Foundation Concerns – What Are These Small Holes in My Foundation?

I cannot think of any good concrete books off the top of my head, sorry.

However, you listed two tasks that you wish to pursue, one of which I believe can be achieved well with book learning and the other which cannot. As far as building concrete foundations goes the trick is in the forms. I would look for books specifically geared toward concrete formwork. If it is an existing house then your formwork is going to be significantly different from building forms in a meadow. Again not sure if there are any books out there that will tell you the things that concrete contractors know from years of experience.

As far as finishing slabs goes I would like to offer a word of warning based on 20 years in the trades. If you want it to look good and function the way it should you can't expect to learn the techniques involved without a lot of time and effort, not to mention a lot of ugly permanent concrete "test slabs." Hire a finisher if your slab is going to be more than 20' sq. Here in the San Francisco Bay Area the cost of hiring a finishing expert is usually around $500/day or $300 for a fraction thereof.

Assuming the flue is not shared by any other devices of combustion on the first floor or above, you can use anything temporarily to block the draft and keep vermin out. you can use some mortar with a metal backing plate. Cut a piece of sheet metal in a rectangular shape slightly narrower than the hole diameter and a few inches taller than the hole. Put a long skinny bolt in the center to use as a handle. Insert the metal and move it until it is flush against the back blocking the hole. You can then put a scrap of wood with a hole drilled in the center over the bolt and use a nut to secure the metal plate against the back of the hole in the flue. This will stop your mortar from falling down into the flue and allow you to fill the void completely. To make it look OK until you renovate, cover the repair with a thimble cover. There is no need to remove the flue adapter ring.