Predicting the Microstructural Degradation of Concrete in Marine Environment

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Title: Predicting the Microstructural Degradation of Concrete in Marine Environment

Author(s): J. Marchand, E. Samson, D. Burke, P. Tourney, N. Thaulow, and S. Sahu

Publication: Special Publication

Volume: 212

Issue:

Appears on pages(s): 1127-1154

Keywords: chloride transport; field concrete; marine environment; numerical modeling; sulfate transport

Date: 6/1/2003

Abstract:
As part of a U.S. Navy program for the Modular Hybrid Pier to predict long-term behavior of lightweight concrete in marine environments, the condition of a series of concrete samples taken from a floating boat dock exposed to the Pacific Ocean since 1978 were assessed. Samples originating form the top deck, tidal and submerged zones were tested. Microstructural alterations were investigated by petrographic examinations using optical and scanning electron microscopy. Chloride profiles were measured by chemical analyses. The hulk properties of each series of concrete samples were also determined by porosity measurements, pore solution extraction, chloride migration tests and moisture transmission measurements. The actual state of deterioration of each series of samples was compared to the results yielded by a numerical model. This numer- ical model accounts for the coupled transport of moisture and eight different ionic species (such as chloride and sulfate ions) within unsaturated concrete structures. The software also takes into consideration the chemical equilibrium of ten different solid phases (e.g. ettringite, gypsum and Friedel's salts). Parameters affecting the long-term performance of concrete in seawater are discussed.