Longitudinal Joint Forming in PCC Pavements, MLR-00-05, Construction Report, 2003

(2003) Longitudinal Joint Forming in PCC Pavements, MLR-00-05, Construction Report, 2003. Transportation, Department of

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Abstract

In conventional construction practices, a longitudinal joint is sawed in a PCC (Portland Cement Concrete) pavement to control concrete shrinkage cracking between two lanes of traffic. Sawing a joint in hardened concrete is an expensive and time consuming operation. The longitudinal joint is not a working joint (in comparison to a transverse joint) as it is typically tied with a tie bar at 30 inch spacing. The open joint reservoir, left by the saw blade, typically is filled or sealed with a durable crack sealant to keep incompressibles and water from getting into the joint reservoir. An experimental joint forming knife has been developed. It is installed under the paving machine to form the longitudinal joint in the wet concrete as a part of the paving process. Through this research method, forming a very narrow longitudinal joint during the paving process, two conventional paving operations can be eliminated. Joint forming eliminates the need of the joint sawing operation in the hard concrete, and as the joint that is formed does not leave a wide-open reservoir, but only a hairline crack, it does not need the joint filling or sealing operation. Therefore, the two conventional longitudinal joint sawing and sealing operations are both being eliminated by this innovation. A laboratory scale prototype joint forming knife was built and tested, initially forming joints in small concrete beams. The results were positive so the method was proposed for field testing. Initial field tests were done in the construction season of 2001, limited to one paving contractor. A number of modifications were made to the knife throughout the field tests. About 3000 feet of longitudinal joint was formed in 2001. Additional testing was done in the 2002 construction season, working with the same contractor. About 150,000 feet of longitudinal joint was formed in 2002. Evaluations of the formed joints were done to determine longitudinal joint hairline crack development rate and appearance. Additional tests will be done in the next construction season to improve or perfect the longitudinal joint forming technique.