Concrete is required for an exterior column to be located above ground level in an area where it will be wet and subjected to substantial freezing and thawing. The concrete is required to have an average 28-day compressive strength of 28 MPa. For the conditions of placement, the slump should be between 75 and 100 mm (3 and 4 in.). The column is 635 mm (25 in.) square with a minimum clear space for aggregate of 50 mm (2 in.).

The properties of the materials are as follows:

• This value takes into account the difference between the average strength required and the specified design

• Cement: Type I, specific gravity = 3.15

• Fine aggregate: Bulk specific gravity (SSD) = 2.56; absorption capacity = 1.8%; surface moisture = 4.6% based on SSD state; fineness modulus = 2.85

• Coarse aggregate: Maximum size = 19 mm (3 /4 in.); bulk specific gravity (SSD) = 2.68; absorption capacity = 3.0%; surface moisture = 0.6% based on SSD state; dry-rodded unit weight = 1600 kg/m3 (100 lb/ft3 )

Step 1: Required material information

Step 2: Choice of slump.

Step 3: Maximum aggregate size.

Step 4: Estimation of mixing water and air content.

Step 5: Water/cement ratio.

Step 6: Calculation of cement content.

Step 7: Estimation of coarse aggregate content.

Step 8: Estimation of fine aggregate content

Step 9: Adjustment for moisture in the aggre