Two decades ago, imagine entering a room full of Civil, Structural, and Geotechnical Engineers and proposing a scenario where a lightweight material, weighing no more than 4 lbs per cubic foot, could be utilized to raise an entire Bridge Approach under the constant cyclic loading of 40,000 lbs due to traffic. The response at the time would likely have been incredulous laughter. However, since 1995, the incredible potential of Structural Polyurethane, a groundbreaking, rapid-acting polymer, has transformed this seemingly implausible concept into a tangible reality.
Structural Polyurethane, pioneered in the 1990s by NCFI Geotechnical, has disrupted the constraints of traditional engineering methodologies. This versatile material has revolutionized various industries, with bridge approach and departure leveling and stabilization being its most prominent application. This innovation has achieved global recognition for its proficiency in addressing a wide array of challenges, including varying weight distributions, footprints, and subsurface soil conditions.
Common applications of structural polyurethane in civil and geotechnical engineering include lifting and leveling bridge approaches, stabilizing weak or eroded soils, filling voids beneath slabs and structures, and sealing areas subject to water infiltration. These applications allow engineers and contractors to address settlement and instability without the need for large-scale excavation or replacement, making polyurethane a practical solution for both rehabilitation and new construction support.
A remarkable example from a California-based affiliate company showcases the extraordinary capabilities of Structural Polyurethane. In a project involving a 6-foot diameter manhole encased in a 10-foot diameter casing, engineers faced the daunting task of raising an astonishing 115,000 lbs by 5 inches to reach the desired grade. The solution lay in the utilization of a 4-lb density Structural Polyurethane material the Terrathane™ 24-003. Not only did this approach succeed in achieving the desired elevation, but the entire lifting operation was completed in less than 6 hours. This project serves as a testament to the transformative potential of Structural Polyurethane within the field of engineering.
This type of application highlights the material’s ability to deliver precise, controlled lifting while maintaining structural integrity, even under significant loads and challenging site conditions.
Such success stories are not isolated incidents. Structural Polyurethane has consistently demonstrated its prowess, from elevating 8-foot deep pyramid footings under industrial warehouse buildings exposed to hydrostatic pressure, high shear strength, and substantial friction resistance using a specialized 6-lb polymer, to the more routine task of raising single-story wood-frame residential homes averaging 13,000 lbs in weight. These diverse applications demonstrate the adaptability of structural polyurethane across varying load requirements, soil conditions, and project types, making it a reliable option for both large-scale infrastructure and smaller structural repairs.
Structural polyurethanes are also being used in spray applications such as void filling, cavity filling, or forming structural systems. The Louisville Stormwater Overflow Cavity Fill Project is an excellent example of this. On this project in Louisville, KY, a substantial excavation project involved digging a large pit, measuring 40 feet deep, 300 yards long, and 150 yards wide, to construct an overflow facility for the city’s combined stormwater and sewage systems. This excavation revealed unstable rock formations with sizable cavities in the top 4 feet. To address this challenge and prepare for the construction of concrete walls and foundations, the general contractor, Purefoam, reached out to NCFI. They employed the Strata-Fill 24-023 system, chosen for its low exothermic properties, enabling efficient mass polymer placement. With the help of a boom lift, Purefoam completed the installation of 9,000 pounds of 24-023 over eight days, effectively filling approximately 4,000 cubic feet of voided areas. This solution successfully established a flat plain and allowed the project to progress with minimal disruptions to its timeline. This project illustrates how structural polyurethane can be used in large-volume applications to address subsurface challenges efficiently while maintaining project schedules.
As infrastructure demands continue to grow, structural polyurethane remains a valuable tool for engineers seeking efficient, minimally disruptive solutions to complex geotechnical challenges.
