Active fillers in foamed asphalt mixes used to be added either to modify the fine fraction of aggregate gradation and/or to reduce moisture sensitivity of the mix. While some countries use cement as active filler, others use Lime or Fly-Ash as well others. However, limited efforts have been taken to evaluate and compare the influence of every active filler on the properties of the final mix when use it same RAP material. This document presents the results of the project carried out to study the amount of influence that active fillers have on the properties of recycled mixes with foamed asphalt. Four active fillers – Portland Cement, Cement Kiln Dust, Hydrated Lime and Fly-Ash Class C – were studied. Only one material type was used it with inert fines particles passing the 0.075 mm sieve. Indirect Tensile Strength tests, Triaxial Resilient Modulus Tests and Triaxial PermanentDeformation Tests were carried out in order to quantify the degree of influence of these active fillers on the properties of each mix. Different curing methods and moisture conditioning were carried out in order to evaluate the role of active fillers on the different stages of foamed asphalt mixes. As a result of this study it is possible to state that, for the RAP tested, while some active fillers have an important influence on mechanicalproperties and long term performance of foamed asphalt mixes, others onlyact as mineral fillers of the aggregate gradation. Also, since foamed asphalt takes a long time to cure, some active fillers play an important rolein helping to improve early strength of these mixes.
Samenvatting