Influence of specimen size and orientation on the mechanical properties of laboratory compacted asphalt specimens

Iwama, Masahiko (2009) Influence of specimen size and orientation on the mechanical properties of laboratory compacted asphalt specimens. MPhil thesis, University of Nottingham.

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Abstract

It is always desirable for laboratory compaction to simulate actual site compaction in terms of the volumetric proportions, aggregate structure and mechanical properties of the compacted asphalt mixture, when specimens are manufactured, especially for mixture design. However, finding a laboratory compaction method that is able to achieve this requirement for all asphalt mixture types is in most cases extremely difficult. Some of the reasons for this lack of agreement between site and laboratory compaction include the influence of laboratory factors such as specimen geometry and size, mould confinement and compaction mechanism. Therefore, this study examines the effect of these factors on the volumetric proportions, aggregate matrix and mechanical properties of a typical UK continuously graded asphalt mixture with a maximum aggregate size of 28 mm.

Three types of laboratory asphalt mixture compaction (i.e. gyratory, vibratory and slab) were used to compact either 150 mm diameter cylindrical specimens or 300 mm by 300 mm slabs both to a height of 100 mm. Then, the volumetric proportions and mechanical properties were determined on the 150 mm diameter cylinders and 150 mm diameter cores taken from the slabs; and these proportions compared to those obtained on 100 mm diameter specimens cored from the original 150 mm specimens or cored directly from slabs. In addition, image analysis technique were applied to investigate the internal aggregate structure of these specimens as a function of compaction method, specimen size and specimen orientation.

The results proved that specimen size, especially for mould based compaction methods such as gyratory and vibratory, has a significant effect on volumetric proportions, aggregate orientation and mechanical properties. Also, slab specimens cored from the three orthogonal directions showed significant variation in mechanical properties. The reason for change in mechanical properties between the mould based 150 mm and cored 100 mm diameter specimens were related in part to change in combined effects such as aggregate volumetric composition, orientation and segregation. Finally, the image analysis results indicated that the variation in mechanical properties for the three orthogonal slab specimens may be associated with particle segregation.

Item Type:Thesis (MPhil)
Supervisors:Airey, G.D.
Faculties/Schools:UK Campuses > Faculty of Engineering > Department of Civil Engineering
ID Code:809
Deposited By:Mr. Masahiko Iwama
Deposited On:10 Dec 2009 11:43
Last Modified:10 Dec 2009 11:43

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