Performance Characteristics of an Acrylic Rubber Protective Coating System for Concrete Durability in a Marine Environment

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Title: Performance Characteristics of an Acrylic Rubber Protective Coating System for Concrete Durability in a Marine Environment

Author(s): Shin Tanikawa, R. Narayan Swamy, and Tony Laiw

Publication: Special Publication

Volume: 163

Issue:

Appears on pages(s): 275-294

Keywords: alkalies; bonding; carbonation; chlorides; coatings; concrete durability; reinforced concrete; salt water; slabs; underwater structures; Materials Research

Date: 8/1/1996

Abstract:
Concrete structures exposed to a salt-laden environment often suffer from both carbonation and chloride contamination. This paper presents test data on the ability of a highly elastic acrylic rubber coating to resist the penetration of both chloride ions and carbon dioxide. In addition, the bond strength of the coating to the concrete substrate when subjected to repeated cyclic wetting by chloride solution and drying is also reported. The chloride ion penetration resistance of the coating and its bond strength to concrete were studied by exposing reinforced concrete slabs, some fully coated and others half-coated, made with three water-cement ratios, to cycles of wetting with four percent sodium chloride solution and drying. The tests were carried out for 50 cycles extending over a period of over 500 days. The carbonation resistance of the coating was established through tests on cores taken from four structures exposed to aggressive marine conditions and subsequently repaired with the acrylic rubber coating. The results show that this acrylic rubber coating has excellent resistance to both chloride ion penetration and carbonation. No chloride ions were found in slabs fully protected with the acrylic coating. The migration of chlorides from the uncoated into the coated parts was confined to the immediate boundary between the two and was small and slow. Chloride penetration occurred by a time-dependent diffusion process, but largely in the direction of gravity. In a carbonating environment, coated concrete showed significant reduction in carbonation depth; there was evidence of realkalization of the carbonated concrete.