Project on Concrete Mix Design for various grades of Concrete
Ans 1-
Mix Design M35 Grade Concrete with Fly Ash/GGBS – IS10262
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 the method of finding the precise proportion of cement, sand and aggregates for concrete to achieve the target strength in structures, 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.
EQUATIONS USED:
1)Target mean strength
f’ck =fck + 1.65s
Where
- f’ck = target average compressive strength at 28 days
- fck = characteristics compressive strength at 28 days, and
- s = standard deviation
2)Cement content
Cement content = water content / water-cement ratio
3) Volume Calculations
- (a) Volume of concrete
- (b) Volume of cement = [Mass of cement] / [Specific Gravity of Cement] x 1/1000
- (c) Volume of water = [Mass of water] / [Specific Gravity of water] x 1/1000
- (d)Volume of chemical admixture = [Mass of admixture] / [Specific Gravity of admixture] x 1/1000
- (e) Volume of all in aggregate =[a-(b+c+d)]
- (f) Mass of coarse aggregate= e x Volume of Coarse Aggregate x Specific Gravity of Fine Aggregate x 1000
- (g) Mass of fine aggregate= e x Volume of Fine Aggregate x Specific Gravity of Fine Aggregate x 1000
PART 1:To Calculate the Concrete Mix Design for M35 grade concrete with fly ash:
| 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
Materials must be tested to find its below physicals and chemical properties. Standard values are considered 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 concrete may vary depending on the quality of the material, the mixing method and the construction procedures. Therefore the target strength (Fck) must be greater than the required strength of the concrete (fck).
Table 1 of IS456 gives the standard deviation value (s) for different grade concretes.
| 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 ratios for different grades of concrete are given in Table 5-IS456. You can reduce the water-cement ratio based on your needs.
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 |
The water content above is for a slump of 25 to 50 mm, but according to the specification our concrete requires a slump of 100 mm. Therefore, to get the desired slump, the water content must be increased. Clause 4.2 of IS1026 recommends increasing the water content by 3% to obtain an additional 25 mm slump. Therefore, to obtain a slump of 50 mm in addition to our concrete, the water content must be increased by 6%.
| Water-content for 100mm Slump | =186+(0.06*186) |
| =197.16 L |
As we use super plasticizers we can reduce the water content to gain strength in the concrete
| 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 flying ash is used, the amount of cementitious content (cement + fly ash) should be increased to get good performance and strength. The percentage of increasing cementitious content depends on 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 |
# Design mix of M50 grade concrete without using fly ash
Parameters for mix design M50
Grade Designation = M-50
Type of cement = O.P.C-43 grade
Brand of cement = Vikram ( Grasim )
Admixture = Sika [Sikament 170 ( H ) ]
Fine Aggregate = Zone-II
Sp. Gravity
Cement = 3.15
Fine Aggregate = 2.61
Coarse Aggregate (20mm) = 2.65
Coarse Aggregate (10mm) = 2.66
Minimum Cement (As per contract) =400 kg / m3
Maximum water cement ratio (As per contract) = 0.45
Mix Calculation: –
1. Target Mean Strength = 50 + ( 5 X 1.65 ) = 58.25 Mpa
2. Selection of water cement ratio:-
Assume water cement ratio = 0.35
3. Calculation of water
Approximate water content for 20mm max. Size of aggregate = 180 kg /m3 (As per Table No. 5 , IS : 10262 ). As plasticizer is proposed we can reduce water content by 20%.
Now water content = 180 X 0.8 = 144 kg /m3
4. Calculation of cement content:-
Water cement ratio = 0.35
Water content per cum of concrete = 144 kg
Cement content = 144/0.35 = 411.4 kg / m3
Say cement content = 412 kg / m3 (As per contract Minimum cement content 400 kg / m3 )
Hence O.K.
5. Calculation for C.A. & F.A.: [ Formula’s can be seen in earlier posts]-
Volume of concrete = 1 m3
Volume of cement = 412 / ( 3.15 X 1000 ) = 0.1308 m3
Volume of water = 144 / ( 1 X 1000 ) = 0.1440 m3
Volume of Admixture = 4.994 / (1.145 X 1000 ) = 0.0043 m3
Total weight of other materials except coarse aggregate = 0.1308 + 0.1440 +0.0043 = 0.2791 m3
Volume of coarse and fine aggregate = 1 – 0.2791 = 0.7209 m3
Volume of F.A. = 0.7209 X 0.33 = 0.2379 m3 (Assuming 33% by volume of total aggregate )
Volume of C.A. = 0.7209 – 0.2379 = 0.4830 m3
Therefore weight of F.A. = 0.2379 X 2.61 X 1000 = 620.919 kg/ m3
weight of F.A. = 621 kg/ m3
Therefore weight of C.A. = 0.4830 X 2.655 X 1000 = 1282.365 kg/ m3
Say weight of C.A. = 1284 kg/ m3
Considering 20 mm: 10mm = 0.55: 0.45
20mm = 706 kg .
10mm = 578 kg .
Hence Mix details per m3
Increasing cement, water, admixture by 2.5% for this trial
Cement = 412 X 1.025 = 422 kg
Water = 144 X 1.025 = 147.6 kg
Fine aggregate = 621 kg
Coarse aggregate 20 mm = 706 kg
Coarse aggregate 10 mm = 578 kg
Admixture = 1.2 % by weight of cement = 5.064 kg.
Water: cement: F.A.: C.A. = 0.35: 1: 1.472: 3.043
Result
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 and it's water cement ratio was found to be .45
Mix Ratio of M50 Grade of concrete by weight is Water: cement: F.A.: C.A. = 0.35: 1: 1.472: 3.043 and it's water cement ratio was found to be .35