Measuring the crack width on concrete surfaces by light-dependent resistor

The theory is presented and the equipment is described for a technique which may be used when measurements of crack width have to be made on the surfaces of concrete structures. The technique is of most value when other, more standard methods for measuring crack width by microscope or mechanical and electrical gauges would be unsuitable. Measurements may be easily and accurately made by using the apparatus described and an application to crack width measurement during repeated loading is given. The equipment, which may be remotely controlled, may also be encapsulated and sealed against moisture for use in field conditions either underwater or underground.