LONG-TERM LEACHING OF METALS FROM CONCRETE PRODUCTS

The long-term leaching of metals from concrete products made with spen t abrasive media was investigated using a sequential extraction proced ure employing both an acidic extraction fluid and seawater. By using s eawater, leaching behavior under conditions encountered in the environ ment (especially coastal areas) can be determined. Chromium, cadmium, and lead concentrations were substantially less for the seawater seque ntial extractions than for the acidic sequential extractions. The envi ronment created during the acidic sequential extractions resulted in t he leaching of substantial amounts of alkalinity from the concrete, an d leachate pH levels dropped below 4 where metals are highly soluble. Also, as only one-tenth of the alkalinity that leached in the acidic e xtractions leached in the seawater extractions, the integrity of the c alcium matrix within the concrete seemed to play a role in the success ful stabilization of cadmium and lead. Acidic extraction tests provide more severe conditions than concrete products are likely to encounter in real-world applications.