2016 - South Africa - Long Term Seal Performance

Bituminous surfacing seals are used on a high percentage of the southern African road network to protect the mostly granular pavement base layers and to provide wet weather skid resistance, appropriate for the conditions at hand. A study has been designed to empirically model crack initiation and texture loss to assist with the development and calibration of a Finite Element Model (FEM) for seals. Thirty five road sections have been selected throughout South Africa covering different seal and binder types (Single seals, multiple stone seals and Cape seals), age of seal, traffic volume and climatic region for performance investigation. Two samples were taken from each site (In the wheel-path and outside the wheelpath) to also evaluate the effect of traffic on ageing of the binder. In addition to this the performance of different seals on more than six hundred road sections, over a period of fourteen years, has been evaluated to quantify the effect of binder type and film thickness on crack reflection. A synthesis of the key performance variables has led to the development of survivor curves for different seal types, which is a strategic output of the study This paper provides an overview of findings related to the long term performance of seals in the South African environment. Conclusions are drawn regarding the contribution of different factors influencing crack initiation and texture loss.