Asphalt Review - Volume 29 Number 2 (June / July 2010)

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ASPHALT REVIEW AAPA/Austroads Warm Mix Asphalt Validation Protocol In order to validate the performance of WMA (including WMA with varying amounts of RAP) against hot mix, AAPA and the sate roads authorities developed an evaluation protocol. This protocol was developed through the Asphalt Research Reference Group, a group comprising state road authorities and the AAPA National Technology Committee, which was established to advise the Austroads Pavement Technology Review Panel. The scope of the protocol was confined to wearing courses consisting of densegraded asphalt and conventional binders. Recycled asphalt pavement (RAP), if included in the WMA, could also be addressed. The key issues addressed by the protocol were: • the testing of asphalt containing additives and surfactants, both in the laboratory and during production; • the testing of asphalt containing foamed bitumen: during production only; • desirable site conditions for a field trial; • the timeframe for the evaluation; and • data and information exchange. The Protocol specified four stages in a Validation Project – Initial Testing; Field Validation; Performance Monitoring, Reporting and Data Sharing. Initial Testing • WMA Incorporating Additives and Surfactants - Testing of (laboratory) design mixes. The Protocol proposed that a series of tests be conducted on both WMA with additives and surfactants, and the same asphalt mix composition without additives and surfactants (the control hot mix). The protocol includes the following asphalt tests: • resilient modulus (indirect tensile); • moisture sensitivity (stripping potential); • wheel tracking; • fatigue; • maximum density (voids free bulk density); • Marshall stability and flow; • air voids at the design binder content; • bulk density at the design binder content; and • recovered binder viscosity. Optimisation of an additive may then be further investigated by varying the amount of additive and reducing the production temperature. • WMA Incorporating a Foaming Process Foamed asphalt must be produced 22 ROADS JUNE 2010/JULY 2010 through the asphalt plant as it cannot be readily replicated in the laboratory. Once the mix design and production criteria (i.e. production temperature) have been established, the same procedures as for WMA incorporating Additives and Surfactants should be adopted with the following two additions: • moisture content; and • moisture content of aggregates used in production mixes. Field Validation Site selection Field validation requires that a suitable site is identified that would enable the performance of the WMA materials to be compared against hot mix controls. Suitable sites should meet the following criteria: • minimum hot mix and WMA sections of length of 100 metres; • straight section, consistent crossfall and longitudinal grade; • reasonable shape (assessed visually and by roughness and shape testing using a Multi-Laser Profilometer (MLP); • strong structural condition (assessed visually and by pavement strength testing); • uniform distress condition; • known traffic counts and commercial vehicle percentage; • medium to heavy traffic conditions; and • minimum level of rutting and uniform rutting. Once a site is selected the following information should be recorded: • site ID (a suitable site ID should be assigned for easy reference); • road name and location; • lane number (where appropriate) and lane width; • direction of travel; • chainage; and • other relevant information, e.g. drawings, other reference points, the location of structures, intersections, etc. Production and Placement details Once a validation site has been selected, the following detailed information must be recorded on the production and placement of materials: • Production details: o mix and bitumen type; o bitumen content; o other additives used (if any); o WMA type and concentration; o date and time of production; o production temperature; o mix design details; o tonnage of asphalt produced; and o haulage time (from plant to site). • Placement details: o site details, eg. site ID, road name, etc; o overlay, or mill and replace; o thickness of asphalt laid; o asphalt temperature upon arrival at the site; o temperature at first compaction; o paver type; o shuttle buggy (if used); and o roller type and pattern. Performance Monitoring The field performance under traffic is the key factor in validating WMA. Trial sites must therefore be monitored for a number of critical performance parameters. Field monitoring Given the importance of demonstrating the viability of WMA and its adoption into practice by road authorities in Australia and New Zealand as soon as possible, the protocol recommended that validation sites initially be monitored for two summers. This recognised that should there be any early problems with WMA they would be identified during that period. At the end of that period, the following performance parameters would be measured and recorded: • cracking; • rutting at 10 metre interval; • texture at 10 metre interval; and • stripping potential. Reporting and Data Exchange It was noted in the introduction that the purpose of the protocol was to assess the performance of WMA and share data, experience and knowledge among the road authorities and industry in Australia and New Zealand using the Austroads framework. The Protocol recommended that all information be readily shared between all participants as a means of ensuring a consistent understanding of the performance of WMA. Reporting All information related to the evaluation of WMA should be collated for processing and to ensure a consistent and comprehensive report. This information includes: • Process type (eg. foamed, additive) and name of additive (if used) of WMA technology/processes considered; • asphalt mix type and aggregate size; • bitumen grade and percentage; continued on next page...
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Page 3 and 4: Chairman’s report ASPHALT REVIEW
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Page 21 and 22: Fulton Hogan and PRS Join Together
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Asphalt Review - Volume 29 Number 2 (June / July 2010)

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