Technischer Bericht NTB 85-52

In this report the results are presented of compaction tests on quartz sand/bentonite mixtures. The selected quartz sand exhibited a steep grading curve in the range 1 to 1.5 mm. The bentonites used were those previously investigated, i.e. the Na-bentonite MX-80 and the Ca-bentonite Montigel. The mixtures were statically compacted in a compaction mold. Altogether about 80 tests were carried out, in which the bentonite content was varied between roughly 20 and 50 % of the weight of sand and the compacting pressure was between 80 and 320 MN/m². The tests showed that the pressures required to reach a given dry density of the bentonite filling the pores of the sand's grain structure were 10 to 20 times greater than those required for specimens of bentonite alone. It was also observed that the mixtures with MX-80 were easier to compact than those with Montigel. On the other hand, it was found that the specimens with MX-80 were more brittle, especially at low compacting pressures. Mixtures with 35 to 45 % Montigel compacted at pressures in the range 160 – 240 MN/m² resulted in homogeneous, compact specimens with bentonite dry densities of about 1.5 Mg/m³.