Holes in Concrete Driveway - Lignite or Shale Problem
Stage 1 Stage 2 Stage 3
Problem: The small pop outs or holes that are occurring on your concrete driveway are results of lignite or shale carbons that were in the sand when the concrete was installed. The lignite or shale particles near the top of the concrete expand when freeze thaw happens and causes the pop out creating a hole. At first, it is a small hole, (picture) Stage 1; the dark material inside the hole is lignite and shale if it is white. As time goes by the edges of the hole will grow Stage 2, the growth effect will continue until treated. About the only way to reduce, the expansion of the pop out is to seal the concrete to reduce the water penetration into the concrete.
Solution: Reduce the water pentration by sealing the concrete. Filling the holes or pop outs will not stop the problem.
Sealer Type: By using a penetrating chemically reactive sealer it will bond the edges of the pop out and seal the pores to prevent water penetration