Concrete Mix Design

The process of selecting suitable ingredients of concrete and determining their relative amounts with the objective of producing a concrete of the required, strength, durability, and workability as economically as possible, is termed the concrete mix design.

The main objectives for concrete mix design includes:

• To determine the proportions of concrete mix constituents of; Cement, Fine aggregate (or normally Sand), Coarse aggregate, and Water.
• To produce concrete of the specified properties.
• To produce a satisfactory of end product, such as beam, column or slab as economically as possible.

Concrete Mix Design Methods & Tools

1. Process of Mix Design
The method of mix design applied here is in accordance to the method published by the Department of Environment, United Kingdom (in year 1988).

There are two categories of initial information required:

1. Specified variables; the values that are usually found in specifications.
2. Additional information, the values normally available from the material supplier.

The design process can be divided into 5 primary stages. The details of each stage is posted at the website of CivilCraftStructures.Com.

2. Pensacola Testing Laboratories, Inc.  

To determine proportions for a mix design follow these steps:

• Enter specific gravities for all materials to be used in the right column.
• Enter the water demand in gallons per yard.
  Example: From known batch requirements, 32 gallons/yd³ is required to achieve a 4 inch slump using chemical additives.
• Choose the water to cement ratio required to achieve overdesign requirements as indicated by ACI 301 and 318 (1200 psi for 3000 to 5000 psi mix design). Example: I want a 3000 psi mix. I find the 4200 psi point on the curve above, which is at 0.519.
• Enter pozzolin percentages if used.
• Enter the % Entrained air desired for this mix.
• The remaining volume required to achieve 27 ft³ will be filled with coarse and fine aggregates. Enter the % of the Aggregate volume the Coarse Aggregate will fill. The remaining aggregate volume is filled with fine aggregate. Entering 0 in this field would fill 100% of the aggregate volume with fine aggregate.

Factors used by this calculator are as follows,

• CEMENT: 1 Sack = 94 lbs. Equivalent to 1 ft³ loose volume.
• WATER: 62.4 lbs/ft³
• WATER: 8.33333 lbs/Gallon