Overview of mix design
In the past mix design was achieve by trial and error. This experience was ‘formalised’ in methods based on defined grading curves and particle shapes, e.g. Road Note 4, Design of concrete mixes (Road Research Laboratory, 1962). The approach is still used in Design of normal concrete mixes (BRE, 1975 revised 1988 and 1998) that still relies on test results to refine the mix design but provides a step by step method to an adequate, if not economic, mix.
Other methods have been published including that used by the UK ready-mixed concrete producers although computer software packages are increasingly being adopted. Mix design simulation packages are now available based on optimisation techniques for any given set of materials. The actual material parameters, grading, density, shape etc. need to be known although default values are available.
Whatever the method of mix design, the final arbiter of a suitable mix is when it has been trialled and tested against the purpose and characteristics for which it was designed.