ROLE OF CARBONATION IN TRANSIENT LEACHING OF CEMENTITIOUS WASTEFORMS

A combined experimental and modeling program approach was applied to e valuate the role of the carbon dioxide reactive component of soil gas on the long-term performance of cementitious wasteforms. Small wastefo rms were cast with Portland cement and synthetic wastewater containing metals and nitrate as a tracer. A series of wasteforms was exposed to an accelerated environment for carbonation and then subjected to tran sient leaching tests in deionized water. A second set of control waste forms was not carbonated but was otherwise treated identically. Result s are analyzed by comparison of experimental data with theoretical mod els of the leaching process. The results indicate that carbonation inc reases the apparent diffusion coefficient for unreactive species while resulting in chemical binding of metals through solid solution in cal cite. For strontium, carbonation resulted in lower net leaching while leaching of calcium and nitrate was increased by carbonation.