Project on Concrete Mix Design for various grades of Concrete
1) STIPULATIONS FOR PROPORTIONING
- a) Grade designation : M35
- b) Type of cement : OPC 53 grade conforming to IS 269
- c) Type of mineral admixture : Fly ash conforming to IS 3812 (Part1)
- d) Maximum nominal size of aggregate : 20 mm
- e) Minimum cement content and maximum
water-cement ratio to be adopted : Severe(for reinforced concrete)
and/or Exposure conditions as per Table 3 and Table 5 of IS 456
- f) Workability : 100 mm (slump)
- g) Method of concrete placing : Pumping
- h) Degree of supervision : Good
- j) Type of aggregate : Crushed angular aggregate
- k) Maximum cement content (OPC content) : As per IS 456
- m) Chemical admixture type : Superplasticizer- normal
B-2 TEST DATA FOR MATERIALS
- a) Cement used : OPC 53 grade conforming to IS 269
- b) Specific gravity of cement : 3.15
- c) Fly ash : Conforming to IS 3812 (Part 1)
- d) Specific gravity of fly ash : 2.2
- e) Chemical admixture : Superplasticizer conforming to IS 9103
- f) Specific gravity of
1) Coarse aggregate (at SSD condition) : 2.74
2) Fine aggregate (at SSD condition) : 2.65
3) Chemical admixture : 1.145
- g) Water absorption
1) Coarse aggregate : Nil
2) Fine aggregate : Nil
- h) Fine aggregate : Confirming to grading Zone II of table 9 of IS383
- Target Strength for mix Proportioning
f’ck = fck+1.65 S
whichever is higher.
where
f’ck = target average compressive strength at
28 days,
fck = characteristic compressive strength at
28 days
S = standard deviation,
From Table 2, standard deviation, S = 5 N/mm2
f’ck= 35+1.65 x 5 = 43.25 N/mm2
SELECTION OF WATER-CEMENT RATIO
From Fig. 1, the free water-cement ratio required for
the target strength of 43.25 N/mm2 is 0.45 for OPC 53
grade curve. This is lower than the maximum value of
0.45 prescribed for ‘severe’ exposure for reinforced
concrete as per Table 5 of IS 456.
0.45 = 0.45, hence O.K.
SELECTION OF WATER CONTENT
From Table 4, water content = 186 kg (for 50 mm
slump) for 20 mm aggregate.
Estimated water content for 100 mm slump (increasing
at the rate of 3 percent for every 25 mm slump)
= 186+ (006 x186)
=197.16 kg Say 197 kg
As superplasticizer is used, the water content may be
reduced.
Based on trial data, the water content reduction of
20 percent is considered while using superplasticizer
at the rate 1.0 percent by weight of cement.
Hence the arrived water content = 197 × 0.8= 157.6 kg say 158 kg.
CALCULATION OF CEMENT CONTENT
Water-cement ratio = 0.45
Cement content =
158 /0.45= 351.11 kg/m3 ≈ 352 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.
NOTE — This illustrative example is with increase of 10 percent
cementitious material content.
Cementitious material content
= 352x1.10 = 387.2 kg/m3 ≈388 kg/m3
Water content = 158 kg/m3
So, water-cementitious ratio= Fly ash @ 30 percent of total cementitious material
content = 388 × 30 percent = 116.4 ≈117 kg/m3
Cement (OPC) = 453 – 91 = 362 kg/m3
From Table 5 of IS 456, minimum cementitious content
for ‘severe’ exposure condition
= 340 kg/m3
362 kg/m3 > 340 kg/m3, hence O.K.
