Accelerated Pavement Testing of Tough-Cell-reinforced Bases over Weak Subgrade, Pokharel, Han, et al (2011)

Moving wheel tests found that Neoloy reinforced pavement performed the same as much thicker pavement and that Neoloy Tough-Cells save 13cm of base material and increases pavement life by up to 3.5x.


Pokharel and Han conducted accelerated pavement testing at Kansas State University, in order to evaluate the effect of NPA Tough-Cell reinforcement on base courses for low-volume unpaved roads over weak subgrade. Using moving wheel tests, they compared the impact of Neoloy Tough-Cell reinforcement on three different types of infill material. The study found that by distributing loads to a wider area, reinforced pavement experienced the same vertical stress level as much thicker unreinforced pavement. The results demonstrated that reinforcement with Neoloy Tough-Cells saves 13cm of base material and increases pavement life by up to 3.5x.

Challenge – Testing low-volume, unpaved road under traffic conditions

Nearly 80 per cent of the world’s roads are low-volume and unpaved. They require strong base course, with geocell reinforcement a suitable solution to achieving this. Yet, most studies on geocell reinforcement for low-volume roads has been either small-scale or large-scale box testing. Tests on low-volume, unpaved roads under traffic loading are rare.

Validation – Moving wheel tests

A test pit at Kansas State University was divided into 4 equal areas. 3 of these were filled with 17cm of different infill (AB3, QW and RAP) reinforced with Neoloy Tough-Cells, while the other was filled with 30cm of an unreinforced base.

Each of the 4 areas was subjected to the same moving wheel test, in which single-axle dual tire wheel loading was repeated. Rut depth was subsequently measured. Following testing, all geocells were exhumed and examined to assess patterns of rut and heave.

Results – Reduced thickness, increased pavement life

When measured, the 17cm thick reinforced AB3 sample had a smaller rut depth as the 30cm thick unreinforced section.

Similar results were recorded when vertical stress was measured, with the 17cm thick reinforced AB3 sample performing similarly to the 30cm thick unreinforced section. The authors noted that the Neoloy Tough-Cell reinforced section could have recorded yet more impressive results, had the same level of compaction been achieved.

The stress distribution angle of the unreinforced sample was 29.2 degrees. By comparison, the angle of the QW reinforced sample was 35.7 degrees, the RAP reinforced sample 40.8 degrees and the AB3 reinforced sample 43.6 degrees.

Consequently, it was calculated that Neoloy Tough-Cell reinforcement can save 13cm of base material and increase pavement life by up to 3.5x

Benefits – Stronger pavement, reduced costs

Pokharel and Han concluded that Neoloy Tough-Cell reinforcement can provide lateral confinement, beam effect, and wider stress distribution to the subgrade, reducing base and subgrade deformations and rut depth at the surface. This results in the following benefits:

  • Less deformation and rutting, reduced maintenance costs
  • Reduced pavement thickness, fewer construction costs
  • Fewer aggregate materials required, improved carbon footprint

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