On contracts where Hollow core slabs are used indoors and no structural topping is specified a simple 40 - 50mm levelling screed is required.
All loose material is to be removed from the tops of the slabs, which should be thoroughly wetted and screed applied immediately. The levelling screed should comprise 1:4 mix by volume of cement to clean river sand. Water should be added to the mixture to an extent that the mixture is relatively dry but remains easy to float finish. The screed should be laid to an approximate thickness of 40 - 50mm. After laying the screed it should be steel floated and then wetted for 48 hours to prevent shrinkage cracks.
Further technical information on this procedure is available on request.