I am looking for some advise on how to go about fixing my horribly cracked garage apron. My house is three years old and the apron is cracked all along where the garage door is at when in a closed position. I plan on chipping out the remaining loss cement and patching it. What cement type or patch should I use? Would it be best to lay some plywood over the apron and re-adjust the height at which my garage door would close through the electric opener while the cement cures? Besides vacuuming and spraying with water, is there any other prep work that I should do prior to applying the cement? I would appreciate any suggestions. Thanks.