Sand and kaolin compacted mixtures were tested in the laboratory to investigate the effect of applied hydraulic gradient on the hydraulic conductivity measurement. Kaolin clay was added to the samples at a percentage 15, 30, 50, 70, 85 and 100% by dry weight, and hydraulic conductivity tests were performed on specimens prepared at 2% above optimum moisture content. The tests were conducted under different hydraulic gradients, using a rigid wall pressure permeameter. A definite pattern of non-Darcy behavior was recognizable in the poorly graded samples with low plasticity and fines content less than 30%. For samples with greater amount of fines and medium plasticity, Darcy behavior was observed, without a noticeable change in the flow behavior.