If reinforcement needs to be laid in advance during the construction of concrete carriageways, the concrete can be fed in laterally using a placer/spreader. The placer/spreader travels in front of the slipform paver over the pre-placed reinforcement, while a truck mixer feeds the belt conveyor with concrete from the side. The concrete is poured evenly over the pre-placed reinforcement, in front of the slipform paver, and distributed across the entire working width. Once the truck mixer is empty, the belt conveyor can be folded away in a very short time to clear the path for the next mixer.