Concrete material

Concrete should be specified, supplied and assessed in accordance with:

• BS 8500: 2015 + A1: 2016

Concrete strength class, cement type, minimum cement content, maximum water/cement ratio and aggregate weight / size should always be specified by the party responsible for the overall composite slab design, typically the project structural engineer. Approval of the intended concrete mix design/s must be sought from the relevant party prior to any concrete placement works proceeding.

Concrete surface finish

Surface finish specifications are defined in

• BS EN 13670: 2009
• National Structural Concrete Specification (NSCS) 4th edition
• Concrete Society Technical Report No. 75 – Composite concrete slabs using steel decking

For unformed finishes it is important not to over-specify the quality of finish, particularly where it is covered by following finishes. Irrespective of the finish specification, the concrete must always be fully compacted.

Concrete surface regularity

There are two common concrete surface regularity specifications used when specifying composite floor slabs:

• BS EN 13670: 2009, adopted by NSCS 4th edition
• BS 8204-2: 2003 + A2:2011

Typically, the NSCS Basic or BS 8204-2 SR3 are considered applicable.