How do you attach glass to concrete lining? (discussion revised)
The pic shows steel bars reinforcement as skeleton for concrete lining/frame. On top of that (and by the side) a piece of 19mm glass will sit and creating a viewing window which has no support by the top (like of those ADA tanks). There are two viewing windows which will meet at right angle (divided by small concrete pillar for strength), one measuring 150cm and another one 200cm, both glass will be around 55-60cm tall (depending on installation) from the concrete frame.
There are several ways I know of people attaching glass to concrete lining.
1. Stick it with silicone on one side only and let water pressure work to secure the glass. Easiest to install but somewhat less support at the top of the glass).
2. Stick it with silicone inbetween concrete frame. Much more difficult to install, require good hands and timing to install.
My contractor prefers option #2 due to the strength which will affect longevity and safety. However, I feel that they underestimate the pressure from water that will be there once the pond is filled. It is going to be a mere 55cm water height that the glass must hold off - the water height that will be held back by concrete portion need not be accounted for (even 12mm glass would be sufficient and very safe, not to mention thick 19mm) so they are pretty sure about installing just 5cm of the glass into the frame. I might sound paranoid but I'm not sure about that mere 5cm, they said that even in aquariums you silicone only less than 2 cm on the joint no matter how thick is your glass (say 12-15mm) so 5cm would be overkill and enough to hold off that kind of depth. Everybody knows that in this condition the point of greatest glass stress is at the bottom, right at the frame-glass joint.
Sooo... you experts right here must let me know whether the contractor will screw up and cause the glass to blow up (hopefully during test and not after I decor) or whether 5 cm will do fine and safe for years. Please help me with experience/theory and no better safe than sorry precaution (doing being safe better than sorry would simply insert the whole thing for 8 inches!
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