My driveway was poured in sections with lengths of 2x4 which remained between the slabs as expansion joints. Due to heaving and moisture many of these are in poor shape. I replaced one once by carefully carving a 2x4 on a table saw to fit the oddly shaped gap, but I'd like a better solution.
Is there some pourable product I can use to replace these joints? Should I just grout them now with additional concrete?