Project on Concrete Mix Design for various grades of Concrete
1.
Aim : To develop the Concrete Mix Design for M35 grade concrete with fly ash.
Introduction :
Concrete mix design is the method of finding the precise proportion of cement, sand and aggregates for concrete to achieve the target strength in structures, therefore concrete mix design can be stated as concrete mix in terms of cement: sand: aggregates. The design is done according to the requirements of concrete strength. So, we can achieve the desirable properties of concrete either it is in fresh stage or in hardened stage. The fresh concrete properties like workability, setting time and hardened concrete properties like compressive strength, durability etc. are attained surely by this method. Use of additives like admixtures, retarders etc. other than basic ingredients are used to improve the properties of mix. This project consist of two parts, the first part deals with the design of M35 grade cement with fly ash.
OBJECTIVE:
The objective of this project is to produce a mix design for M35 grade concrete containing fly ash .The mix will be prepared as per IS METHOD: Concrete mix proportioning guidelines from IS 10262:2009 and recommented guide lines from IS 10262:1982.
Available Data:
- Grade designation : M35
- Type of cement : OPC 43 grade conforming to IS 269
- Type of mineral admixture : Fly ash conforming to IS 38I2 (Part I)
- Maximum nominal size of aggregate : 20mm
- Minimum cement content : 340 kg/m'
- Maximum water-cement ratio : 0.45
- Workability ; 100 mm (slump)
- Exposure condition : Severe (for reinforced concrete)
- Method of concrete placing : Pumping
- Degree ofsupervision : Good
- Type of aggregate : Crushed angular aggregate
- Maximum cement (OPC) content : 450 kg/m3 As per IS 456
- Chemical admixture type : Superplasticizer
TEST DATA FOR MATERIALS
- Cement used : OPC 43 grade conforming to IS 8112
- Specific gravity of cement : 3.15
- Fly ash : Conforming to IS 3812 (Part I)
- Specific gravity of fly ash : 2.2
- Chemical admixture : Superplasticizer conforming to IS 9103
- Specific gravity of:
Coarse aggregate : 2.74
Fine aggregate : 2.65
Chemical admixture : 1.145
- Water absorption:
Coarse aggregate : 0.5 %
Fine aggregate : 1.0 % - Free (surface) moisture:
Coarse aggregate : Nil (absorbed moisture also nil)
Fine aggregate : Nil - The coarse and fine aggregates are wet and their total moisture content is 2 percent and 5 percent
respectively. Therefore, the free moisture content in coarse and fine aggregate shall be as shown in (j)
below - Free (surface) moisture
Coarse aggregate : Free moisture = Total moisture content –Water absorption
= 2.0 – 0.5 = 1.5 %
Fine aggregate : Free moisture = Total moisture content –Water absorption
= 5.0 – 1.0 = 4.0 %
- Sieve analysis:
Coarse aggregate : Conforming to grading Zone II of Table 4 of IS 383
Fine aggregate : Conforming to grading Zone II of Table 4 of IS 383
TARGET STRENGTH FOR MIX PROPORTIONING
f'ck =Fck + 1.65 s
f’ck = f ck + X
F'ck = target average compressive strength at 28 days,
Fck = characteristics compressive strength at 28 days, and
s = standard deviation.
X = factor based on grade of concrete.
From Table 2, standard deviation, S = 5 N/mm2
From Table 1, X = 6.5
Therefore, target strength using both equations, that is,
a) f’ck =fck+1.65 S
= 35 + 1.65 × 5
= 43.25 N/mm2
b) f’ck = fck + 6.5
= 35 + 6.5
= 41.50 N/mm2
The higher value is to be adopted.
Therefore, target strength will be 48.25 N/mm2
as 43.25 N/mm2 >41.5 N/mm2
APPROXIMATE AIR CONTENT
From Table 3, the approximate amount of entrapped air to be expected in normal (non-air-entrained)
concrete is 1.0 percent for 20 mm nominal maximum size of aggregate.
SELECTION OF WATER-CEMENT RATIO
From Fig. 1, the free water-cement ratio required for
the target strength of 43.25 N/mm2
is 0.38 for OPC 43 grade curve.
This is lower than the maximum value of0.45 prescribed for ‘severe’ exposure for reinforced
concrete as per Table 5 of IS 456
Adopted W/C ratio=0.38
SELECTION OF WATER CONTENT
From Table 4, water content = 186 kg (for 50 mm slump) for 20 mm aggregate.
Estimated water content for 120 mm slump (increasing at the rate of 3 percent for every 25 mm slump)
=186+(8.6/100) x 186
= 201.62 kg
As superplasticizer is used, the water content may be reduced.
Based on trial data, the water content reduction of 23 %is considered while using superplasticizer at the rate 1.0 percent by weight of cement.
