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Sunday, November 27, 2016

Concrete Mix Design 16 MPA


Concrete Mix Design 16 MPa

(Fcr = 0.9Fc+2.3S

Fcr = Design Compressive Strength of Concrete

Fc = Characteristics compressive strength of Concrete

S = Standard Deviation

If the data of Standard deviation is not available then we will use this equation

Fcr = Fc+ 10MPa)

Fcr = 16+10
Fcr= 26MPa

Strength = 36 MPa
Cement = OPC ( Ordinary Portland Cement)
Fine Aggregate = Natural Sand and Crush sand
Fine Aggregate fine Modulus = 2.7 23
FA Specific Gravity  = 2.602
FA absorption = 2.60

(CA)Coarse Aggregate NMS = 19 mm
CA Specific Gravity =  2.619
Absorption = 1.123
Dry density = 1510 kg/m3

Step No 1

 Selection of Slump and compressive Strength
Slump = 80 mm
Compressive strength


Fcr = Fc + 10 MPa

Fcr = 16+10

Fcr= 26 MPa

Step 2
Selection of Coarse aggregate proportion

NMS = 19 mm
So from table 8 when Nominal Max size is 19 then CA Volume = 0.64

Weight of Coarse Aggregate = 0.64*1510 =  966.4

Step 3
Calculation of water Cement and Air Content
From  table 2 & 3 when NMS =19mm then
Water = 205 Kg
Air content = 2%
Selection of w/c ratio
From table 6 when compressive strength = 26 MPa
Then w/c = 0.57

Step 6
Calculation of Cement Content
Weight of Cement = 205/0.57   = 359 kg/m3
Step No 7
Calculation of  Volume of All mix Ratios
Volume of cement = Wt of Cement/ Specific gravity (C/γc)
                                =359/3.15*1000            =  0.1139638

Volume of  Water =  Mixing water / Sp g * 1000
                                
= 205/1*1000                     =0.205
                                                                                     

Absolute Volume of Coarse Aggregate = 966.4/2.619*1000  = 0.368899
                                                                                 
Volume of Air = 2/ 10000           =0.002                     
                                                                                    

Total Absolute volume             =0.6898628


Wt of Fine Aggregate
 =1- Summation of Volume of Cement, Water                                                      Coarse aggregate

              =1 – 0.6898628
              =0.310372
Wt of Fine Aggregate = Volume of Fine aggregate * Sp gravity*1000
                                      = 0.33501*2.602*1000
                                     = 871 kg
Trail Batch
So Finally we will get these weight for trail either in laboratory or batching Plant

Cement                 = 410 Kg
Water                    =164 kg
Coarse Aggregate  =966.4 kg
Fine Aggregate       =871 kg

40 MPA CONCRETE MIX DESIGN ACI 211


Example according to ACI  211


Strength = 40 MPa
Cement = OPC ( Ordinary Portland Cement)
Fine Aggregate = Natural Sand and Crush sand
Fine Aggregate fine Modulus = 2.7 23
FA Specific Gravity  = 2.602
FA absorption = 2.60

(CA)Coarse Aggregate NMS = 19 mm
CA Specific Gravity =  2.619
Absorption = 1.123
Dry density = 1510 kg/m3
Step No 1
Selection of Slump and compressive Strength
Slump = 80 mm
Compressive strength
There is no available data for s so we use this equation
Fcr = Fc + 10 MPa
Fcr = 40+10
Fcr= 50 MPa
Step 2
Selection of Coarse aggregate proportion
NMS = 19 mm
So from table 8 when Nominal Max size is 19 then CA Volume = 0.64

Weight of Coarse Aggregate = 0.64*1510 =  966.4

Step 3
Calculation of water Cement and Air Content

From  table 2 & 3 when NMS =19mm then

Water = 205 Kg

Air content = 2%

Selection of w/c ratio

From table 6 when compressive strength = 40 MPa

Then w/c = 0.40
Step 6
Calculation of Cement Content
Here we are using 2 percent super plasticize which reduces water content
Up to 20%
205*80% =  164
Weight of Cement = 164/0.41   = 410 kg/m3


Step No 7
Calculation of  Volume of All mix Ratios


Volume of cement = Wt of Cement/ Specific gravity (C/γc)
                                =410/3.15*1000                       =  0.1301

Volume of  Water =  Mixing water / Sp g * 1000
                                = 164/1*1000                =0.164
                                                                                    

Absolute Vol of Coarse Aggregate = 966.4/2.619*1000
                                                                                  = 0.368899

Volume of Air = 2/ 10000                                          =0.002
                                                                                     
Total Absolute volume                                              =0.66499

Wt of Fine Aggregate
                     =1- Summation of Volume of Cement, Water                                                                    Coarse aggregate

                     =1 – 0.66499
                     =0.33501



Wt of Fine Aggregate = Volume of Fine aggregate * Sp gravity*1000
                                      = 0.33501*2.602*1000
                                     = 871 kg

Trail Batch
So Finally we will get these weight for trail either in laboratory or batching Plant



Cement                  = 410 Kg
Water                     =164 kg
Coarse Aggregate  =966.4 kg

Fine Aggregate      =871 kg

CONCRETE MIX DESIGN ACI 211 STANDARD



Concrete Mix Design ACI 211 Method

Concrete Mix Design is the process of selecting suitable ingredients of concrete and determining their relative proportions to produce a concrete of certain minimum strength and durability as economically as possible.

Concrete Mix designer required a great knowledge so that if there any difficulty comes he handles this problem. He must aware these essential steps which are the basics of concrete mix Design in ACI 211 method.

