Blowup can be accelerated by joint spalling, durability cracking and freeze-thaw damage. If these stresses are great enough, the slabs may buckle and shatter to relieve the stresses. If these openings become filled with incompressible material subsequent PCC slab expansion during hot periods may cause high compressive stresses. During cold periods concrete slabs contract leaving wider joint openings. Blowups usually occur at joints or cracks in the pavement. There is no typical pattern of drying shrinkage cracking as the cracks form at any location where there is a restraint to shrinkage movement.īlowups are joint failures that are caused due to excessive expansion related to high temperatures and high moisture content. Concrete near to corners and edges is particularly prone to cracking as loss of moisture takes place from the adjacent surfaces. The surfaces of large cross-section members may crack because the movement is restrained by the inner section of concrete. Drying out occurs from the surface and hence the surface layer is first affected. Thin members with a large surface area such as slabs are particularly vulnerable. When the stress exceeds the tensile capacity of the concrete, cracks develop. If the shrinkage movement is opposed by some external or internal restraint, stresses will develop. The loss of moisture from fresh concrete results in a reduction in volume.
The time at which shrinkage cracks occur depends on the rate of drying but is usually several months to three or four years after casting. It is important to understand the type of crack formed and its effects on structural stability.ĭiscussed below are different types of cracks that may occur in concrete slab pavement. Cracks in concrete slabs are caused by several variables including water intrusion, expansion and contraction from seasonal temperature changes, and sun exposure. This distress may appear in the form of cracks. Any negligence during the construction process may lead to distress in concrete slab pavement.
0 kommentar(er)
