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 involves a process of preparation in which a mix of ingredients creates the required strength and durability for the concrete structure. Because every ingredient in the mix consists of different properties, Therefore concrete mix design can be stated as concrete mix in terms of cement: sand: aggregates. The design is done according to the requirements of concrete strength. So, we can achieve the desirable properties of concrete either it is in fresh stage or in hardened stage. The fresh concrete properties like workability, setting time and hardened concrete properties like compressive strength, durability etc. are attained surely by this method. Use of additives like admixtures, retarders etc. other than basic ingredients are used to improve the properties of mix. This project consist of two parts, the first part deals with the design of M35 grade cement with fly ash as a part of it and second part is the design of M50 grade concrete without fly ash.
OBJECTIVE:
The objective of this project is to produce a mix design for M35 grade concrete containing fly ash and M50 grade concrete. The mix will be prepared as per IS METHOD: Concrete mix proportioning guidelines from IS 10262:2009 and recommented guide lines from IS 10262:1982.
PART 1:To Calculate the Concrete Mix Design for M35 grade concrete with fly ash:
M35 grade concrete with Fly ash
STEP 1:STIPULATIONS FOR PROPORTIONING:
| a. | Grade designation : | M 35 |
| b. | Type of cement : | OPC 43 grade conforming to IS 8112 |
| c. | Type of mineral admixture : | Fly ash conforming to IS 3812 (part 1) |
| d. | Maximum nominal size of aggregate: | 20 mm |
| e. | Minimum cement content : | 320 kg/m^3 (From Table 5 of Is 456:2000-Exposure condition) |
| f. | Maximum water-cement ratio : | 0.45 (From table 5 of IS 456:2000-Exposure condition) |
| g. | Workability : | 100 mm (Slump value for 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 : | Superplasticizer |
STEP 2: TEST DATA FOR MATERIALS:
| a. | Cement used : | OPC 43 grade conforming to IS 8112 |
| b. | Specific gravity of cement : | 3.15 |
| c. | Fly ash : | Conforming to IS 3812 (Part 1) |
| d. | Specific gravity of fly ash : | 2.2 |
| e. | Chemical admixture : | Superplasticizer 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 : | 1.0 % | |
| h. | Free Surface moisture : | |
| Coarse aggregate : | Nil | |
| Fine aggregate : | Nil | |
| i. | Sieve Analysis : | |
| Coarse aggregate : |  |
|
| Fine aggregate : |  |
STEP 3: TARGET STRENGTH FOR MIX PROPORTIONING:
f'ck = fck + 1.65*S
Where, f'ck = Target average compressive strength at 28 days.
fck = Characteristic compressive strength at 28 days.
S = Standard deviation
From above Table 1 of IS 10262: 2009, Standard deviation(S) = 5N/mm^2
Therefore, Target strength = 35 + 1.65*5 = 35 + 8.25 = 43.25N/mm^2
i.e., Target mean strength = 43.25N/mm^2
STEP 4: SELECTION OF WATER-CEMENT RATIO:
- From Table 5 of IS 456:2000 for sever exposure, maximum water-cement ratio= 0.45
Based on experience, adopt water-cement ratio as 0.40
so, 0.40<0.45, Hence OK.
i.e. Water Cement ratio taken as 0.40
STEP 5: SELECTION OF WATER CONTENT:
- From Table 2 of IS 10262:2009,
maximum water content corresponding to 20mm size aggregate= 186 litre (for 25mm to 50mm slump range).
Note:- {For additional slump 3% may be added for every increase in 25mm to 50mm slump}
Here, for good pumpable concrete, Estimated water content for 100mm slump is required to increase
the additional 6% slump.
So., The Estimated water content for 100mm slump = 186 + 6/100^*186 = 186+11.16 = 197.16 litre = appro. 197 litre
i.e., Water Content(W) = 197 litre.
As a Superplasticizer is used, the water content can be reduce up to 20% and above,
Based on trials water content reduction of 29% is achived with plasticizer.
