Practical Accuracy of Crack Measurement
One fifth of the thickness of a U.S. dime is the approximate width of a 0.01 inch crack. (According
to the United States Mint, a dime is 1.35 mm thick). When cracks occur in new reinforced concrete pipe (RCP) installations, they are typically equal to or less than 0.01 inch wide. Pipe industry professionals have observed the use of precision measurement technology without a full appreciation of the limitations of the equipment and the human factors involved. This results in inaccurate crack measurements. In general, pipe utility contractors have come to accept and support final inspection results. However, inconsistency and unreliability of field measurements erodes confidence in the inspection process. This, in turn, threatens the future of final inspection and crack measurement as a useful tool in approximating crack widths when assessing pipe conditions. For this reason, the pipe inspection and construction engineering communities must fully understand the practical accuracy of using precision crack measurement technology.