Degree of Influence of Active Fillers on Properties of Recycled Mixes with Foamed Asphalt

Abstract

Active fillers in foamed asphalt mixes are added to modify the fine fraction of aggregate gradation or to reduce the moisture sensitivity of the mix. Some countries use cement as an active filler, and other countries use lime or fly ash, among other ingredients. However, limited information is available concerning the influence of different types of active fillers on the mechanical properties of foamed asphalt mixes. This paper presents the results of a project carried out to study the relative influence of active fillers on the mechanical properties of recycled mixes with foamed asphalt. Four active fillers were studied: portland cement concrete, cement kiln dust, hydrated lime, and fly ash Class C. Indirect tensile strength, triaxial resilient modulus, and triaxial permanent deformation tests were carried out to quantify the influence of these active fillers on the properties of one particular full-depth reclamation material. Different curing methods and moisture conditioning were used to evaluate the role of active fillers after the mix production process. As a result of this study, it was concluded that, for the full-depth reclamation material tested, whereas some active fillers have an important influence on the mechanical properties and long-term performance of foamed asphalt mixes, others act only as mineral fillers of the aggregate gradation. Also, because foamed asphalt takes a long time to cure, some active fillers play an important role in contributing to the early strength of foam recycled mixes.