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Stokes, J. (2025) Influence of aggregate topology and mineralogy on the long-term skid resistance performance of asphalt surface course material. PhD thesis, University of Nottingham.

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Abstract

Skid resistance is a critical safety property of road pavements, directly affecting wet braking performance and accident risk. Traditional prediction methods—including the Polished Stone Value (PSV) test—focus solely on a small fraction of the coarse aggregate performance and have demonstrated limited reliability in forecasting in situ skid resistance over the service life of an asphalt surface course. This thesis investigates whether a more holistic laboratory measurement—the Friction After Polishing (FAP) test—combined with quantitative characterisation of aggregate topography and mineralogy, can improve prediction of long term in-situ skid resistance as measured by the Sideways Force Coefficient Routine Investigation Machine (SCRIM).

A structured experimental programme was devised to (1) characterise polished aggregate micro texture via Mineral Liberation Analysis (MLA), Mohs hardness grouping, and Alicona infinite focus microscopy; (2) quantify friction evolution during controlled polishing of aggregate mosaics and full asphalt cores using FAP; (3) assess changes in three dimensional surface texture across incremental polishing cycles; and (4) correlate laboratory friction outcomes with extensive SCRIM survey data collected between 2014–2024 on matching asphalt designs under varied traffic volumes.

Results reveal that aggregate mineralogical composition—and specifically the proportion of hard versus soft mineral phases—influences both micro texture retention and friction coefficient trajectories under polishing. FAP measurements reached equilibrium beyond the standard 90 000 polishing cycles, suggesting that current European test protocols underestimate long term wear effects. Alicona G5 Infinite Focus-derived surface and volumetric texture parameters demonstrated statistically significant relationships with FAP friction values. Critically, asphalt cores exhibited stronger FAP–SCRIM correlations than aggregate mosaics alone, validating the importance of binder aggregate interactions and macro texture contributions.

This thesis establishes that combined mineralogical and topographical characterisation integrated with FAP provides a robust predictor of in situ skid resistance performance. These findings support a shift toward performance based surfacing specifications designed to maximise road safety and lifecycle efficiency.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Airey, Gordon Large, David
Keywords:	Skid resistance prediction; Friction After Polishing (FAP) test; Sideways-Force Coefficient Routine Investigation Machine (SCRIM)
Subjects:	T Technology > TE Highway engineering. Roads and pavements
Faculties/Schools:	UK Campuses > Faculty of Engineering > Department of Civil Engineering
Item ID:	82762
Depositing User:	Stokes, James
Date Deposited:	09 Dec 2025 04:40
Last Modified:	09 Dec 2025 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/82762

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