Working of a Crack Meter

The crack & joint meters are generally used for measuring the movement. These measurements are important for monitoring the behaviour of civil structures and buildings. The crack meter is used to measure any change in width of a surface crack. It is employed to monitor cracks in concrete structures, rock, bridges, pavement slabs, etc. On the other hand, the joint meter is ideally suited for measurement of displacement/movement across joints such as joint opening between two concrete/masonry blocks in a dam.

The crack meter is capable of measuring the change in width of a surface crack with a resolution of 0.5 mm. it consists of a graduated scale with a resolution of 0.5 mm and a transparent acrylic plate with a hairline cursor mark. The graduated scale and the transparent acrylic plate are joined across the crack with expendable anchors in 5 mm diameter holes drilled to a depth of 30 mm. As the crack expands or closes, the graduated scale and the cursor more relative to each other representing the amount of movement happening. The reading of the marking is initially noted and it considered as a base.

There are different types of crack meters used for monitoring different types of crack and in different conditions. They provide reliable and accurate deals related to cracks and joints. Another advantage lays in its simple installation procedure. They are simple to read. Other features are rugged construction and low cost. A crack meter is used in different applications including concrete and arch dams, concrete structures, rock, soil and masonry structures, and buildings affected due to nearby construction ore excavation activity.
Another type of crack meter consists of two stainless steel round datum blocks installed on either side of the opening. Each datum block has a groove on the surface along the circumference to assist in taking readings. A through monitoring hole helps mounting the datum block on concrete, masonry or rock surface using expandable anchors. M8 nuts are provided to tighten the expandable anchor.

The distance between the grooves of the datum blocks is initially measures by a digital inside caliper with a resolution of 0.01 mm. The measurement is made by anchoring the two elements on either side of the joint and accurately measuring the distance between them over a period of time. The precision elements are made of aluminium and are epoxy painted to make it corrosion proof. The micrometer rest blocks and mounting buttons are of stainless steel.