Effects of Cracks in Concrete Sanitary Sewer Pipe
The ultimate strength of reinforced concrete pipe is determined by application of a factor of safety on the 0.01 inch crack design strength. This safety factor ranges between 1.5 for loads up to 2000 D0.01 and 1.25 for loads greater than 3000 D0.01. Many tests of concrete pipe have proven the conservatism of this safety factor and, in fact, design strengths are generally exceeded. Field surveys have still to produce a single sewer project exhibiting any structural distress which can be attributed to reinforcement corrosion. Regardless of such information, the attitude of some construction inspectors can be summed up by the statement, “A concrete pipe with a hairline crack has failed and should be rejected.” This attitude is usually justified by a concern for structural integrity. This CP Info article shows that such concerns have little basis in fact, as indicated by the results of tests of reinforced concrete pipe installed for a Texas Brazos River Authority sanitary sewer project.