This study by Kief and Toan, published in Geotec Hanoi, surveys worldwide research, demonstrating that NPA Tough-Cells improve layer modulus by up to x5 and reduce total costs of pavement construction by up to 20%. The study shows that NPA Tough-Cells are a sustainable solution for the structural base of all roadway and railway applications. They also enable the utilization of on-site or recycled materials. Consequently, NPA Tough-Cells can be used to meet affordable, sustainable construction goals in Vietnam and other rapidly developing countries.
R&D and Field Demos
- University of Kansas – Performance, Evaluation and Design of Tough-Cell Reinforced Bases
The comprehensive geocell testing and evaluation studies conducted by Han, Pokharel, Yang and Thakur testing included static and repeat plate-loading tests and full-scale moving wheel tests, to fully understand geocell reinforcement mechanisms and contributing factors. It demonstrated the following advantages of NPA Tough-Cell reinforcement:
- Increase granular base course stiffness x2, bearing capacity x2.5
- Significantly reduce permanent deformation
- Significantly reduce creep of recycled asphalt pavement (RAP)
- Strain measurements confirmed “beam effect”
- Design methodology was validated for roads with NPA Tough-Cell reinforced bases
- Netherlands KIWI (previously KOAC) NPA Tough-Cells vs Geogrids, Road Base Field Trial
Controlled field trials compared NPA Tough-Cells and 7 brands of geogrids and recorded unprecedented road base thickness reduction factor of 0.73 for NPA Tough-Cells. Highest previously recorded was 0.5.
- Clausthal Technical University, Germany – NPA Tough-Cell Contribution to Load Bearing and Stress Distribution in Base Layer
Static plate loading, in-situ road field test and dynamic trafficking tested the impact of NPA Tough-Cells in base layer reinforcement of asphalt structural pavements. They demonstrated the following advantages of NPA Tough-Cells:
- Improved load-bearing capacity x5
- 30-40% less stress than unreinforced surfaces
- Reduced vertical stress by 53%
- Modulus ratio x5 compared to unreinforced layers
- Indian Institute of Technology – Plate Load Tests of NPA Tough-Cell for Determination of Modulus Improvement Factor (MIF)
Plate load tests comparing NPA Tough-Cell reinforced sections with unreinforced sections at the Govind Dairy, Phaltan, demonstrated an NPA Tough-Cell modulus improvement of 2.75.
- Israel National Roads Authority – Cross-Israel Highway 6 Demonstration Project
Investigation into the economic impact of structural reinforcement in the base layer of a new section of road reinforced with NPA Tough-Cells, showed the following results:
- 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)
- Columbia University – Railway Embankments Maintaining Ballast Geometry under Static and Dynamic Loads
Loading tests on NPA Tough-Cell reinforced and unreinforced representations of railroad ballast embankments, demonstrated the following advantages of NPA Tough-Cells:
- Significantly restrict vertical displacement by 31-52% and lateral displacement by 24-31%
- Significantly increase stiffness and strength, reduce permanent deformation
Developing a Design Methodology
- University of Kansas – NPA Tough-Cell Reinforced Pavement Design According to Mechanistic-Empirical Method
Han, Pokharel, Yang and Thakur developed an NPA Tough-Cell design method, modifying a previous model from Giroud and Han. The study accepted a modulus improvement factor for NPA Tough-Cells of 1.5 to 5.0, depending on the infill material, subgrade, relative location and depth of the reinforced layer.
- Hanoi University of Transport and Communications – Vietnamese Design Methodology for Flexible Pavement Design
The research developed a design methodology to incorporate NPA Tough-Cell reinforced pavement structure into the current Vietnamese design procedure. It found that in heavy-duty pavement structures, an NPA Tough-Cell reinforced layer combined with local granular material, can replace a cement stabilized base, improving resistance and reducing construction time.
Benefits – Stronger pavements, reduced costs, environmental advantage
The research, tests and field demos validate that novel polymeric alloys, specifically NPA Tough-Cells, significantly improve reinforcement, with the following benefits:
- Better pavement performance, longer pavement life
- Reduced construction and maintenance costs, up to 20%
- Use of local infill material, requiring less fuel use and reduced carbon footprint