Project on Concrete Mix Design for various grades of Concrete
Aim : To Calculate the Concrete Mix Design for M35 grade concrete with fly ash & M50 grade concrete without Fly ash
Introduction :
Concrete mix design is complex material. It's property is fresh as well as hardened concrete, if the mix design is not done properly it will adversely affect the properties of concrete.Concrete mix design is the scentific and systematic process of choosing economical relative proprtion ofvarious ingredients from available material.It also depends upon mixing, batching, placing, compaction and curing
It's objective is to achieve the pre-determined minimum strength and durability in most economical manner.The cost of concrete mainly depends upon two factors, Cost of material and cost of labour.
1. Mix Design for M35 grade concrete with fly ash
Concrete Mix Proportioning : the below are the following steps
i) Stipulations for Proportioning
| a) Grade designation | M35 |
| b) Type of cement | OPC 43 grade confirm to IS : 8112 |
| c) Type of Mineral admixture | Fly ash confirm to IS : 3812 ( Part 1) |
| d) Maximum nominal size of aggregate | 20 mm |
| e) Minimum cement content | 320 Kg / m^3 ( According to Table 5 of IS : 456 - 2000 ) |
| f) Max. w/c ratio | 0.45 ( According to Table 5 of IS : 456 - 2000 ) |
| g) Workability | 100 mm ( for Pumpable concrete ) |
| h) Exposure condition | Severe ( According to Table 5 of IS : 456 - 2000 ) |
| i) Method of concrete placing | Pumping |
| j) Degree of supervision | Good |
| k) Type of aggregate | Crushed angular aggregate |
| l) Max.cement content | 450 Kg/mm^3 |
| m) Chemical admixture | Super Plasticizer |
ii) Test data for materials :
| a) Cement used | OPC 43 grade confirming to IS 8112 |
| b) Specific gravity of cement | 3.15 |
| c) Fly ash | Confirming to IS 3812 ( Part 1 ) |
| d) Specific gravity of Fly ash | 2.2 |
| e) Chemical admixture | Superplasticizers confirming to IS 9103 |
| f) Specific gravity of coarse aggregate | 2.74 |
| g) Specific gravity of fine aggregate | 2.74 |
| i) Water absorption of coarse aggregate | 0.5% |
| j) Water absorption of fine aggregate | 1.0% |
| k) Free surface moisture of coarse aggregate | Nil ( because the aggregate should be in dry condition ) |
| l) Free surface moisture of fine aggregate | Nil ( because the aggregate should be in dry condition ) |
| m) Sieve analysis - coarse aggregate | Confirming to table 2 of IS: 383 |
| n) Sieve analysis - fine aggregate | Confirming to Grading zone I of table 4 of IS: 383 |
Concrete Mix Design
iii) Target Mean Strength for Mix Proportioning :
From Table 1 of IS 10262 : 2009
f'ck = fck + 1.65 S
= 35 + (1.65 x 5)
ft = 43.25 N/mm^2
Where,
f'ck - Target avg compressive strength @ 28 days
fck - Charac. compressive strength @ 28 days
S - Std Deviation
iv) Selection of w/c ratio :
According to exposure condition - severe ,from Table 5 of IS : 456 - 2000
Max w/c ratio - 0.45
Adopted w/c ratio - 0.35
0.35 < 0.45, hence ok
v) Selection of water content :
According to Table 2 of IS : 10262 - 2009, water content for 20mm aggregate = 186 ltrs ( range from 25 to 50 mm slump )
therefore, estimated water content = 186 + ( 6% *186 )
= 186+11.16
= 197.16 ltrs
As superplasticizer used, the water content can be reduced upto 20 %, as many trials water content is reduced by 29%
Hence water content = 197 * ( 100-29%)
= 197.16 * 0.71
= 140 ltrs ( round off )
vi ) Calculation of Cement Content :
Water cement ratio = 0.35
Cement content = 140 / 0.35
= 400 kg/mm^3
According to exposure condition - severe ,from Table 5 of IS : 456 - 2000
Min cement content = 320 kg/mm^3
therefore, 400 kg/mm^3 > 320 kg/mm^3. hence ok
Now, to proportion a mix containing fly ash the following steps are suggested which are to be mandadtory
a) The % of fly ash to be decided based on the project required and the quality of materials
b) In some cases Increase in Cementitious content Percentage may be based on experience (ie) 10 %
Cementitious material content = 400 * 1.10
= 440 kg/mm^3
Water content = 140 kg/mm^3
therefore, w/c ratio = 140 / 385
= 0.364
Fly ash @ 30% total Cementitious material content = 440 * 0.3
= 132 kg/mm^3
Cement = 440-132
= 308 kg/mm^3 ( deducted from fly ash and cement )
Saving of cement while using fly ash = 400 - 308
= 92 kg/mm^3
Fly ash utilised = 132 kg/mm^3
vii) Proportion of Volume of Coarse aggregate and Fine aggregate Content :
According to table 3 of IS 10262:2009,
Volume of coarse aggregate to 20mm size aggregate and fine aggregate for water cement ratio is "0.60"
In present, the water-cement ratio is "0.35". Therefore the volume of coarse aggregate needs to be increased to decrease fine aggregate content.
