Hydraulic Compatibility of Geotextile Drains with Fly Ash in Pavement Structures

The legislations have been promulgated in many states that remove barriers to large-scale beneficial re-use of waste materials. As a result, there is a renewed emphasis on incorporating suitable waste products into highway construction. Fly ash is one of these materials, and is increasingly being used as fill materials for highway embankments, and as grout mixes for road bases. In most cases, a geotextile is in contact with the fly ash or fly ash-treated soil, and drainage is one of the duties expected from the geotextile. Hydraulic compatibility of geotextile drains with fly ash was evaluated through laboratory gradient ratio tests. The results indicate that fly ash is compatible with a variety of woven and nonwoven geotextiles. Clogging of the geotextile or excessive piping of fly ash was not observed, even under relatively high hydraulic gradients. The gradient ratio test had some limitations when used with fly ash. Long-term tests should be performed for evaluating the performance of the fly ash-geotextile systems, and changes in hydraulic conductivity should be analyzed along with the measured gradient ratios.