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This research explores the contribution of the aggregate skeleton and the bituminous mortar towards the resistance to permanent deformation of asphalt mixtures. Towards this end, laboratory material testing was performed on porous asphalt concrete (PAC), stone mastic asphalt (SMA) and dense asphalt mixtures (DAC). An identification process was developed to determine the composition of the skeleton and the bituminous mortar. In order to prepare test specimens with reasonable compaction homogeneity, specimen preparation protocols were developed with the help of X-ray tomography. Separate laboratory tests were performed on the asphalt mixture, aggregate skeleton, bituminous mortar and bitumen. The results showed that the aggregate skeleton and degree of compaction is important for the permanent deformation behaviour of stone skeleton asphalt mixtures such as PAC and SMA. The test results also underscored the importance of the contribution of the mastic in permanent deformation behaviour of the DAC. In addition, the permanent deformation behaviour in two test pavements was analysed. The analysis showed that the behaviour could be explained by the approach developed in this research.

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Patrick M. Muraya holds a Ph.D. from the Delft University of Technology, Delft; Master of Road Engineering from IHE /Delft University of Technology, Delft; Bachelor of Science in Civil Engineering from University of Nairobi, Nairobi.

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