Impulsive and vibrational compaction of bituminous mixtures

As well known, the laboratory testing of mechanical and volumetric properties of asphalt concrete is carried out by working on test specimens compacted according to specific reference Standards. One of the major problems, that still undertake the scientific research sector, is to successfully reproduce in laboratory the compaction process that asphalt concretes undergoes during the in situ placement. Traditionally the mainly technique of compaction is the unidirectional-impulsive one that leads to the creation of appreciably different structures from those that occur in the pavement layers. In unidirectional-impulsive compaction the aggregate moves mainly along vertical direction with limited rotation possibility, so it is difficult to reach the maximum density and resistance configuration. These limitations are overcome with the introduction of the SHRP gyratory compaction which is capable of continuously changing the direction of compaction with combined normal and tangential actions. In this paper the Authors propose an alternative to the unidirectional-impulsive bituminous mixtures compaction procedure based on the use of the vibratory compactor, a device introduced by UNI-EN-12697-32 (2007) in order to determine the bituminous mixtures’ density. The objective of the study is, therefore, to assess and compare the mechanical resistance and porosity performed by bituminous mixtures, compacted by the two mentioned compaction techniques (unidirectional-impulsive and vibrational). With reference to bituminous mixtures object of study, the Authors propose correlations that allow to link mechanical and volumetric parameters of mixtures to the change of the compaction technique, the compaction energy and the compaction time.