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Lab 8 Concrete Mix Design
Object Oriented Software Engineering (CoSc3092)
Hawassa University
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Lab on Concrete Mix Design
Given Information:
Materials
Coarse Aggregates
Gravel with crushed particles NMAS = ¾ inch Bulk oven-dry specific gravity = 2. Oven-dry-rodded density = 105 pcf (2835 lb/yd 3 ) Moisture Content = 0% Absorption = 2%
Fine Aggregates
Natural sand Bulk oven-dry specific gravity = 2. Moisture Content = 3% Absorption = 1% Fineness modulus = 2.
Cement Specific Gravity = 3.
Strength Information
Specified strength of concrete = 4 ksi (Old data says the standard deviation of compressive strength is 300 psi when tested more than 30 samples)
Project Environment
Concrete will be used in interior beam (width of 12 inches) with both clear space between bars and clear cover is 3 inch.
Air Entrainer
None as the concrete will not be exposed to freeze-thaw conditions and deicing salts.
Design the mix of the concrete using the ACI 318 Weight and Absolute Volume Method.
Design:
Step 1. Strength Requirements
The required average strength is the larger of the following:
cr c .1 sff 450034 .1 490230034 psi
cr c .2 sff 450050033 .2 469950030033 psi
Therefore, the required average strength is 4902 psi ≈ 4 ksi
Step 2. Water-Cement Ratio Requirements
From Table 7, .0 49 C
W (by interpolation) for the required strength of 4 ksi
Tables 7 and 7 support this ratio.
Step 3. Coarse-Aggregate Requirements
The ¾ inch NMAS corresponds to 1 inch maximum size.
The permissible maximum aggregate size is the smallest of the following:
1/5 of the minimum form dimension = 1/5 (12) = 2 inch ¾ of the minimum clear cover = ¾ (3) = 2 inch ¾ of the minimum clear space = ¾ (3) = 2 inch
Therefore, aggregate size is good with the beam dimensions, clear cover and bar spacing.
From Table 7, for the max. agg. size of ¾ inch and FM of 2, coarse aggregate factor is 0.
Therefore, dry-weight of coarse aggregate = 0 (2835 lb/yd 3 ) = 1758 lb/yd 3
Step 4. Air Entrainment Requirements
From Table 7, Target air content is 2% for non-air-entrained concrete.
Step 5. Workability Requirements
From Table 7, slump range for beam = 1 to 4 inch (use, 3 inch)
Step 6. Water Content Requirements
From Table 7, for 3-inch slump and ¾ inch NMAS, water content is 340 lb/yd 3. For Gravel with crushed particles, reduction of water is 35 lb/yd 3.
Required water = 340 – 35 = 305 lb/yd 3
Step 7. Cement Content Requirements
Now, you can adjust your material quantity based on the amount of mix you will prepare.
Example 2 Given Information:
Materials
Coarse Aggregates
Gravel with crushed particles NMAS = ¾ inch Bulk oven-dry specific gravity = 2. Oven-dry-rodded density = 105 pcf (2835 lb/yd 3 ) Moisture Content = 0% Absorption = 4%
Fine Aggregates
Natural sand Bulk oven-dry specific gravity = 2. Moisture Content = 2% Absorption = 1% Fineness modulus = 2.
Cement Specific Gravity = 3.
Strength Information
Specified strength of concrete = 4 ksi (Old data says the standard deviation of compressive strength is 300 psi when tested more than 30 samples)
Project Environment
Concrete will be used in interior beam (width of 12 inches) with both clear space between bars and clear cover is 3 inch.
Air Entrainer
None as the concrete will not be exposed to freeze-thaw conditions and deicing salts.
Design the mix of the concrete using the ACI 318 Weight and Absolute Volume Method.
From Step 2, .0 49 C
W
From Step 6, required water = 305 lb/yd 3
Cement = 305 lb/yd 3 /0 = 622 lb/yd 3
No need to check the minimum cement content as the mix will be used inside a building.
Step 8. Admixture Requirements
None.
Step 9. Fine Aggregate Requirements
G w
W V
Unit wt.
