Photo courtesy GCP Applied Technologies
The Governor Mario M. Cuomo Bridge in New York needed to be replaced with a new 5-km (3-mi) twin span bridge across the Hudson River. To ensure a high level of protection and face variable and extreme weather conditions, restricted working hours, and short possession times, the designers specified a high-performance liquid waterproofing membrane system.
The bridge is constructed of precast concrete deck panels sitting atop steel girders, and is designed to achieve a 100-year service life.
Waterproofing of the bridge required surface preparation as well as the application of two layers of liquid waterproofing over 111,484 m2 (1.2 million sf) in three months.
The waterproofing specifications were developed after conducting an in-depth site visit, including inspection of the bridge deck. This called for a solution that would provide speed and ease of installation, minimizing traffic disruption and facilitating contract progression. The waterproofing system satisfied these requirements, as it is spray applied and cures quickly (typically within the hour) to form a durable, seamless membrane.
A compatibility testing of the bridge deck with the membrane showed good adhesion results. The specifications also called for the use of a thin asphalt wearing course.
There were also additional logistical challenges to the project. Work was being executed at other locations on the bridge deck at the time the waterproofing commenced. This could have created a problem with other waterproofing systems. However, the specified waterproofing system gave the applicators the flexibility to have multiple crews working at the same time. They could stop the waterproofing application at a certain place and come back at time later to tie-in the day joints.
Additionally, the waterproofing membrane was being applied at the height of the summer. Many liquid waterproofing membranes react with naturally occurring moisture and suffer severe limitations in hot conditions, hampering productivity onsite. The versatility of the specified system meant the crews could maintain productivity in hot temperatures (up to 49 C [120 F]) and high periods of humidity without shutting down.
Quality assurance (QA) was also an integral part of each step of the waterproofing project. First, adhesion testing was done to validate early on that there was a full chemical bond between both the waterproofing layer and the substrate below. Wet film-thickness testing was then performed to verify the liquid waterproofing was being applied at the specified thickness. Film thickness was checked at the time of application rather than post-application, enabling real-time QA checks.
Since this QA step could be done immediately, applicators were able to identify and touch up areas in need of additional waterproof coating. The waterproofing system was applied in two color-coded layers, making it easy to see at a glance that all surface areas were covered.
