Project on Concrete Mix Design for various grades of Concrete
AIM:
To calculate the concrete mix design for M35 grade concrete with fly ash and M50 grade concrete without fly ash.
INTRODUCTION: Concrete mix design is a procedure of selecting the suitable ingredients of concrete and their relative proportions with an objective to prepare concrete of certain minimum strength, desired workability and durability as economically as possible. The design is done according to the requirements of concrete strength. So, we can achieve the desirable properties of concrete either in the fresh stage or hardened stage. This project consists of two parts, the first one is designed for M35 grade concrete with fly ash and second one is designed for M50 grade concrete without fly ash.
OBJECTIVE: The objective of this project is to achieve the desired workability in the plastic stage to achieve the desired minimum strength in the hardened stage, to achieve the desired durability in given environmental conditions and to produce concrete as economically as possible.
The main objective of this project is to determine the mix design for M35 grade concrete with fly ash and M50 grade concrete without fly ash as per IS method.
CODE USED : IS 10262:2009, IS 456 :2000
EQUATIONS USED:
1. Target means strength
`"f"_t="f"_"ck" + 1.65s`
where
`"f"_t` = Target average compressive strength at 28 days.
`"f"_"ck"` = Characteristic compressive strength at 28 days.
s = Standard deviation
2. Cement content
Cement Content = `"Water Content"/"Water-Cement Ratio"`
3. Volume calculations
- Volume of concrete.
- Volume of cement = `"Mass of cement"/"Specific gravity of cement" xx 1/1000`
- Volume of water = `"Mass of water"/"Specific gravity of water" xx 1/1000`
- Volume of chemical admixture = `"Mass of admixture"/"Specific gravity of admixture" xx 1/1000`
- volume of all in aggregate = a-(b+c+d)
- Mass of coarse aggregate = `e xx "Volume of course aggregate" xx "Specific gravity of Fine aggregate" xx 1000`
- Mass of fine aggregate = `e xx "Volume of fine aggregate" xx "Specific gravity of Fine aggregate" xx 1000`
PART A - Calculate the concrete mix design for M35 grade concrete with fly ash
STEP 1 - Stipulations for proportioning
i) Grade designation = M35.
ii) Type of cement = OPC 53 grade confirming to IS 8112.
iii) Type of mineral admixture = Fly ash confirming to IS 3812. (Part 1)
iv) Maximum Nominal size of aggregate = 20mm.
v) Minimum cement content = 320 kg/`m^3` (From table 5 os IS 456:2000 - exposure condition)
vi) Maximum water cement ratio = 0.45 (From table 5 os IS 456:2000 - exposure condition)
vii) Workability = 100mm (Slump value for pumpable concrete)
viii) Exposure condition = Severe (For reinforced concrete)
ix) Method of concrete placing = Pumping
x) Degree of supervision = Good
xi) Type of aggregate = Crushed Angular Aggregate
xii) Maximum cement content = 450 kg/`m^3`
xiii) Chemical admixture = Super plasticizer
STEP 2 - Test data for material
i) Cement used = OPC 53 grade confirming to IS 8112.
ii) Specific gravity of cement = 3.15
iii) Fly ash = Confirming to IS 3812 (Part 1)
iv) Specific gravity of fly ash = 2.2
v) Chemical admixture = Superplasticizer conforming to IS 9103
vi) Specific gravity of coarse aggregate = 2.74
vii) Specific gravity of fine aggregate = 2.74
viii) Water absorption of coarse aggregate = 0.5%
ix) Water absorption of fine aggregate=1.0%
x) Free surface moisture of coarse aggregate = NIL
xi) Free surface moisture of fine aggregate =NIL
xii) Sieve analysis of coarse aggregate = conforming to table 2 IS 383
xiii) Sieve analysis of fine aggregate = Zone 2 = conforming to table 4 IS 383
STEP 3 - Target strength for mix proportioning
`"f"_t="f"_"ck" + 1.65s`
where
`"f"_t` = Target average compressive strength at 28 days.
