adhesive for mud sill to concrete slab

Use a urethane adhesive. I don't recall the brand I used but I built a stone wall with it about 10 years ago. Local hardware store had it in a caulking gun cartridge. Loctite makes one too.

Does this sound (and look) familiar?

the best thing to do is go to a local supplier and not a big box and talk to informed staff about your application

or research it yourself

doing both is best

Maybe Butel, fills gaps well and remains pliable years later but pretty messy.

found one that is waterproof too

loctite was not waterproof but was recommended alothough they do make a waterproof product there was none and usually they do have at marine supply

waterproof was not a complete necessity but good to have and not much more

both brands stay flexible

forget the brand sika i think

some products will be formulated to work with a lot of different materials

some will specify concrete and masonry and i found out that if the do not specify concrete and only masonry you need to find one that specifies concrete

concrete remains reactive whereas masonry is pretty much inert

Now he's talking to himself. ;-)

So don't confuse him with the facts!