Assessing Premature Cracks in Urban Concrete Pavements

Abstract

There are many urban jointed plain concrete pavements (JPCPs) constructed annually in the U.S. by counties, cities, and municipalities, which typically use state department of transportation standards but are not part of a systematic check to determine if design, construction, and performance are meeting expectations. A field evaluation survey with nondestructive testing was initiated on urban JPCPs throughout Illinois to assess performance and identify any deficiencies in design and construction. A total of 67 JPCPs were selected based on their design features and age. A significant number of sections (57%) were selected because they exhibited some level of premature cracking. Based on the field investigation, multiple mechanisms were proposed to explain the premature cracks. Many transverse and longitudinal cracks observed had excessive slab lengths or widths that were inconsistent with best slab geometry practices. There was no link established between observed cracking and the slab-base frictional restraint or the concrete mixture. For some sections, ultrasonic tests over the contraction joints determined certain joints had not activated and likely contributed to transverse cracks in adjacent slabs. Lack of dowel bar lubrication at the transverse contraction joints was also a plausible mechanism that restrained joint movements and produced excessive tensile stresses in the slab, which led to premature transverse cracks. The mechanisms leading to almost all observed premature cracks for these urban JPCPs were attributed to not adhering to existing state standards (slab geometry limits) and specifications (saw-cut timing/depth and dowel lubrication) during the pavement design and construction phases.