Warm mix asphalt vs. hot mix asphalt : flexural stiffness and fatigue life evaluation

[摘要] ENGLISH ABSTRACT: The UNFCCC (United Nations Framework Convention on Climate Change), enabledby the Kyoto Protocol, set enforced responsibilities on industrialised countries toreduce the amount of emissions (greenhouse gases) produced. This global call forthe reduction of greenhouse gas emissions ensured that the manufacturing sectorcommit to emission reduction.The asphalt industry has embarked on a quest to find alternative methods ofproducing and constructing asphalt mixes which will release less greenhouse gassesinto the atmosphere. These new methods include the reduction in production andconstruction temperatures which in turn will reduce the amount of greenhouseemissions produced. These new methods introduced the concept of warm mixasphalt (WMA) to the alternative hot mix asphalt (HMA).To produce a WMA mix at lower temperatures the binder needs to be in a workablestate so to effectively coat the aggregate and produce a good quality mix. WMAtechnologies have been developed to enable production of mixes at lowertemperatures (effectively reducing emissions) whilst retaining the required binderviscosity and properties needed to produce a quality mix. The question which needsto be answered is whether the performance of these WMA mixes can compare withthat of HMA mixes.In this study several WMA mixes (with different WMA technologies) are evaluatedagainst their equivalent HMA mixes in terms of fatigue life and flexural stiffness.Phase angle results were also considered. Flexural stiffness is a mix property whichis dependent on loading time and temperature. It is used to measure the load spreadability of a mix and also influences fatigue behaviour. Fatigue cracking occurs in thematerial as a result of repeated cyclic loading.The evaluation and analysis conducted in this study show that WMA mixes cancompare favourably and even exceed that of HMA mixes in certain cases, althoughsome WMA mixes resulted in lower fatigue life or flexural stiffness than itscorresponding HMA mixes, which could be attributed to differences in mixcomponents and variables.In this study a literature study, methodology, laboratory test results, a comparison ofmix results and conclusions and recommendations are made.

[发布机构] Stellenbosch University