How would you handle the logistics of casting and installing 1200lb GFRC hotel benches?

At $15,000 a unit and for a high-traffic spot like a Hilton entrance, you definitely need more than just epoxy. Sika is top-tier stuff, but chemical bonds are best at resisting compression or shear, not the leverage of someone leaning or jumping on a backrest. With a 1200-lb bench, the liability if that bond fails is huge. You shold absolutely be looking at mechanical fasteners—stainless steel **threaded inserts** cast directly into the main body and the backrest during the pour. I'd suggest using 1/2-inch or 5/8-inch stainless all-thread or heavy-duty bolts trough those inserts, then capping them with GFRC paste to hide the hardware. The epoxy then becomes your secondary bond and your gasket to keep water out of the joint. If you rely solely on Sika, even the slightest movement over time from thermal expansion or heavy use coud micro-crack that bond line, and once water gets in there, you're on a clock. You don't want a backrest coming loose in a commercial lobby. Also, keep an eye on those clean edges you mentioned. Polycarbonate molds give you an incredible finish, but if those edges are too crisp, they're going to chip the first time someone’s luggage hits them. Plus, for the user, a razor-sharp concrete edge is a literal pain. Even a 1/8-inch or 3/16-inch radius makes a massive difference in how premium it feels. Think about how those old unibody MacBooks used to dig into your wrists compared to something with a softer bezel; your clients will notice the difference in comfort.

The 16,000 psi mix with GFRP rods is solid, and the foam core is the right move for weight management. Just make sure your GFRP is tied into the areas where your mechanical fasteners are located. You want that structural load to transfer from the backrest through the rods and into the main bench mass. At this scale, you're building furniture that's basially a small building; treat the connections like structural engineering rather than just a glue job.

I'm just starting out with GFRC and 16,000 psi sounds like a lot for a bench. Is that standard for high-end hotel stuff or just extra insurance? Also, if you use a foam core to keep the weight down, how do you make sure those stainless inserts actualy stay put? I'd be worried the bolts might pull right trough the thin concrete shell into the foam if someone realy slammed against the backrest. Is there a specific way to thicken the mix around those connection points?

I usually block out a 4x4 inch square of solid concrete around every bolt site that ties directly into the structural GFRC. If you just have foam behind the fastener, it’ll eventually wiggle and crush the core under leverage. You want that bolt anchored into a solid mass that bridges the gap between the front and back shell faces so it can't move.