Example 26: Draft a mix for a bridge deck. Use the followings: a. 20% Fly Ash b.
ID: 1732696 • Letter: E
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Example 26: Draft a mix for a bridge deck. Use the followings: a. 20% Fly Ash b. 14mm max size of aggregate c. Fine/Coarse agg 48/52 d. Corrected for moisture content Cement RD: 3.15 Fly Ash RD: 1.99 Water RD: 1 Fine Aggregate RD: 2.67 Coarse Aggregate RD: 2.70 Course aggregate in SSD condition Fine Aggregate absorption: 0.95% Fine aggregate moisture content in the field: 0.2% Summary: Material Relative Volume (L Mass (Kg) Mass Corrected Mass for for moisture 80L Trial Density (Kg) Cement Fly Ash Water Fine Aggregate Coarse Aggregate Admix 1 Admix 2 Admix 3 Design density:Explanation / Answer
Sep 1:
Given data:
Cement relative density=3.15
Fly Ash relative density=1.99
20% Fly ash
14mm maximum size of coarse aggregate
Maximum rodded density of coarse aggregate will be around 1600 kg/m3
Step 2:
Selection of W/C
The bridge deck will be having a maximum slump of 50-100 mm
W=200 kg/m3
Volume of water=200/1000=0.2m3
W/C=0.4
C=500 kg/m3
Volume=500/(1000x3.15)
Volume=0.158m3
Step 3:
Estimation of Coarse aggregate:
Volume of coarse aggregate=0.52x1600=832 kg
SSD=832 Kg
Step 4:
Estimation of fine aggregate
Since 832 kg is 52% of the volume
let us calculate 48% of the volume
832x48/52=768 kg
Weight of sand=768 kg
Step 5:
Corrections for fine aggregate
W=W[1+M.C/(1+ABS)]
W=1+0.2%/(1+0.95%)
W=0.99x768=762.29 kg
Step 6:
The extra water provide by fine aggregate=768-762.29=5.71 kg
The total water required=200-5.71=194.29 kg
Step 7:
Estimation of cementitious materials:
Cement =0.158x3.15x0.8x1000=398.16 kg
Fly Ash=0.158x1.99x0.2x1000=62.884 kg
Cement materials =461.044 kg
Step 8:
Cement=461.044 kg
Water=194.29 kg
Fine aggregate=768 kg
Coarse aggregate=832 kg
Cement:Water:Fine Aggregate:Coarse aggregate=461.044:194.29:768:832
Mix design ratio=1:0.42:1.66:1.8
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