CONCRETE MIX DESIGN

CONCRETE MIX DESIGN

CONCRETE MIX DESIGN

CONCRETE MIX DESIGN

CONCRETE MIX DESIGN Basically, the problem of designing a concrete mix consists of selecting the correct proportions of cement, fine and coarse aggregate and water to produce concrete having the specified properties. There are many properties of concrete that can be specified, eg workability, strength, density, thermal characteristics, elastic modulus and durability requirements. The properties most usually specified are: The workability of the fresh concrete The compressive strength at a specified age The durability, by means of specifying the minimum cement content and/or the maximum free-water/ cement ratio and, in some cases, requiring the use of selected types of materials

CONCRETE MIX DESIGN - SPECIFICATION Characteristic Compressive Strength = 40N/mm2 @28 days Spec. strength margin = 5 N/mm2 PC Class 42.5N Slump Required 60 – 180mm Max aggregate size = 10mm Coarse aggregate = crushed Fine aggregate = uncrushed Relative density of aggregates (SSD) = 2.7 Fine aggregate passing a 600μ sieve = 70%

40 28 5 40 5 45

Produce your chart

Free water/ cement ratio 0.53

40 28 5 40 5 45 0.53 0.53 60-180 10

Free water Content (Coarse agg)

Free water Content (Fine agg)

2/3 Wf + 1/3 Wc 2/3 225 + 1/3 250 150 + 83 = 233

40 28 5 40 5 45 0.53 0.53 60-180 10 233

233 0.53 440 440 2.7

Stage 4 requires an estimate of the density of the fully compacted concrete 2370

233 0.53 440 440 2.7 2370 2370 233 440 1697 Wet density of concrete Figure 5 Cement Content Free Water Content

233 0.53 440 440 2.7 2370 2370 233 440 1697 70

Stage 5 requires determination of the proportion of fine aggregate 40%

233 0.53 440 440 2.7 2370 2370 233 440 1697 70 40 1697 40% 679 1697 679 1018 Total Aggregate

SUMMARY OF QUANTITIES 440 235 680 1020 1 440 235 680 1020