I am in the middle of replacing a section of sill plate along my foundation wall. When I pulled the old rotted sill plate out there was a significant gap between the plate and the foundation wall. Under the old sill plate it looks like the original builder put shims made of shards of rock (pictured below) in the low areas. On the front side of the plate it looks like they tried to push cement into the crack around the shims but it looks like it never went completely under the sill plate. It also looks like the top of the foundation wall may have deteriorated a little from water damage.
Now that I have a new sill plate in I am wondering how to fix this. I was originally thinking I could level the concrete with Quickcrete and then put the sill plate in. With the area I have to work in though it is going to be very hard to do this and then get the sill plate back in. Any suggestions? Is there a new type of shim that fixes this?
The house was built in 1958 and has a poured concrete foundation.