What are the parameters to be considered when selecting a concrete mix design for a SFRC flooring application?
Concrete for floors is submitted to intense loading and so should offer durability. The concrete selected should have a more or less uniform sieve curve analysis and contain enough fines to allow for proper surface compaction and closure. The use of steel fibres requires a higher cement dosage rate. Minimum cement content should be 300 kg/m³. Generally dosage rates of 310 to 350 kg/m³ or even more are used. One of the major problems in flooring is shrinkage behaviour. Therefore the cement used should be chosen such that their shrinkage is minimal and W/C ratio should not be higher then 0.5 for jointless floors and 0.55 for floors with joints. To reach these values, it is mandatory to use high range water reducers (HWRA) or plasticizers to guarantee workability as SFRC is stiffer then normal concrete. Gravel/Sand ratio should be between 1.0 and 1.3. The maximum size of the aggregates should be adapted to the fibre type and fibre dosage rate. Often a maximum aggregate size of 16mm or 20
