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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Title: Autogenous Healing; Ingress of Chloride and Sulfate through Cracks in Concrete Under Marine Environment
Author(s): I U. Mohammed, H. Hamada, and H. Yokota
Publication: Special Publication
Appears on pages(s): 135-154
Keywords: chloride; concrete; crack; healing; marine environment; sulfate
Abstract:Autogenous healing of cracks; and ingress of chloride and sulfate through the cracks in concrete were investigated utilizing 15 years old precracked prism specimens. The size of the specimens was100x 100x600 mm. The specimens were made with ordinary portland, slag (Types A, B and C), and fly ash (Type B) cements. A round steel bar of diameter 9 mm was embedded in each specimen. W/C were 0.45 and 0.55. Crack widths were varied from 0.1 to 5 mm. The specimens were exposed to the tidal and sub-merged zones. Deposits along the path of the healed cracks as well. as the de-bonded areas over the steel bars located at the root of the crack were investigated by scanning electron microscope (SEM) and X-ray diffraction (XRD). Mappings for chloride, sulfate, and magnesium oxide through the cracks in concrete were carried out by electron probe micro analyzer (EPMA). Autogenous healing is observed for narrower cracks (5 0.5 mm) irrespective of the cement types and exposure zones. Healing continues along the crack path. It extends to the debonded area over the steel bars at the cracked region. The deposits are con-firmed as calcium carbonate, ettringite, magnesium hydroxide, and rust. Accumulation of more chloride is found in the vicinity of the unhealed wider cracks (> 0.5 mm), especially for slag cements with a high amount of slag content. Sulfate ingress was limited over a very thin region from the crack plane. Interestingly, chloride concentration at the sulfate rich region is remarkably low. It indicates dissolution of chemically ad-sorbed chloride as well as the loss of ability of adsorption of chloride in the pore structures with the presence of sulfate.
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