Hi all, I work in an old garage building that is being used as a auto repair shop. We pull cars in and out all day. A certain spot about 4 foot around keeps cracking and crumbling and I have patched it time after time. I have used patching cement but it doesn't last. I clean it real good down to about 2 inches and dampen it. My question is what type of cement should I be using that will last for a while under car traffic? Someone suggested portland cement and someone said I would have to find road grade cement. I'm just not sure and don't want to have to keep patching it every couple of months. Thanks for your help.