I have several expansion joints in my home’s concrete sidewalks that need to be repaired/refilled. There is a lot of info regarding this out on Internet…too much in fact. I can’t determine from online research if it is most appropriate to use asphalt impregnated felt/fiber board for this, or if foam backer rod and Sika-flex is what is required (or best solution). Areas to be repaired are about 1/2-3/4 inches wide, ~4 feet long, and ~4 inches deep (i.e. fairly typical).
I prefer the look of the fiber board; if I decide to go with it, I am not sure how best to fix or “glue” it in place?