Description Value Unit

1 Characteristic strength (fc) at 28 days & 2.5% defective 30 N/mm2

Standard deviation (s) for less than 20 results - from Fig 1 8 N/mm2

Probability factor (k) for 2.5% defective -from Table 1 1.96

Margin (M = k.s) 15.68 N/mm2

Target mean strength (fm = fc + k.s) 45.68 N/mm2

Cement strength class - OPC 42.5 N/mm2

Aggregate type - Coarse aggregate Crushed

Aggregate type - Fine aggregate Uncrushed

Approximate compressive strength -from Table 2 49 N/mm2

By establishing corresponding curve & intersecting lines fromFig. 2

Free water cement ratio - from Figure 2 0.51

Checking for maximum W/C - BS8110-1:1997 0.65

Therefore Free W/C ratio (taking lower value) 0.51

2 Specific slump required 60 - 180 mm

Specific maximum aggregate size 20 mm

Approx. free water content - uncrushed aggr. (Wf) 195

Approx. free water content - crushed aggr. (Wc) 225

Free water content - from Table 3 (W={2Wf+Wc}/3) 205 kg/m3

3 Cement content (=W/wc ratio) 400.00 kg/m3

Checking (in accordance with BS8110-1:1997)

Minimum cement content - Table 3.3 275 kg/m3

Maximum cement content - Cl. 6.2.4.1 550 kg/m3

Hence Cement content 400.00 kg/m3

4 Relative density of combined aggregate (SSD) 2.6

Wet density of concrete against free water content 2332 kg/m3

Total aggregate content (= Wet concrete density - Water

content - Cement content) 1727.00 kg/m3

5

Grading of fine aggregate passing 600micron sieve (to be

determined through a sieve analysis) - Assumed 70 %

Relevant fine aggregate grading line drawing in respective

graph of required slump range on Figure 4, and using free

water cement ratio;

Proportion of fine aggregate - from Figure 4 31 %

Fine aggregate content (=Total aggregate content x proportion

of fine aggregate/100) 535.37 kg/m3

BRE MIX DESIGN - C30|60-180mm SLUMP

Establishing parallel curve in Figure 3, corresponding to relative density of combined

aggregate

Coarse aggregate content (=Total aggregate content - Fine

aggregate content) 1191.63 kg/m3

Note: Since aggregates are in SSD condition, no adjustments

are needed

Mix Design Summary

Grade of Concrete - Assumed C30

Slump specified - Assumed 60 - 180 mm

Cement Class (OPC) 42.5

Aggregate Condition SSD

Maximum aggregate size 20 mm

Coarse aggregate (SSD) - 1192 kg/m3 1191.63 kg/m3

Fine aggregate (SSD) - 535 kg/m3 535.37 kg/m3

Cement OPC 42.5 - 400 kg/m3 400.00 kg/m3

Water - 205 kg/m3 205 kg/m3

Note: Water we have taken randomly as per 0.45 W/C ratio,

as a trial to manage floating of rubber aggregate