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“Basic“ concrete mix design method

The Basic Mix design method was devised by Philip Owens when at the C&CA, now the BCA. It gives tabulated data to provide initial trial mix proportions for 4 fine aggregate grading zones to BS 882 (now withdrawn), 3 workabilities and 3 aggregate sizes (10, 15, 20mm to BS 882). Suggestions are given for adjusting the initial mix (after the trial) to produce the “basic mix“ of correct workability and cohesion. A procedure is given to modify the basic mix over a range of cement contents, with a constant free water content to maintain the required fresh concrete properties, such that further trials can be undertaken on a systematic basis. This procedure exploits the near-linear relationship between strength and w/c ratio for medium strength mixes and provides a range of strengths within which a suitable mix can be selected for the required strength value.

Other simplified methods include the BRE (1987) and ACI (1991).

 



 


Acknowledgement: The Concrete Society


Other references:Owens PL, Basic mix design method, selection of proportions for medium strength concretes, C&CA, London, 1973.
ACI Standard practice for selecting proportions for normal, heavyweight and mass concrete, ACI 211.1-91