A new look at the use of coated pet geogrid reinforcement in highly alkaline environments

It has historically been assumed that coated polyester geogrids are not suitable for applications where the pH of the soil around the geosynthetic is greater than 9. These applications primarily include cohesive soils treated with lime, or ground hardened concrete or cement mixtures. The pH of these admixtures is often suggested to be in the range of 11-12 but actual field data are difficult to locate. However, it is known that a target pH of greater than 12.4 is used when clayey soils are stabilized with hydrated lime. Another environment of high pH is freshly cured concrete, which is reported to have a pH of greater than 12. There is a new interest in looking at the hydrolysis behavior of coated PET geogrids at pH levels greater than 9. This effort is buoyed by some of the limitations of the work previously done on this topic.