Project on Concrete Mix Design for various grades of Concrete
1.I. STIPULATIONS FOR PROPORTIONING OF M35 GRADE CONCRETE
This section has Specifications of the materials and requirements of the concrete to be made.
| 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 |
II. TEST DATA FOR MATERIALS
Various laboratory tests on materials are required to use in this action. Standard values are assumed below.
| 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 | @0.6% | IS9103 |
| F | Specific Gravity of | Test – IS 2386 | |
| Coarse Aggregate | 2.74 | ||
| Fine Aggregate | 2.74 | ||
| Admixture PCE based | 1.12 | ||
| G | Water Absorption | Test – IS 2386 | |
| Coarse aggregate | 0.5 % | ||
| Fine aggregate | 1 % | ||
| H | Sieve Analysis | Test – IS 2386 | |
| Coarse aggregate | Confirming to Table 2-IS383 |
||
| Fine aggregate | Zone II | Confirming to Table 4-IS383 |
III. TARGET STRENGTH FOR MIX PROPORTIONS OF M35 GRADE CONCRETE
The strength of the concrete may deviate based 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). The value of standard deviation(s) for different grades 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
The maximum water-cement ratio for different grades of concrete is given in Table 5-IS456. You can reduce the water-cement ratio based on your requirements. The 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 we need 100mm slump for our concert as per specification. So we need to increase the water-content to get the required slump. Clause 4.2 of IS1026 suggests to increases 3% of water-content to get an extra 25mm slump. Hence we to increase water content by 6% to get an additional 50mm slump for our concrete.
| Water-content for 100mm Slump | =186+(0.06*186) |
| =197.16 L |
Since we are using superplasticizers water-content can be reduced inorder to get strength in concrete. The amount of water-content to be reduced depends on the type of superplasticizer.
| 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
| Adopted 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 cementitious content to be increased depends on the experience and research. Here we have increased the cementitious content by 10%.
| Final Cementitious Content (Cement+Fly ash) |
= 356*1.10 | |
| =391.6 kg | ||
| Minimum Cement Content required for ‘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 .05 and vice versa) |
| 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 | = Cement/(S.G*1000) |
| = 275/(3.15*1000) | ||
| = 0.087 cu.m | ||
| C | Total Volume of Fly ash | = Flyash/(S.G*1000) |
| = 118/(2.5*1000) | ||
| = 0.041 cu.m | ||
| D | Volume of Water | =Water /(S.G*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 * C.A ratio * S.G * 1000 |
| = 0.71*0.63 *2.74 *1000 | ||
| = 1225.6 kg | ||
| I | Fine Aggregate (F.A) | = F * F.A ratio * 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
| S.No. | MATERIALS | QUANTITY |
| 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 |
To find the design mix ratio divide the calculated value of all materials by the weight of cement. 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
M50 Concrete mix design without flyash
I. STIPULATIONS FOR PROPORTIONING OF M50 GRADE CONCRETE
a)Grade design-M50
b)Type of cement-OPC 43 Grade confirming IS 8122
c)Maximum nominal size of aggregate-20mm
d)Minimum cement content-320KG/`m^3`(From table no 5 of IS456:2000)
e)Maximum water cement ratio-0.45(From table no 5 of IS456:2000)
f)Workability-100mm
g)Exposure condition-severe(For reinforcement concrete)
h)Methord of concrete placing-Pumping
I)Degree of supervision-good
j)Type of aggregate-Crushed angular aggregates
k)Maximum cement content-450KG/`m^3`
l)Chemical admixture type-Superplastisizer
II. TEST DATA FOR MATERIALS
a)cement used-OPC43 grade confirming IS 8122
b)Specific gravity of cement-3.15
c)Chemical admixture-Superplastisizer confirming IS 9103)
d)Specific gravity of
1.coarse aggregate 20 mm-2.74
2.Fine aggregate-2.74
e)Water absorption
1.Coarse aggregate-0.5%
2.Fine aggregate-1.0%
f)Free surface moisture
1.Coarse aggregate-nil
2.Fine aggregate-nil
g)Sieve analysis-
1.Coarse aggregate-Confirming to all in aggregates of Table 2 of IS 383
2.Fine aggregate-Confirming to grading zone of table 4 IS 383
III. TARGET STRENGTH FOR MIX PROPORTIONS OF M50 GRADE CONCRETE
.f'ck=fck+1.65s
where,
.f'ck-Target avg.compressive strength at 28 days
.fck-Characteristics compressive strength at 28 days
.s-Standard deviation
here fck=50N/`mm^2`
From table 8 of IS 10262:2009.Standard deviation,s=5N/`mm^2`
Therefore Target strength=50+1.65x5=58.25N/`mm^2`
IV. SELECTION OF WATER-CEMENT RATIO
.From table no 5 of IS 456:2000,for severe exposed maximum water cement ratio is 0.45
.Based on experience,adopted water cement ratio is 0.4
.0.4<0.45 Hence OK.
