bonding new concrete floor to just poured concrete garage floor

by Julie McCarthy
(Grove, Ok, USA)

Q. I am having a new home built. The concrete people did the garage floor and my husband wanted a small pitch to the floor Needless to say when they poured the floor, it's level except for the back of the garage. The back of the garage dropped 5/8th of an inch. So we are level for 3/4's of the garage floor and drop 5/8 at the back of the garage. The width of the garage is at least 40 feet wide being an over-sized 3 car garage(pretty much a 4 car with 3 doors.)

Anyway, when we told the builder we were not happy when water sat at the back of the garage, he spoke with the concrete people. Their solution is to pitch the floor like we asked and build it 4 more inches at the back so it will slope from 4 inches to 2 inches. Will this crack? Our concern is...that they are pouring on top of an existing floor with a thin coat where a car will be driving. They tell us it will be fine and it might be for a few years, but I'm more worried about 10 years down the road. If this cracks and chips, we'll be footing the bill.

A. When we bond new concrete to existing concrete we use a product from Sika called Sikadur 32. First, we lightly grind or shotblast the existing concrete to open the surface. This will create a good bond for the epoxy. We mix the sikadur 32 and roll it on the existing concrete, then pour the new concrete right over it while it is still wet.

If your concrete contractor uses this bonding agent the new floor will not delaminate from the existing concrete floor.