Dowels serve an important purpose in many floor slabs and pavements. They prevent faulting and subsequent cracking at joints by transferring wheel loads from one slab to the next. Unfortunately, dowels sometimes prevent joints from opening. This defeats the purpose of jointing and can cause slabs to crack between joints.
HOW DOWELS RESTRAIN JOINT MOVEMENT
To allow movement, dowels must be smooth and straight so they can slide in and out of the concrete without resistance. Dowels also must be parallel with each other and with the sides and surface of the slab. If dowels are misaligned, they have to bend to permit the joint to open. This puts a restraining force on the concrete and can cause cracking.
DOWELS DESIGNED TO REDUCE RESTRAINT
Using a square cross-section dowel allows a compressible material to be attached to one side of the bar along its full length. Because the material is compressible, there is no restraint to movement in the plane of the slab at right angles to the dowel.