One World Trade Center is a world-class structure of symbolic importance. At 104 stories tall with an antenna reaching 1776 feet, New York’s tallest skyscraper pushed the boundaries of what can be achieved with concrete. High-performance concrete criteria included heat reduction in the mass concrete placements, high strength for structural performance and blast resistance, superior rheology for pumping concrete, and a reduced environmental footprint to achieve sustainable design objectives. A unique design aspect of the structure is a high-strength concrete center core with specified strengths up to 14,000 psi. This core is designed to withstand explosive and high impact forces, while maintaining structural integrity to allow a safe exit passage for building occupants.

Because of its innovative design, much research was undertaken to meet concrete performance requirements for high strength, heat control, blast resistance, superior rheology, and sustainability. Several concrete mixtures containing slag cement were developed to meet performance criteria for various One World Trade Center foundation and structural elements and for World Trade Center Memorial and Museum mass concrete placements. Concrete mixtures included a quaternary mixture used in lower elevations that contained 52% slag cement with portland cement, fly ash and silica fume. This combination was used to control heat gain and at the same time achieve the 14,000-psi strength requirement. This was such a large project with many phases that it included multiple concrete suppliers and two slag cement suppliers.

Project credits: Port Authority of New York and New Jersey, Owner; Skidmore, Owings and Merrill, Architect; Cantor Seinuk, Engineer; Tishman Construction, Contractor; Eastern Concrete, Empire Transit Mix, Ferrara Bros. Building Materials Corp., and Quadrozzi Concrete, Concrete Suppliers; Holcim US Inc. and Lafarge North America, Slag Cement Suppliers.