Supplement to the Bridge Resource Program: State-of-the-Art Practices of Mass Concrete - A Literature Review.

摘要

The mission of Rutgers University's Center for Advanced Infrastructure and Transportation (CAIT) Bridge Resource Program (BRP) is to provide bridge engineering support to the New Jersey Department of Transportation (NJDOT)'s Bridge Engineering and Infrastructure Management Unit. The program is a partnership between federal and state transportation agencies and Rutgers University, which provides technical and educational services to address infrastructure needs in New Jersey. CAIT supports the NJDOT by providing staff and resources to address the most pressing bridge engineering and training challenges in New Jersey (through advanced materials development, design enhancements, construction improvements, evaluation, monitoring, data mining, management enhancement and support, and bridge research). The purpose of this grant is to supplement the Bridge Resource Program through the on-call investigation of mass concrete construction practices, which resulted in a report to NJDOT on state-of-the-art practices in mass concrete construction. The findings in the report were used to compare with the Thermal Control Plan for the Route 7 Wittpenn Bridge Pier 1W cap as well as the current mass concrete specifications included in the NJDOT 2007 Standard Specifications. The review focused on material composition, with description of each components contribution to heat of hydration. The team observed that the literature focused on two areas of concern, maximum temperature reached during curing and thermal differentials between the core and surface of the mass concrete element. The literature has extensively documented the urgency of maintaining the maximum curing temperature below 160 degrees F. The adverse effects associated with exceeding the maximum temperature threshold are severe, but not visible for months or years after construction. This threshold should never be exceeded. The literature also documents damages resulting from exceeding temperature differential thresholds, which are more immediate and can be identified during construction. The thermal-induced cracking that results may be repaired through industry accepted means, from seals, coatings for hairline cracking, to more comprehensive repairs. During early stages of curing, the concrete has not developed sufficient strength to resist excessive thermal gradients. Thus, form insulation and other methods to protect the concrete surface from dissipating heat greatly or reach excessively high peak temperatures reduces the likelihood of deleterious effects.