging at 85 °C in the laboratory and on 11 sets of compacted samples after subjecting them to 1, 2, 3, and up to 12-months of field aging. The ITS tests were also performed on a third set of samples whose loose mixes were subjected to 8, 16, 32, 48, 72 and 100 h oven aging at 135 °C. As expected, ITS of the laboratory (both compacted and loose) and field aged samples increase and flow number decrease with the aging period. It is found in this study that one-day laboratory aging is close to approximately one-year of field aging measured in terms of ITS value. Results from loose mix aging show that the ITS value increases with the conditioning period, reaches a peak and then decreases with the conditioning period. Overall, the flow number decreases as aging intensity increases, that is, the brittleness increases with aging.