Q: We built a very large parking area for an industrial plant and installed contraction joints but no expansion joints. The area was adjacent to a building and was more than 1,000 feet long and about 125 feet wide in most areas. In one area, however, part of the building extended into the parking area. During the summer, surface concrete chipped off in two areas, as shown in the drawing. To correct the problem, we sawed two slots that were 1 foot wide and 40 feet long, removed the damaged concrete full depth and replaced it with new concrete. These patched strips later chipped in the same manner as the original concrete.

Even though publications of several concrete-related organizations say that expansion joints aren't needed in concrete pavements or parking lots, we decided that the damage was being caused by expansion. We recommended that the owner remove the repair concrete and fill the slots with asphaltic concrete that could easily be trimmed or recompacted to correct bumps caused by future expansion.

Are there other possible causes of the problem? It occurred only in the narrowed area of the parking lot. And are there other solutions for the problem?

A: Your description certainly seems to indicate that the distress was caused by expansive forces in the concrete. When you filled the slots with concrete, did you use full-depth expansion-joint material at the interface between the old and new concrete? That might have provided enough room for the expansion and prevented the surface spalling.