Construction Technology - Concrete Mix Design- Project 1
CONCRETE MIX DESIGN FOR M35 GRADE CONCRETE WITH FLY ASH
I. STIPULATIONS FOR PROPORTIONING OF M35 GRADE CONCRETE:
A) Grade Designation : M35
B) Type of Cement: OPC 53
C) Type of Admixture: Fly ash
D) Maximum Nominal: Size of Aggregate 20mm
E) Minimum Cement Content: 340kg Table 5-IS456
F) Maximum Cement Content: 450kg As per code
G) Partial replacement of cement by Fly ash: 30% as per requirement
H) Maximum W/C ratio : 0.45 Table 5-IS456
I) Workability: 100mm
J) Chemical Admixture: PCS Type k) Exposure conditions: very severe(for reinforced conctere)
L) Method of concrete placing : pumping M) Degree of supervision: good N) Type of aggregate: Crushed angular aggregates. O) Maximum cement content: 450kg/m3
II. TEST DATA FOR MATERIALS:
A) Cement Used: OPC 53 Confirming to IS8112
B) Specific Gravity of Cement: 3.15 Test – IS: 2720
C) Mineral Admixture Fly ash: Confirming to IS12089
D) Specific Gravity of Fly ash: 2.90
E) Chemical Admixture @: Super plasticizer 0.6% IS9103
F) Specific Gravity of Test – IS 2386
Coarse Aggregate: 2.74
Fine Aggregate: 2.74
G) Water Absorption Test – IS 2386
Coarse aggregate: 0.5 %
Fine aggregate: 1 %
H) Sieve Analysis Test – IS 2386
Coarse aggregate Confirming toTable 2-IS383
Fine aggregate Zone II Confirming to Table 4-IS383
III. TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE:
Strength of the concrete may deviate slightly depends on the quality of the material, method of mixing and construction practices. Hence target strength (Fck) should be higher than the required strength of the concrete (fck). Value of standard deviation(s) for different grade of concrete is given in Table 1 of IS456.
Fck = fck+1.65s “S” from Table1-IS10262
Fck = 35+1.65×5
Fck = 43.25 N/mm2
IV. SELECTION OF WATER-CEMENT RATIO:
From the table the maximum water-cement ratio for different grade of concrete is given in Table 5-IS456. You can reduce the water-cement ratio based on your requirements. Water-cement ratio directly affects the strength of the concrete.
Maximum W/C ratio =0.45 Table 5-IS456
Adopted W/C ratio =0.45
V. SELECTION OF WATER CONTENT
Maximum Water Content =186 L Table 2-IS1026
Above water-content is for 25 to 50mm slump, but the slump we require is 100mm. hence we need to increase the water content to get the required slump for good workability. Clause 4.2 of IS1026 suggests an increase of 3% of water content from its original value for every increase of 25mm. Here we have a 50mm increase in the water content hence we have to increase the water content by 6 %.
Water-content for 100mm Slump =186+(0.06*186)
=197.16 L
Since superplasticizers are used water content can be reduced to get good strength of concrete. Percentage of reduction of water depends on the type of superplasticizers used in the concrete.
Percentage of Reduction in water content =20%
Water content requirement after SP =198 – (0.20*198)
=157.73
Adopted Water Content =160 L
VI. CALCULATION OF CEMENT AND FLY ASH CONTENT:
Water Cement Ratio =0.45
Total Cementitious (Cement +Fly ash) requirement = Water Content / WaterCement ratio:
=160/0.45
=355.55 kg
Since Fly ash is used the amount of Cementitious content (Cement+Fly ash) shall be increased to get good workability and strength. the percentage of increase depending on experience and research. Here we increased the cementitious content by 1.1 %.