WWeight
Water Volume = x 1 62 cf
yd
lb 3053 = 4 ft 3 /yd 3
Cement Volume = p cf 62 x 3.
yd
lb 622. 453 = 3 ft 3 /yd 3
Air Volume = 0 yd 3 /yd 3 = 0 x 27 = 0 ft 3 /yd 3
Coarse Aggregate Volume = 2 x 62 cf
yd
lb 17583 = 9 ft 3 /yd 3
Sub-total volume = 18 ft 3 /yd 3
Fine Aggregate = 27 – 18 yd 3 /yd 3 = 8 ft 3 /yd 3
Fine Aggregate dry weight = 8 ft 3 /yd 3 (2 x 62 pcf) = 1403 lb/ft 3
Step 10. Moisture Correction
Dry-weight of coarse aggregate = 1758 lb/yd 3 Moist-weight of coarse aggregate = 1758 (1+ 0) = 1765 lb/yd 3
Dry-weight of Fine Aggregate = 1403 lb/yd 3 Moist-weight of fine aggregate = 1403 (1 + 0) = 1446 lb/yd 3
Moisture content of coarse aggregate is less than the absorption and moisture content of fine aggregate is more than the absorption. Therefore, water quantity may need to be adjusted.
####### Cement 622.
####### Cement 622.
Now, you can adjust your material quantity based on the amount of mix you will prepare.
- Shortage of moisture in coarse aggregate to reach to absorption = 1758 (0 – 0) = 28.
- lb/yd
- Excess of moisture in fine aggregate above the absorption = 1403 (0 – 0) = 28 lb/yd
- Therefore, additional moisture required = 28 – 28 = 0 lb/yd
- Total water required = 305 + 0 = 305 lb/yd
- Material Amount, lb/yd
- Water
- Moist Coarse Aggregate
- Moist Fine Aggregate - Cement 622.
- Moist Coarse Aggregate
- Shortage of moisture in coarse aggregate to reach to absorption = 1758 (0 – 0) = 63.
- lb/yd
- Excess of moisture in fine aggregate above the absorption = 1403 (0 – 0) = 14 lb/yd
- Therefore, additional moisture required = 63 – 14 = 49 lb/yd
- Total water required = 305 + 49 = 354 lb/yd
- Material Amount, lb/yd
- Water 354.
- Moist Coarse Aggregate
- Moist Fine Aggregate - Cement 622.
- Moist Coarse Aggregate
- 1 lb/yd 3 = 0 kg/m Remember:
- 1 lb/yd 3 = 593 g/m
Design:
Step 1. Strength Requirements
The required average strength is the larger of the following:
cr c .1 sff 300034 .1 333525034 psi
cr c .2 sff 300050033 .2 308350025033 psi
Therefore, the required average strength is 3335 psi
Step 2. Water-Cement Ratio Requirements
From Table 7, for air-entrained concrete, .0 55 C
W (by interpolation) for the required strength
of 3335 psi
Table 7 recommends .0 45 C
W [freeze and thaw and deicing chemicals]
Step 3. Coarse-Aggregate Requirements
The 2-inch NMAS corresponds to 3-inch maximum size.
The permissible maximum aggregate size = 1/3 of the slab thickness = 1/3(12) = 4 inch
Therefore, aggregate size is GOOD
From Table 7, for the max. agg. size of 3-inch and FM of 2, coarse aggregate factor is 0.
Dry-weight of coarse aggregate = 0(120 pcf) = 90 pcf = 90 pcf x27 (ft 3 /yd 3 ) = 2430 lb/yd 3
Step 4. Air Entrainment Requirements
From Table 7, Target air content is 5% for air-entrained concrete with severe exposure. Job range = 4% to 7% (Select 6%)
Step 5. Workability Requirements
From Table 7, slump range for beam = 1 to 3 inch (use, 2 inch)
Step 6. Water Content Requirements
From Table 7, for 2-inch slump and 2-inch NMAS, angular aggregate, water content is 240 lb/yd 3.
Step 7. Cement Content Requirements
From Step 2, .0 45 C
W
From Step 6, required water = 240 lb/yd 3
Cement = 240 lb/yd 3 /0 = 533 lb/yd 3
Increase for the minimum criterion of 564 lb/yd 3 for exposure.
