This study investigated the curing mechanism of foamed asphalt mixes, based on which proposed standard curing procedures that are appropriate for use in project level mix design. Mixes with various asphalt and portland cement contents were subjected to two relatively extreme curing conditions,and multiple types of laboratory tests were performed. It was found thatportland cement enhances certain properties of foamed asphalt mixes by strengthening the mineral filler phase, with the curing mechanism similar tothat of normal cement treated materials. The curing mechanism of foamed asphalt mastic is primarily related to water evaporation. The bonding between asphalt mastic and aggregate particles cannot fully develop until most of the water retained at the interface evaporates. This bonding, once formed, is only partially damaged by reintroduced water. This mechanism was supported by direct fracture face observations on tested specimens. Two curing methods are proposed as standard procedures for project level mix design. The proposed strategy tests materials under two extreme conditionsinstead of attempting to precisely replicate field conditions, allowing the engineer to judge whether the tested materials suit the actual range ofconditions at a specific project site. Portland cement or other appropriate active filler is recommended to be used in conjunction with foamed asphalt, which has a slow curing rate under most field conditions, to obtain early strength and allow early opening to traffic.
Abstract