The containment of contaminants is an on-going problem that can be solved in some cases by sealing or encapsulating the contaminant.  Research conducted on grouting non-aqueous phase liquid contaminated soil with cement-based suspensions has revealed that multi-phase flow within the pore structure of the soil results in various configurations of residual saturation.  Electron scanning microscopy of the grouted soil has evidenced that grout adhesion is influenced by the surface “wetness” of the soil and that the process of grouting can encapsulate contaminants.

Residual saturation is the amount of a particular fluid material that is retained on the porous surface of soil particles and resides in the interparticle space.  Depending on the wettability of the fluid in the pores, which can be water, air, or both, prior to contamination, and the wettability of the contaminant, the amount of contamination will vary.  Consequently, different residual saturation configurations will manifest due to the various fluids present as seen in Figures 1 and 2. The type of configuration will influence the mobility of the contaminant prior to grouting, during the grouting process, and after encapsulation.

                            Figure 1                                                      Figure 2

Research with containment and encapsulation of contaminants by grouting must take into consideration the interaction of the contaminant with the soil and also the interaction of the contaminant with the grout. Figure 3 shows the effect of a contaminant within the hardened structure of the grout itself and Figure 4 shows the remains of contaminant within grouted soil.  For the particular contaminant used, bubble-like structures of the contaminant are evident and their size is dependent on the amount of contamination both prior to and after grouting.  To assess the potential hazard of the encapsulated contaminant within the grouted mass, leaching experiments are conducted to quantify the amount of contaminant that is capable of migrating from the grouted mass.  

                                       Figure 3                                                     Figure 4