Implementation of a performance-grade bitumen specification in South Africa

CITATION: Bredenhann S. J. et al. 2019. Implementation of a performance-grade bitumen specification. Journal of the South African Institution of Civil Engineers, 61(3):20-31. doi:10.17159/2309-8775/2019/v61n3a3The original publication is available at https://saice.org.za/journal/saice-journal-publication-issues/South Africa has been experiencing higher traffic volumes and heavier loads over the past several years. This has been accompanied by an increase in premature asphalt failures. Selection of the appropriate asphalt binder is critical for improving performance. Empirical bitumen testing has increasingly failed to relate test results to pavement performance, as the traffic volume and loading have changed. Moreover, empirical tests cannot effectively characterise polymer-modified bitumens that are increasingly being used in South Africa. This changing environment calls for the establishment of specifications based on fundamental engineering properties which relate to actual pavement performance. This paper discusses the fundamental principles of the performance grade (PG) specification being introduced in South Africa. It explains how these fundamental principles create a rational framework for the specification, and present a clear set of compliance criteria to ensure the optimal selection of bituminous binders. The reasons for transitioning to a PG specification are discussed, along with the basis of the specification, rheological concepts, measurements required to characterise bituminous binders, and the simulation of ageing in relation to durability. The framework of the specification, including test procedures, provisional compliance limits and mandatory reporting of test results as an interim measure, are discussed in this paper. Finally, some test results received to date for selected typical South African binders are reported and evaluated. These results indicate that current binders being used in South Africa can easily conform to the proposed PG specification in terms of deformation requirements without any disruption to the processes of the refineries or secondary manufacturers. The fatigue properties of binders are still under evaluation and thus not included in the specification framework. Only information gathered will inform the final decision.https://saice.org.za/journal/saice-journal-publication-issues/Publisher’s versio

Design and Construction of Ultra-Thin Continuously Reinforced Concrete (UTCRC) on N1 near Hugenote Tunnell

In 2009, the National Route 1 Section 1 between km 56.1 and km 61.5, located North East of Paarl in the Western Cape Province of South Africa, was rehabilitated and widened. As part of the rehabilitation and widening contract the downhill truck crawler lane was constructed as an experimental pavement section. This experimental pavement section was constructed with a 50 mm thick Ultra-Thin Continuously Reinforced Concrete Pavement (UTCRCP). Early in 2010 sections of the experimental UTCRCP started to fail and consequently necessitated repair. In October 2014 a service provider was appointed for the special maintenance of the truck crawler lane on the National Route 1 Section 1. The project called for the reinstatement of the failed experimental UTCRCP with a re-engineered UTCRCP and a Enrobé à Module Élevé (EME) asphalt base layer with an Ultra-Thin Friction Course (UTFC), at various locations along the southbound (downhill) truck crawler lane. The project objective was specifically formulated to enable a long term performance comparison of both the re-engineered UTCRCP and the EME with UTFC under repeated traffic loading. The focus of this paper is the documentation and assessment of the initial pavement (structural analysis) and material design process, the construction of the UTCRCP, with cognizance of the challenges experienced during construction as well as the initial performance comparison. EME will not be discussed in this paper

Design and Construction of Ultra-Thin Continuously Reinforced Concrete (UTCRC) on N1 near Hugenote Tunnell

In 2009, the National Route 1 Section 1 between km 56.1 and km 61.5, located North East of Paarl in the Western Cape Province of South Africa, was rehabilitated and widened. As part of the rehabilitation and widening contract the downhill truck crawler lane was constructed as an experimental pavement section. This experimental pavement section was constructed with a 50 mm thick Ultra-Thin Continuously Reinforced Concrete Pavement (UTCRCP). Early in 2010 sections of the experimental UTCRCP started to fail and consequently necessitated repair. In October 2014 a service provider was appointed for the special maintenance of the truck crawler lane on the National Route 1 Section 1. The project called for the reinstatement of the failed experimental UTCRCP with a re-engineered UTCRCP and a Enrobé à Module Élevé (EME) asphalt base layer with an Ultra-Thin Friction Course (UTFC), at various locations along the southbound (downhill) truck crawler lane. The project objective was specifically formulated to enable a long term performance comparison of both the re-engineered UTCRCP and the EME with UTFC under repeated traffic loading. The focus of this paper is the documentation and assessment of the initial pavement (structural analysis) and material design process, the construction of the UTCRCP, with cognizance of the challenges experienced during construction as well as the initial performance comparison. EME will not be discussed in this paper