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Necessary Information

Necessary Information. Required compressive strength at 28days: 30 Mpa Type of structure: mass concrete, beam, column. Maximum size of aggregate: 20 mm Fineness modulus of sand: 2.7 Dry- rodded weight of coarse aggregate: 1600 kg/m 3 Moisture absorption: 2% for coarse aggregate and

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Necessary Information

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  1. Necessary Information • Required compressive strength at 28days: 30 Mpa • Type of structure: mass concrete, beam, column. • Maximum size of aggregate: 20 mm • Fineness modulus of sand: 2.7 • Dry-rodded weight of coarse aggregate: 1600 kg/m3 • Moisture absorption: 2% for coarse aggregate and 1.5% for fine aggregate

  2. Fineness Modulus (FM) • where the standard sieve sizes are No.100 (0.15 mm), No.50 (0.3 mm), No.30 (0.6 mm), No.16 (1.18 mm), No.8 (2.36 mm), and No.4 (4.75 mm)

  3. Step 1Estimate w/c based on required 28 days compressive strength

  4. 0.54

  5. 1. 30 MPa = 4350 psi w/c = 0.54

  6. Step 2Obtain slump value based on types of construction

  7. 75 – 100 mm 2.

  8. Step 3Estimate amount of water requirement for mixing based on maximum size of aggregate and slump value

  9. 20 mm

  10. 195 kg/m3

  11. Step 4Calculation of cement content based on required water and w/c values

  12. 4. 360 kg/m3

  13. Step 4Estimate weight of aggregates based on unit weight of fresh concrete

  14. Unit weight of fresh concrete Unit weight = Cement + Water + Aggregates 1800 kg/m3

  15. Step 5Calculate coarse aggregate content based on volume of dry-rodded and dry-rodded weight of coarse of aggregate

  16. Coarse aggregate content 1008 kg/m3 (CA) = (V) x (CA dry-roddedwight) (CA) = coarse aggregate (V) = Volume of dry-rodded coarse aggregate per cubic meter of concrete (CA dry-rodded unit weight) = 1600 kg/m3

  17. Step 6Calculate fine aggregate content

  18. Fine aggregate content FA = Total aggregates – CA 792 kg/m3

  19. Step 7Calculate net weight of fine aggregate based on its moisture absorption

  20. Net weight of fine aggregate Net FA = FA x (1+MAf) MAf: moisture absorption or moisture content of FA Net FA = 792 x (1+ 0.015) = 804 kg/m3

  21. Step 8Calculate net weight of coarse aggregate based on its moisture absorption

  22. Net weight of coarse aggregate Net CA = CA x (1+MAc) MAc: moisture absorption or moisture content of CA Net CA = 1008 x (1+ 0.02) = 1028 kg/m3

  23. Step 9Calculate net weight of water based on FA and CA and their moisture absorptions

  24. Net weight of water Net W = W – FAx(MAf) – CAx(MAc) Net W = 195 – 792(0.015) – 1008(0.02) = 163 kg/m3

  25. Step 10Adjust the concrete ingredient contents

  26. Cement = 360 kg/m3 Fine aggregate = 804 (800 kg/m3) Coarse aggregate = 1028 (1030 kg/m3) Water = 163 (160 kg/m3) Slump = 75 – 100 mm Strength (28days) = 30 MPa

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