Robert Moses Causeway, New York, USA
Eliminator system waterproofs and extends life of the Fire Island Inlet Bridge
The Eliminator system from Stirling Lloyd, the market leaders in structural protection, has recently played an important role in extending the life of one of New York’s most distinctive structures. The Robert Moses Causeway forms part of the route to the South Shore beaches along the Great South Bay of Long Island and the Atlantic Ocean.
The Fire Island Inlet Bridge, which is an integral part of the Causeway, is a two lane, steel arch span and causeway with a concrete deck, carrying Route 908 over Fire Island Inlet.
New York, USA
New York State Department Of Transport
Hardesty & Hanover
Alarming rates of corrosion
Construction of the Bridge was completed in 1964 and although a relatively young structure, less than 40 years old, its concrete deck has suffered from severe chloride ingress resulting in cracks, spalling and the formation of pot-holes. The Robert Moses Causeway carries approximately 30,000 vehicles each day.
Studies carried out on the substrate and the evident alarming level and rate of corrosion indicated that no protective waterproofing system was used on the deck when the bridge was built.
The extent of the deterioration is such that New York State Department of Transportation (NYSDOT), who took over responsibility for the maintenance of the structure in 1977, is soon to begin design studies to replace the bridge, highlighting the importance and cost-effectiveness of installing such a system during the initial construction.
Any new structure built as a result of these design studies, in the longer term, will give the opportunity to alleviate some of the congestion at this well-known choke point as the increasing recreational activity on Fire Island generates more traffic. However, in the meantime the NYSDOT wished to extend the life of the current structure by preventing further chloride ingress and slowing the rate of corrosion.
To achieve these goals a complete refurbishment of the deck was vital. The design engineers on the project, Hardesty & Hanover, specified the use of the Eliminator bridge deck waterproofing membrane, in conjunction with a 19mm microsurfacing overlay. This combination would not only extend the life of the structure, but by milling off 19mm of the concrete surfacing and replacing it with the same depth of microsurfacing would ensure matching with existing joint elevations. More importantly the specified system would be lightweight - reducing dead load, and could be applied rapidly so minimizing disruption to traffic and would be very cost effective.
The Eliminator system was selected for a number of reasons, not least for its past performance in similar circumstances. The shear forces exerted on the waterproofing / wearing course interface when using micro-surfacing are far greater than those associated with “normal” surfacing depths, however the Eliminator system has proved that such is the bond it achieves to deck and micro-surfacing alike, it can easily withstand these forces. The system’s ability to follow the contours of the rough milled concrete deck with no vulnerable seams or joints was also paramount.
Following the correct deck preparation, Stirling Lloyd’s fast curing PAR1 methyl methacrylate primer was applied to the substrate. This sealed the deck and enhanced the adhesion of the Eliminator membrane to the deck, which was subsequently spray applied in two colour contrasting coats to aid quality control and membrane integrity. As part of the unique on-site Quality Assurance programme, tests were carried out to confirm adhesion to the concrete was greater than the 0.7N/ mm² required by the specification.
Wet film thickness checks were used to constantly monitor the required 80mils (2mm) thickness of the yellow first coat and 40mils (1mm) thickness of the grey second coat of Eliminator. Whilst still in its liquid state aggregate was broadcast into the second coat to provide a mechanical shear key, enhancing the bond to the subsequently applied microsurfacing. Each coat cured and could be trafficked within 1 hour.
Such is the speed and ease of application of the Eliminator system that despite the work restrictions imposed by the traffic management system and the work schedule of the micro-surfacing operation, application of the complete system to the 10,225m² of deck took just 12 days.
The use of the Eliminator system in conjunction with a micro-surfacing overlay has not only enabled NYSDOT to extend the life of the Fire Island Inlet Bridge but also succeeded in ensuring the successful strategy was completed in a timely and cost-effective way - adding another success to the hundreds of structures already waterproofed with the system throughout the USA.