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MAINTENANCE & MANAGEMENT OF ASSETS
Foamed bitumen to the rescue PROJECT: Central Waikato Network Outcome Contract – Renewal Sites CONTRACTOR: Hiway Stabilizers NZ CLIENT: Waka Kotahi NZ Transport Agency VALUE: $4.4m The Central Waikato NOC rehabilitation treatments have been undertaken using a refined Catalogue Design, meaning a single design is proposed for all rehabilitation sites. The philosophy reduced the number of test pits needed and laboratory testing was limited to confirmation that foamed bitumen stabilisation is a suitable treatment for the job. Extensive workshopping with Waka Kotahi NZ Transport Agency and Downer sped up the design process – and implementation. A collaborative approach between the parties meant FWD testing was assessed and used in conjunction with site walkover to determine the locations of test pits; finding the most appropriate locations is critical to success. Construction methodology was amended to mitigate risk of incorporating unsuitable materials into the stabilised basecourse layer, particularly with the level of testing for each site.
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The proposed treatment is assessed against each rehabilitation section and confirmed to be appropriate through interpretation of deflection data, test pits and laboratory testing. Any amendments due to geometric constraints or other factors are considered. During construction, Hiways has a full time Quality Assurance technician monitoring every aspect of stabilisation to ensure that the design parameters are met. With active traffic management, traffic can be directed across the site with very low risk of damage to the surface of the stabilised layer. Assessment of foamed bitumen stabilisation has found it to have lower than normal whole of life carbon emissions. It can be constructed quickly and opened to traffic immediately if required. Foamed bitumen stabilisation is also a highly sustainable treatment option for recycling / reuse of existing basecourse materials – allowing the reuse of “tired” aggregate, saving significant quantities of new quarried material.
CCNZ / HIREPOOL CONSTRUCTION EXCELLENCE AWARDS 2022
