Effect of Fly Ash on Alkali-Aggregate Reaction in Marine Environment


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Title: Effect of Fly Ash on Alkali-Aggregate Reaction in Marine Environment

Author(s): H. Ohga and S. Nagataki

Publication: Special Publication

Volume: 132


Appears on pages(s): 577-590

Keywords: Alkali aggregate reactions; alkalies; cements; chloride ions; expansion; exposure; fly ash; marine atmospheres; mortars (material)

Date: 5/1/1992

Heavy damage due to alkali-aggregate reaction has been observed in concrete structure in and along the sea. An accelerated test is performed on mortar to evaluate effectiveness of fly ash for controlling alkali-aggregate reaction in the marine environment. Mortar bars using Pyrex as aggregate and cements with 0.6 and 1.1% of equivalent sodium oxide are made. The alkali content in the mixture is adjusted by adding NaOH or NaCl. Specimens are stored in distilled water, NaCl solution, and under more than 95% of relative humidity. The controlling effect of fly ash and the effect of internal and intruded chloride ion in mortar on alkali-aggregate reaction is studied by measuring the expansion of mortar. Expansion of mortar depends on the type of cement and chemical reagents used for alkali adjustment, the amount of fly ash used and the exposure condition. Even with the same equivalent sodium oxide in the mixture, mortar using NaCl for alkali adjustment shows higher expansion than mortar using NaOH. The highest expansion is revealed for mortar cured in NaCl solution. The controlling effect of fly ash also depends on the type of cement and the exposure condition.