This study by Kief and Toan, published in Geotec Hanoi, surveys worldwide research, demonstrating that NPA Geocells improve layer modulus by up to x5 and reduce total costs of pavement construction by up to 20%. The study shows that NPA Geocells 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 Geocells 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 Geocell 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 Geocell 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 geocell reinforced bases
- Netherlands KIWI (previously KOAC) NPA Geocells vs Geogrids, Road Base Field Trial
Controlled field trials compared NPA Geocells and 7 brands of geogrids and recorded unprecedented road base thickness reduction factor of 0.73 for NPA Geocells. Highest previously recorded was 0.5.
- Clausthal Technical University, Germany – NPA Geocell 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 Geocells in base layer reinforcement of asphalt structural pavements. They demonstrated the following advantages of NPA Geocells:
- 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 Geocell for Determination of Modulus Improvement Factor (MIF)
Plate load tests comparing NPA Geocell reinforced sections with unreinforced sections at the Govind Dairy, Phaltan, demonstrated an NPA Geocell 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 Geocells, 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 Geocell reinforced and unreinforced representations of railroad ballast embankments, demonstrated the following advantages of NPA Geocells:
- 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 Geocell Reinforced Pavement Design According to Mechanistic-Empirical Method
Han, Pokharel, Yang and Thakur developed an NPA Geocell design method, modifying a previous model from Giroud and Han. The study accepted a modulus improvement factor for NPA Geocells 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 Geocell reinforced pavement structure into the current Vietnamese design procedure. It found that in heavy-duty pavement structures, an NPA Geocell 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 Geocells, 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