Crack width measurement
The widths of cracks on the surface of concrete can be measured using a simple comparator consisting of a plastic strip with fixed width lines. Alternatively a hand-held microscope with a suitable scale can be used.
It may be necessary to assess if a crack is still moving, for example to determine whether it is due to temperature changes or to early thermal contraction. This may be done by using simple ‘tell-tales’ bonded across cracks, which will show if further movement takes place. If a more precise measure of the movement is required a Demec gauge, or similar may be used to measure the relative movement of studs bonded on the concrete’s surface at a set distance apart across the crack.