Design of concrete mix involves economical relative proportion of various ingredients of concrete.
Apart from meeting the criteria of strength, it is desired that concrete must be workable in fresh state and impermeable and durable in hardened state.
Several methods of mix design have been developed over the years in many countries.
In India, we follow IS:10262-1982 and SP23-1982 for recommendations and guidance of mix design.
Determine target mean strength (fcm) from the desired characteristic strength (fck).
fcm = fck + 1.65σ
fcm= target mean strength
fck= Characteristic strength
σ= Standard deviation
|Grade of Concrete||Assumed Standard Deviation|
Determine the water-cement ratio, based on the 28th day strength of cement and the mean target strength of concrete. This ratio should not exceed the limits specified in graph-
Exposure conditions and requirements for RC work with normal aggregate (20mm nominal size)
Water Content for every 25-50mm slump value-
For Every +25mm slump value, water content will increase 3%.
Find the Cement content by solving the equation of water/cement ratio.
According to IS: 456:2000, there are some limits-
Find Volume of cement, water, and aggregate by,
Volume = Density * Weight
For finding the volume of aggregate, there are some criteria-
Volume of Coarse aggregate is defined by the zone of fine aggregate as shown above. Volume of Coarse aggregate is multiplied in the total volume (coarse + fine aggregate) by the number according to nominal size of aggregate.
Find the weight of Aggregates.
By having weight of all ingredients, you will get the ratio of Mix design.