PRS-Neoweb

PRS-Neoweb is a developed and manufactured by PRS Mediterranean Ltd. (PRS-Med). Manufactured in welded strips which open to a 3D honeycomb-like matrix, the PRS-Neoweb geocell is infilled with granular soil material to stabilize and reinforce soil. In addition to reinforcement of the pavement structure of roads, railways and container yards, PRS-Neoweb cellular confinement is also used in soil stabilization and erosion control in slopes, channels and earth retention structures.
PRS-Neoweb is made from Neoloy, a novel polymeric alloy (NPA), which provides a higher modulus, creep resistance and tensile strength to geocells than HDPE (High-density polyethylene)(Pokharel, et al., 2009). Research has shown a stiffer geocell wall retains the cell geometry (dimensional stability) better and therefore confinement and reinforcement. PRS-Neoweb is a sustainable solution for road construction as it enables the use of locally available lower grade (cost) materials for infill, thereby saving virgin aggregate; reduces the pavement layer thicknesses; and extends the service life of pavements, contributing to lower cost operations and maintenance.
History
The geocell concept was originally developed by the US Army Corps of Engineers in the 1970s as "sand-grids" to improve the soft subgrades of unpaved roads for short-term use by heavy military vehicles (Webster and Alford, 1977). Subsequent production of geocells for civilian use began several years later, based on HDPE, in slope stabilization and erosion control and in temporary and low volume roads.
PRS Mediterranean (est. 1996) began manufacture of the PRS-Neoweb brand of geocells. However, in order to improve the stiffness and long-term durability required by critical long-term applications PRS sought to develop a suitable geocell. This required a geocell with the low creep and the high-modulus of engineering thermoplastics. The result of the R&D program was Neoloy, a novel polymeric alloy (NPA), based on a polyolefin matrix reinforced by polyamide nano-fibers. This NPA, as is it is termed in the research literature is used to create a multi-layered tough geocell featuring durable outer layers in between a high strength inner core layer for optimal performance. PRS-Neoweb geocells made from Neoloy are designed for long-term structural reinforcement in critical applications such as the structural pavements, embankments and high retention walls.
Research
Extensive research on exploring geocell reinforcement for roadway applications has been ongoing at the University of Kansas, University of Delaware, and Colombia University (NY) in the past few years. The objectives of this comprehensive research was to understand the mechanisms and influencing factors of geocell reinforcement, evaluate its effectiveness in improving roadway performance and develop design methods for roadway applications. This research included laboratory box tests, accelerated moving wheel tests, field demonstration and development of design methods.
Performance
The following geocell performance parameters are used by PRS-Neoweb. Although commonly used to test polymers in the geotextile, pipe and other industries, these parameters provide an accurate predictor of geocell performance in the field. Temperature increases are often used in these tests to simulate accelerated performance as an indicator of long-term durability.
High tensile strength >21 kN/m; Low creep reduction factor 2.7 according to Stepped Isothermal Method; High dimensional stability - CTE (Coefficient of Thermal Expansion) < 120 ppm/°C; Resistance to elevated temperatures as per >600 MPa at 35°C and >400 MPa at 60°C, and; High resistance to oxidation and UV degradation, according to OIT (Oxidative Induction Time) >100 minutes @200°C and HPOIT - High Pressure OIT >200 minutes @200°C.
Applications
PRS-Neoweb with NPA (Neoloy) is designed for use in the base layer reinforcement of paved roads. The high tensile strength, dimensional stability (low creep) and resistance to high temperature of PRS-Neoweb are suitable for long-term use in the base of flexible pavements, in order to retain the geocell geometry even under repeated dynamic & cyclical load stresses. PRS-Neoweb has also been used to create reliable and safe roads for the military in areas of conflict (see Route Trident, Afghanistan).
Design methodologies
Recent research also calibrated and integrated the use of Neoloy-based PRS-Neoweb geocells in existing road design methodologies. In particular, the Modulus Improvement Factor (MIF), verified in research and field demos provides a reliable method for quantifying PRS-Neoweb contribution to the pavement structure in unpaved and paved roads and railways. The MIF value obtained from field tests, laboratory tests and finite element studies varies between 1.5-5 dependent upon the material of infill, subgrade and location of reinforced layer.
Environmental durability
PRS-Neoweb is a non-corrosive, inert engineering thermoplastic resistant to extreme environmental conditions, heat, cold, water, wind and dust. It operates in temperature extremes of -50°C to +50°C, and has been successfully deployed in all environments from deserts to saturated peat bogs to the arctic tundra. Special additives and manufacturing processes make PRS-Neoweb highly resistant to environmental influences, such as UV radiation and oxidation, during long-term outdoor storage, installation as well for long-term project design-life.

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