The apparatus has been designed and manufactured to the recommendations laid down in BS, EN and ASTM standards where tests are required on laboratory specimens, or on specimens taken from existing structures. The test procedure specifies a method for determining the change in length of a concrete or mortar sample brought about by a change in moisture content.

1. Initial drying shrinkage: the difference between the length of the moulded and cured specimen (under specified conditions), and its final (constant) length when dried 

2. Drying shrinkage: the difference between the length of a matured specimen cut from concrete and saturated, and its final (constant) length when dried 

3. Moisture movement: the difference between the constant length of a speciman whend dried, and its length when subsequently saturated with water.