Hence, the arrived water content(W) = 197.16*0.8 = 157.728 litre = approx. 158 litre.
i.e., Required water content(w) = 158 litre.
STEP 6: CALCULATION OF CEMENT AND FLY ASH CONTENT:
- From Table 5 of IS 456:2000,
- Taken, Water-Cement Ratio (w/c) = 0.45
- Cementitious material (Cement + Fly ash ) Content = water content (w)/ water-cement ratio (w/c) =158/0.45=351.11kg = approx. 351kg/m^3
Here, For minimum Cement content for very severe Exposure condition = 340kg/m^3
So, here 351kg/m^3 > 340kg/m^3, Hence, OK.
Now, to proportion a mix containing fly ash the following steps are suggested:
- The percentage of fly ash needs to be decided based on project requirement and quality of materials.
- In some cases increase in cementitious material can be warranted. Increase in cementitious material content and its percentage may be based on experience and trial. (This example is with increase of 10% cementious material content)
- Cementitious material content = 351*1.10 = 386kg/m^3
- Water content = 158kg/m^3
- So, Water-Cement ratio = 158/386 = 0.40
- Fly ash@ 30% total cementitious material content = 386*30% = 115.8 kg/m^3
- Cement (OPC) = 386 - 115.8 = 270.2 kg/m^3
- Saving of Cement while using fly ash = 351 - 270.2 = 80.8 kg/m^3
- And, Fly ash being Utilized = 115.8 kg/m^3
- Hence, From The above Calculation we, get the Required value of Cementitious material, Cement and Fly ashis 386 kg/m^3, 351 kg/m^3, 115.8 kg/m^3 and the water-cement ratio is 0.40 respectively.
STEP 7: PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:
- From Table 3 of IS 10262:2009,
Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone ll) for water-cement
ratio of 0.5 = 0.62
In the present case the water cement ratio is 0.40
- Therefore, the volume of coarse aggregate need to be increased to decrease the fine aggregate content.
- As, water-cement ratio is lower by 0.10, 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 0.40 = 0.64
note:{ If coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be
increased suitably, based on experience.}
For pumpable concrete these values are reduced by 10%.
Therefore, volume of Coarse aggregate = 0.64*0.9 = 0.576 kg/m^3
Volume of Fine aggregate content = 1- 0.57 = 0.424 kg/m^3
- Hence, from the above calculation we get the Volume of Coarse aggregate and Fine aggregate are 0.576 kg/m^3 & 0.424 kg/m^3 respectively.
STEP 8: MIX. CALCULATION:
- The mix. Calculation per unit volume of concrete shall be as follows:
a.) Volume of concrete = 1m^3
b.) Volume of Cement = Mass of Cement /Specific gravity of cement^*1/1000
= 270.2 / 3.15^*1/1000
= 0.0857 m^3
c.) Volume of Fly ash = Mass of Fly ash / Specific. gravity of fly ash ^*1/1000
= 115.8/2.2^*1/1000
= 0.0526 m^3
d.) Volume of water = Mass of water / Specific gravity of water ^*1/1000
= 158/1^*1/1000
= 0.158 m^3
e.) Volume of Chemical admixture = Mass of chemical admixture / Specific gravity of admixture ^*1/1000
= 7.72/1.145^*1/100
= 0.006 m^3
Since, { Mass of chemical admixture = 2% of the cementious material = 386*2/100 =7.72 kg/m^3 )
f.) Volume of aggregate ( FA & CA ) = {a- (b+c+d+e)}
= { 1- (0.0857+0.0526+0.158+0.006)}
= {1- 0.302}
= 0.698 m^3
g.) Mass of Coarse aggregatre = f * Volume of coarse aggregate * Specific gravity of coarse aggregate *1000
= 0.698 * 0.576 * 2.74 * 1000
= 1101.61
= approx. 1101 kg/m^3
h.) Mass of Fine aggregate = f * Volume of Fine aggregate * Specific gravity of Fine aggregate *1000
= 0.698 * 0.424 * 2.74 *1000
= 810.90
= approx. 810 kg/m^3
STEP 9: MIX. PROPORTION:
- Cement = 270.2 kg/m^3
- Fly ash = 115.8 kg/m^3
- Water = 158 kg/m^3
- Fine aggregate = 810 kg/m^3
- Coarse aggregate = 1101 kg/m^3
- Chemical admixture = 7.72 kg/m^3
- Water-Cement ratio = 0.40
- Mix. Proportion by Weight = 1 : 2.99 : 4.07
STEP 10: The slump shall be measured and the water content and dosage of admixture shall be adjusted for achiving 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 10 shall be carried out and a graph between three water-cement ratios and corresponding strengths plotted to work out the mix proportions for the given target strength for field trials. However, durability shall be met.
