Some notes concerning the dry density testing standards

The results of two doctoral programs concerning the dry density of sands are as follows: (i) the ratio of the minimum and the maximum dry density of sands is about constant, (ii) the dry density of the soil fractions slightly increases with the maximum grain diameter d(max) being the diameter range doubled with increasing grain diameter. These results are used through a statistical analysis to show that the e(max) test of the German DIN may be biased. The possible reason for the bias is arching due to the too small ratio of the diameter and the height of the mold. As a by-product of the research, the earlier finding that the maximum density of the specimens may be obtained indifferently using a Modified Proctor procedure or a vibrating table is extended to the DIN (implying that the density methods of the calibration chamber sands are basically equivalent to the DIN).