51313-02153-Condition Assessment of 27 Years Old Concrete Cylinder Pipes (CCP) Buried in Saline Soils

Available for download

Product Number: 51313-02153-SG

ISBN: 02153 2013 CP

Author: Zia Chaudhary

Publication Date: 2013

Member Price: $0.00

Non Member Price: $20.00

Price: $20.00

Qty:

In SABIC industrial plants a large quantity of seawater is used in providing a cooling system for removal of exothermic heat generated in the reactors. Large size concrete cylinder pipes (CCP) are used as supply and return lines between the reinforced concrete seawater reservoirs and the plants. These CCP pipes are buried in soil which is contaminated with chlorides due to very low seawater table. This paper describes the results of diagnostic investigations carried out to determine the condition of two (supply & return) pipelines that have been in service since 1984.

The CCP pipes are manufactured conforming to AWWA C303 and consist of a 4-6 mm thick steel cylinder and 6-8 mm diameter steel bars wounded helically around the cylinder. The steel cylinder and bars are encased in 20 mm thick 1:1.5 or 1:2 cement mortar on the internal and external surfaces applied by centrifugal spraying to obtain a dense internal lining and external cover. The pipes are factory coated with coal tar epoxy on the exterior to protect the concrete and the reinforcement against corrosive action of the salts in the soil and groundwater.

Condition survey investigations included close interval potential survey visual inspection crack mapping sampling for chloride penetration profiles half-cell steel potential mapping and corrosion rate measurements etc..

The seawater supply pipes exhibited no signs of concrete distress. Chloride levels were less than the threshold limit. Exposed steel bars and the steel cylinder showed no signs of corrosion. On the contrary seawater return pipes showed severe concrete cracking and delamination at all tested locations. Both steel bars and steel cylinder were found severely corroded. Chloride levels in delaminated and cracked areas were higher than the threshold limit. A cathodic protection (CP) trial using different anode types was conducted to determine its feasibility and the afforded protection level.

The condition survey and the CP trial results and findings will be described and discussed in the paper.