Toxicity Characteristic Leaching Procedure (TCLP). Measures how much of each regulated contaminant leaches from the solidified matrix under a standardized mild-acid extraction, confirming the S/S product no longer exhibits the toxicity characteristic.
Unconfined compressive strength (UCS) test. Measures the physical strength of the cured solidified matrix, confirming it can support its own weight (and any overburden/traffic load) as landfilled monofill material.
Permeability (hydraulic conductivity) test. Measures how readily water can move through the solidified matrix — a low permeability limits the rate at which infiltrating water can contact and leach the encapsulated contaminants.
Wet-dry durability test. Cycles the cured specimen through repeated wetting and drying to confirm the matrix does not disintegrate or lose strength under long-term field moisture cycling.
Freeze-thaw durability test. Cycles the cured specimen through repeated freezing and thawing to confirm the matrix withstands seasonal temperature cycling without cracking or crumbling.
Paint filter liquids test. A pass/fail screening test confirming the treated waste contains no free liquid, which is a land-disposal-restriction prerequisite independent of the strength/leaching results.
No single test in this list is sufficient on its own to certify an S/S product for land disposal — a formulation can pass TCLP on the day it is tested and still fail in the field years later if it lacks the physical durability to survive freeze-thaw or wet-dry cycling, which is exactly why the durability tests are run alongside, not instead of, the leaching test. In practice a full S/S bench-scale evaluation runs several candidate binder/waste mix ratios through this whole battery of tests simultaneously, so the mix design that is ultimately selected for full-scale treatment is the one that clears every test, not just the cheapest or fastest one to run.
