Dormant Joint

Summary

Dormant Joint - Sawn joint that does not open usually because of failure of crack to form below the saw cut; generally associated with dominant joints.

Technical Information

Dominant joints and Dormant joints are phrases used to describe joints where some joints have opened significantly more than others despite the spacing of the joints being similar.

Often dominant and dormant joints occur in fabric reinforced slabs where the construction joints open wide but the sawn joints do not open at all. This can occur when the steel reinforcement is heavier than recommended and therefore it cannot yield under the shrinkage stresses locking the sawn joints closed. To avoid this the designer should ensure that the reinforcement within the slab is within the limits identified in TR34.

It is hypothesised that this may also be caused by the subbase and slip membrane reducing friction on the bottom of the slab to a level where very little restraint is created so the slab is able to shrink unimpeded.