`"f"_"ck"` = Characteristic compressive strength at 28 days.
s = Standard deviation
From table 1 of IS 10262:2009, standard deviation = 5N/`mm^2`
`"f"_t="f"_"ck" + 1.65s`
=`35 + (1.65 xx5)`
= 43.25 N/`mm^2`
Target mean strength = 43.25 N/`mm^2`
STEP 4 - Selection of water cement ratio
From table 5 of IS 456:2000, for severe exposure,
maximum water cement ratio = 0.45
Based on experience, Adopted water cement ratio= 0.44
0.44 < 0.45, Hence ok.
STEP 5 - Selection of water content
From table 2 of IS 10262 : 2009, Maximum water content for 20mm aggregate = 186 liters ( For 25 to 50 mm slump range)
clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm. So 6% to be added to it.
Estimated water content for 100mm slump = `186 + (6/100) xx 186`
= 197 liters.
As a superplasticizer is used , the water content can be reduced 20% and above. Based on trials, water content reduction of 20% is achieved with plasticizers.
Hence, the arrived water content = `197 - (197 xx(20/100))`
= 158 liters.
Water required = 158 litres
STEP 6 - Calculation of cement content
Adopted water cement ratio = 0.44
Cementitious material (cement + fly ash ) content = water content/ water cement ratio
= 158/ 0.44
= 359 kg/`m^3`
The cementitious content has to be increased in order to attain good workability and strength. The increment required is determined on the basis of experience and research.
Here, we are increasing cementitious content by 10%.
Final cementitious content = 359 `xx`1.10
= 395 kg
From table 5 of IS 456: 2000, minimum cement content for severe exposure condition = 320 kg
395 kg/`m^3`> 320 kg/`m^3`
Hence ok .
Cementitious material content =395
New water cement ratio = `158/395`
= 0.4
Fly ash content is taken as 30 % of the total cementitious content = `395 xx0.30`
= 118.5 kg/`m^3`~ 118 kg/`m^3`
Cement required = cementitious content - Fly ash
= 395 - 118
= 277 kg/`m^3`
Cement quantity saved due to fly ash addition = 350 - 277
= 73 kg/`m^3`
STEP 7 - Proportion of volume of coarse aggregate and fine aggregate:
From table 3 of IS 10262: 2009, volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (ZONE -2) for water cement ratio is 0.50 = 0.62
In the present case, the water cement ratio is 0.44. Therefore, volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
As water cement ratio is lower by 0.06, the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every +/- 0.05 change in water cement ratio).
Therefore, corrected volume of coarse aggregate for the water cement ratio of 0.44 = 0.632
For pumpable concrete these values are reduced by 10%.
Volume of coarse aggregate = 0.632 `xx` 0.9
= 0.568
Volume of fine aggregate content = 1- 0.568
= 0.431
So , volume of coarse aggregate = 0.568
Volume of fine aggregate = 0.431
STEP 8 - MIX CALCULATION:
The mix calculations per unit volume of concrete shall be as follows:
- Volume of concrete = 1 `m^3`
- Volume of cement = `"Mass of cement"/"Specific gravity of cement" xx 1/1000`
= `277/3.15` `xx` `1/1000`
= 0.087 `m^3`
3.Volume of fly ash = `"Mass of fly ash"/"Specific gravity of fly ash " xx 1/1000`
= `118/2.2` `xx` `1/1000`
= 0.053 `m^3`
4.Volume of water = `"Mass of water"/"Specific gravity of water" xx 1/1000`
= `158/1` `xx` `1/1000`
= 0.158 `m^3`
5.Volume of chemical admixture = `"Mass of admixture"/"Specific gravity of admixture" xx 1/1000`
= `7.6/1.145` `xx` `1/1000`
= 0.006 `m^3`
6.Volume of aggregate (fine and coarse aggregate) = (a-(b+c+d+e))
= (1-(0.087+ 0.053+ 0.158+0.006))
= 0.696 `m^3`
7.Mass of coarse aggregate = f `xx` volume of coarse aggregate `xx` specific gravity of coarse aggregate `xx` 1000
= 0.696 `xx` 0.568 `xx` 2.74 `xx`1000
= 1077 kg/`m^3`
Mass of fine aggregate = f `xx` volume of coarse aggregate `xx` specific gravity of coarse aggregate `xx` 1000
= 0.696 `xx` 0.431`xx` 2.74 `xx` 1000
= 822 kg/`m^3`
STEP 9 - Mix proportion:
Cement = 277 kg/`m^3`
Fly Ash = 118 kg/`m^3`
Water = 158 kg/`m^3`
Fine aggregate = 822 kg/`m^3`
Coarse aggregate = 1077 kg/`m^3`
Chemical admixture = 7.18 kg/`m^3`
Water cement ratio = 0.4 (lowest water cement ratio is selected)
Mix proportion by weight = cement : fine aggregate : coarse aggregate
= 277 : 822 : 1077
= 1 : 2.08 : 2.72
STEP 10 - The slump shall be measured , the water content and dosage of admixture shall be adjusted for achieving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirements.
