Circular reinforced concrete shaft cracking caused by moisture differential
Moncarz P., Coetzee B., Noakowski S.
CICIND REPORT Vol. 15, No. 2, 1999
Order No: CR-193
The typical situation included in the design of reinforced concrete tubular structures such as industrial stack shields is a temperature gradient across the wall thickness. This paper discusses an analogic stress condition caused primarily, however, by shrinkage gradient resulting from extremely different internal and external moisture conditions. With the new environmental protection driven smoke-cleaning technologies, a high moisture content of smoke might become a serious consideration in the prediction of wall behaviour. A six-block coal-fired power plant with approximate power of 4000Mwe, located in a hot and arid region of South Africa is cooled with the use of a dry cooling water system. The chillers are elevated about 60m off the ground by 72 reinforced concrete tubular columns 43,5m tall with a wall thickness of 280mm. At least 21 of these columns were diagnosed with vertical through wall cracking. The paper describes the investigation of the problem, discovery of the probable cause and the remedial venting proposals.