3. OVERVIEW AND RECOMMENDATIONS 3.1 Surface Treatments Observations Sprayed are used extensively under wide range conditions including heavily trafficked roads. Under these conditions Crumb Rubber binders have provided an increase in service life over other modified binders. Periodic maintenance (sealing, slurry) is scheduled as a preventative maintenance treatment rather then applied on a worst first basis Rejuvenation is a widely accepted practice that can extend the life of seal by 3 – 4 years Triple and sand seals could prove useful in specific situations that currently are not catered for. Recommendations Provide guidance and assess risks on the use of spray seals under heavy traffic for reseals and new works Trial South African spray seal configurations and aggregate spread rates Continue the use of rejuvenation to extend the life of seals. Provide input on South African asset management practice into Austroads project AT1536 Good practice in reseal programming 3.2 Binders Observations Bitumen supply constraints will support importation with consideration being given to performance based testing and specifications Use of wet blend field blended crumb rubber bitumen in seals and asphalt Use of polymer modified bitumen emulsions to extend sealing season Recommendations Increase the use of field blended CRB for spray seals and wet blend CRB for asphalt wearing courses Use PME’s for constructing in winter based on TG1 specifications Make use of dilute emulsion for cover sprays Make greater use of rejuvenation treatments to extend the life of existing aged Improved binder handling and test methods trial trial
addition of small quantities of bitumen emulsion during construction n to enhance the durability of material marginally in or out of specification are also ongoing Certification of non-standard products Developed to match the advantages of the UK Highways Agency Product Assessment System (HAPAS) and the French Avis Technique methods of certifying non-standard products for the built environment. The system is managed by the CSIR and the Agrement Board of South Africa and has three relevant road construction products: Bridge deck joints Ultra Thin Friction Courses (UTFC) Cold mix patching materials The system is on the British Board of Agrement, assesses available historical data and track record including inspections of existing sites. Appropriate laboratory tests are conducted; trials and QC are witnessed leading to an interim certification. Installation trials are monitored for a period of two years after which a certificate to a given class of performance is issues. Continuous monitoring takes place. Ultra Thin Friction Courses Three products have been certified to the Agrement Board South Africa requirements and are being used in the country. UTFC has a wide range of applications and fits well into the perpetual pavement concept. The 15 to 25mm thick high friction surfacing is placed upon a pavement structure of sufficient thickness to prevent bottom up cracking. The sole maintenance measure for that pavement is then the periodic removal and replacement of the UTFC. UTFC is required to meet the performance matrix included in the following table from “Erik Denneman – Fit for purpose certification of road products” – Tour UTFC has been successfully used in airport applications and SANRAL has endorsed its use on their major highways and airports. (Corne Roux - CAPSA, Pieter Molenaar “The development and performance of a new Ultra Thin Friction Course for OR Tambo International Airport in South Africa” ) Ultra Thin Friction Course nearing the end of its service life Summary and recommendations
7. SUSTAINABILITY Working Group Leader: Rob Vos Group: David Angell, Trevor Distin, Russell Lowe Tour Sustainability – recycling, warm mix asphalt, efforts to reduce carbon footprint, carbon calculators and the impacts for road asset management Cold in-plant manufactured Bitumen Stabilised Material using Recycled Asphalt – eThekwini / Durban Feedback from Krishna Naidoo,, Dave Collings,Tony Saied Solomons, Kim Jenkins Observations Sustainability was an underlying for each of the four centres visited and was included in the CAPSA 2011 conference theme Roads of the Future and in the conference focus areas: Reducing energy consumption in the construction of bituminous layers Reducing the impact of road building activities on the environment Designing for extended performance of asphalt Flexible pavement systems for extended life Meeting the of society Observations are drawn from the papers presented both from a South African perspective and from the international participants. Green Circle Road – from rehabilitation to failed pavement and back – the road materials bank During the visit to the eThekwini Municipality / Durban there was clear focus on the need for sustainable use of materials, this included the policy of the 100% reuse of all municipal materials and “waste”. This included the concept of the “Green Circle Roads” where the municipality is the owner of the network, the road, and the residual pavement materials. When rehabilitation is required, it considers the deconstruction of the asset and its engineered and managed reuse, reducing the introduction of virgin materials to a minimum and tracking the most beneficial path for the reuse of the materials from design through to project completion. trial