Challenges or criteria that had to be met on the project.
Real Estate in Manhattan, NY is very expensive and land to build is very rare. At 432 Park Avenue the owner wanted to have as much square footage for luxury condominiums as possible. This, of course, meant to build skyward. Until recently, unfortunately, it was very hard to construct a very tall concrete building on a small footprint because of the limits of concrete strength.
However, in the last few years, optimizing the use of Supplementary cementitious materials along with portland cement and chemical admixtures have enabled very high strengths to be achieved. This now has made it possible to build taller buildings than ever before. High strength concrete was once described as meeting a 8,000 psi strength threshold. With these new combinations of materials strengths are now reaching 14,000 psi and above.
How our employees helped the customer find a solution to solve the project challenge.
To meet the requirement of the building owner of this project Holcim US worked with our Ready Mix customers to obtain this needed strength by the use of our cement and slag materials. Different combinations of our slag and cement were tried for optimum performance. The best mix designs were decided upon and presented to the NYC Building Department for approval. These high strength mixes now have enabled the successful construction of the highest residential building in the Western Hemisphere (this building) with strengths reaching over 14,000 psi and a modulus of elasticity of over 7 million. This building now reaches a height of 1396 feet built on a small footprint of 95 feet by 95 feet which provides the owner with more square footage than he could have ever imagined.
This 86 story building is now being used as an example to other designers who are in the process of erecting similar projects for Manhattan. Over 18,000 psi was obtained using 345 lbs of cement, 120 lbs of fly ash, 620 lbs of slag and 40 lbs of SF. This is not only a super strength mix but a sustainable one as well. With these new efficient mixes the skyline of NYC will change significantly in the near future.