I need to replace a 3x5 section of sidewalk near our Bilco door. I our area, the precast steps are bolted to the foundation wall, then the foundation is backfilled. They often don't get good compaction in the clay soil and eventually a gap opens under the steps. One segment of sidewalk started falling into that gap. I had some other concrete lifted and the company recommended replacing that section.
I broke up the existing concrete and used a lot of the little pieces to fill the gap as best I could. I'll be dumping some sand as well to fill the smaller gaps. I KNOW I did not completely fill the void--he said that would be impossible short of using a ton of very runny cement mix. He suggested pinning the new concrete to the stair casting and the adjacent good sidewalk with rebar because it will drop again. I'm also planning to use some rebar in the slab so I can basically have a bridge when, not if, it drops again. I'm wondering what, if anything I need to use to "glue" the rebar in place once I drill the holes in the existing concrete? I think my options are basically hydraulic cement or epoxy. Or should I just install it loose and let the newly poured concrete hold it in place?