Impact of the formulation of aggregate gradations on the mechanical and functional properties of dense asphalt mixes

ABSTRACT

The main aim of this manuscript is to evaluate the impact of the formulation of aggregate gradations on the mechanical and functional properties of dense asphalt mixes, comprising methodologies so-called by trial, theoretical and controlled. The first is standardized by Brazilian official road departments for producing asphalt mixes, in which the goal is to fit formulated gradation curves into the thresholds of gradation bands. With regards to the theoretical method, also named rational, it comprises a discrete selection of particle diameters in sieving plants, allowing to control precisely the percent distribution of the grains, without the need to consider gradation bands, by using Füller-Talbot equations. The controlled method means an adjustment performed in that research, in which was proceeded the individual fractioning of the granular particles predicted to by trial formulation, however, maintaining the same sieve sequence and the percent distribution originally adopted. They were characterized and used granular particles provided by gneissic crushed massive rock located in the metropolitan region of Joinville/SC and bituminous binder 50/70 (0.1mm) penetration supplied by a refinery placed in Paulínia/SP. They were tested mechanical properties such as compacting ability with Compacting Shear Press, resistance to deleterious action of water in Duriez test at 18ºC and to rutting, while functional properties as macrotexture and surface run-off time were evaluated by sand path height and drainability tests. The results obtained indicate the theoretical method is more efficient than the others studied, due to have presented the best mechanical and functional indicators in all evaluated parameters, while the method by trial proved to be the worst technically, and should be replaced by a more scientific and accurate methodology in Brazil.

Keywords
Aggregate gradations; Dense asphalt mixes; Formulation methods; Mechanical properties; Functional properties