10124 Deterioration and Rehabilitation of a Newly Built Pre-Cast Reinforced Concrete Seawater Cooling Tower

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Product Number: 51300-10124-SG

ISBN: 10124 2010 CP

Author: Zia Chaudhary, Saad Awaad Al-Shehri, Fallatah Baker, Tahir Iqbal and Abduh Hakami

Publication Date: 2010

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The support structure of the seawater cooling tower (CT) comprised of pre-cast columns, beams, and slab panels and in-situ cast foundations and pedestals. Several leaks appeared across the entire support structure in the high density polyethylene (HDPE) liner that was laid over the slab panels to contain seawater. About 40% of the slab panels, beams, and columns were contaminated with seawater. Thick salt deposits covering large areas were visible at several locations.

The 2005 condition survey results showed, chloride ion content at the rebar depth in well excess of the threshold limit, 95% corrosion probability and very high corrosion rates, i.e. >1 uA/cm2 in 60% of the tested areas. But no sign of concrete cracking were visible or noted in 2005 survey, however by 2007, cracks appeared on almost all the slab panels, beams, and columns that were seawater contaminated. Chemical analysis and electrochemical measurement results from 2007 condition survey also showed that chloride content at the rebar level across the entire structure was 2 to 3 times higher than threshold limit and steel was actively corroding underneath the sound concrete, which if not arrested would lead to further cracking of concrete elements.

Key Words: concrete deterioration, chloride content at rebar, half-cell potential measurements, probability of corrosion, patch repairs, cathodic protection, titanium mesh anode