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Horizontal Cracking in Portland Cement Concrete Pavements: Literature Review

Until recently, full-depth punchout was considered the only structural distress in continuously reinforced concrete pavement (CRCP). However, over the last few years, during punchout repair projects, it was discovered that CRCP distresses identified as full-depth punchout were actually caused by partial-depth horizontal cracking (HC) at the depth of longitudinal steel. Quite often, the bottom portion of concrete was solid, with no cracking. It appears that horizontal cracking in CRCP might have existed from the early days of CRCP usage, although not recognized until recently. Consequently, there are very few publications available on this issue. As a first report in this research project, this report summarizes the findings of three papers related to horizontal cracking. Two papers were identified that addressed HC in CRCP. Out of those two, one paper provides general discussion on HC in CRCP, without detailed analysis. The other paper investigated the effects of environmental loading, material properties, and design variables on HC in CRCP. Two-dimensional plain strain finite element modeling was used to analyze the effects of temperature variations along the slab depth, coefficient of thermal expansion (CTE) and modulus of elasticity of concrete, and number of steel layers. The findings are in agreement with what’s been observed in the actual CRCP: larger temperature variations, higher values of CTE and modulus of elasticity of concrete, and one-mat steel, rather than double-mat steel, produce higher potential for HC in CRCP. One additional paper was identified that addressed HC in semiconductor application. Thermal stress as well as mechanical stress is the primary cause of the cracking. The mechanism of the horizontal crack in the electrical circuit board is very similar to that of PCC pavement. Even though the findings in one paper show a clear relationship between design/environmental/materials variables and horizontal cracking potential, the modeling was made with simplified assumptions that are not realistic. As a result, the finite element modeling is of value as far as identifying the relationships is concerned, but not sophisticated enough to provide quantifiable relationships, which could be used to develop design standards or specifications to mitigate horizontal cracking. More realistic and sophisticated modeling using advanced theories of concrete cracking is needed, which is one of the objectives of this research project.