Abstract
This study explores the effects of foaming on three selected bituminous binders: 50/70 paving grade bitumen, 45/80-55 polymer modified bitumen and 45/80-80 HiMA binder. The first part of the investigations included the evaluation of the foaming performance in terms of foaming temperature and foaming water content with the utilization of desirability functions and based on the equality of maximum expansion ratio and bitumen foam half-life. The second part of the study investigated the effects of foaming on the chemical structure of the binders using Fourier-transform infrared spectroscopy. The results of the spectroscopic measurements permitted calculation of structural indices specific to functional groups associated with bitumen oxidation, as well as those indicative of elastomeric modification. The results have shown that the different types of bitumen exhibited different foaming characteristics, which was most evident in bitumen foam half-lives, with the HiMA binder performing the best. The spectrometric measurements did not show any significant effects of foaming on the chemical structure of the evaluated binders related to oxidative stress, neither were any major changes in the PmB-specific regions found.
Highlights
The study investigated the effects of foaming on a road paving bitumen, polymer modified bitumen and a highly modified binder (HiMA), all representing grades typically used in surface course asphalt mixtures
Similar to other works (e.g., [27,40]), the foaming trials were conducted with the use of a Wirtgen WLB 10 laboratory foamer (Windhagen, Germany) and the foaming performance was evaluated based on the following properties of the bitumen foam, acquired using a steel measure and a stopwatch [7,11,27]:
The significance of this work relates to the high requirements regarding bitumen used for surface courses due to their direct exposure to such factors as traffic loads, abrasion, as well as water and moisture
Summary
In the growth of environmental awareness and government-imposed regulations encouraging the shift towards a “green” economy, the road construction industry faces expectations for decreasing the energy-intensity of its operations while increasing the quality and longevity of the constructed infrastructure. These conditions require the introduction of new, energy efficient techniques (e.g., bitumen foaming [1,2] and fluxing [3]). Materials (e.g., industrial by-products [4] and reclaimed materials [5,6]), while preserving the high performance of the produced infrastructure In this scope, the utilization of various foaming processes for producing bituminous mixtures for road courses is notably adequate [7,8].
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