Essentials steps of Concrete Mix Design ACI 211
1.     Determination of Slump
2.     Determine the Maximum Size of Aggregate
3.     Determination of Mixing water and Air Content
4.     Determine Water Cement Ratio
5.     Calculate Cement Content
6.     Estimation of Coarse Aggregate Content
7.     Estimation of Fine Aggregate Content
8.     Adjustment of Aggregate Moisture
9.     Adjustment of trail Batches

Step 1. Determination of Slump

To measure the consistency of concrete is called Slump
If we are making design first step is to determine the slump that for this project which slump value we will use.
Normally during selection of Slump we determine the how much distance from our batching plant to Our work area i.e. Bridge, Culvert or building. If the Distance is 30 mint so when at last step we will make trail then our slump must come according to the below mentioned table.

The slump ranges shown below apply when Vibrations used to consolidate the Concrete.

So from this table below first we select Slump according to our structure

Recommended Slump For Various Types of Construction
(Table 1)

Note. Slump can be increased when chemical admixture used but provided here two cases
1.     Admixture treated concrete has lower water cement ration. Because admixture reduce amount of water so in this case we can’t use higher w/c ratio.
2.     Use limited amount of admixture so that there is no segregation potential or excessive bleeding. Normally how much dosage we will use is mentioned on admixture.
Step 2
Determine the Maximum Size of Aggregate

According to ACI 211 large Nominal size of well graded aggregate have less voids than smaller sizes. So concrete with large Aggregate size require less mortar.
The Nominal maximum size of Aggregate should not exceed

1.     1/5th of Narrowest dimension between sides of forums,
2.     1/3rd the depth of slab,
3.     3/4th of  spacing between reinforced bars

When high strength concrete is required we must decree Nominal maximum size of Aggregate. So smaller the size greater will be the Strength of Concrete.

Step 3
Determination of Mixing Water and Air Content
The quantity of Water per unit volume of concrete required to produce a given slump is depends on
1.     The nominal maximum Size of Aggregate
2.     Particle Shape
3.     Grading of Aggregate
4.     Concrete Temperature
5.     The amount of Air entrained
6.     & use of Chemical admixture
Approximation of Mixing Water and Air Content  for different Sump and Aggregate Sizes
                ( Table 2 Non Air entrained)
    

The table shows three points
1.     The Maximum Size of Aggregate is increase the Amount of Water Decreases.
2.     As the slump increases Quantity of Water increase.
3.   This table shows that as the size of aggregate increases amount of air entrapped decreases 



Air Entrained Concrete
                               
                                    (Table 3)
    

You can here clearly observe that in Air entrained concrete we need less amount of water .

Air Content percentage in (Air Entrained Concrete) is different in three condition
                                     

So these table shows that greater the size of Aggregate lesser will be air entrained so good will be packing of aggregate.

Step 4
Determination of Water Cement Ratio

The w/c ratio is determined by following factors
1.     Strength
2.     Durability
3.     So there is relationship is present between w/c ratio and strength.

Note. Values are estimated average strength of concrete contains not more than 2 percent air for non air entrained concrete and 6 percent total air content for air entrained concrete..
                                          (Table 4)

This table shows that greater the w/c ration lesser will be the concrete strength.

Step 5
Calculate Cement Content

Selection of Cement is depends upon above two step
1.Estimated Water  content table 2 and table 4
2.Estimated w/c ratio Table 6

So weight of cement will be =    Weight of water/
                                                   Water to cement ratio
 



Maximum w/c ratio for concrete in Severe Exposure
                                (Table 5)

So this table shows that maximum amount of w/c ratio for these structures

Step 6
Estimation of Coarse Aggregate Content

Aggregate of essentially same the same Nominal maximum Size and grading will produce concrete of satisfactory workability when a given volume of coarse aggregate on a oven dry rodded basis.
Below table shows that for equal workability the volume of coarse aggregate in unit volume of concrete is dependent only on its Nominal maximum Size and the fines modulus of fine aggregate.
                                      (Table 6)

Step 7
Estimation of Fine Aggregate Content

        The weight of fine aggregate is simply the difference between the Weight of Fresh Concrete and the total weight of other ingredient.
Volume of Fine Aggregate=
   1 – Summation of Volume of Cement, Water, Air, Coarse Aggregate.

Weight of Fine Aggregate= ABS Volume of Fine Aggregate* Sp gravity                                         of Fine aggregate                                                                    
                                        (Table 7)


               First estimate weight of Fresh Concrete
Step 8
Adjustment For aggregate moisture

      When we take material from stock pile for design Moisture present in Aggregate. Without correcting this batch aggregate will be incorrect.
We correct the weight of Coarse aggregate with this formula

Adjusted Weight of Coarse Agg=Wt of C Agg*(1+%CA Moisture/100)
Adjusted Weight of Fine Agg=Wt of Fine Agg*(1+%FA Moisture/100)
Adjusted Weight of Water

   We have to correct the weight of Water which we are choosing for our design. Because Coarse and fine aggregate also has Absorption. For example we select water according to our design is 160 kg. But material also has absorption. So in this case or design need more water.
So to adjust Weight of water we need Value of Absorption and Percentage of Moisture. So we adjust weight of water with this formula.

  Adjusted Wt of Water    =     Wt. C.A. * (%Abs - %MC)/100=(A)
                                                 WT. F.A. X (%Abs - %MC)/100=(B)



Adjusted Weight of Water = 160+A+B

Step 9
Trail Batch Adjustment

The calculated mixture proportions should be checked by means of  trail batches prepared and tested accordance with  ASTM C 192. Only Sufficient water should be used to produce the required slump



Example of Concrete Mix Design

(Fcr = 0.9Fc+2.3S

Fcr = Design Compressive Strength of Concrete

Fc = Characteristics compressive strength of Concrete

S = Standard Deviation

If the data of Standard deviation is not available then we will use this equation

Fcr = Fc+ 10Mpa)