With the increasing demand for electricity on one hand and the depleting resources of natural gas and oil on the other, the coal industry has been working hard for satiating the demand. The use of the fossil fuel to produce electricity may be cheaper but it has its own limitations because of the amount of nondegradable waste that it generates as a byproduct. Although coal is being primarily used to produce electricity, researchers are striving to develop cost effective and environmentally safe uses of coal combustion products. The use of bottom ash generated from burning of pulverized coal to produce electricity amended with various admixtures as a structural fill and low hydraulic conductivity barriers has been studied by several researchers. In general, the fill material in the field is compacted close to the maximum dry unit weight obtained from a standard Proctor test. In this investigation, change in the strength and stiffness of PCC bottom ash samples amended with varying amount of bentonite and compacted to various dry unit weights was studied. The stiffness was measured in terms of secant modulus at maximum stress, secant modulus at half of the maximum stress, and initial tangent modulus. The results presented show that both the strength and secant moduli of the mixtures increased with the increase in the unit weight. The initial tangent modulus of the mixtures also increased with the increase in dry unit weight, but beyond a unit weight of approximately 15 kN/m(3) (100 pcf), the change in the initial tangent modulus was observed to be negligible.