As water-cement ratio is lowered by "0.10", the proportion of volume of coarse aggregate is increased by "0.02"( @ rate of +/- 0.01 for every +/- 0.05 change in water-cement ratio.
therefore, the corrected volume of coarse aggregate for water cement ratio of 0.35 is 0.62.
NOTE- If coarse aggregate is not of angular type, then also volume of coarse aggregate may be required to increase based on experience.
For pumpable concrete these values reduced by 10%
therefore, Volume of coarse aggregate= 0.62 x 0.9
= 0.558
Volume of fine aggreagtes = 1 - 0.558
= 0.442
viii) Mix calculations :
a) Volume of Concrete = 1m^3
b) Volume of Cement = ( Mass of cement / Specific gravity of cement ) * ( 1/1000)
= ( 308/3.15 ) * (1/1000)
= 0.097 m^3
c) Volume of fly ash = ( Mass of Fly ash / Specific gravity of fly ash) * ( 1/1000)
= ( 132/2.2) * (1/1000)
= 0.06 m^3
d) Volume of Water = ( Mass of Water / Specific gravity of water) * ( 1/1000)
= ( 140/1) * (1/1000)
= 0.140 m^3
e) Volume of Chemical admixture = ( Mass of Chemical admixture / Specific gravity of admixture ) * ( 1/1000)
= ( 6.16/1.145) * (1/1000)
= 0.005 m^3
f) Volume of aggregate ( FA & CA ) = ( a-(b+c+d+e) )
where, a - Vol of concrete
b - Vol of cement
c - Vol of water
d - Vol of chemical admixture
Volume of aggregate = 1 - ( 0.097 + 0.06 + 0.140+0.005 )
= 0.698 m^3
g) Mass of coarse aggregate = f x Vol of coarse aggregate x Specific gravity of coarse aggregate x 1000
= 0.698 * 0.56 * 2.74 * 1000
= 1071 kg / m^3
g) Mass of fine aggregate = f x Vol of fine aggregate x Specific gravity of fine aggregate x 1000
= 0.698 * 0.442 * 2.74 * 1000
= 845 kg / m^3
ix) Trial 01 Mix Proportion :
Cement = 308 kg/mm^3
Fly ash = 132 kg/mm^3
Water = 140 kg/mm^3
Coarse aggregate = 1071 kg / m^3
Fine aggregate = 845 kg / m^3
Chemical admixture = 6.16 kg / m^3
Water Cement Ratio = 0.35
Trial Mix Ratio = Cement : Fine : Coarse
= 308 : 845: 1071
= 1 : 2.74 : 3.47
Two conditions to be followed for mix design
x)The slump shall be measured and water content shall be adjusted for achieving the required slump on trial, the slump value is calculated by the slump cone test of concrete.These mix proportion shall be reworked for the actual water content.
xi) Two or more trials of variation of 10% of w/c ratio should be carried out and their value should be plotted out as per the graph denoted in the calculation of w/c ratio for the given target strength of the concrete.
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2. Mix Design for M50 grade concrete without Fly ash :
Concrete Mix Proportioning : the below are the following steps
i) Stipulations for Proportioning
| a) Grade designation | M50 |
| b) Type of cement | OPC 43 grade confirm to IS : 456 |
| c) Maximum nominal size of aggregate | 20 mm |
| d) Minimum cement content | 320 Kg / m^3 ( According to Table 5 of IS : 456 - 2000 ) |
| e) Max. w/c ratio | 0.45 ( According to Table 5 of IS : 456 - 2000 ) |
| f) Workability | 100 mm ( for Pumpable concrete ) |
| g) Exposure condition | Severe ( According to Table 5 of IS : 456 - 2000 ) |
| h) Method of concrete placing | Pumping |
| i) Degree of supervision | Good |
| j) Type of aggregate | Crushed angular aggregate |
| k) Max.cement content | 450 Kg/mm^3 |
| l) Chemical admixture | Super Plasticizer |
ii) Test data for materials :
| a) Cement used | OPC 43 grade confirming to IS 8112 |
| b) Specific gravity of cement | 3.15 |
| c) Chemical admixture | Superplasticizers confirming to IS 9103 |
| d) Specific gravity of coarse aggregate | 2.74 |
| e) Specific gravity of fine aggregate | 2.74 |
| f) Water absorption of coarse aggregate | 0.5% |
| g) Water absorption of fine aggregate | 1.0% |
| h) Free surface moisture of coarse aggregate | Nil ( because the aggregate should be in dry condition ) |
| i) Free surface moisture of fine aggregate | Nil ( because the aggregate should be in dry condition ) |
| j) Sieve analysis - coarse aggregate | Confirming to table 2 of IS: 383 |
