Evaluation of slab shape under controlled environmental conditions

As portland cement concrete (PCC) pavements cure, permanent deformations develop from nonuniform temperature and moisture conditions in the slabs. Subsequent daily and seasonal environmental cycling cause the slabs to expand and contract horizontally with changes in average temperature and moisture conditions, and curl and warp vertically as temperature and moisture gradients change through the slab depth. These deformations affect the magnitude of load transferred to adjacent slabs and vertical support provided by the underlying base layer. Dowel bars are often placed at pavement joints to facilitate load transfer. Two 3.66 m (12 ft) wide, by 13.72 m (45 ft) long, by 254 mm (10 in.) thick concrete pavements were constructed in the Ohio Accelerated Pavement Loading Facility (APLF). Transverse contraction joints were placed at 4.57 m (15 ft) intervals to create three contiguous 4.57 m (15 ft) long slabs in each pavement. Dowel bars were added to the joints in one pavement, and the other pavement was left undoweled. Pavement deformation, response, and temperature were monitored over a range of controlled environmental conditions with sensors installed at the time of construction. Large upward vertical deformations were observed along the slab edges early in the curing cycle, and these deformations continued to increase throughout the duration of the tests. The slightly smaller vertical movements observed in the doweled pavement were attributed to the presence of the dowel bars.