New Tappan Zee Bridge Relies on Lafarge High-Performance Blended Cements to Achieve Resiliency, 100-Year Service Life Goals
From top to bottom, high-performance concrete used in signature cable-stayed Hudson River crossing contains Lafarge SFTM and NewCem® slag cements to attain high strength and long-term durability.
Lafarge North America is making a strong contribution to building more durable, better-connected cities with innovative blended cement mix designs to achieve the goals of high strength, resiliency and extended service life for the new signature Tappan Zee Bridge (New NY Bridge)-the largest bridge construction project in New York history.
The New NY Bridge's landmark design has already received international acclaim for its unique and pleasinglylit angled main-span towers.The visually striking,3.1-mile twin-span Hudson River crossing-which replaces the Tappan Zee Bridge built in 1955-will be one of the widest cable-stayed structures of its kind in the world. It will comprise eight traffic lanes, four breakdown lanes, a bicycle and pedestrian lane, and state-of-the-art traffic-monitoring systems, as well as bus rapid transit and commuter-rail trains. Lafarge blended cements play a crucial role in constructing the colossal new bridge, as more than 300,000 cubic yards of high-performance concrete will be used.
The project required the crossing's primary structural components (foundations, substructures, superstructures and bridge decks) to provide a 100-year service life before needing major maintenance. This dictated the use of materials with proven long-term performance characteristics. To meet these stringent requirements for the substructure, Lafarge collaborated with engineers from Tappan Zee Constructors, LLC, to conduct sophisticated life cycle analysis and testing of different high-slag content mix recipes with numerous aggregates and admixture combinations. The analysis in Lafarge's concrete testing laboratory over several months included tests for compressive strength, permeability, durability, flowability, shrinkage, slump and consistency.
Primary considerations in selecting the optimum concrete mix formulation for the bridge towers, piles, columns, caps and piers were strength, long-term durability, low heat of hydration, and excellent ASR mitigation and sulfate resistance. To achieve these performance goals, the team decided on a high-performance concrete containing a 64%/36% mix of NewCem® slag cement and Portland Type I/II cement. Engineered for long-term durability, NewCem® slag cement helps structures achieve greater strength potential, reduced permeability, and increased resistance to sulfate attack and alkali silica reaction. High replacement levels of slag cement in properly proportioned mixes also help control shrinkage, creep and thermal cracking in mass concrete structures.
The full bridge is supported by 86 piers, most of which bolster the long approaches (encompassing about 2 million square feet) to the bridge's main span. To meet the challenges of the approach spans over the river, their driving surface comprises nearly 6,000 precast deck segments of high-performance concrete containing Lafarge's high-performance SFTM blended cement. This Portland-silica fume cement blend produces concrete with a significantly higher compressive strength than normal concrete and is recommended for structures exposed to seawater, chloride ions, deicing salts and chemical attack. For the crossing's main spans, approximately 1,000 precast concrete deck panels containing Lafarge Portland I/II cement will serve as the roadway. When fully installed, the concrete deck panels for the approaches and main span will comprise a surface area of 65 acres and meet the project's required 100-year service life without major maintenance.
Photo credit: New York State Thruway Authority
As the world leader in the building materials industry, LafargeHolcim Ltd. and its subsidiaries have the assets necessary to meet the building and design challenges of today's increasing urbanization. Globally, LafargeHolcim has 115,000 employees, a well-balanced local presence in 90 countries and combined net sales of CHF 33 billion (EUR 27 billion) in 2014. With the most innovative cement, concrete and aggregates solutions, strong R&D, and a commitment to health, safety and sustainability, LafargeHolcim has the building solutions to meet customers' needs, from the individual homebuilder to the largest and most complex project. We are committed to drive sustainable solutions for better building and infrastructure while contributing to a higher quality of life. We are positioned to deliver on this commitment.
In the United States, LafargeHolcim companies include close to 350 sites in 43 states and employ 6,000 people. Our customers rely on us to help them design and build better communities with innovative solutions that deliver structural integrity and eco-efficiency. We are committed to contributing to Building Better Cities and are an active participant in local environmental, educational and sustainable construction initiatives, including relationships with the Wildlife Habitat Council and Habitat for Humanity.
Lafarge North America Inc., Holcim (US) Inc. and their subsidiaries are LafargeHolcim companies, and together constitute the largest diversified supplier of construction materials in the United States. These companies are sometimes referred to as "LafargeHolcim US" for editorial convenience.