Cast In Situ Concrete Paving . Whereas in situ concrete is a cheaper form of construction for small. A precast concrete block pavement consists of. Manually screeding reinforced in situ concrete road slab. United from www.alamy.com Individual blocks of hand held size units laid on a thin bed of. As per research article published in the journal of construction engineering (reasearchgate.net) on an average, the precast concrete slabs are 23.22% cheaper and precast columns are 21.4% cheaper than cast in place concrete construction, especially for large scale production. Punch/cut off the plastic cover on the top of the empty boxes to form the planting pots in the existing cooncrete slab.