Meaning
Load distribution across adjacent concrete pavement slabs relies on mechanical reinforcement across joints. This mechanical action, known as dowel bar shear transfer, allows wheel loads to pass from a loaded slab to its unloaded neighbor without causing excessive differential deflection. The mechanism operates through smooth steel rods embedded across transverse joints, which permit horizontal thermal expansion while restricting vertical movement.
Its effectiveness terminates where the concrete matrix surrounding the steel degrades or where joint widths exceed the design limits of the steel reinforcement.
Joint Performance
Joint stability during high-volume vehicle crossings is determined by the spacing and alignment of the steel rods. Correct alignment ensures that dowel bar shear transfer occurs without inducing internal stresses that cause concrete spalling. When rods are misaligned, they lock the joint, which leads to cracking during thermal cycles.
Load Efficiency
Evaluation of the joint is conducted using a falling weight deflectometer. This test measures the deflection on both sides of the joint under an impulse load to calculate the transfer efficiency percentage. Low efficiency values signal that the dowel bar shear transfer is inadequate and will lead to accelerated pavement deterioration.
Failure Mechanism
Inadequate concrete compaction around the metal inserts creates voids that lead to localized stresses. Under repetitive heavy wheel passes, these stresses cause progressive crushing of the concrete housing the bar. This degradation increases the free play in the system and leads to slab pumping.