V. SELECTION OF WATER CONTENT
.From Table2 of IS10262-2009 maximum water content for 20 mm aggregate=186 lt.(for 25 to 50mm slump range)
.For additional slump,3% of water content is added for every 25mm slump value.
Estimated water content for 100mm slump=186+(6/100)x186=197lt.
.As super plasticizer is used ,the water content can be reduced up to 20% and above.
.Based on trials with superplasticizer,water content reduction of 29% has been achieved.
.Hence,the arrived water content=197-[197x(29x100)]=140lt.
VI. CALCULATION OF CEMENT CONTENT
.Water cement ratio=0.4
.Cement content=140/0.4=350Kg/`m^3`
.From table 5 of IS 456:2000,minimum cement content for 'severe' exposure condition 320Kg/`m^3`
Thus,350Kg/`m^3`>320Kg/`m^3`
Hence,OK
VII PROPORTION OF VOLUME OF COARSE AND FINE AGGREGATE
From table 3 of IS 10262:2009,Volume of coarse aggregate corresponding to 20mm size aggregate & fine aggregate for water cement ratio0.5=0.6
.In the present case,water cement ratio is 0.4,therefore volume of coarse aggregate needs to be increase to decrease the fine aggregate content.
.As the water cement ratio is lower by 0.1,the proportion of volume of coarse aggregate is increased by 0.02
Therefore corrected volume of coarse aggregate for water cement ratio of 0.4=0.62
Now,For pumpable concrete these value should be reduced by 10%.
.Therefore volume of coarse aggregate =[0.62x(10/100)x0.62]=0.56
.Volume of fine aggregate content=1-0.56=0.44
VIII MIX CALCULATIONS OF M50 GRADE CONCRETE
The mix calculations per unit volume of concrete shall be as follows:
a)Volume of concrete=1`m^3`
b)Volume of cement=(Mass of cement)/(specific gravity of cementx1000)
=350/(3.15x1000)
=0.111`m^3`
c)Volume of water=(Mass of water)/(specific gravity of waterx1000)
=140/(1x1000)
=0.140`m^3`
d)Volume of chemical admixture=(Mass of admixture)/(specific gravity of admixturex1000)
@2.0%by mass of cementiouc material=7/1.145x1000
=0.006`m^3`
e)Volume of all in aggregate =[a-(b+c+d)]
=[1-(0.111+0.14+0.006)]
=0.743`m^3`
f)Mass of coarse aggregate=exvolume of coarse aggregate specific gravity of coarse aggregatex1000
=0.743x0.56x2.74x1000
=1140Kg/`m^3`
g)Mass of fine aggregate=exvolume of fine aggregate specific gravity of fine aggregatex1000
=0.743x0.44x2.74x1000
=896Kg/`m^3`
IX MIX PROPORTION
Cement 350Kg/`m^3`
Water 140lt/Kg/`m^3`
Fine aggregate 896Kg/`m^3`
Coarse aggregate 1140Kg/`m^3`
Chemical admixture 7Kg/`m^3`
Water cement ratio 0.4
MIX RATIO 1:2.56:3.26