Concrete @ your Fingertips

Parameters for mix design

The selection of concrete proportions for a economical structural concrete should be based on test data or experience with the materials actually to be used. The parameters to be considered in any mix design will include the following, some will be specified, while others are dependant on the available materials

Aggregate: type, grading, density, maximum particle size, minimum fines content, strength, abrasion qualities, chemical stability, water absorption, porosity.
Admixtures: plasticisers, air entrainers, retarders, pumping aids, corrosion inhibitors, viscosity modifiers
Cement: type, strength class
Additions: Ground granulated blastfurnace slag, pulverised fuel ash, silica fume, ground limestone.

plus the following;

Concrete compressive strength,
Maximum aggregate size,
Maximum free water/cement ratio,
Maximum chloride content,
Minimum and maximum cement content
Stiffening time

These parameters can be used in the mix design process whether developing a mix from scratch using unknown combinations of materials or modifying an existing design.

Acknowledgement: The Concrete Society