By gravel, I asssume you mean uncrushed river stone. There should be no real difference between using river gravel verses granite or limestone aggregates in concrete. However each is regulated by ASTM gradation specifications suitable for concrete along with proper mix proportions of mixing water and cement for the required 28-day strengths. Another issue is the uncrushed river gravel is round and smooth and unlike granite or limestone which are angular is shape, a Proper mix design will adjustfor any issues.