Project on Concrete Mix Design for various grades of Concrete
1. Calculate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash?
Answer : Mix design for M 35 grade concrete with fly ash
Procedure:
Stipulations for proportioning
a. Grade designation : M35
b. Type of cement : OPC 43 grade conforming to IS 8112
c. Type of mineral admixture: Fly ash confirming to IS 3812 ( Part 1)
d. Maximum nominal size of aggregates : 20mm
e. Minimum cement content : 320 kg/m^3 (Table :5 IS 456-2000,based on exposure condition)
f. Maximum water-cement ratio : 0.45 (Table :5 IS 456-2000,based on exposure condition)
g. Workability :100mm slump value of pumpable concrete
h. Exposure condition : Severe ( for reinforced concrete)
i. Method of concrete placing : Pumping
j. Degree of supervision : Good
k. Type of aggregate: Crushed angular aggregate
l. Maximum cement content : 450 kg/m^3.
m. Chemical admixture type : Superplaticizer.
Test data for materials
a. Cement used : OPC 43 grade confirming to IS 8112
b. Specific gravity of cement : 3.15
c. Fly ash : Conforming to IS 3812 part 1
d. Specific gravity of flyash : 2.2
e. Chemical admixture : Superplaticizer conforming to IS 9103
f. Specific gravity of :
Coarse aggregate : 2.74
Fine aggregate : 2.74
g. Water absorption :
Coarse aggregate : 0.5%
Fine aggregate : 1%
h. Free surface moisture
Coarse aggregate : Nil
Fine aggregate : Nil
i. Seive analysis
Coarse aggregates:
| IS seive size (mm) | Analysis of coarse aggregate fraction | % of different fraction | Remarks | |||
| I | II | I | II | Combined | ||
| 20 | 100 | 100 | 60 | 40 | 100 | Confirming to |
| 10 | 0 | 71.2 | 0 | 28.5 | 28.5 | Table 2 |
| 4.75 | 9.4 | 3.7 | 3.7 | of | ||
| 2.36 | 0 | IS 383 |
Fine aggregate : Conforming to grading Zone 1 of table 4 IS 383.
To find target mean strength for mix proportioning
Target mean strength f'ck = fck +1.65s
= 35 +1.65*5 =43.25 Nmm2">Nmm2
fck- Characteristic compressive strength
s- Standard deviation
Selection of water-cement ratio
Maximum water-cement ratio =0.45 (for severe condition ,from table 5 of IS 456-2000)
On experience water- cement ratio =0.4
0.4 <0.45, Hence OK.
Calculation of cement content
Water - cement ratio = 0.4
Cementatious material ( Cement +flyash ) = 140/0.4 =350 kg/m3
To proportion the mix containing flyash the following steps are suggested :
a. The percentage of flyash need to be decided based on project requirement and qualityof materials.
b. In some cases increase in cementatious materials can be warrned . Increase in cementatious material content and its percentage may be based on experience and trial
In this increase of 10% cementatious material content is considered.
Cementatious material content = 350*1.1 =385kg/m3
Water content = 140kg/m3
So, water- cement ratio = 140/385 =0.364
Fly ash at 30% total cementatious material content = 35-30% =115kg/m3
Cement (OPC) =385-115 =270kg/m3
Saving of cement while using flyash = 350-270=80kg/m3
Fly ash beign utilized = 115kg/m3
Mix calculations
Mix calculation per unit volume of concrete:
a. Volume of concrete = 1 m^3.
b. Volume of cement = (Mass of cement / Specific gravity of cement ) *1/1000
= (270/3.15 )*1/1000 =0.086 m3
c. Volume of flyash = (Mass of flyash / Specific gravity of flyash )*1/1000
= (115/2.2) *1/1000 = 0.052m3
d. Volume of water = ( Mass of water / Specific gravity of water)*1/1000
= (140/1)*1/1000 =0.140 m3">m3m3
e. Volume of chemical admixture = ( Mass of admixture / specific gravity of admixture)*1/1000
=( 7.6/1.14)*1/1000 =0.006 m3
f. Volume of aggregate ( Fine and coarse) = a- (b+c+d+e)
= 1-(0.086+0.052+0.140+0.006) =0.716 m3
g. Mass of coarse aggregate = f* Volume of coarse aggregate * Specific gravity of coarse aggregate *1000
= 0.716*0.576*2.74*1000 =1130kgm3
h. Mass of fine aggregate = f* Volume of fine aggregate* Specific gravity of fine aggreate*1000
= 0.716*0.424*2.74*1000= 831kgm3
Mix proportion
Cement = 270 kg/m3
Fly ash = 115 kg/m3
Water = 140kg/m3
Fine aggregate = 831 kg/m3
Coarse aggregate = 1130 kg/m3
Chemical admixture = 7kg/m3
Water- cement ratio = 0.364
Mix ratio 1: 2.15: 2.94
The slump shall be measured and the water content and dosage of admixyure shall be adjusted for achieving the required slump on trial . The mix proportion shall be reworked for the actual water content and checkedd for durability requirements.
