DATA Concrete strength purpose, f’c = 30 dan 40 Mpa at 28 days, @ n=2 cube Standar DeviationSr = 0 Mpa (in case, there is no history of trial mix) Margin -> 8,5 Mpa Sumber : SNI-03-2847-2002
DATA Cement type I (Portland Cement) Fine Aggregate; uncrushed (alamiah); zone 1 Coarse Aggregate; crushed (Batu pecah); max size 40 mm Slump test purposes -> 120 mm (tabel SNI) Specific gravity fine aggregate= 2,7 Specific gravity course aggregate = 2,67
Mix Design Steps Determine Standar deviation Sr = 0 Determine f’cr (target mean stregth) f’cr = 30 Mpa + 8,5 Mpa = 38,5 Mpa Determine free water cement ratio from graph 1. w/c -> 0,45graph 1. from table 3. free- water contents -> Wf = 175 kg/m3 dan Wc = 205 kg/m3table 3 Free water content = 2/3 Wf + 1/3 Wc = 185 kg/m3 Determine cement content Cement content = Free water content / free w/c = 185/0,45 = 411,11kg/m3
Determine proportion of fine agregate From graph 3. proportion of fine aggregate zone 1 = 42%graph 3 Determine proportion of course aggregate = 100% - 42% = 58 % Gs assumssion Gs = (42% x 2,7) + (58% x 2,67) = 2,68 = 268 % Wet Density of concrete From graph2. wet density of concrete = 2430 kg/m3graph2 Total Aggregate content = Concrete density – Free water content – cement content = 2430 – 185 – 411,11 = 1833,90 kg/m3 Fine aggregate content 42% x 1833,90 = 770,238 kg /m3 Course aggregate content 58 % x 1833,90 = 1063,662 kg/m3
Correction Proportion Water Fine aggregate Course aggregate
MIX PROPORTION NUMBER OF SAMPLES = n WATER Correction water proportion x Volume mold x n CEMENT Correction cement proportion x volume mold x n FINE AGGREGATE Correction fine aggregate proportion x volume mold x n COURSE AGGREGATE Correction course aggregtae proportion x volume mold x n
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