User blog comment:Unownshipper/Metallurgists Wanted: Rapture's Natural Resources/@comment-75.36.142.53-20140810062120/@comment-75.36.136.107-20140812095634

One use for ceramics would be  in making the aggregate for the cement where instead of using natural rock/sand you process your own aggregate for the better properties you want (the aggregate is the bulk of concretes volume and its attributes (like compression strength) is important to make the concrete strong.

Ceramics start as powder (you can quality control and be selective about its makeup) which you can mold and the 'fire' (fuse the material together). Large pieces will have shrinkage stress issues, but usually is improved by adding complementary substances into the base powder material (called temper - like indians adding powdered bone to their potting clay to give better strength/fireresistance properies). SO huge well-controlled electric furnaces would likely be used (burnings stuff uses ALOT of air, besides having to obtain the fuel).

Melted/fused Basalt making large panels to imbed in concrete would probably work  - and using the preformed 'ceramic' parts for embedded pouring forms for normal concrete 'fill' would facilitate assembly - you want to result in making large monolithic prefab building sections (manufactured inside to eliminate all the complications/clumsiness/lack of control of doing it outside in the sea) with minimal tie together points (where the metal comes in more or in-sea concrete pours at the final positioning (which you do to anchor it to the seabed rock anyway).