Combined Effects of Oxidation, Moisture, and Freeze–Thaw on Asphalt Mixtures

Abstract

This article demonstrates the need to laboratory condition asphalt mixtures to simulate combined environmental effects and then to test unconditioned and conditioned specimens in a manner that damage from these environmental effects can be accumulated. The current state-of-the-art for evaluating asphalt mixtures for use on projects relies on either single-mechanism laboratory conditioning such as oxidation in AASHTO R30, or test methods that cannot accumulate combined effects such as indirect tensile strength in AASHTO T283. This article evaluated hundreds of laboratory-conditioned and field-aged specimens in a hot and no-freeze climate to demonstrate a laboratory conditioning protocol that was able to simulate at least 4 years of field aging, whereas conventional single-mechanism protocols were not. Temperature and moisture conditions within asphalt mixtures were measured over time and used as part of the assessment. The conditioning protocol that showed the most promise consisted of combined exposure to oxidation, moisture, and freeze–thaw mechanisms. The specific combined-effects conditioning protocol used here was 5 days of oxidation at 85°C, 14 days of moisture while submerged in 64°C water, and one freeze–thaw cycle. Other combined-effects protocols could be more suitable for other environments or situations; the main point of this article is that inclusion of oxidation, moisture, and freeze–thaw conditioning into one protocol is promising. The environmental conditions and mechanical property test data presented here suggest the asphalt industry needs to be harsher on mixes during laboratory evaluations, and that combined environmental effects conditioning should be given implementation consideration.

Plastic Crisis: Responsible Recycling Within Military Railroad Infrastructure

“…Surface temperatures on crossties exceeding outside air temperatures by 50°F further explain the gage issues that are being seen throughout DoD railroad track. Bazuhair et al ( 42 ) measured in-service temperatures in several conditions in Mississippi, and the maximum asphalt temperature recorded was 138°F which is modestly lower than the 145°F measured on one of the recycled plastic railroad ties.…”

Data Mining Statewide Department of Transportation Volumetrically Designed Asphalt Mixture Records

“…Given the realities illustrated by Figures 1 and 2, these issues will likely continue to be difficult to address exclusively with volumetrics. Mechanical tests are badly needed, and many practitioners and agencies are already working to this end with tests such as the Illinois Flexibility Index Test (I-FIT) ( 23 , 24 ), Disc-Shaped Compact Tension (DCT) ( 30 ), Cantabro Mass Loss (CML) ( 22 , 54 – 57 ), and others as described in Howard et al ( 16 ).…”

Evaluation of the Impact of Oxidation and Moisture Conditioning on Indirect Tensile Asphalt Cracking Test Parameters and the Tensile Strength Ratio

“…Environmental factors (oxidative aging) usually dominate at the early age of asphalt pavement and moisture damage typically comes into play after few years of pavement construction ( 1 ). During the asphalt pavement service life, moisture damage occurs in two ways: reducing the cohesion in the asphalt binder (cracks within the binder) and compromising the adhesion between the asphalt binder and aggregate (also known as stripping).…”

“…In addition to the above limitations, the oxidative conditioning procedure (to simulate pavement aging) in the current AASHTO T283 test may not necessarily be representative of field climatic conditions. A severely aged asphalt binder (or mixture) can accelerate the occurrence of moisture damage in flexible pavements ( 1 , 30 , 31 ). After being built for many years, asphalt pavements suffer moisture damage, where aging has already taken place.…”

“…Moisture damage of asphalt mixtures is usually evaluated using two types of tests: qualitative tests performed on loose mixes and quantitative tests performed on compacted specimens. The most common tests on loose samples are as follows: (1) the static immersion test (American Association of State Highway and Transportation Officials [AASHTO] T182) (3,4); and (2) the boiling water test (ASTM D3625) (5,6). Qualitative tests are carried out on asphalt-coated aggregate mixes submerged in water.…”