Spent 3 years cutting cracks wider before filling them, a retired paver in Dayton set me straight
Everyone on here says open the crack up with a chisel or a grinder so the filler grabs. I did that for 3 years on my 60 foot driveway. Hairline cracks turned into half inch trenches and came back worse each winter.
Last spring a retired paver from Dayton was walking his dog past my place while I was at it. He watched me hammer a cold chisel into a thin crack and just shook his head. He said all I was doing was giving water a bigger place to sit. He told me to leave hairline cracks alone and use a thin pourable filler, and save the widening only for cracks wider than a pencil. I tried it on the north half of the drive and those thin cracks have held through two freezes now. The widened ones on the south half are already splitting again.
So I'll say it plain: stop widening small cracks. What filler do you all use for the thin ones that actually pours in?
Leave the small ones shut, he's right. A chisel just gives winter more room to wedge ice in, then it pops wider every year. I use the self leveling pourable stuff for hairline and it flows down in. Saved me from turning my whole slab into a trench.