Final Cementitious :
Content (Cement+Fly ash) = 356*1.1
=391.6 kg
Minimum Cement Content:
required for ‘very severe’ exposure =340kg Table 5-IS456
Adopted Cementious content =391.6 kg > 340kg
Fly ash content requirement = 391.6 * 0.30 30% replacement
= 117.48 ~ 118 kg
Cement Content requirement =Cementious content – Fly ash
=391.6-117.48
= 274.12
Calculation of Super Plasticiers @ 0.6 percent to the mass of cementitious content = 391.6*(0.6/100)
= 2.35 kg
VII COARSE AND FINE AGGREGATE:
Coarse Aggregate ratio = 0.62 Table3-IS10262
(For W/C =0.5)
Coarse Aggregate ratio for 0.45 w/c ratio = 0.63 (adding 0.01 for every
decrease 0.05 )
Final Fine Aggregate ratio = 0.37 (1-0.63) = 0.37
VIII MIX CALCULATIONS OF M35 GRADE CONCRETE:
A) Volume of Concrete = 1 cu.m
B) Total Volume of Cement = Mass ofCement/Specific gravityof cement*1/1000
= 275/(3.15*1000)
= 0.087 cu.m
C) Total Volume of Fly ash = Mass of fly ash/Specific gravity of flyash*1/1000
= 118/(2.5*1000)
= 0.041 cu.m
D) Volume of Water =Mass ofwater/Specific gravityofwater*1/1000
= 160/(1*1000)
= 0.160 cu.m
E) Volume of Superplasticizers = Superplasticizers /(S.G*1000)
= 2.35/(1.12*1000)
= 0.002 cu.m
F) Total Aggregates requirement = A – (B+C+D+E)
=1 -(0.087 +0.041+0.160+0.002)
=0.71 cu.m
G) Coarse Aggregate (C.A) = F *volume of C.A * S.G * 1000
= 0.71*0.63 *2.74 *1000
= 1225.6 kg
I) Fine Aggregate (F.A) = F *volume of F.A * S.G * 1000
= 0.71*0.37*2.74 *1000
=719.8 kg
Cement Flyash Sand Aggregate Water and Superplasticizer needed for M35 grade concrete
IX.MIX PROPORTIONS FOR TRIAL NUMBER 1:
1. Cement :275 kg
2. Flyash: 118 kg
3. Fine Aggregate: 720 kg
4. Coarse Aggregate (20mm): 1226 kg
5. WATER :160 L
6. PCE based SuperPlasticizer: 2 L
Therefore Mix Ratio of M35 Grade concrete by weight is Cement : Flyash: F.A : C.A : Water = 1:0.4:2.6:4.46:0.58
X. The slumpshall be measured and the water content and dosage of admixture shall be adjusted for acheving the required slump work on trial. The mix proportion shall be reworked for the actual water content and checked for durablity requiremets.
XI. Two more trials having variations of 10% of water-cement ratio is clause X shall be carried out a graph between the three water - cement ratio and corresponding strength shall be plotted to work out the mix proportions for the given target strength for the trials, and also durability is also shall be met.
