Thoughts on melamine vs. rubber liners for reception desks?

I’ve done a few of these long-span shells using 3/4-inch melamine, and honestly, that glass-like finish is hard to beat if you want the concrete to feel intentional. If you’re worried about it looking like "fake" plastic, the trick is in the sealer. I usally go with a satin finish from Buddy Rhodes or a penetrating sealer so it still feels like stone to the touch. For a twelve-foot run, you definitely need to internalize some 1/2-inch rebar or even carbon fiber mesh to handle the tension, expecially if you’re trying to keep the thickness under three inches.

Regarding the air bubbles and vibration, I’d skip the heavy vibrating and look into a self-consolidating mix or at least adding a dose of Sikament. If you vibrate melamine forms too aggressively, you risk "honeycombing" or blowing out your seams. I use a palm sander on the outside of the forms for about ten minutes; it’s enough to move the air without sending all your aggregate to the bottom of the pour. For the corners, definitely don't leave them sharp. I always glue in a small 1/8-inch radius PVC chamfer strip. It gives you a clean, eased edge that won't chip the first time a heavy bag or a vacuum cleaner hits it. It softens the brutalist look just enough to make it feel finished rather than raw.

I'd actually steer away from melamine for a lobby. It shows every single fingerprint and water spot once people start leaning on it. I’ve had much better results using sandblasted cedar boards for the formwork. It creates a subtle wood-grain relief that hides those inevitable minor imperfections and feels much less clinical in a reception area. It gives you that architectural 'board-formed' look that feels premium rather than industrial. To handle the weight and blowout fears on those twelve-foot spans, I'd skip the internal vibrator. If you use a high-flow SCC mix with some Fritz-Pak superplasticizer, you won't need to shake the forms to death. The mix settles on its own, and you won't end up with that heavy aggregate settling at the bottom of the form. For the corners, definitly use a 1/4-inch chamfer strip. A dead-sharp 90-degree corner in concrete is basicly a ticking clock untill the first suitcase or cleaning cart slams into it.

Forget the cedar and melamine; if you want a lobby that stands the test of time, look into GFRC. I’d spray a face coat into the forms using a Hopper gun and back it up with a structural mix loaded with 19mm Alkali-Resistant glass fibers. For a twelve-foot span, I’d integrate 1" square carbon fiber grid from Tech-Fab to keep the profile slim without the weight of 3-inch slabs. If you're dead set on the texture, Reckli makes some incredible elastomeric liners that pull clean every time. Also, don't skimp on the admixtures—hit it with some Fritz-Pak Supercizer 5 to get that flow without compromising the PSI. You’ll get a surface that’s bulletproof and looks premium.

Kids today and thier fancy chemicals. Back in '82, we did a bank counter longer than this using high-density plywood coated in floor wax—old school, but it popped right out. If you're worried about the cold vibe, don't mess with rubber. Just mix in some iron oxide pigment to warm up the grey. As for the corners, forget those plastic strips; I take a block of green marble and hand-sand the edges after the pull. It gives a natural radius that looks like it was carved, not molded. Just watch your water-to-cement ratio or you'll be staring at shrinkage cracks before the sealer even dries.

Have you ruled out the thermal expansion and contraction issues with a twelve-foot continuous pour? Even indoors, a lobby with floor-to-ceiling glass can see huge temprature swings. If you don't incorporate a control joint or some way for those shells to breathe, you might end up with a hairline crack right down the middle in six months regardless of your reinforcement. Also, have you considered the subfloor's load capacity? Twelve feet of cast-in-place is a massive amount of dead weight hitting a small footprint. I'd be worried about the slab settling and throwing your levels off.

Quick update — I’m really leaning toward that GFRC approach now. The idea of spraying a face coat with a hopper gun seems like the best way to handle those vertical faces without the blowout risk. I'm still worried about the 'cold' look, so I might try mixing in some iron oxide like the old-school suggestion mentioned. Has anyone had issues with the pigment clumping when using the glass fibers?