PART 2:To Calculate the Concrete Mix Design for M50 grade concrete without fly ash:
M50 grade concrete without Fly ash
STEP 1:STIPULATIONS FOR PROPORTIONING:
| a. | Grade designation : | M 50 |
| b. | Type of cement : | OPC 53 grade conforming to IS 12269:1987 |
| c. | Maximum nominal size of aggregate: | 20 mm |
| d. | Minimum cement content : | 320 kg/m^3 (From Table 5 of Is 456:2000-Exposure condition) |
| e. | Maximum water-cement ratio : | 0.45 (From table 5 of IS 456:2000-Exposure condition) |
| f. | Workability : | 100 mm (Slump value for 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 : | Superplasticizer |
STEP 2: TEST DATA FOR MATERIALS:
| a. | Cement used : | OPC 53 grade conforming to IS 12269:1987 |
| b. | Specific gravity of cement : | 3.15 |
| c. | Specific gravity of fly ash : | 2.2 |
| d. | Chemical admixture : | Superplasticizer conforming to IS 9103 |
| e. | Specific gravity of : | |
| Coarse aggregate : | 2.74 | |
| Fine aggregate : | 2.74 | |
| f. | water absorption : | |
| Coarse aggregate : | 0.5 % | |
| Fine aggregate : | 1.0 % | |
| g. | Free Surface moisture : | |
| Coarse aggregate : | Nil | |
| Fine aggregate : | Nil | |
| h. | Sieve Analysis : | |
| Coarse aggregate : | |
|
| Fine aggregate : | |
STEP 3: TARGET STRENGTH FOR MIX PROPORTIONING:
f'ck = fck + 1.65*S
Where, f'ck = Target average compressive strength at 28 days.
fck = Characteristic compressive strength at 28 days.
S = Standard deviation
From above Table 1 of IS 10262: 2009, Standard deviation(S) = 5N/mm^2
Therefore, Target strength = 50 + 1.65*5 = 50 + 8.25 = 58.25N/mm^2
i.e., Target mean strength = 58.25N/mm^2
STEP 4: SELECTION OF WATER-CEMENT RATIO:
- From Table 5 of IS 456:2000 for sever exposure, maximum water-cement ratio= 0.45
Based on experience, adopt water-cement ratio as 0.40
so, 0.40<0.45, Hence OK.
i.e. Water Cement ratio taken as 0.45
STEP 5: SELECTION OF WATER CONTENT:
- From Table 2 of IS 10262:2009,
maximum water content corresponding to 20mm size aggregate= 186 litre (for 25mm to 50mm slump range).
Note:- {For additional slump 3% may be added for every increase in 25mm to 50mm slump}
Here, for good pumpable concrete, Estimated water content for 100mm slump is required to increase
the additional 6% slump.
So., The Estimated water content for 100mm slump = 186 + 6/100^*186 = 186+11.16 = 197.16 litre = appro. 197 litre
i.e., Water Content(W) = 197 litre.
As a Superplasticizer is used, the water content can be reduce up to 20% and above,
Based on trials water content reduction of 29% is achived with plasticizer.
