Department of Civil Engineering

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Browsing Department of Civil Engineering by Author "Abrahams, Mohammad Shafee"

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    Towards the development of a standard test protocol : application of the MMLS3 for evaluating the performance of surfacing seals
    (Stellenbosch : Stellenbosch University, 2015-12) Abrahams, Mohammad Shafee; Jenkins, K. J.; Rudman, Chantal; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: For a road to perform optimally, both functionally and structurally; a durable, waterproof, skid-resistant, all-weather and dust-free surfacing is required to provide the road user with an acceptable level of service. Surfacing seals serve to protect the structural layers of the pavement from the abrasive forces of traffic and from the detrimental effects of the environment especially moisture. Surfacing seal design, in South Africa, and many parts of the world is governed mainly by empirical rules and experience guided practices. There is thus a need for a performance related seal design method, with a more scientific foundation. This study aims to address this challenge by investigating the failure mechanisms of seals with the aim of simulating its manifestation using an accelerated pavement tester, the Model Mobile Load Simulator (MMLS3). Based on this investigation, seal stone embedment was identified as the target failure mechanism. Key seal variables were identified which are thought to directly influence the embedment of the stones in a seal. This research project was then centred around this failure mechanism and an experimental seal testing setup was developed along with an analysis procedure to measure and quantify the embedment of the stones in a seal. Based on the literature study the factors influencing the performance of seals were identified along with the capabilities of the MMLS3 for application on seals. The following key seal design parameters were identified and selected for comparison: - Tack coat binder type - Aggregate spread rate configuration - Aggregate size A seal construction method was developed along with a software aided embedment calculation method for use with the Laser Texture Meter (LTM). This integral part of this study allowed for the processing of large amounts of data obtained from the LTM and subsequent analysis of the processed data. Based on the analysis of the data it was established that more than 70% of the total embedment observed over 100 000 load cycles occurred during the initial embedment period i.e. the first 10 000 load cycles. The statistical analysis also provided an idea as to the level of influence of the variables on the embedment measured. The following was noted: - Aggregate configuration showed the lowest influence - Binder type showed an intermediate influence - Aggregate size showed the highest influence This study shows that with an effective testing setup and an efficient analysis procedure, the application of the MMLS3 can successfully be used for evaluating the performance of surfacing seals. Through further research and refinement the development of an effective accelerated seal testing protocol would be possible. Such a protocol should able to quantify and analyse the performance of seals. The major recommendations for the improvement of similar research include: - The inclusion of more testing variables allowing a greater comparative scope. - The use of more precise laser measurement technology with capabilities extending beyond the LTM used in this study. - The establishment of performance index parameters to quantify and rank the variables investigated from which an acceptable protocol can be developed.