Investigation of Longitudinal Cracking in Concrete Repair Sections Adjacent to Bridge Deck Expansion Joints

Cracking of newly placed Portland cement concrete adjacent to bridge deck expansion dam replacements has been observed on several newly rehabilitated sections of bridge decks in Pennsylvania. This paper investigates the causes of cracking by assessing the Pennsylvania Department of Transportation (PennDOT) concrete mixtures specified for bridge deck rehabilitation projects, as well as reviewing the structural design of decks and the construction and curing methods implemented by the contractors. The work consists of: (1) a comprehensive literature review of the causes of cracking on bridge decks; (2) a review of previous bridge deck rehabilitation projects that experienced early-age cracking along with construction observations of active deck rehabilitation projects; and (3) an experimental evaluation of the two most commonly used bridge deck concrete mixtures implemented by PennDOT. Based on the literature review, the causes of concrete bridge decks cracking can be classified into three categories: concrete material properties, construction practices, and structural design factors. A review of these categories found that excessive cement content, excessive compressive strengths and improper curing methods are variables that contribute the most to early-age cracking of bridge decks. The results of the construction inspection and experimental evaluation show that one of PennDOT’s concrete mixtures is more susceptible to early-age cracking. However, the most likely causes of the observed early-age cracking were found to be inadequate curing and failure to properly eliminate the risk of plastic shrinkage cracking. These results underscore the significance of proper moist curing methods for concrete bridge decks, including repair sections.