CONCRETE CALCULATIONS Volume | Weight | Area | Pressure FACTORS AFFECTING READY MIXED CONCRETE 1.+ 5 L Water = Increases Slump 20 mm 2.+ 1% Air = Increases Slump 20 mm 3.+ 15 Min Overmixing = Reduces Strength 1 MPa 4.+ 10 Min Overmixing = Increases Temperature 1° c 5.+ 1° c over 25° c = Reduces Strength 0.5 MPa 6.+ 20° c over 25° c = Reduces Strength 10 Mpa 7.+ 10° c over 25° c = Decreases Slump 30 mm 8.+ 20 L Water = Decreases Strength 5 MPa 9.+ 20 L Water = Increase Cement Content 32 Kg To Maintain Strength 10.+ 1 MPa = Increase Cement Content 5 Kg for 20 MPa Concrete 11.+ 1 MPa = Increase Cement Content 10 Kg for 35 MPa 12.+ 10° c = Increase H2O 5 L to Maintain Equivilant Slump 13.+ 1% Extra Air = Reduces Strength 1 - 3MPa 14.+ 7 Kg Ice = Reduces Temp 1° c 15.+ 7 Kg Ice = Increasses Strength 0.5 MPa 16.+ 7 Kg Ice = Decrease Cement Content 2.5 Kg   Generally - One Cubic Metre of Concrete Will: a) Cover an Area of 105 square feet, 4 inches thick b) Fill 6.5 linear feet of standard 8 feet by 8 inch foundation wall c) Fill 35 linear feet of standard 18 inch by 8 inch footing forms d) Fill 44 linear feet of 12 inch drilled piles Strengths and Specifications Residential All exterior flat work ( driveways, sidewalks, and garage slabs ) must have proper air- entrainment ( 5 - 8 % ) and a maximum water / cement ratio of 0.45 for freeze thaw durability Foundations should have minimum 20 MPa and 3-6% Air-entrainment Concrete Basement floors shall be 20 MPa non air-entrained concrete * Remember: never POWER-TROWEL air-entrained concrete as power-trowelling destroys the air-void structure and can cause blistering of the surface.