Contech won a competitive tender to undertake concrete repairs, and FRP deck strengthening works to five bridges on SH3 in Waioeka Gorge. Contech utilised an alternative approach to the extruded FRP product specified, using SikaWrap 103-C. SikaWrap 103-C is a woven unidirectional carbon fibre fabric used extensively to strengthen buildings, bridges and other civil structures. It also holds a CodeMark certificate providing the asset owner with confidence that the FRP meet the Building Code’s durability requirements.

Working with the designer Beca, an alternative fabric scheme was developed, including a layout that maximised the fabric solution’s benefits. Utilising Contech’s expertise, we were also able to optimise the specified stand-down periods for resin curing to reduce the impact on traffic. The result was a revised TMP layout which avoided the need for lane closures and instead heavily controlled the speed of traffic through the work sites.

Comprehensive quality assurance testing included coring and pull-off tests to confirm that the SikaWrap Hex 103-C solution met all of the technical requirements.

Due to the weather conditions in Waioeka Gorge, FRP installation work could only proceed during the warmer summer months. The first bridge was completed between February and April 2021 with the remaining four bridges completed between January and March 2022.

The revised solution, along with optimisation of the sequencing of the four bridges meant that the work was completed five months ahead of the original contract programme. This early completion resulted in significantly less disruption to traffic flows through the Gorge, a major heavy traffic route for Gisborne’s farming and food production sectors.