Hence, the arrived water content(W) = 197.16*0.8 = 157.728 litre = approx. 158 litre.
i.e., Required water content(w) = 158 litre.
STEP 6: CALCULATION OF CEMENT CONTENT:
- From Table 5 of IS 456:2000,
- Taken, Water-Cement Ratio (w/c) = 0.45
- Cement Content = water content (w)/ water-cement ratio (w/c) =158/0.45=351.11kg = approx. 351kg/m^3
Here, For minimum Cement content for severe Exposure condition = 320kg/m^3
So, here 351kg/m^3 > 320kg/m^3, Hence, OK.
i.e., Required Cement Content (C) = 351 kg/m^3.
STEP 7: PROPORTION OF VOLUME OF COARSE AGGREGATE AND FINE AGGREGATE CONTENT:
- From Table 3 of IS 10262:2009,
Volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone ll) for water-cement
ratio of 0.5 = 0.62
In the present case the water cement ratio is 0.40
- Therefore, the volume of coarse aggregate need to be increased to decrease the fine aggregate content.
- As, water-cement ratio is lower by 0.10, 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 0.40 = 0.64
note:{ If coarse aggregate is not of angular type, then also the volume of coarse aggregate may be required to be
increased suitably, based on experience.}
For pumpable concrete these values are reduced by 10%.
Therefore, volume of Coarse aggregate = 0.64*0.9 = 0.576 kg/m^3
Volume of Fine aggregate content = 1- 0.57 = 0.424 kg/m^3
- Hence, from the above calculation we get the Volume of Coarse aggregate and Fine aggregate are 0.576 kg/m^3 & 0.424 kg/m^3 respectively.
STEP 8: MIX. CALCULATION:
- The mix. Calculation per unit volume of concrete shall be as follows:
a.) Volume of concrete = 1m^3
b.) Volume of Cement = Mass of Cement /Specific gravity of cement^*1/1000
= 351/ 3.15^*1/1000
= 0.111 m^3
c.) Volume of water = Mass of water / Specific gravity of water ^*1/1000
= 158/1^*1/1000
= 0.158 m^3
d.) Volume of Chemical admixture = Mass of chemical admixture / Specific gravity of admixture ^*1/1000
= 7.02/1.145^*1/1000
= 0.006 m^3
Since, { Mass of chemical admixture = 2% of the cementious material = 351*2/100 =7.02 kg/m^3 )
e.) Volume of aggregate ( FA & CA ) = {a- (b+c+d)}
= { 1- (0.111+0.158+0.006)}
= {1- 0.275}
= 0.725 m^3
f.) Mass of Coarse aggregatre = e * Volume of coarse aggregate * Specific gravity of coarse aggregate *1000
= 0.725 * 0.576 * 2.74 * 1000
= 1144.224
= approx. 1144 kg/m^3
g.) Mass of Fine aggregate = e * Volume of Fine aggregate * Specific gravity of Fine aggregate *1000
= 0.725 * 0.424 * 2.74 *1000
= 842.276
= approx. 842 kg/m^3
STEP 9: MIX. PROPORTION:
- Cement = 351 kg/m^3
- Water = 158 kg/m^3
- Fine aggregate = 842 kg/m^3
- Coarse aggregate = 1144 kg/m^3
- Chemical admixture = 7.02 kg/m^3
- Water-Cement ratio = 0.45
- Mix. Proportion by Weight = 1 : 2.39 : 3.25
STEP 10: The slump shall be measured and the water content and dosage of admixture shall be adjusted for achiving 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 10 shall be carried out and a graph between three water-cement ratios and corresponding strengths plotted to work out the mix proportions for the given target strength for field trials. However, durability shall be met.
- RESULTS:
- Mix Proportion by weight of M35 grade of concrete with fly ash is 1 : 2.99 : 4.07 and its water-cement ratio was found to be 0.40
- Mix Proportion by weight of M50 grade of concrete without fly ash is 1 : 2.39 : 3.25 and its water-cement ratio was found to be 0.45