Hence the arrived water content = 201.62 × 0.77
=155.25 kg ≈ 155 kg
CALCULATION OF CEMENT CONTENT
Water-cement ratio = 0.38
Cement content =(155/0.38)
=407.89 ≈408 kg/m3
To proportion a mix containing fly ash the following steps are suggested:
a) Decide the percentage fly ash to be used based on project requirement and quality of fly ash.
b) In certain situations, increase in cementitious material content may be warranted. The decision on increase in cementitious material
content and its percentage may be based on experience and trials.
Cementitious material content
= 408 × 1.10
= 448.8 kg/m3 ≈ 449 kg/m3
Water content = 155 kg/m3
So, water-cementitious ratio =155/449
= 0.345
Fly ash @ 30 percent of total cementitious material content = 449 × 30 %
= 134.7 ≈138 kg/m3
Cement (OPC) = 449 – 138 = 311 kg/m3
From Table 5 of IS 456, minimum cementitious content for ‘severe’ exposure condition = 320 kg/m3
449 kg/m3 > 320 kg/m3 , hence O.K.
PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGRAGETE CONTENT
From Table 5, volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II)
for water-cement ratio of 0.50 = 0.62.
In the present case water-cementitious ratio is 0.345.
Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.173, the proportion
of volume of coarse aggregate is increased by 0.034 (at the rate of ± 0.01 for every ± 0.05 change in watercement ratio). Therefore, corrected proportion of
volume of coarse aggregate for the water-cementitious ratio of 0.345 = 0.62 + 0.0345 = 0.6545
For pumpable concrete these values may be reduced by up to 10 percent. (see 5.5.2). Here, 10 percentreduction is considered.
Therefore, volume of coarse aggregate = 0.6545 ×0.9 = 0.589, say 0.59 m3
Volume of fine aggregate content = 1 – 0.59 = 0.41 m3
MIX CALCULATIONS
The mix calculations per unit volume of concrete shall be as follows:
a) Total volume = 1 m3
b) Volume of entrapped air in wet concrete = 0.01 m3
c) Volume of cement =Mass of cement/ Specificgravity of cement x 1/1000
=311/3.15 x 1/1000
= 0.0987 m3
d) Volume of fly ash =Mass of fly ash / Specificgravity of fly ash x 1/1000
=138/2.2 x 1/1000
=0.0627 m3
e) Volume of water = Mass of water / Specificgravity of water x 1/1000
= 155/1 x 1/1000
= 0.155 m3
f) Volume of chemical admixture (superplasticizer) (@ 1.0 percent by mass of cementitious material)
=Mass of chemical admixture /Specific gravity of admixture x 1/1000
= 4.74 /1.145 x 1/1000
= 0.0041 m3
g) Volume of all in aggregate = [(a-b)-(c+d+e+f)}]
= [(1-0.01)-(0.0987+0.0627+0.155+0.0041)]
= [0.999-0.3205]
= 0.6785 m3
h) Mass of coarse aggregate = g × volume of coarse aggregate × Specific gravity of coarse aggregate × 1 000
= 0.6785x0.59x2.74x1000
= 1096.8 ≈1097
j) Mass of fine aggregate = g × Volume of fine aggregate × Specific gravity of fine aggregate × 1 000
= 0.6785 x 0.41 x2.65 x1000
= 737.19 ≈ 737
MIX PROPORTIONS
Cement = 311 kg/m3
Fly ash = 138 kg/m3
Water (Net mixing) = 155 kg/m3
Fine aggregate (SSD) = 737 kg/m3
Coarse aggregate (SSD) = 1 097 kg/m3
Chemical admixture = 4.74 kg/m3
Free water-cementitious materials ratio = 0.38
Mix Proportion By weight = 1:2.3:3.5
RESULTS:
Mix Proportion by weight of M35 grade of concrete with fly ash is 1:2.3:3.5 and its water-cement ratio was found to be 0.38
2.
Aim : To develop the Concrete Mix Design for M50 grade concrete without fly ash.
Introduction :
Concrete mix design is the method of finding the precise proportion of cement, sand and aggregates for concrete to achieve the target strength in structures, therefore concrete mix design can be stated as concrete mix in terms of cement: sand: aggregates. The design is done according to the requirements of concrete strength. So, we can achieve the desirable properties of concrete either it is in fresh stage or in hardened stage. The fresh concrete properties like workability, setting time and hardened concrete properties like compressive strength, durability etc. are attained surely by this method. Use of additives like admixtures, retarders etc. other than basic ingredients are used to improve the properties of mix. This project consist of it and second part is the design of M50 grade concrete without fly ash.
OBJECTIVE:
The objective of this project is to produce a mix design for M50 grade concrete containing fly ash .The mix will be prepared as per IS METHOD: Concrete mix proportioning guidelines from IS 10262:2009 and recommented guide lines from IS 10262:1982.
