We have concrete balconies: some have been enclosed to create ‘sun rooms’. The balconies were cast as part of the reinforced (not post‑tensioned) slab, so they are very effective radiators of our central heating to the outdoors. A few years ago the corporation had them examined and repair work was prescribed to stop spalling and delamination, and rust where the reinforcing rods had become exposed.
The treatment involved sand‑blasting and repairing the concrete, then coating the concrete with epoxy to match the colour of the buildings. We had to remove everything from the balcony to allow the work, of course.
As Terry Gibson suggested, look for an engineering consultant familiar with condominiums to evaluate what is needed, prepare a specification, and oversee work by the contractor after bids have been evaluated. The list of CCI‑SA professional members should yield good results.
We had installed removable plastic tiles to make the concrete more attractive; that brand is no longer available, but Ikea Altappen is similar:
Do not put down outdoor carpet on the concrete (and especially not on wood). It traps moisture, causes rot, and breeds mould. Our tiles allow air circulation and drainage, so the balcony is usable as soon as the rain stops.
How Do We Maintain Concrete Balconies?