Influence of Fineness of Fly Ash on the Carbonation and Electrical Conductivity of Concrete

The paper presents an investigation on the influence of the fineness of fly ash on the carbonation and electrical conductivity of concrete. Fly ash collected from three thermal power stations in India (with a Blaine's fineness of 200, 255, and 305 m(2)/kg, respectively) were used for this study. The study also involved three replacement levels (15, 25, and 35% of cementitious materials) for each fly ash sample. Accelerated carbonation studies were performed on specimens cured for 3, 7, and 28 days. The electrical conductivity of concrete was evaluated by measuring the charge passed in coulomb (per ASTM C1202) on 28-day-cured specimens. The test results indicated that the carbonation depth of concrete increased as fly ash replacement increased. However, the carbonation resistances of concrete increased with increased fly ash fineness. Furthermore, the carbonation resistance of concrete increased significantly with a prolonged curing time. The coulomb charge passed through the concrete at an age of 28 days was significantly reduced with the incorporation of fly ash, and the magnitude of reduction increased with increased in fly ash fineness and replacement level. DOI:10.1061/(ASCE)MT.1943-5533.0000298. (C) 2011 American Society of Civil Engineers.