Autogenous healing; Ingress of chloride and sulfate through cracks in concrete under marine environment

T. U. Mohammed, H. Hamada, H. Yokota

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Citations (Scopus)

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 was 100x 100x600 mm. The specimens were made with ordinary portland, slag (Types A, Band 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 submerged 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 (S: 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 confirmed 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 adsorbed chloride as well as the loss of ability of adsorption of chloride in the pore structures with the presence of sulfate.

Original languageEnglish
Title of host publication7th CANMET/ACI International Conference on Recent Advances in Concrete Technology
EditorsV.M. Malhotra
PublisherAmerican Concrete Institute
Pages135-154
Number of pages20
ISBN (Electronic)9780870311475
Publication statusPublished - May 1 2004
Externally publishedYes
Event2004 7th CANMET/ACI International Conference on Recent Advances in Concrete Technology - Las Vegas, United States
Duration: May 26 2004May 29 2004

Publication series

NameAmerican Concrete Institute, ACI Special Publication
VolumeSP-222
ISSN (Print)0193-2527

Conference

Conference2004 7th CANMET/ACI International Conference on Recent Advances in Concrete Technology
Country/TerritoryUnited States
CityLas Vegas
Period5/26/045/29/04

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Building and Construction
  • Materials Science(all)

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