Browsing by Author "Goosen, Elaine Simone"
Now showing 1 - 1 of 1
Results Per Page
Sort Options
- ItemModelling of surfacing seal binder ageing and rheology(Stellenbosch : Stellenbosch University, 2021-12) Goosen, Elaine Simone; Jenkins, Kim Jonathan; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: This thesis aims to develop a model that accounts for in-service changes in seal binder rheology. South Africa is in a transitional period from penetration-viscosity to performance grade specifications. Current practices and ageing analysis are still prima- rily focused on empirical approaches. The study addresses the gap in engineering know- ledge by asking the extent to which fundamental performance parameters can explain binder ageing. Samples include extracted and recovered binders from seal specimens and original, artificially aged binders. Shift and master curve models are determined from DSR and BBR testing. Numerical model and performance parameters are analysed extensively to establish primary indicators of changes in rheology and ageing. Machine learning models are developed from the significant properties to predict the correspond- ing surfacing age. Adjustments are suggested to the extraction and recovery, and Mod- ified Kaelble shifting procedures. The regression efficiency of the Generalised Logistic and CAM master curve models are compared. Specific performance properties, e.g. G-R, ωc and Gvet , are notably capable of accounting for ageing-related changes in mechanical responses. Ageing ratios specifically indicate the relative ageing potential of binders in different behavioural ranges. Emphasis is given to machine learning model optimisation and feature selection strategies for smaller data sets. The final ageing model combines linear and non-linear, e.g. k-Nearest Neighbour and Decision Trees with bagging and boosting, machine learning models in a voting ensemble. Rheology indicators, e.g. Gvet , Tmax and C2, and crude estimators of climate and seal type are among the properties used to estimate surfacing age within an acceptable tolerance.