Long-Term Durability of Concrete Breakwaters in Cold Marine Environment

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Title: Long-Term Durability of Concrete Breakwaters in Cold Marine Environment

Author(s): T. HoriguchiI, N. Saeki, and H. Kudoh

Publication: Special Publication

Volume: 163

Issue:

Appears on pages(s): 171-184

Keywords: chlorides; compressive strength; concrete cores; concrete durability; marine atmospheres; microstructure; seawater; underwater structures; wear; x-ray diffraction; Materials Research

Date: 8/1/1996

Abstract:
The deterioration of concrete structures for breakwaters in cold marine environment, situated in the northernmost part of Japan, was examined by means of physical inspections as well as chemical analysis. A total of 76 points from 16 breakwaters were selected for measuring deterioration. The 16 breakwaters consisted of 10 fishing ports: four of them are situated in the north islands; two are situated along the Sea of Japan; and four are along the Sea of Okhotsk. At the time of examination, the ages of concrete ranged from six to 35 years. Physical inspection entailed measuring the vertical profile using a special frame. In addition, nondestructive tests were conducted to estimate the compressive strength of the concrete. Cylindrical cores (diameter 150 mm) were drilled from each breakwater for measuring the compressive strength, chloride contents, and degree of carbonation. Chloride contents were measured at several depths, from the submerged surface to 80 cm inside of concrete. X-ray diffraction analysis, as well as atomic absorption spectrometry, were conducted for microscopic analysis. In some instances, more than 1.0 m depth of wear was found at the tidal zone between high and low tide level. The shapes of wear showed the typical hourglass shape. A high value of correlation coefficient was found between the wear depth and in situ compressive strength estimated by a nondestructive test method. No significant correlation was found between the wear depth and the age of construction. It was found that the maximum chloride content was not always at the skin of concrete breakwaters, but was frequently deep inside of the structures. From the test results of the X-ray diffractometry and the atomic absorption spectrometry, aragonite, gypsum, ettringite, and calcite were observed. This indicates the possibility of decomposing action of seawater on the constituents of hydrated portland cements. Finally, reliability analysis was used to predict the remaining service time based on the field data collected. Three factors were selected by the statistical significance, these are the strength of concrete from nondestructive test results, the chloride penetration content, and the depth between high and low tide levels.