The effect of aging on binder proporties of porous asphalt concrete

In this dissertation, the results of a research on the effects of aging on the binder properties of porous asphalt concrete (PAC) are described. The research has been done on laboratory and field aged specimens. In addition to the conventional aging methods for short and long term aging of the binder in the laboratory, a new mixture aging protocol in a 'weatherometer' was proposed that combines the main environmental factors influencing field aging, i.e. temperature, UV light, and humidity/moisture. The field binders were recovered from specimens taken from road sections immediately after construction and after 1, 3, 7, and 12 years service life. Rheological, mechanical, and chemical characterization of the binders was conducted on the laboratory and field binders to understand the effects of aging. To this end, the determination of fundamental rheological binder properties was performed in addition to conventional empirical properties such as penetration and softening point. Low temperature tensile and stiffness properties of the binder/mastic were determined using the Direct Tensile Test (DTT) and Bending Beam Rheometer (BBR). The Dynamic Shear Rheometer (DSR) was used to determine the viscoelastic properties (complex modulus and phase angle) of the binders in a wide range of temperatures. Furthermore, the DSR was used to determine the fatigue properties of the binders using strain controlled repeated loading at different strain levels. Chemical characterization using Infrared spectroscopy (IR) and Gel-Permeation Chromatography (GPC) were performed to determine, respectively, the development of the functional groups responsible for aging and the Molecular Weight Distribution (MWD). All the test results have provided insight into laboratory and field aging simulations, the impact of the filler, and at the same time has provided material properties for constitutive modelling. An important finding in this research signifies that aging greatly influences the low temperature performance of the binding material leading to a higher rate of damage accumulation (fatigue) and ultimately ravelling of PA. To illustrate the implications of the research results, a limited number of finite element calculations have been made to determine the stress conditions in the binder/mortar due to traffic loads. Because aging has a negative influence on the fatigue resistance and relaxation behaviour of the binder, aging negatively influences the performance of PAC