STEP 11 - Two more trials having variation of 10 % of water cement ratio in clause x shall be carried out and a graph between three water cement ratio and corresponding strength shall be plotted to work out the mix proportion for the given target for field trials. However , durability shall be met.
PART B - Calculate the concrete mix design for M50 grade concrete without fly ash
STEP 1 - Stipulations for proportioning
i) Grade designation = M50.
ii) Type of cement = OPC 53 grade conforming to IS 8112.
iii) Maximum Nominal size of aggregate = 20mm.
iv) Minimum cement content = 320 kg/`m^3` (From table 5 os IS 456:2000 - exposure condition)
v) Maximum water cement ratio = 0.45 (From table 5 os IS 456:2000 - exposure condition)
vi) Workability = 100mm (Slump value for pumpable concrete)
vii) Exposure condition = Severe (For reinforced concrete)
viii) Method of concrete placing = Pumping
ix) Degree of supervision = Good
x) Type of aggregate = Crushed Angular Aggregate
xi) Maximum cement content = 450 kg/`m^3`
xii) Chemical admixture = Super plasticizer
STEP 2 - Test data for material
i) Cement used = OPC 53 grade conforming to IS 8112.
ii) Specific gravity of cement = 3.15
iii) Chemical admixture = Superplasticizer conforming to IS 9103
iv) Specific gravity of coarse aggregate = 2.74
v) Specific gravity of fine aggregate = 2.64
vi) Water absorption of coarse aggregate = 0.5%
vii) Water absorption of fine aggregate=1.0%
viii) Free surface moisture of coarse aggregate = NIL
ix) Free surface moisture of fine aggregate =NIL
x) Sieve analysis of coarse aggregate = conforming to table 2 IS 383
xi) Sieve analysis of fine aggregate = Zone 2 = conforming to table 4 IS 383
STEP 3 - Target strength for mix proportioning
`"f"_t="f"_"ck" + 1.65s`
where
`"f"_t` = Target average compressive strength at 28 days.
`"f"_"ck"` = Characteristic compressive strength at 28 days.
s = Standard deviation
From table 1 of IS 10262:2009, standard deviation = 5N/`mm^2`
`"f"_t="f"_"ck" + 1.65s`
`= 50 + (1.65 xx5)`
= 58.25 N/`mm^2`
Target mean strength = 58.25 N/`mm^2`
STEP 4 - Selection of water cement ratio
From table 5 of IS 456:2000, for severe exposure,
maximum water cement ratio = 0.45
Based on experience, Adopted water cement ratio= 0.44
0.44 < 0.45, Hence ok.
STEP 5 - Selection of water content
From table 2 of IS 10262 : 2009, Maximum water content for 20mm aggregate = 186 liters ( For 25 to 50 mm slump range)
clause 4.2 suggests increasing of 3% of water content for every extra 25mm slump from 50mm. So 6% to be added to it.
Estimated water content for 100mm slump = `186 + (6/100) xx 186`
= 197 liters.