Result : The mix design for M 35 grade of concrete with flyash is 1: 2.15:2.94
2.M50 grade concrete without Fly ash?
Answer: Mix design of M 50 grade concrete
Procedure :
Stipulation for proportioning
a. Grade designation : M50
b. Type of cement : OPC grade 43 conforming to IS 8112
c. Maximum nominal size of aggregate: 20mm
d. Minimum cement content : 320 kgm3
e. Maximum water-cement ratio : 0.45 (Table :5 IS 456-2000,based on exposure condition)
f. Workability :100mm ,slump value of pumpable concrete
g. Exposure condition : Severe ( for reinforced concrete)
h. Method of concrete placing : Pumping
i. Degree of supervision : Good
j. Type of aggregate: Crushed angular aggregate
k. Maximum cement content : 450 kg/m^3.
l. Chemical admixture type : Superplaticizer.
Test data for materials
a. Cement used : OPC 43 grade confirming to IS 8112
b. Specific gravity of cement : 3.15
c. Chemical admixture : Superplaticizer conforming to IS 9103
d. Specific gravity of :
Coarse aggregate : 2.74
Fine aggregate : 2.74
e. Water absorption :
Coarse aggregate : 0.5%
Fine aggregate : 1%
f. Free surface moisture
Coarse aggregate : Nil
Fine aggregate : Nil
g. Seive analysis
Coarse aggregates:
| IS seive size (mm) | Analysis of coarse aggregate fraction | % of different fraction | Remarks | |||
| I | II | I | II | Combined | ||
| 20 | 100 | 100 | 60 | 40 | 100 | Confirming to |
| 10 | 0 | 71.2 | 0 | 28.5 | 28.5 | Table 2 |
| 4.75 | 9.4 | 3.7 | 3.7 | of | ||
| 2.36 | 0 | IS 383 |
Fine aggregate : Conforming to grading Zone 1 of table 4 IS 383.
To find target mean strength for proportioning
Target mean strength , f'ck =fck +1.65 s
= 50+1.65*5 =58.25 N/mm2
fck = Characteristic strength
s=standard deviation
Selection of water cement ratio
From Table :5 of IS 456-2000, by exposure condition
Here severe condition is considered , Maximum water-cement ratio=0.45
Based on experience water- cement ratio =0.4
0.4 <0.45 ,Hence OK.
Selection of water content
Maximum water content for 20mm aggregate =186 litres ( Table 2 of IS 1026:2009) for 25mm to 50mm slump range
For 100 mm slump ,= 186+(6/100)*186 =197 litres
As superplaticizer is used, the water content is reduced upto 30%
Based on trials water content reduction of 29% is achieved with plasticizer
Hence arrived water content = 197*0.71 = 140 litres
Calculation of cement content
Water - cement ratio = 0.4
Cement content = 140/0.4 =350 kg/m3
In table 5 of IS 456-2000, the cement content for severe exposure =320 kg/m3
350 kgm/3 > 320kg/m3
Hence OK.
Mix calculation
For unit volume of concrete
a. Volume of concrete = 1 m3
b. Volume of cement = ( Mass of cement / Specific gravity of cement ) *1/1000
=(350/3.15)*1/1000 =0.111 m3
c. Volume of water = (Mass of water/ Specific gravity of water )*1/1000
= (140/1)*1/1000 =0.140 m3
d. Volume of chemical admixture = (Mass of admixture/Specific gravity of admixture)*1/1000
= (7.6/1.145)*1/1000 =0.006m3
e. Volume of agggregate (fine adn coarse) = a-(b+c+d)
=1-( 0.111+0.140+0.006) =0.743m3
f. Mass of coarse aggregate = ex Volume of coarse aggregate x Specific gravity of coarse aggregate x 1000
=0.743*0.576*2.74*1000= 1173kg/m3
g. Mass of fine aggregate =e* Volume of fine aggregate* Specific gravity of fine aggregate *1000
= 0.743*0.424*2.74*1000 =863 kg/m3
Mix proportion
Cement = 350 kg/m3
Water = 140 kg/m^3
Fine aggregate= 863 kg/m3
Coarse aggregate = 1173 kg/m3
Chemical admixture = 7 kg/m3
Water cement ratio =0.4
Mix ratio =1: 2.46: 3.35
The slump shall be measured and the water content and dosage of admixyure shall be adjusted for achieving the required slump on trial . The mix proportion shall be reworked for the actual water content and checkedd for durability requirements