I have just had a driveway repaired by a 'builder'. he did not compact (well, he claims to have compacted with his 4 x 4) or lay a screed benieth the bricks. he laid them in place, then put cement and river sand down and wet it all. a few days later cracks started appearing and he claims it is because we should not have driven on it for a minimum of 7 days, but preferably 10. I drove on it after 5. does this sound correct. how long is it supposed to cure, and what can i do to improve the cracks, some of them are opening up and i can see sand through the cement. i dont know much about building but that does not sound right to me. pls help