Practical Application of Digital Image Processing in Measuring Concrete Crack Widths in Field Studies

Cracking in concrete structures is a ubiquitous problem and affects the serviceability of such structures. In many cases, it is imperative to properly measure and monitor a crack's size to identify locations for repair and rehabilitation. This paper describes two field studies that used digital image processing to measure the width of cracks in concrete structures. The first field study compared crack measurements from digital image processing, a handheld microscope, and a crack gauge card. In the second field study, digital image processing was used to measure end region cracks in precast pretensioned concrete girders. Guidance is provided for engineers who wish to use digital image processing in field studies. Conditions where digital image processing may lead to errors are identified, and limitations of the methods are discussed. In general, the studies demonstrate that image processing methods can efficiently measure the size of cracks in concrete structures in field settings and that image-based measurements are comparable to microscope measurements.