hey ya;all just my 2-cents worth, i am a marine contractor and have done quite a few commercial jobs where city engineers are involved, in most applications where anything is fastened to concrete by means of bolt-screw ect the engineers call for a 2 part epoxy system to be injected into hole prior to bolt ect, being inserted. What we have used is a concrete epoxy made by Simpson. Its the same company that makes all the hardware for structural fasteners ie: hurricane ties . It is the most tenacious stuff ive ever worked with. and will result in concrete failure prior to epoxy failure,and it has a self mixing nozzle,so no messy mixing then attempting to smear it into the hole. Good Stuff.