Firstmix only deals with concrete with fine and coarse aggregates that approximate to the requirements of to BS 882 (see References 5) and cannot deal with aggregates, which have a larger maximum size than 40mm (1.5 in).
Firstmiix does not deal explicitly with admixtures, with the exception of air-entraining agents and water-reducing agents.
Special materials and special types of concrete such as flowing or pumped concrete are not dealt with.