Browsing by Author "Tredoux, Carlie"
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- ItemRheological performance of seals in South Africa based on binder ageing considerations(Stellenbosch : Stellenbosch University, 2020-03) Tredoux, Carlie; Jenkins, Kim Jonathan; Rudman, Chantal; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: Ageing is a fundamental phenomenon that affects the durability and performance of bituminous binders in a pavement. Ageing increases the risk of premature pavement failures whilst reducing the material durability and flexibility thus shortening pavement life. For this reason the South African pavement industry is currently moving away from Penetration and Viscosity Grade (empirical) Specifications and towards Performance Grade (fundamental) Specifications, as the current specifications do not account for ageing in a comprehensive, fundamental manner. To facilitate the transitional process, a proposed technical specification for SA Performance Grade (PG) Specification for Bitumen (SATS 3208) was published by the South African Bureau of Standards (SABS) in 2018. Currently, this Performance Grade Specification is based on asphalt as per SHRP Superpave, hence the need for consideration of seal binders. In order to make a meaningful contribution towards the formulation of a comprehensive PG specification for SA bituminous binders with respect to seals this study’s aim is to investigate the performance of seals in South Africa. In particular, changes in the fundamental rheological properties of seal binders during ageing are of interest. These measurements provide performance-based properties that are essential as binder selection criteria. This study was undertaken by performing laboratory testing on seal binders. It includes Dynamic Shear Rheometer (DSR) testing in accordance with SATS 3208 at intermediate temperatures and on seven different levels of ageing (unaged, RTFO, PAV2, RTFO+PAV2, PAV4, RTFO+PAV4 and recovered age). The seal binder’s behavioural data was analysed with the Modified Kaelble shift factor model, CAM and GLS empirical models to determine / investigate rheological parameters that describes the durability and performance of seals in relation to ageing. Results from the investigation show the Glover-Rowe (G-R) parameter to be the best rheological parameter to identify seal performance with age, as the Rheological Index (R) showed no correlation to seal ageing. Further investigation is required on SA seals, regarding the VET parameters influence on aggregate loss (failure mechanisms) before performance limits can be proposed for performance specifications. Ageing influences the rheological properties of modified seal binders, as long-term artificial ageing of polymer modified seal binder provides an increased viscous component, thus showing that the polymer degrades at high temperatures as the binder ages. Visual assessment on seal roads is recommended after 6-8 years of in-service to determine deterioration (failure mechanisms) of the pavement, based the G-R data findings of this study and others.