An advantage of portland cement concrete (PCC) pavement is, among others, the low deflection under traffic load due to the high modulus of elasticity of concrete. Pavements expand and shrink due to environmental conditions, among others. PCC pavements may be constructed with joints between slabs. The joints may provide space to accommodate the movement of slabs during expansion and shrinkage.
Concrete slabs may bow and or curve due to, among other factors, temperature induced differential expansion/contraction, gravity, structural loads, and/or pressure from the ground below. This curving and bowing may be referred to as slab deflection. Slab deflection may be uneven across the surface of the slab, for example, deflection may be greater at the joints than in the interior slab regions. This uneven deflection may result in greater damage occurring at or near joints. To address and reduce slab damage near the joints, a load transfer system may be used to link adjacent slabs together. Load transfer between slabs is crucial to pavement performance and most performance problems with concrete pavements result from poorly performing joints. Distresses such as faulting, pumping and corner breaks occur in part due to joints with poor load transfer efficiency.
The load transfer across the joints may be achieved with aggregate interlock between two faces of the joint or using dowel bars, or both. To mobilize aggregate interlock, the concrete slab may be allowed to crack naturally below the saw cut locations. Under this method, the irregular fracture surface below the joint offers aggregate interlock, which helps with load transfer between slabs. Aggregate interlock is highly influenced by climatic conditions. Therefore, aggregate interlock is adequate only for roads and streets with a low volume of traffic and light trucks. Where the traffic volume increases beyond the load carrying capacity of the pavement, aggregate interlock joints may be retrofitted by dowel bar as the traffic increases (FHWA, 1990)