Investigation of Moisture Dissipation in Foam-Based Warm Mix Asphalt Using Synchrotron-Based X-Ray Microtomography

Investigating physical and rheological properties of foamed bitumen

“…There is no statistical evidence on the exact diameter of the bubbles since different results could be obtained by sampling the bubbles in a position that does not pass for the center of the bubble (smaller diameter), for instance. However, the results seemed to be consistent with other previous studies [13]. The qualitative evaluation based on the measurements conducted, resulted useful to verify roughly the magnitude range of bubbles in bitumens.…”

“…Bubble diameters were roughly evaluated to be between 170 lm and 330 lm for FWC = 1%, whereas they increased to the range of 600 lm to 1000 for FWC = 4%. In [13], diameters of bubbles for different foamed bitumens were reported with a similar order of magnitude. There is no statistical evidence on the exact diameter of the bubbles since different results could be obtained by sampling the bubbles in a position that does not pass for the center of the bubble (smaller diameter), for instance.…”

“…A specific protocol was designed to preserve the bitumen-air-water system that is supposed to form the foamed bitumen after foaming [10,12,13]. To this end, foamed bitumen samples were collected in different containers and then left for cooled for 15 min at room temperature.…”

“…By using this protocol the bitumen-air-water system of the collapsed foam was preserved by spontaneous curing processes such as water evaporation and air-releasing phenomena. This approach was also adopted in other research studies on foamed bitumens [12,13]. Standard penetration containers according to [11] were directly filled by pouring from the foaming bucket and stored at 25°C until testing; penetration tests were performed within 4 h after foaming.…”

“…If left at ambient temperature for a long time, foamed bitumen might lose part of its air content (bubbles). Sunarjono [12] tried to preserve the foam-condition state by exposing samples of foamed bitumen to very low temperatures in a refrigerator just after spraying in order to conduct testing later; Kutay et al [13] soaked foamed bitumen samples in liquid nitrogen to instantly freeze the foam and conduct tests later.…”