As a superplasticizer is used , the water content can be reduced 20% and above. Based on trials, water content reduction of 20% is achieved with plasticizers.
Hence, the arrived water content = `197 - (197 xx(20/100))`
= 158 liters.
Water required = 158 liters
STEP 6 - Calculation of cement content
Adopted water cement ratio = 0.44
Cement content = water content/ water cement ratio
= 158/ 0.44
= 359 kg/`m^3`
From table 5 of IS 456: 2000, minimum cement content for severe exposure condition = 320 kg
359 kg/`m^3`> 320 kg/`m^3`
Hence ok .
Cement required =359 kg/`m^3`
STEP 7 - Proportion of volume of coarse aggregate and fine aggregate:
From table 3 of IS 10262: 2009, volume of coarse aggregate corresponding to 20mm size aggregate and fine aggregate (ZONE -2) for water cement ratio is 0.50 = 0.62
In the present case, the water cement ratio is 0.44. Therefore, volume of coarse aggregate needs to be increased to decrease the fine aggregate content.
As water cement ratio is lower by 0.06, the proportion of volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every +/- 0.05 change in water cement ratio).
Therefore, corrected volume of coarse aggregate for the water cement ratio of 0.44 = 0.632
For pumpable concrete these values are reduced by 10%
Volume of coarse aggregate = 0.632 `xx` 0.9
= 0.568
Volume of fine aggregate content = 1- 0.568
= 0.431
So , volume of coarse aggregate = 0.568
Volume of fine aggregate = 0.431
STEP 8 - MIX CALCULATION:
The mix calculations per unit volume of concrete shall be as follows:
- Volume of concrete = 1 `m^3`
- Volume of cement = `"Mass of cement"/"Specific gravity of cement" xx 1/1000`
= `359/3.15` `xx` `1/1000`
= 0.114`m^3`
4.Volume of water = `"Mass of water"/"Specific gravity of water" xx 1/1000`
= `158/1` `xx` `1/1000`
= 0.158 `m^3`
5.Volume of chemical admixture = `"Mass of admixture"/"Specific gravity of admixture" xx 1/1000`
= `7.6/1.145` `xx` `1/1000`
= 0.006 `m^3`
6.Volume of aggregate (fine and coarse aggregate) = (a-(b+c+d))
= (1-(0.114+ 0.158+0.006))
= 0.722 `m^3`
7.Mass of coarse aggregate = f `xx` volume of coarse aggregate `xx` specific gravity of coarse aggregate `xx` 1000
= 0.722 `xx` 0.568 `xx` 2.74 `xx`1000
= 1123 kg/`m^3`
Mass of fine aggregate = f `xx` volume of coarse aggregate `xx` specific gravity of coarse aggregate `xx` 1000
= 0.722 `xx` 0.431`xx` 2.64 `xx` 1000
= 821 kg/`m^3`
STEP 9 - Mix proportion:
Cement = 359 kg/`m^3`
Water = 158 kg/`m^3`
Fine aggregate = 821 kg/`m^3`
Coarse aggregate = 1123 kg/`m^3`
Chemical admixture = 7.18 kg/`m^3`
Water cement ratio = 0.44 (lowest water cement ratio is selected)
Mix proportion by weight = cement : fine aggregate : coarse aggregate
= 359 : 821 : 1123
= 1 : 2.28 : 3.12
STEP 10 - The slump shall be measured , the water content and dosage of admixture shall be adjusted for achieving the required slump on trial. The mix proportion shall be reworked for the actual water content and checked for durability requirements.
STEP 11 - Two more trials having variation of 10 % of water cement ratio in clause x shall be carried out and a graph between three water cement ratio and corresponding strength shall be plotted to work out the mix proportion for the given target for field trials. However , durability shall be met.
RESULTS:
Mix proportion by weight of M35 grade of concrete with fly ash is 1: 2.08 : 2.72 and its water cement ratio was found to be 0.4.
Mix proportion by weight of M50 grade of concrete without flyash is 1:2.28 : 3.12 and its water cement ratio was found to be 0.44.