So, cement = 564 lb/yd 3
Step 8. Admixture Requirements
6% air, cement = 564 lb/yd 3 Admixture = (0) (6) (564/100) = 5 fl oz/yd 3 Admixture = 5 fl oz/yd 3
Step 9. Fine Aggregate Requirements
G w
W V
tUnit weigh
WWeight
Water Volume = p cf 1x62.
yd
lb 2403 = 3 ft 3 /yd 3
Cement Volume = p cf3.
yd
lb 5643 = 2 ft 3 /yd 3
Air Volume = 0 yd 3 /yd 3 = 0 x 27 = 1 ft 3 /yd 3
Coarse Aggregate Volume = p cf2.
yd
lb 24303 = 15 ft 3 /yd 3
Sub-total volume = 23 ft 3 /yd 3
Fine Aggregate = 27 - 23 ft 3 /yd 3 = 3 ft 3 /yd 3
Fine Aggregate dry weight = 3 ft 3 /yd 3 (2 x 62 pcf) = 559 lb/yd 3
Step 10. Moisture Correction
Dry-weight of coarse aggregate = 2430 lb/yd 3 Moist-weight of coarse aggregate = 2430 (1+0) = 2454 lb/yd 3
Dry-weight of Fine Aggregate = 559 lb/yd 3 Moist-weight of fine aggregate = 559 (1 + 0) = 584 lb/yd 3
Moisture content of coarse aggregate is less than the absorption and moisture content of fine aggregate is more than the absorption. Therefore, water quantity may need to be adjusted.
Example 4 Given Information:
Materials
Coarse Aggregates
River gravel NMAS = 19 mm Bulk oven-dry specific gravity = 2. Oven-dry-rodded density = 1761 kg/m 3 Moisture Content = 2% Absorption = 4%
Fine Aggregates
Natural sand Bulk oven-dry specific gravity = 2. Moisture Content = 2% Absorption = 4% Fineness modulus = 2.
Cement Specific Gravity = 3.
Strength Information
Specified strength of concrete = 27 MPa (Old data says the standard deviation of compressive strength is 2 MPa when tested more than 30 samples)
Project Environment
Building frame with minimum dimension of 150 mm, minimum clear space between bars of 50 mm and minimum clear cover of 40 mm.
Air Entrainer
6 ml/1% air/100 kg cement
Design the mix of the concrete using the ACI 318 Weight and Absolute Volume Method.
Design:
Step 1. Strength Requirements
The required average strength is the larger of the following:
cr c .1 sff 2734 .16. 34 MPa 30.
cr c .2 33 sff .3 2745 .26. 33 MPa29.03.
Therefore, the required average strength is 30 MPa
Step 2. Water-Cement Ratio Requirements
From Table 7, for air-entrained concrete, .0 45 C
W (by interpolation) for the required strength
of 30 MPa. Tables 7 and 7 are okay with it.
Step 3. Coarse-Aggregate Requirements
The 19-mm NMAS corresponds to 25-mm maximum size.
The permissible maximum aggregate size is the smallest of the following:
1/5 of the minimum form dimension = 1/5 (150 mm) = 30 mm ¾ of the minimum clear cover = ¾ (50 mm) = 37 mm ¾ of the minimum clear space = ¾ (40 mm) = 30 mm
Therefore, aggregate size is GOOD
From Table 7, for the max. agg. size of 25-mm and FM of 2, coarse aggregate factor is 0.
Dry-weight of coarse aggregate = 0(1761 kg/m 3 ) = 1145 kg/m 3
Step 4. Air Entrainment Requirements
From Table 7, Target air content is 3% for air-entrained concrete with mild exposure.
Step 5. Workability Requirements
From Table 7, slump range for beam = 25 to 100 mm
Step 6. Water Content Requirements
From Table 7, for 25 to 50 mm slump and 19-mm NMAS, angular aggregate, water content is 168 kg/m 3.
Reduction in water content because of round aggregate is 27 kg/m 3 Required water content = 168 – 27 = 141 kg/m 3
Moist-weight of coarse aggregate = 1145 (1+0) = 1168 kg/m 3
Dry-weight of Fine Aggregate = 726 kg/m 3 Moist-weight of fine aggregate = 726 (1 + 0) = 740 kg/m 3
Moisture content of coarse and fine aggregates are less than the absorption. Therefore, water quantity may need to be adjusted.
Shortage of moisture in coarse aggregate to reach to absorption = 1145 (0 – 0) = 22 kg/m 3 Shortage of moisture in fine aggregate above the absorption = 726 (0 – 0) = 14 kg/m 3 Therefore, additional moisture required = 22 + 14 = 37 kg/m 3 Total water required = 141 + 37 = 178 kg/m 3
Material Amount, kg/m 3 Water 178. Moist Coarse Aggregate 1168 Moist Fine Aggregate 741 Cement 320 Admixture 71 ml
Now, you can adjust your material quantity based on the amount of mix you will prepare.
Lab 8 Concrete Mix Design
Course: Object Oriented Software Engineering (CoSc3092)
University: Hawassa University
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