Concrete Mix Design Example 5t6g5e

BRE MIX DESIGN - C30|60-180mm SLUMP 1

Description Characteristic strength (fc) at 28 days & 2.5% defective Standard deviation (s) for less than 20 results - from Fig 1 Probability factor (k) for 2.5% defective -from Table 1 Margin (M = k.s) Target mean strength (fm = fc + k.s) Cement strength class - OPC Aggregate type - Coarse aggregate Aggregate type - Fine aggregate

0.51

Checking for maximum W/C - BS8110-1:1997 Therefore Free W/C ratio (taking lower value)

0.65 0.51

Specific slump required Specific maximum aggregate size Approx. free water content - uncrushed aggr. (Wf) Approx. free water content - crushed aggr. (Wc) Free water content - from Table 3 (W={2Wf+Wc}/3)

3

Cement content (=W/wc ratio) Checking (in accordance with BS8110-1:1997) Minimum cement content - Table 3.3 Maximum cement content - Cl. 6.2.4.1 Hence Cement content

5

Unit N/mm2 N/mm2 N/mm2 N/mm2

42.5 N/mm2 Crushed Uncrushed

Approximate compressive strength -from Table 2 By establishing corresponding curve & intersecting lines fromFig. 2 Free water cement ratio - from Figure 2

2

4

Value 30 8 1.96 15.68 45.68

49 N/mm2

60 - 180 mm 20 mm 195 225 205 kg/m3 400.00 kg/m3 275 kg/m3 550 kg/m3 400.00 kg/m3

Relative density of combined aggregate (SSD) 2.6 Establishing parallel curve in Figure 3, corresponding to relative density of combined aggregate 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 Grading of fine aggregate ing 600micron sieve (to be determined through a sieve analysis) - Assumed 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 Fine aggregate content (=Total aggregate content x proportion of fine aggregate/100)

70 %

31 % 535.37 kg/m3

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 Slump specified - Assumed Cement Class (OPC) Aggregate Condition Maximum aggregate size Coarse aggregate (SSD) - 1192 kg/m3 Fine aggregate (SSD) - 535 kg/m3 Cement OPC 42.5 - 400 kg/m3 Water - 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

C30 60 - 180 mm 42.5 SSD 20 mm 1191.63 535.37 400.00 205

kg/m3 kg/m3 kg/m3 kg/m3