Available Data:
Available Data:
- Grade designation : M50
- Type of cement : OPC 53 Grade confirming to IS BIS 12269 - 1987
- Maximum nominal size of aggregate : 20mm
- Minimum cement content : 320 kg/m'
- Maximum water-cement ratio : 0.45
- Workability ; 100 mm (slump)
- Exposure condition : Severe (for reinforced concrete)
- Method of concrete placing : Pumping
- Degree ofsupervision : Good
- Type of aggregate : Crushed angular aggregate
- Maximum cement (OPC) content : 450 kg/m3 As per IS 456
- Chemical admixture type : Superplasticizer
TEST DATA FOR MATERIALS
- Cement used : OPC 53 Grade confirming to IS BIS 12269 - 1987
- Specific gravity of cement : 3.15
- Fly ash : Conforming to IS 3812 (Part I)
- Specific gravity of fly ash : 2.2
- Chemical admixture : Superplasticizer conforming to IS 9103
- Specific gravity of:
Coarse aggregate : 2.74
Fine aggregate : 2.65
Chemical admixture : 1.145
- Water absorption:
Coarse aggregate : 0.5 %
Fine aggregate : 1.0 % - Free (surface) moisture:
Coarse aggregate : Nil (absorbed moisture also nil)
Fine aggregate : Nil - The coarse and fine aggregates are wet and their total moisture content is 2 percent and 5 percent
respectively. Therefore, the free moisture content in coarse and fine aggregate shall be as shown in (j)
below - Free (surface) moisture
Coarse aggregate : Free moisture = Total moisture content –Water absorption
= 2.0 – 0.5 = 1.5 %
Fine aggregate : Free moisture = Total moisture content –Water absorption
= 5.0 – 1.0 = 4.0 %
- Sieve analysis:
Coarse aggregate : Conforming to grading Zone II of Table 4 of IS 383
Fine aggregate : Conforming to grading Zone II of Table 4 of IS 383
TARGET STRENGTH FOR MIX PROPORTIONING
f'ck =Fck + 1.65 s
f’ck = f ck + X
F'ck = target average compressive strength at 28 days,
Fck = characteristics compressive strength at 28 days, and
s = standard deviation.
X = factor based on grade of concrete.
From Table 2, standard deviation, S = 5 N/mm2
From Table 1, X = 6.5
Therefore, target strength using both equations, that is,
a) f’ck =fck+1.65 S
= 50 + 1.65 × 5
= 58.25 N/mm2
b) f’ck = fck + 6.5
= 50 + 6.5
= 56.5 N/mm2
The higher value is to be adopted. = 58.25N/mm2
SELECTION OF WATER-CEMENT RATIO
The maximum water-cement ratio to design M50 grade concrete can be found from Table 5 of IS 456-2000 for
Maximum W/C ratio =0.45
Based on experience adopted water cement ratio is 0.44
0.44<0>
Adopted W/C ratio=0.44
SELECTION OF WATER CONTENT
From Table 2 of IS 10262:2009, maximum water content for 20 mm aggregate = 186 litre (for 25 to 50 mm slump range)
Clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm slump. So a 6% is to be added to it
= 186+ (6/100)*186 = 197L
Estimated water content for 100 mm slump
(Note: If Super plasticizer is used, the water content can be reduced up to 20% and above.)
Based on trials with Super plasticizer water content reduction of 20% has been achieved, Hence the arrived water content
=197 X 0.8 = 158 L
CALCULATION OF CEMENT CONTENT
Water-cement ratio = 0.44
Cement Content = 158/0.44 = 359 kg/m3
From Table 5 of IS 456, Minimum cement content for ‘Severe’ exposure conditions 320kg/m3
359 kg/m3 > 320 kg/m3 hence ok.
Cement required is 359 kg/m3
VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT
From Table 3 of (IS 10262:2009) Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for water-cement ratio of 0.50 is = 0.62
In the present case water-cement ratio is 0.44. Therefore, volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.06. The proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in water-cement ratio).
Therefore, corrected proportion of volume of coarse aggregate for the water-cement ratio of 0.44 = 0.632
For pumpable concrete these values should be reduced up to 10%. Therefore, volume of coarse aggregate = 0.632 x 0.9 =0.568.
Volume of fine aggregate content =1 – 0.576
=0.431
Volume of fine aggregate 0.431
Volume coarse aggregate 0.568
MIX CALCULATIONS
a) Volume of concrete = 1 m3
b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000
= (359/3.15) X (1/1000)
=0.114m3
c) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000
=(158/1) X (1/1000)
= 0.158m3
d) Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000
=(7.6/1.145) X (1/1000)
=0.006 m3
e) Volume of all in aggregate = [a-(b+c+d)]
=[1-(0.114+0.158+0.006)]
= 0.722m3
f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000
= 0.722x 0.568 x 2.74 x 1000
= 1123 kg/m3
g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000
= 0.722x 0.431x 2.64 x 1000
= 821 kg/m3
MIX PROPORTIONS
Cement = 359 kg/m3
Water = 158 kg/m3
Fine aggregate = 821 kg/m3
Coarse aggregate 20mm = 1123 kg/m3
Chemical admixture = 7.18kg/m3
Water-cement ratio = 0.44
Mix Proportion By weight = 1:2.28:3.12
RESULTS:
Mix Proportion by weight of M50 grade of concrete without fly ash is 1:2.28:3.12 and its water-cement ratio was found to be 0.44.