Farklı boşluk sıvılarında bentonitin şişme ve çökelme davranışı

In this study, swell index tests were performed using 14 bentonites that have different properties and it was aimed to find out pore medium chemistry which can give similar swell index as in deionized water (DIW). For this purpose, swell index tests were conducted in NaCl and CaCl2 concentrations ranging between 5 mM to 30 mM. At the end of these test, swell indices were found quite similar in NaCl solutions and 5 mM CaCl2 with respect to those obtained with DIW. On the other hand, a slight reduction was observed in the swell indices with respect to DIW when 10 mM CaCl2 solution was used. As a result of sedimentation tests conducted after swell index tests, three different sedimentation behaviors were observed: Diffused Particle Settling (or Accumulation Settling, AS), Flocculation Settling (FS) and Mixed Settling (MS). It was also observed that the settling behavior of bentonites exhibiting AS type of settling in DIW changed to FS when the pore medium chemistry was changed. Since the FS behavior was observed for most bentonites in 10 mM CaCl2 concentration, it was selected as the critical salt solution. The swell index and sedimentation characteristics/final sediment volume (FSV) of bentonites were related with some physico-chemical properties of bentonites such as liquid limit, cation exchange capacity and specific surface area. Either observational or quantitative relationships, liquid limit, rather than the others, has fair correlation with the swell index and sedimentation characteristics/FSV. Increase in the swell index led to increase the liquid limit. The relationship with sedimentation was evaluated in two ways. Bentonites mostly exhibited AS type of settling in DIW and mostly FS type of settling in 10 mM CaCl2 concentration. Thus, liquid limit decreased as the FSV increased in AS, whereas liquid limit increased as the FSV increased in FS. The swell indices and sedimentation behaviors/FSVs were also related with the hydraulic conductivity. For this time, an opposite behavior of liquid limit was obtained. Hydraulic conductivity decreased as the swell index of bentonites increased. The relationship established with the sedimentation was done in two ways as well. Hydraulic conductivity increased when FSV increased in AS, whereas it decreased as the FSV increased in FS.