Replacement of Fiji Central and Western Critical Bridges – Bulu Bridge Repairs and Overlay with Latex Modified Concrete Reinforced with Fibres
摘要
Clients, structural engineers, and contractors continue to explore and advance their respective bridge delivery programs through the implementation of new technics and materials, that require innovative construction methodologies. The latter can be challenging for contractors when there is very limited know-how in the industry. The objective of this case study of a composite curved deck bridge with 34 m span, was to analyze the differential and excessive outer girders deflections and rotation during concrete deck pour, concrete cracking and deck crossfall loss. A thoroughly monitoring of each girder deflection, at every stage of construction, was conducted and the data analyzed against the design estimated defections. After deck pour, a visual inspection, survey and cracks study was carried out to assess the deck condition. Being a design and built contract, the designer and contractor worked together in a method statement to deliver the required remedial works. The proposal included a deck overlay with fibre reinforced latex modified concrete using fibrillated polypropylene fibres and an aqueous emulsion of styrene-butadiene copolymer latex and the cracks sealed with a low viscosity, free flowing and fast curing injection resin and primer/coating based on a 2-component solvent free epoxy resin. Different trials and testing were conducted to adjust the concrete mix design to ensure that the required workability, strength, finishing and adhesion to the prepared substrate would be achieved onsite. Understanding that the concrete strength and adhesion to the substrate can have a major impact on its long-term performance, the trials and testing conducted have shown to be of high value for the outcome of the works delivered. The teamwork between client, designers and contractors ensured the delivery of a high quality, resilient structure. Such solution can be implemented with more confidence in future remedial projects where a concrete deck overlay and/or crack repairs are required.