We have a sidewalk from the front of the house to the street out front. This was put in at the same time as the concrete porch and the driveway. Over time, however, the tree by the curb apparently put roots out under the sidewalk and lifted it up. It was an inch or two higher than the curb. This seemed to me to be a safety issue and for several years now I've been meaning to take out the old sidewalk and put in a new one.
The sidewalk is actually 3 or 4 sections -- broken up by 1x2 pieces of wood. The wood lets the concrete expand in the summer without breaking. So I only have to replace the one section that goes to the curb.
The first problem is to remove the old sidewalk. I used my jackhammer to break it up into 8 pieces, roughly square, each about 2 feet by 2 feet. These are just small enough to be manageable by me so I could move them out of the way. I eventually posted them on Craig's list and offered them as concrete pads, suitable for making a walkway. I got several responses, and a guy came and took them away, saying he was going to put a path in his backyard with them.
Next I dug down to bedrock and took everything out. Mostly it was the sand and gravel that they had put under the sidewalk, but once I was under that, there was native dirt and then rock. I dug out everything where the old sidewalk was, plus a little more to leave room for the new framing, going all the way to bedrock. In this area, that's only about a foot.
Next, I put in framing to pour a concrete wall under the edge of where the sidewalk will be, next to the tree. The idea is to create a barrier to prevent it from sending roots under the sidewalk again. I used masonite boards to frame the wall and then a couple of bags of Quikcrete cement to fill it in and make the wall. I only did this on the one side -- next to the tree.
I filled the excavation back in with rock and cement pieces and sand and gravel that I had been accumulating for this sort of project. I used a pile of decomposed granite on top, and watered it all down to try to get it to fill the area. The idea here is to (a) get rid of debris that I've dug up, and (b) make the contents of this area unlikely to support anything growing (like tree roots).
To do a good job on the actual pouring, I asked Dillo Construction to send out a couple of guys to do the final pour. The rest of the sidewalk is a "pebble finish", and they matched it very well. $520.00
To customize it a bit, after it was all poured, I threw a handful of some blue rocks we had on the top. Just sort of randomly tossed and then pushed down into the top of the concrete. Once it set, the top layer of concrete is washed off to create the pebble finish, and these blue rocks are then part of the pebble finish. It adds a nice touch, in my opinion. A minor distinguishing feature.