Alternate Procedures for Swell Index Testing of Granular Bentonite from GCLs

Abstract

Abstract Two procedures are proposed for expediting swell index (SI) tests on the bentonite component of geosynthetic clay liners (GCLs) based on ASTM D5890, Standard Test Method for Swell Index of Clay Mineral Component of Geosynthetic Clay Liners. The Fast Alternative Swell Test procedure involves testing 2.0 g of bentonite that passes the No. 40 sieve but is retained on the No. 60 sieve that is added to the graduated cylinder in 0.5-g increments over a period of 10 s with 1 min between each additional increment; for a single test, this procedure is >50 times faster than the standard SI test. The Multiple Alternative Swell Test procedure involves testing 2.0 g of bentonite that passes the No. 40 sieve but is retained on the No. 60 sieve added to the graduated cylinder in 1.0-g increments over a period of 30 s with a 10-min interval between incremental additions; for ten tests conducted concurrently, this procedure is >10 times faster than the standard SI test. Replicate comparative tests were conducted with seven bentonites used in GCLs with the following hydration liquids: deionized (DI) water; 5, 10, 50, 100, and 500 mM potassium chloride (KCl); and 5, 10, 50, 100, and 500 mM calcium chloride. Both expedited methods yield similar SIs with DI water and KCl solutions and slightly underestimate the SI obtained with the standard method.