ABSTRACT
Two bentonites have been used in this investigation: the Spanish FEBEX bentonite and the American MX-80 bentonite.
The FEBEX bentonite comes from the Cortijo de Archidona deposit (Almería, Spain) and its characterisation can be found in ENRESA (2006), Villar (2002) and Lloret et al. (2004). The smectite content of the FEBEX bentonite is higher than 90 percent (92±3%) and it contains variable quantities of quartz (2 ± 1%), plagioclase (2 ± 1%), K-felspar, calcite and opal-CT. The CEC varies from 96 to 102 meq/100 g, and the major exchangeable cations are Ca (35-42 meq/100 g), Mg (31-32 meq/100 g), Na (24-27 meq/100 g) and K (2-3 meq/100 g). The liquid limit of the bentonite is 102±4 percent, the plastic limit is 53±3 percent, the total specific surface area is 725 ± 47 m2/g and the specific gravity 2.70 ± 0.04. The hygroscopic water content in equilibrium with the laboratory atmosphere is 13.7 ± 1.3 percent.
