Identification of a fuel contamination problem in the production of warm mix asphalts

Abstract

A number of new processes and products that have the capability of reducing the temperature at which hot mix asphalt (HMA) is mixed and compacted, apparently without compromising the performance of the pavement, has become available. These technologies, usually referred as warm mix asphalt (WMA), can reduce the production temperature of bituminous mixtures by as much as 40 °C. While there is a great deal of promise that comes along with lower temperatures, there are also concerns about some field performance characteristics of WMA mixtures. Thus, a thorough work was carried out in order to answer some questions that are still open about WMA performance in laboratory and in situ. Three bituminous mixtures were studied, namely a conventional HMA control mixture (AC 14 surf 50/70), and other two WMA mixtures with the same composition but using binders modified with different additives (a synthetic wax, Sasobit®, and a surfactant, Cecabase®). These mixtures were initially designed and characterized in the laboratory. Then, they were produced in an asphalt plant and laid down in a pavement trial in order to validate the good laboratory performance of the WMA mixtures in situ. The comparison between the laboratory and in trial performance showed that the rutting resistance of the studied mixtures was severely affected during their production in the asphalt plant. Some authors have referred that WMA mixtures have higher susceptibility to be contaminated with fuel, because it is difficult to adjust the burners with low production temperatures combined with low quantities produced, particularly in pavement trials. Therefore, additional tests were carried out with the studied mixtures and their binder (recovered with the rotary evaporator), thus being possible to conclude that the performance of the mixtures in situ was influenced by their contamination with fuel during the heating of the aggregates.