n Journal of the South African Institution of Civil Engineering = Joernaal van die Suid-Afrikaanse Instituut van Siviele Ingenieurswese - Towards modelling road surfacing seal performance : performance testing and mechanistic behavioural model : technical paper

Volume 47, Issue 3
  • ISSN : 1021-2019



Pavement designers have a choice of two types of wearing course: either an asphalt wearing course or a surfacing seal. While asphalt surfacing design has received much attention, road seal design has remained dependent on empirical modelling and experience. With the modern trend of increased traffic loading and contact stresses, varying oil resources and related refining processes and by-products, it is postulated that current seal design assumptions and practice may not be directly applicable to the changing situation in practice, and require re-examination (Milne 2004). In 1998 performance testing of road surfacing seals was initiated under the Chair in Pavement Engineering, University of Stellenbosch. The model mobile load simulator (MMLS3) was identified and a test method developed. From 1998 to 2002 a test regime using five different seal binders and three temperature regimes was implemented. A method of evaluating seal performance was developed to enable evaluation of the seals' behaviour. This paper presents a summary of the test results and provides an insight to the performance of the different seal binders under similar imposed loads and environment. Insight is provided for the identification of critical seal performance influences and criteria. A comparative performance test protocol was developed, with an initial seal performance visual assessment method. <br>The need for a mechanistic based numerical model enabling comparative numerical prediction of seal performance was identified as an additional design tool (Milne 2004). A finite element methods (FEM) prototype model of a single seal was developed and is demonstrated. The potential value to practice of both methods of comparative performance assessment were postulated after synthesis of the results.

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