Improved performance grading of asphalt cement and hot mix asphalt in Ontario, Canada
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International Journal of Pavement Research and Technology Journal homepage: www.springer.com/42947
Improved performance grading of asphalt cement and hot mix asphalt in Ontario, Canada Moses Akentuna, Haibo Ding, Ahmad Nawaz Khan, Yiming Li, Simon A.M. Hesp* Department of Chemistry, Queen’s University, Kingston, ON K7L 3N6, Canada Received 9 March 2020; received in revised form 19 July 2020; accepted 6 August 2020
Abstract
Ontario municipal government agencies have recently been afflicted by significant premature pavement cracking. In response, stricter specifications were developed and implemented for acceptance on contracts. All but a few proven additives are banned in order to provide a cleaner product and the asphalt is graded after extraction and recovery from the loose mix. A set of highly sensitive rheological and failure properties are used to effectivel y control hard to detect constituents (e.g., reclaimed asphalt, oils, waxes, other unknowns). This paper discusses the background t o the specification, the development of acceptance criteria, potential moisture susceptibility issues to be monitored, and early implementation experience. Keywords: Asphalt binder; Specification grading; Cold temperature cracking; Fatigue cracking; Ductile strain tolerance; Mixture design; Rutting; Thermoreversible aging
1. Introduction Pavements in northern climates suffer from a number of distresses that are often challenging to control. Cold winters, wet springs, and hot summers conspire to do damage to the asphalt, eventually resulting in a deterioration of surface condition and ride quality. In the Province of Ontario the winters can be particularly cold, with air temperatures occasionally reaching below ˗50°C in the north. The record provincial low was recorded in Iroquois Falls in northeastern Ontario, on January 23, 1935, when the temperature in the early morning hours dropped to ˗58.3°C [1]. Similarly, in early 2004 the air temperature reached below ˗48°C at a pavement trial in nearby Timmins [2]. The temperature in the area reaches below ˗40°C regularly, likely due to the prevailing polar vortices coming straight from the arctic [3]. More recently, the airport in the City of Kingston in southeastern Ontario recorded ˗32.8°C on January 1, 2018, and temperatures below ˗30°C on two additional occasions over the last four years [1]. In southwestern Ontario the temperature reaches below ˗30°C only on sporadic occasions [1]. Summer air temperatures have reached above +35°C on regular occasions with a record of +42°C in the south [1], but infrequently and not for more than a few hours during July and August. * Corresponding author E-mail address: [email protected] (Prof. S. A.M. Hesp). Peer review under responsibility of Chinese Society of Pavement Engineering.
It is the asphalt cement hardening due to irreversible processes (oxidation and volatilization) and thermoreversible processes (wax crystallization, asphaltene aggregation, phase separation), in conjunction with low temperatures during winter, that causes th
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