Kief, O., Schary, Y., Pokharel, S.K. (2014). Indian Geotechnical Journal, Springer. September.
Technological innovation in geosynthetics such as high modulus (stiff) Tough-Cells (cellular confinement systems) can help achieve a more sustainable highway infrastructure. Research, testing, field trails, and case studies demonstrate how geocells increase pavement performance on one hand, while achieving sustainable goals on the other.
Summary
A review of published research on NPA (Novel Polymeric Alloy) Tough-Cells in the Indian Geotechnical Journal, Kief, et al (2014) demonstrates how technological innovation in geosynthetics such as NPA Tough-Cells can achieve a more sustainable highway infrastructure. Studies and field tests validate that NPA (Neoloy®) Tough-Cells improve road base modulus by 2.75x and reduce structural thickness by 50% while using marginal or recycled materials for structural infill. In addition to reducing the use of virgin resources, the environmental footprint, and maintenance expenditures, roads built with NPA Tough-Cells can lower total life cycle costs by 20% or more.
Researchers from the University of Kansas Preparing Neoloy Tough-Cells for Moving Wheel Testing
University of Kansas – Comprehensive Research Program
Comprehensive studies have been conducted at University of Kansas since 2006, including laboratory box studies and full-scale moving wheel tests, demonstrating the following advantages of NPA Tough-Cell reinforcement:
- Significantly reduced permanent deformation of granular base
- Granular base course stiffness increased up to 2 times and bearing capacity up to 2.5 times
- Significantly reduced creep deformation of recycled asphalt pavement
NPA Tough-Cell Reinforced RAP Road Base Research Project
Han and Thakur investigated how NPA Tough-Cell confinement and reinforcement reduces creep in Reclaimed Asphalt Pavement (RAP) base layers and improves RAP strength and stiffness. The advantages of using NPA Tough-Cell reinforcement with RAP is
- 10 times increased pavement life
- Equivalent performance of 50% thicker layer
- 50% higher stress distribution angle
- Enable onsite use of RAP without processing
Comparative Test in Strategic Highways Research Program CH PROGRAM (SHRP2)
The SHRP 2 “Roadeo” was an integrated field test in State Road 9B in Jacksonville, Florida for the US DOT comparing geosynthetic products – NPA Tough-Cells, geogrids and geotextiles – in sand embankments and evaluated by 8 conventional testing methods. The tests demonstrated “that sand and gravel are improved more with NPA Tough-Cells than any other geosynthetic,” recording a MIF of 2.5 to 4.0.
Validation of Modulus Improvement Factor (MIF), India
Rajagopal, et al conducted cyclical plate load tests on NPA Tough-Cell reinforced and unreinforced pavement sections on a rehabilitated access road at the Govind Dairy Factory, Phaltan, India, which validated the standard MIF value of 2.75,
Semi-Cyclical Plate Testing of Vertical Stresses in Neoloy Tough-Cell Reinforced Base, Cross-Israel Highway 6
Cross-Israel Highway 6 Project
The Cross-Israel National Highway 6 (Class I grade highway) utilized Neoloy for structural reinforcement in the pavement base layer to replace high cost base layer quality infill with lower cost subgrade infill quality. Results of this project include
- Asphalt layer reduction of 22.5%, sub-base layer reduction of 7.4%
- Crushed stone base layer can be replaced by lower cost granular subbase infill
- Over a 20-year period, an entire maintenance cycle eliminated
- Total saving of 21.5% over a conventional life-cycle (50% on maintenance, 5.8% on direct construction)
NPA Tough-Cell and Geogrid Reinforcement of Road Base Field Trial
KOAC Institute in Netherlands conducted controlled field trials to compare the reinforcement capabilities of 7 of the leading geogrids and NPA Tough-Cells, with the following results:
- Unprecedented reduction factor in road-base thickness of 0.73 (geogrids did not exceed 0.5)
- NPA Tough-Cells road-base thickness Reduction Factor than seven leading geogrids
Benefits – More Sustainable, Lower Cost, Longer Pavement Lifespan
The investigations, field tests and case studies cited in this paper demonstrate the efficacy of Novel Polymeric Alloy (NPA) Tough-Cell solutions for sustainable for roads and highways:
- Improved performance, higher traffic, fewer repairs and safer roads
- Lower construction and maintenance costs, up to 20%
- Less earthworks and equipment, leading to reduced fuel use and carbon footprint