Sixty-Year-Old Concrete in a Marine Environment


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Title: Sixty-Year-Old Concrete in a Marine Environment

Author(s): S. Ozaki and N. Sugata

Publication: Special Publication

Volume: 109


Appears on pages(s): 587-598

Keywords: age; blast furnace slag; breakwaters; caissons; carbonation; chlorides; concrete durability; corrosion; marine atmospheres; pH; porosity; pozzolans; reinforcing steels; salts; sea water; Materials Research

Date: 8/1/1988

The deterioration of concrete structures due to age, particularly in marine environments, has recently become a subject of great concern. In this study, the properties of 60-year-old concrete in a marine environment were examined. Taking the opportunity of the demolition of the northern breakwater of a port in Japan, samples were taken from the reinforced concrete caissons, from the upper concrete, and from the foot protection blocks. Tests for concrete strength, porosity, salt content, carbonation, and the corrosion status of the reinforcing bars were performed. The concrete seemed to have retained its strength even after sixty years of exposure to sea water environment. The pore sizes were generally smaller than those of ordinary concrete while the total porosity was the same. The salt content was high at approximately 0.3 to 0.6 percent near the surface of concrete. It reduced, however, to a constant value of about 0.1 percent at a depth of approximately 8 cm. As a result of the study, it was found that the concrete, which was made from blast furnace slag and volcanic ash and appeared to contain sea sand, had scarcely deteriorated at all even though it had been exposed to sea water environment for sixty years.