| k) Sieve analysis - fine aggregate | Confirming to Grading zone I of table 4 of IS: 383 |
iii) Target Mean Strength for Mix Proportioning :
f'ck = fck + 1.65 S
= 50 + (1.65 x 5)
ft = 58.25 N/mm^2
Where,
f'ck - Target avg compressive strength @ 28 days
fck - Charac. compressive strength @ 28 days
S - Std Deviation
iv) Selection of w/c ratio :
According to exposure condition - severe ,from Table 5 of IS : 456 - 2000
Max w/c ratio - 0.45
Adopted w/c ratio - 0.36
0.36 < 0.45, hence ok
v) Selection of water content :
According to Table 2 of IS : 10262 - 2009, water content for 20mm aggregate = 186 ltrs ( range from 25 to 50 mm slump )
therefore, estimated water content = 186 + ( 6% *186 )
= 186+11.16
= 197.16 ltrs
As superplasticizer used, the water content can be reduced upto 20 %, as many trials water content is reduced by 29%
Hence water content = 197 * ( 100-29%)
= 197.16 * 0.71
= 140 ltrs ( round off )
vi ) Calculation of Cement Content :
Water cement ratio = 0.36
Cement content = 140 / 0.36
= 388 kg/mm^3
According to exposure condition - severe ,from Table 5 of IS : 456 - 2000
Min cement content = 320 kg/mm^3
therefore, 388 kg/mm^3 > 320 kg/mm^3. hence ok
vii) Proportion of Volume of Coarse aggregate and Fine aggregate Content :
According to table 3 of IS 10262:2009,
Volume of coarse aggregate to 20mm size aggregate and fine aggregate for water cement ratio is "0.60"
In present, the water-cement ratio is "0.36". Therefore the volume of coarse aggregate needs to be increased to decrease fine aggregate content.
As water-cement ratio is lowered by "0.10", the proportion of volume of coarse aggregate is increased by "0.02"( @ rate of +/- 0.01 for every +/- 0.05 change in water-cement ratio.
therefore, the corrected volume of coarse aggregate for water cement ratio of 0.36 is 0.62.
NOTE- If coarse aggregate is not of angular type, then also volume of coarse aggregate may be required to increase based on experience.
For pumpable concrete these values reduced by 10%
therefore, Volume of coarse aggregate= 0.62 x 0.9
= 0.558
Volume of fine aggreagtes = 1 - 0.558
= 0.442
viii) Mix calculations :
a) Volume of Concrete = 1m^3
b) Volume of Cement = ( Mass of cement / Specific gravity of cement ) * ( 1/1000)
= ( 388/3.15 ) * (1/1000)
= 0.12 m^3
c) Volume of Water = ( Mass of Water / Specific gravity of water) * ( 1/1000)
= ( 140/1) * (1/1000)
= 0.140 m^3
d) Volume of Chemical admixture = ( Mass of Chemical admixture / Specific gravity of admixture ) * ( 1/1000)
= ( 7.76/1.145) * (1/1000)
= 0.006 m^3
e) Volume of aggregate ( FA & CA ) = ( a-(b+c+d) )
where, a - Vol of concrete
b - Vol of cement
c - Vol of water
d - Vol of chemical admixture
e) Volume of aggregate = 1 - ( 0.12 + 0.140 + 0.006 )
= 0.68 m^3
f) Mass of coarse aggregate = e x Vol of coarse aggregate x Specific gravity of coarse aggregate x 1000
= 0.68 * 0.558 * 2.74 * 1000
= 1039 kg / m^3
g) Mass of fine aggregate = e x Vol of fine aggregate x Specific gravity of fine aggregate x 1000
= 0.68 * 0.442 * 2.74 * 1000
= 823.53 kg / m^3
ix) Trial Mix Proportion :
Cement = 388 kg/mm^3
Water = 140 kg/mm^3
Coarse aggregate = 1039 kg / m^3
Fine aggregate = 823 kg / m^3
Chemical admixture = 7.76 kg / m^3
Water Cement Ratio = 0.36
Trial Mix Ratio = Cement : Fine : Coarse
= 388 : 823 : 1039
= 1 : 2.12 : 2.67
Two conditions to be followed for mix design
x)The slump shall be measured and water content shall be adjusted for achieving the required slump on trial, the slump value is calculated by the slump cone test for concrete.The mix proportion shall be reworked for the actual water content.
xi) Two (or) more trails of variation of 10% of w/c ratio should be carried out and their value should be plotted out as per the graph denoted in the calculation of w/c ratio for the given target strength of the concrete.
Result :
The Trial mix ratio of M35 grade concrete with fly ash is 1 : 2.74 : 3.47 &
The Trial mix ratio of M50 grade concrete without Fly ash is 1 : 2.12 : 2.67, which is adopted from the step by step procedure of Mixed design