MIX DESIGN OF M50 GRADE CONCRETE WITHOUT FLYASH:
- STIPULATIONS FOR PROPORTIONING:
a). Grade Designation = M50
b). Type of cement = OPC 53 grade conforming to IS 8112
c). Max nominal size of aggregates = 20MM
d). Minimum cement content = 320kg/m^3 (from table 5 IS 456:2000 exposure condition)
e). Max water-cement ratio = 0.45 (from table 5 IS 456:2000 exposure condition)
f).workability = 100mm (Slump value for pumpable concrete)
g). Exposure condition = very severe (for reinforced concrete)
h).Method pf concrete placing = Pumping
i). Degree of supervision = good
j). Type of aggregates = crushed angular aggregates
k).Maximum cement content = 450kg/m^3
l) Chemical admixture = super plasticizer
I.TEST DATA FOR MATERIAL:
a). cement used = OPC 53 conforming to IS 8112
b).specific gravity of cement = 3.15
c).chemical admixture = super plasticizer conforming to IS 9103
d).specific gravity of course aggregate = 2.74
specific gravity of fine aggregate= 2.74
e).water absorption of course aggregates = 0.5% ,
water absorption of fine aggregate= 1.0%
f).Free surface moisture for course aggregate = NIL ,
free surface moisture for fine aggregare = NIL
g).Sieve analysis- course aggregate conforming to table 2 of IS 383
h) fine aggregate conforming to grading zone 1 of table 4 of IS 383
III. TARGET MEAN STRENGTH FOR MIX PROPORTIONING:
f'ck = fck +1.65S (from table 1 IS 10262:2009) S=5N/mm2
= 50+1.65*5 = 58.25 N/mm^2
- SELECTION OF WATER CEMENT RATIO:
from table 5 IS 456:2000 max w/c ratio = 0.45
Based on experience adopt w/c ratio = 0.40
0.40 < 0.45, hence OK
V . SELECTION OF WATER CONTENT:
from table 2 of IS 10262:2009, water content for for 20 mm aggregate = 186 litre , for 25 to 50 mm slump range for the disered workability oher than 50mm slump the water required may increased or decreased by 3% for each increase or decrease of 25mm slump.
Hence,
Estimated water content for 100 mm slump = 186+6/100 *186 = 197 litres
As super plasticizer is used, the water content can be reduced by 30%
Based on water content reduction of 29% is achived with plasticizer
Hence the arrived water content = 197* 0.71= 140 litres
VI . CALCULATION OF CEMENT CONTENT:
w/c ratio = 0.40
cementitious material (cement)= 140/0.40= 350kg/m^3
from table 5 of IS 456:2000 min cement content for severe exposure condition = 320kg/m^3
350kg/m^3 >320kg/m^3, Hence OK.
Proportion of volume of course aggregate and fine aggregate.
VII . PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:
From table 3 of IS 10262:2009, volume of course aggregate corresponding to 20mm size aggregate and fine aggregate (Zone 1) w/c ratio = 0.6
In present case w/c ratio = 0.40
Therefore, volume of course aggregate needs to be increased to decreased fine aggregate content
As w/c ratio is lower by 0.10, the proportion of volume of course aggregate is increased by 0.02 at the water of -/+0.01 for every -/+0.05 change in w/c ratio
Volume of course aggregate for w/c ratio of 0.4 =0.62
For pumpable concrete for these values are reduced by 10%
volume of course aggregate=0.62*0.9=0.56
volume of aggregate content=1-0.56=0.44
VIII . MIX CALCULATION:
- volume of concrete= 1m^3
2. volume of cement= mass of cement/specific gravity of cement*1/1000
= 350/3.15*1/1000=0.111m^3
3. volume of water= mass of water/specific gravity of water*1/1000
= 140/1*1/1000=0.140m^3
4. volume of chemical admixture = mass of chemical admixture/specific gravity of chemical admixture*1/10O0
=7.6/1.145*1/1000=0.006m^3
5. volume of aggregate(Fine aggregate & Course aggregate)=(a-(b+c+d))
= (1-(0.111+0.140+0.006))
= 0.743m^3
6. Mass of course aggregate= e*volume of course aggregate * specific gravity of course aggregate*1000
= 0.743*0.56*2.74*1000
= 1140kg/m^3
7.Mass of fine aggregate= e*volume of fine aggregate * specific gravity of fine aggregate*1000
= 0.743*0.44*2.74*1000
= 896kg/m^3
IX . MIX PROPORTION:
- cement= 350kg/m^3
2. water= 140kg/m^3
3. fine aggregate= 896kg/m^3
4.course aggregate= 1140kg/m^3
5. chemical admixture= 7kg/m^3
6. w/c ratio= 0.4
7.water-cement ratio = 0.4
Trial mix ratio= 1:2.5:3.3
X. The slump shall be used measured and the watr content and dosage of admixture shal be adjusted for achieving the required slump on trial. The mix proportioning shall be reworked for the water content of actual value and checked for durability requirements.