Repairing concrete driveway expansion joints

Hi. What's the best way to repair the expansion joints in a concrete driveway, where the fiber board has deteriorated ? I was thinking of using backer rods and regular or roofing caulk in a tube.
Is the black roofing caulk any better than the stuff in the concrete section of the store ?
Is sand an alternative to the backer rods ? I have about 10 joints to fill, and sand would be a lot cheaper.
I thought about using the expanding insulating foam. It says it is for interior & exterior use, but I wonder how it would hold up in a driveway application.
Thanks for the input.
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