The leaching procedures for evaluation of cement-based stabilization/solidification processes are considered. The difficulties in obtaining a consensus test method are discussed. The relative merits and shortcomings of the equilibrium and dynamic leaching test approaches are underlined, and various leaching models are considered.

Although mass transport and diffusion models have been generally used to describe the leaching behavior of soluble species, the use of these models to describe the cement-solidified heavy metal waste is questioned. This is based on theoretical consideration of the interaction between cementitious materials and waste and experimental evidence of the leaching characteristics. An alternative approach toward modeling the leaching behavior of the solidified waste is presented.

Because the performance of the solidified material is also dependent on the physical properties of the waste form, a physical test procedure in conjunction with an appropriate leach test is proposed as necessary to evaluate the quality of the solidified waste. A tentative approach to formulate such a combined test method is suggested.