cement content = 362-117 = 245 kg/m3
VOLUME OF COURSE AND FINE AGGREGATE
Coarse aggregate ratio = 0.62 Table 3 IS 10262 FOR w/c ratio=0.5
Coarse aggregate ratio for 0.45 w/c ratio = 0.63 (Adding 0.01 for every decrease 0.05)
Fine aggregate ratio = 0.37
Calculation of super plasticizers @ 0.6% to mass of cementitious content = 362*(0.6/100) =2.17k g
MIX CALCULATION
The mix calculation per unit volume of concrete shall
be as follows:
- a) Total Volume = 1 m3
- b) Volume of cement= (Mass of cement/Specific gravity of cement) x (1/1000) =
= (245/3.15) X (1/1000) =0.077 cum
c) Volume of fly ash = (Mass of fly ash /Specific gravity of fly ash) x (1/ 1000) =
= (117/2.2) X (1/1000) =0.053 cum
d) Volume of water = (Mass of water /Specific gravity of water) x 1/1000) =
= (158/1) X (1/1000) =0.158 cu
e) Volume of super plasticizers = (plasticizers /Specific gravity of super plasticizers) x (1/ 1000)
= (2.172/1.145) X (1/1000) =0.0018 cum
f) Total aggregate = a-(b+c+d+e)
= 1-(0.077+0.053+0.158+0.0018) = 0.710 cum
g) coarse aggregate = 0.71 x 2.74 x 1000 x 0.63 = 1225.6 kg
h) fine aggregate = 0.71 x 2.74 x 0.37 x 1000 = 719.79 kg
|
Si no |
Materials |
Quantity |
|
1 |
Cement |
245 kg |
|
2 |
Fly ash |
117 kg |
|
3 |
Fine agg |
720 kg |
|
4 |
Coarse agg |
1226 kg |
|
5 |
Water |
158 lts |
|
6 |
SP |
2 L |
Mix ratio= 1:0.47:2.93:5: 0.64
2)
STIPULATIONS FOR PROPORTIONING
- a) Grade designation : M50
- b) Type of cement : OPC 43 grade conforming to IS 269
- c) Maximum nominal size of aggregate : 20 mm
- d) Minimum cement content and maximum
water-cement ratio to be adopted : Severe(for reinforced concrete)
and/or Exposure conditions as per Table 3 and Table 5 of IS 456
- e) Workability : 50 mm (slump)
- f) Method of concrete placing : Pumping
- g) Degree of supervision : Good
- h) Type of aggregate : Crushed angular aggregate
- i) Maximum cement content (OPC content) : As per IS 456
- j) Chemical admixture type : Superplasticizer- normal
B-2 TEST DATA FOR MATERIALS
- a) Cement used : OPC 43 grade conforming to IS 269
- b) Specific gravity of cement : 3.15
- c) Chemical admixture : Superplasticizer conforming to IS 9103
- d) Specific gravity of
1) Coarse aggregate (at SSD condition) : 2.74
2) Fine aggregate (at SSD condition) : 2.65
3) Chemical admixture : 1.145
- g) Water absorption
1) Coarse aggregate : Nil
2) Fine aggregate : Nil
- h) Fine aggregate : Confirming to grading Zone II of table 9 of IS383
- Target Strength for mix Proportioning
f’ck = fck+1.65 S
whichever is higher.
where
f’ck = target average compressive strength at
28 days,
fck = characteristic compressive strength at
28 days
S = standard deviation,
From Table 2, standard deviation, S = 5 N/mm2
f’ck= 50+1.65 x 5 = 58.25 N/mm2
SELECTION OF WATER-CEMENT RATIO
From Fig. 1, the free water-cement ratio required for
the target strength of 58.25 N/mm2 is 0.35 for OPC 43
grade curve. This is lower than the maximum value of
0.45 prescribed for ‘severe’ exposure for reinforced
concrete as per Table 5 of IS 456.
0.35< 0.45, hence O.K.
SELECTION OF WATER CONTENT
From Table 4, water content = 186 kg (for 50 mm
slump) for 20 mm aggregate.
As superplasticizer is used, the water content may be
reduced.
Based on trial data, the water content reduction of
20 percent is considered while using superplasticizer
at the rate 1.0 percent by weight of cement.
Hence the arrived water content = 186 × 0.8= 148.8 kg say 149 kg.
CALCULATION OF CEMENT CONTENT
Water-cement ratio = 0.45
Cement content =
149 /0.35= 425.71 kg/m3 ≈ 426 kg/m3
VOLUME OF COURSE AND FINE AGGREGATE
Coarse aggregate ratio = 0.62 Table 3 IS 10262 FOR w/c ratio=0.5
Coarse aggregate ratio for 0.45 w/c ratio = 0.63 (Adding 0.01 for every decrease 0.05)
Fine aggregate ratio = 0.37
Calculation of super plasticizers @ 0.6% to mass of cementitious content = 426*(0.6/100) =2.55kg
MIX CALCULATION
The mix calculation per unit volume of concrete shall
be as follows:
- a) Total Volume = 1 m3
- b) Volume of cement= (Mass of cement/Specific gravity of cement) x (1/1000) =
= (426/3.15) X (1/1000) =0.135 cum
- c) Volume of water = (Mass of water /Specific gravity of water) x 1/1000) =
= (149/1) X (1/1000) =0.149 cum
- d) Volume of super plasticizers = (plasticizers /Specific gravity of super plasticizers) x (1/ 1000)
= (2.55/1.145) X (1/1000) =0.0022 cum
- e) Total aggregate = a-(b+c+d+e)
= 1-(0.135+0.149+0.0022) = 0.71 cum
- f) coarse aggregate = 0.71 x 2.74 x 1000 x 0.63 = 1225.6 kg
- g) fine aggregate = 0.71 x 2.74 x 0.37 x 1000 = 719.79 kg
|
Si no |
Materials |
Quantity |
|
1 |
Cement |
426 kg |
|
3 |
Fine agg |
720 kg |
|
4 |
Coarse agg |
1226 kg |
|
5 |
Water |
149 lts |
|
6 |
SP |
2 .55 L |
Mix ratio= 1:1.69:2.87: 0.34