[jsage]

Concept

I realize there is whole thread on this but here is my concept.

Preliminaries

Concrete the new cast iron

Strength is based on reinforcement, aggregate choice, minimizing water content, enhanced by cross linking with Epoxy. Also the fiber content, virgin nylon can enhance characteristics.

My general feeling is provide good structural reinforcement. In this case the vacuum piping is a structural component with of course steel pipe.

There is also room for rebar below. Thickness about 2 1/2 inches. This is one panel there will be two. Reason longer sections will be more prone to cracking.

Each section has two vacuum ports.

Again this is a concept so I expect revisions.

I've done a bit of work with epoxy and with concrete. I don't believe you have sell the farm on polymerizing content, i.e spend a fortune on high end polymerized concrete. Time will tell. Also I purchased an air hammer for $14 which will aid in removing air.

One other thing, not much experience with these things but I expect you could plug unecessary wholes in a recessed manner. Similarly the the holes can be used with bench dogs.