Sustainable Highway Reinforcement For Long-Lasting Roads
Sustainable highway reinforcement with Neoloy®Geocells on section of Israel's Highway 6 reduced asphalt layer by 23%, infill by 37%
The Challenge
The Cross Israel Highway (Highway 6) is a 140 km national electronic toll road traversing the country’s long North-South corridor. Highway 6 is a DBOT (Design, Built, Operate, Transfer) project built by AECON Canada’s largest construction and infrastructure development company, at a cost of $1.4 billion. The Highway 6 concessionaire, Derech Eretz Group, needed to add a third lane in each direction in response to increased traffic intensity, and decided to test the Neoloy Geocell cellular confinement system in pavement sections. The goal was to demonstrate how Neoloy could be integrated in a cost-efficient design by reducing the cost of infill and asphalt while maintaining long-term performance, within the following guidelines:
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- Use standard design methodology and meet national standards
- Pavement thickness should align to the existing elevation
- Reduce overall asphalt layer thickness
- Replace base infill with less expensive granular subbase material
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Neoloy Geocell Design
While the unreinforced conventional design for the Highway 6 pavement consists of: 200 mm asphalt, 200 mm crushed stone base and 170 mm subbase (670 mm total thickness), the alternative design with Neoloy Geocells included two key improvements:
- Replace the crushed stone base infill layer with lower quality granular infill (subbase class A); it was used for the base (240 mm) and subbase (170 mm) layers – TOTAL INFILL SAVINGS = 37%.
- Reduce base of asphalt layer from 100 to 60 mm – TOTAL ASPHALT LAYER REDUCTION = 23%.
Neoloy 330 small size 140 mm height geocells (4 m wide sections) were installed in the base layer. The Neoloy Geocells serve as a reinforcing inter-layer in the upper pavement directly under the asphalt (contrary to conventional geocell use in the subgrade). This maximizes the 3D reinforcement mechanism, thereby increasing the pavement structure bearing capacity and load distribution.
The road design was based on the empirical-mechanistic methodology and Flex-Design pavement design software. The use of Neoloy Geocells resulted in a 2.7x higher elastic modulus for each pavement layer.
BENEFITS
- Stiff and Strong – high tensile strength (24 kN/m) prevents fatigue
- Confinement – increases pavement layer strength (modulus)
- Reinforcement – reduces layer thickness & wearing course
- Beam effect – improves load transfer and bearing capacity by 50%
- Improves elastic modulus – by 2-5x for heavier traffic and longer pavement lifespan
- Simple logistics – fast all-weather installation
- Lower costs – for infill, compaction, construction
- Reduce maintenance – less repairs, maintenance cycles and downtime
- Extended lifespan – lowers life cycle costs
- Lower grade infill – Use locally available, ungraded or recycled materials for infill
- Reduce pollution – quarrying, hauling, fuel, carbon footprint
- Sustainable – reduce infill, quarrying, haul and earthmoving equipment; which decreases fuel use, pollution and the carbon footprint
- Patented technology –high stiffness, dimensional stability, creep resistance
- Durable– long-term performance under heavy dynamic loading
- Advanced engineering – suitable for perpetual pavements
All Geocells Are Not Equal
Conventional geocells made from HDPE are not used in paved highways due to questions about their long-term stiffness and durability. That’s why PRS created a new generation of geocell technology based on Neoloy®. Neoloy is a novel polymeric alloy based on nano-fibers in a polyolefin matrix that offers higher modulus, creep resistance and than HDPE.
Neoloy Geocells are the only geocells specifically designed for the base layer of flexible asphalt pavements. They offer long-term resistance to creep, fatigue, stress-cracking, temperature extremes and oxidation. The mechanical, physical and chemical engineering properties of Neoloy extend the geocell design life well beyond conventional geocell technology and provide a clear value proposition compared to other geocells, geogrids and other reinforcement geosynthetics.
50% Reduction in Vertical Stress
Monitoring was based on pressure cells located in the base layer of the section, which recorded the vertical stresses applied by static load plate loading. The results show that the vertical stress of the two Neoloy Geocell sections is ~ 50% less than the unreinforced control section. Vertical loading on Neoloy infilled with compacted granular material creates a semi-rigid slab or “beam effect”. The load is distributed more effectively over a wider area, thereby increasing bearing capacity and decreasing differential settlement. This beam effect was verified by extensive testing at Kansas state universities (UK and KSU) and the Indian Institute of Technology (ITT) Chennai, India.
Sustainable from Start to End of Project Life
Neoloy Geocells are a green solution that makes civil infrastructure projects more sustainable. It requires less quantity of aggregate for infill than conventional solutions, while utilizing lower quality marginal soils and recycled c materials. This reduces the use of virgin aggregate sources, as well as hauling and earth-moving equipment. This in turn decreases fuel use, pollution and carbon footprint. The ability of Neoloy Geocells to increase road service life is a key component of a sustainable transportation strategy.
