Healing of Voids, Cracks and Joints in
Concrete Exposed under Marine Environments
By T.U. Mohammed and H. Hamada
Concrete Journal, Vol.46, No.3, Mar. 2008
- Synopsis
- Healing of "air voids", "cracks", and "joints" in concrete is summarized here based on the several long-term exposure tests of the concrete specimens under the marine environments. It is observed that the diffused ions from seawater into concrete, such as sulfate, chloride, magnesium etc., help to improve the microstrcutures at the outer region of the concrete specimens with the formation of "ettringite", "Friedel's salt" and "magnesium hydroxide" at the air void in concrete. The improved microstructure helps to screen the chlorides at the surface redion. This improvement is significant for the concrete specimens made with high slag content (60-70% cement replacement) for its inherent denser microstructure. Healing of the cracks and joints is observed with the deposition of "ettringite" and "magnesium hydroxide". It also produces a highly alkaline environment and prevents the corrosion of steel bars in concrete. The results strongly support that if the exposed marine environment allows the healing process, it is possible to make sustainable concrete structures in the marine environment based on the exact material selection, and design requirements to control the crack widths as well as the effective treatment of the joints in the structure.
- Keywords:
- self healing, long term exposure test, marine environment, corrosion, crack, joint
