What is an essential feature of pre-cast concrete panels?

The essential feature of pre-cast concrete panels is that they are formed and cured before placement. This process involves creating the panels in a controlled environment, allowing them to be cured fully and achieve their design strength prior to being transported to the construction site. This pre-fabrication method enhances quality control, as the panels can be produced under optimal conditions, leading to more durable and consistent products. Furthermore, by curing before placement, construction timelines can be significantly improved, as the panels can be installed immediately upon delivery without the need for extended curing periods on-site.

The other options do not accurately describe the nature of pre-cast concrete panels. Assembling on-site is not a defining characteristic, as these panels are ready-made for quicker installation. They are not molded after being poured, as the molding process occurs before the concrete is poured and cured. Immediate finishing is also not a requirement for pre-cast panels, as they can be finished once they are set into place.