ABSTRACT
Geosynthetic clay liners (GCLs) are factory-manufactured products used in various applications mainly for containment purposes. The type of construction, as well as the anticipated function determine the technical requirements that GCLs must fulfil. There are many laboratory test methods that can be used for the characterization of GCLs. Among other tests, the swell index test and the Enslin-Neff water-adsorption test are used for quality control in manufacturing and as performance indicators for the mineral component, i.e. bentonite clay. The paper presents the findings of within-laboratory evaluation of measurement uncertainty in bentonite swell index and water-adsorption testing, and the evaluation of some requirements of the standard test method, such as the influence of time and temperature of drying for the sample preparation phase or the influence of different observers. No statistically significant deviations from normality were found for the Enslin-Neff water-adsorption test. The F-test and t-test were performed to compare variances and means for the same observer at two drying temperatures, as well as for two observers at the same temperature, with some differences. The results of the detailed statistical analysis indicate that the assessment of the measurement uncertainty type A was properly estimated.
