In 2004 a series of concrete blocks containing fly ash and slag were retrieved from the USArmy Corp of Engineers test site at Treat Island, Maine, after 25 years exposure to a marine tidalenvironment. The blocks were tested to establish the depth of chloride penetration and to determine thechloride permeability and chloride diffusion coefficient. The data indicate very significant improvements inchloride resistance in the concretes containing fly ash and slag compared to control mixes without thesematerials. However, the resistance of the surface to scaling was reduced by the presence of fly ash andslag. The results point to the need to optimize concrete mixture proportions to obtain the desiredperformance.
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