David P Whitney

Results of Repairs on Texas Longitudinal Joints and Cracks

Longitudinal joint separations are often observed in concrete pavements. An innovative repair procedure was developed in this study for slot stitching in faulted or separated longitudinal joints. It involves with three stages: (1) low pressure grout to restore support under slabs that exhibited signs of pumping and faulting (2) the slot stitching method of retrofitting tie bars, to restore lateral restraint and load transfer across longitudinal joints, and (3) latex modified concrete overlay to restore proper elevation to slabs that had faulted. This paper discusses the results and lesson learned from the first implementation project on US Highway 75 near Sherman, Texas.

Overlays: A Great Use for Polymer Concrete

Polymer concrete (PC) overlays have been successfully used since the 1970s primarily by transportation agencies on bridges. Polymers used for overlays have seen significant improvements, and the current overlays have proven to be durable, skid resistant, and cost-effective. Over 2400 overlays had been installed by 2009, and overlays are a standard bridge protection system by departments of transportation based on an extensive survey of US and Canadian provinces. Slurry, multiple-layer, and premixed overlays are the most widely used. Epoxies are the most widely used resins. Many states have published specifications on the construction of overlays.

Repair of Longitudinal Joints and Cracks

Longitudinal cracking and longitudinal joint separations are commonly observed distresses in concrete pavements. The Texas Department of Transportation instituted a research project to determine the causes and to recommend repair methods. Repair methods that are generally recommended to repair cracks and joints are (1) cross stitching; (2) slot stitching; and (3) stapling. Finite element modeling was performed to determine the stress distribution in the concrete for each method when a truck tire load was placed on one side of the joint. Assuming no interlock between joint faces, the slot stitching model produced the lowest stress and cross stitching produced the highest stress, when the load was placed on the upper end of the diagonal bar. Cross stitching is recommended for repairing narrow cracks and slot stitching is recommended for wider cracks and joints.