Even distribution of aggregate particles in matrices is the target of random mixing processes that are used in the preparation of construction materials to enhance the postplacement uniformity of characteristics. This is particularly important for waste containment barrier concrete where strength, durability, and minimal permeability are desirable. An index, herein referred to as the deviation index (DI) was developed and applied to the cross-sectional areas and volume elements of concrete containing large aggregate to describe distribution deviations of large aggregate particles from perfectly even volumetric distribution. The Poisson distribution and the goodness of fit test were used to describe deviations. Experimental results were obtained from concrete batching tests, designed and performed to compare two mixing methods (rodding and vibration) and a control. The results show no significant uneven distribution as the χ2 values are less than 19.6 at 5% significance level. Within the bounds of these low deviation values, the rodded samples deviated the most, and had the highest DI values (22, volumetrically and 65.32, areally). Sequentially batched samples show minimal variability in DI, indicating that the batch mixing processes were consistent.