Influence of Aggregate Source and Warm-Mix Technologies on the Mechanical Properties of Asphalt Mixtures
This study evaluated the impact of three aggregate sources (limestone, quartzite, and natural gravel) and three different WMA processes (Advera, Evotherm, and plant foaming) on the properties of asphalt mixtures. The aggregate source and warm-mix process were found to have an impact on the mixing and compaction temperatures of the WMA. The performance of the WMA mixtures was evaluated in terms of moisture damage, rutting, thermal cracking, and fatigue cracking resistance. Based on the results of the analysis of variance (ANOVA) of the data, the aggregate source, WMA technology type, and the interaction between the two were shown to have moderate to significant effects on the performance of the asphalt mixtures for certain tests, whereas having no effect for other tests. Statistical differences were found when comparing indirect tensile strength and tensile strength ratio values, flow number, asphalt pavement analyzer rut depth, and fatigue cracking test results for the various mixtures. None of the WMA mixtures performed, as well as the HMA, except in the beam fatigue test. This was mainly related to the difference between the HMA and WMA short-term aging procedures. However, WMA mixtures exhibited similar or higher moisture damage, rutting, and fatigue cracking resistance than the HMA mixtures produced at the WMA temperatures or with 2-h short-term conditioning, instead of the recommended 4 h by Superpave. Dynamic modulus results showed that, on average, WMA mixtures had significantly lower dynamic modulus values than the HMA mixtures, but similar values to HMA mixtures produced at the WMA temperature and short-term conditioning. The thermal stress restrained specimen test (TSRST) showed that the reduction of production temperatures and short-term aging lowered the fracture temperature, whereas it did not impact the fracture stress. The impact of WMA technology on thermal cracking and fatigue characteristics depended on the type of aggregate.