I'm having some difficult getting a reliable patch in a hole in my basement concrete floor. There were two large holes - one I seemed to be able to fill well using a combination of a base of quickrete fast setting cement topped off using hydraulic cement. The other one isn't working as well.

I tried chiseling out any loose concrete - when done the area needing to be patched was probably close to a foot across at it's widest and at it's deepest went down about
4". Shallow at the edges - most of it not being anywhere near that deep. What seems to be repeatedly happening is at the patch hardens I seem to get areas that sound hollowed out when I tap them. If i tap these areas hard enough they crack.

I've tried both hydraulic cement and a fast setting repair mortar and it's happened both times. The good news is through my repeated efforts most of the hole is filled and reasonably solid. What remains is a relatively shallow (probably less then 1/2" deep irregular area much smaller then the original hole) Is there a way to finish off the surface of this hole so when the patch hardens it is stronger, less "hollow" and brittle?

Thanks

 

You dont want to use standard concrete mix anywhere the thickness will be less than about 1 1/2". So if that's the case, you need to fill the hole with concrete mix and finish it off so that it's about 3/4" below the surface. Then after it has set, wet it and apply a slurry for bonding... then immediately top it off with a Portland rich mix such as mortar mix or use a vinyl patch.