There are three types of stitching methods: cross-stitching, slot-stitching, and U-bar stitching. Cross-stitching is the most widely used method. Project 0-5444 investigated lane separations and the best repair methods.

Cross-stitching should be used to repair cracks/separations that are fairly tight. In cross-stitching, holes are drilled at an angle so that they intersect the longitudinal cracks or joints at about mid-depth of the slab. Dust is removed by compressed air, and epoxy is injected into the holes. Tie bars are inserted, and excess epoxy is removed.

For wider cracks/lane separations, slot-stitching should be used. Slot-stitching is the most economical repair method for restoring load transfer, preventing separations, and improving performance of longitudinal joints and wide cracks. In slot-stitching, slots with lengths no shorter than 25 in. are cut approximately perpendicular to the longitudinal joints or cracks using a slot cutting machine or walk-behind saw. Slots are prepared by removing the concrete and cleaning the slot. Deformed bars are placed and a repair mortar is applied, finished, and cured. In slot-stitching, the concrete slabs are held together by the shear stress of deformed bars. It is important to provide high strength repair mortar with good bond and to have good consolidation around the bars.

In U-bar stitching, slots are cut using a slot-cutting machine, and concrete is broken and removed by pneumatic hammer. Figure 10-16 shows the slots and U-bars. In this method, anchoring action by the U-bars provides most of the restraining force. Use of proper repair materials and consolidating around the ends of the U-bars is important.

Project 0-5444 investigated what causes lane separations and the best repair methods. The following conclusions regarding longitudinal cracking and joint separations in concrete pavements have been made upon completion of the research project.