I need to fill a gap, about 1/2" wide between the garage floor and the approach apron. The stuff I used the last time worked well, held up for a long time, still had a bit of elasticity, and required a chisel to break it away from the edges so the bond was good. But it looks like the apron settled just a slight bit, cracking down the middle, so time to replace. Problem now though is that it lasted a long time, I'm thinking around 15 years or more, and darned if I can remember what I used. So I'm looking at two options, both that I think should be quality products, and wondering if anyone has any preference or whatever for either Quikrete concrete gap filler of Sikaflex gap filler.

Living in Hawaii, the retaining wall between me and my neighbor has broken down. It is tilting 10 degrees and cracked to the ground and the top two rows of cinder blocks are broken off and fallen over. How do we repair this load bearing wall?