Joints in Cement Concrete Roads
Joints are provided in cement concrete road to allow expansion, contraction and warping of the slabs due to the variation in the temperature of slabs.
Increase in temperature cause expansion of the slab horizontally. Similarly, decrease of temperature cause contraction of the slab horizontally.
The slab movements also take place, in the vertical direction due to the difference in temperature between the top and bottom of the pavement slab.
During the mid-day, the top of the pavement slab has a higher temperature than the bottom. This causes the top fibers of the slab to expand more than the bottom fibers and the slab curls at the edge. This phenomenon is known as warping down of the slab.
Similarly, the slab warps up during midnight due to the higher temperature of the bottom slab as compared to the top. To minimize the temperature stresses in the pavement slab, expansion, contraction and warping joints are provided transversely across the full width of the pavement.
Longitudinal joints are provided to allow differential shrinkage and swelling due to the rapid change in subgrade moisture at edge and centre