The aim of the proposed research is to understand unique particle interactions in tank waste relevant systems from chemical physics at solid-liquid interfaces, and to determine how those interactions influence long-range ordering (agglomeration) of colloidal waste particles and bulk suspension rheology. Specifically, we will study particle interactions moderated by solvation/hydration forces, in colloidal suspensions at conditions relevant to Hanford tank wastes (high pH, high-ionic strength), evaluate the consequence of those interactions on agglomerate structure and bulk rheology, and develop computational models that allow prediction of measured aggregate structures and bulk rheology from first principles or through experimentally accessible measurements.