Title: Influence of Fly ash and Moist Curing Time on Concrete Permeability
Author(s): Stella L. Marusin
Publication: Symposium Paper
Appears on pages(s): 257-270
Keywords: chlorides; concretes; fly ash; moist curing; permeability; Materials Research
Cubes and slab specimens prepared from three concrete mixtures containing three types of fly ash (FA), Classes F, C, and F/C, and a control portland cement concrete (PC) were cast and moist cured for either 7 or 28 days. Following 14 days of air drying, the cubes were immersed for 21 days in, and the slabs ponded for 12 months with, 15 percent NaCL solution. Chloride-ion distribution profiles were determined at four depth intervals. For all four concretes, the chloride ion permeability decreased when the length of moist curing was increased from 7 to 28 days. However, after 12 months of testing, the two mixes containing FA Class F and F/C exhibited such low chloride-ion contents at depths below 25 mm that the length of moist curing had little influence on chloride-ion reduction in contrast to that found for PC concrete, and to a lesser degree, concrete containing FA Class F. Use of all thre FA materials resulted in remarkable improvement in concrete impermeability when compared with PC concrete.