Lafarge North America has provided innovative blended cement mix designs to help achieve the goals of high strength, resiliency and extended service life for the new signature Tappan Zee Bridge. It is the largest bridge construction project in New York history.
The New NY Bridge’s landmark design has already achieved international acclaim for its unique and aesthetic main-span towers. The 3.1 mile twin-span Hudson River crossing that 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, 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’s primary structural components were required to provide a 100-year service life before needing major maintenance. This meant hat materials with proven long-term performance characteristics had to be used. 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.
Key considerations in the selection of 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 this, the team selected 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 to the bridge's main span. To meet the challenges of the approach spans over the river, their driving surface comprises nearly 6000 precast deck segments of high-performance concrete containing Lafarge's high-performance SFTMblended 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 1000 precast concrete deck panels containing Lafarge Portland I/II cement will be used for 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.
Adapted from press release by Rebecca Bowden
Read the article online at: https://www.worldcement.com/the-americas/10032016/lafarge-helps-in-construction-of-tappan-zee-bridge-667/