Long-term hydraulic performance of geotextile filtering recycled materials

Use of recycled materials instead of earthen materials is one way to improve the sustainability of highway infrastructure. Since geotextile filters and separators are used in such construction schemes, hydraulic compatibility of geotextile filters with recycled materials and their long-term performance is essential. A series of long-term filtration (LTF) tests were performed to evaluate the hydraulic compatibility of several woven and nonwoven geotextiles with four recycled materials commonly used in construction (recycled concrete aggregate, recycled asphalt pavement, foundry sand, and recycled asphalt shingle). Upon completion of the LTF tests, grain size analyses, permittivity tests, image analyses, and piping measurements were conducted to investigate the clogging and retention behavior of the geotextiles. The results indicated that majority of the recycled materials tested were compatible with the nonwoven and woven geotextiles. Excessive piping was not observed even under relatively high hydraulic gradients. Permittivity and percent open area were the main parameters that influenced the retention performance of the nonwoven and woven geotextiles, respectively. The success of the existing criteria in predicting the filtration performance was inconsistent, suggesting that a detailed parametric study was needed to propose new filter criteria for these materials.