Concrete Mixes GEN 1 MIX: GEN 1 Mix has a minimum content of cement added approximately 170kg/ m and is suited best for strip footing foundations. GEN 3 MIX: GEN 3 Mix is used for over site slabs patios, paths, with a minimum cement content off 220kg/m. P300 MIX: P300 Mix is a mix with 300kg/m cement content used for driveways, garage floors etc. C35 MIX C35 Mix with minimum cement content of 325kg/ is an extremely strong concrete mix recommended for use in barns stables resistant to animal urine. C 40 MIX C 40 Mix Is much stronger mix again with a cement content of 340kg/m recommended for heavy agricultural plant farm machinery and so on. SPEC MIX: SPEC Mix Is a lean mix often used for blinding or insulation for a septic tank, this can be 8-1, 10-1 or 12-1 the most popular being 12-1.