HYDRAULIC COMPATIBILITY OF GEOTEXTILES FILTERING RECYCLED MATERIALS

Abstract

Large amounts of natural aggregate and manufactured materials are needed every year to support highway construction and rehabilitation in the United States. It is important that new construction materials be developed to improve the performance of highway systems, while at the same time providing cost-effective and sustainable technologies. Use of recycled materials instead of earthen materials is one way to improve sustainability of highway infrastructure. Similar benefits exist when sustainability is infused into designing modern landfill covers. Since geotextile filters and separators are used in such construction schemes, hydraulic compatibility of recycled materials with geotextile filters and long-term performance of these geotextiles are 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 (POA) were the main parameters that influence the clogging and retention performance of 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.