Saturday, December 17, 2016

Concrete Mix Design Full procedure from Basic to High Level




Concrete Mix Design
       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.
Here we will explain all steps step by step according to ACI 211. You should read this to clear your every point about Concrete Mix Design . Concrete Mix Design ACI 211  (Note: This process we will explain from beginning so any one who want to make concrete design first time so it can help more .
1.     Selection of Source
2.     Quality tests of  Material (Aggregate, Sand and water)
3.     Determinations of  Slump
4.     Calculation of  concrete mix design and final take batch weight
5.     Trial of Concrete Mix Design
6.     Selection of  final suitable design

1.     Selection of Source
     In this step Designer first see from where he will take material for Concrete Mix Design. He will confirm about below mentioned two points with his Project Manager or Owner of Company that from where company will take material. There are two steps
A.   Buy some near source for Concrete Mix Design.
B.   Take Material from other Company Crusher
A.    Buy some near source for Concrete Mix Design
           In this case you have to visit near companies which are working around your project to meet with their Material Engineer. You ask above out that from where they are taking material for concrete work. You have to conform about location of aggregate Source and natural sand from so he will give you the location that where the source is present. It will give you a great help otherwise it will take a great time to search this.
     Now you will visit this place with Consultant and will take simple from this place and will do quality tests for this source.

2.     Quality tests of  Material (Aggregate, Sand and water)

     After taking material from source you have to make Quality tests some test you will perform inside lab and some from independent lab. Independent lab is outside lab in the city where they have all the apparatus especially for cement, steel if your company doesn’t have apparatus you have to perform these from outside.
       List of Quality test which will you perform from inside and outside lab. The complete procedure of these tests is present in link below of each test
Inside your Company Lab

1.     Sieve analysis of course and fine aggregate
2.     Dry rodded unit weight
3.     Los Angles abrasion test
4.     Soundness of Course and fine Aggregate
5.     Specific Gravity of course and fine aggregate
6.     Thin and elongated for course aggregate
7.     Combined gradation of course aggregate
8.     Combined gradation of fine aggregate
9.     Clay lumps and friable particles
10.            Combined Specific Gravity and Absorption
Outside Independent Lab
 For these test you have to give material to independent lab they will perform all these test. After 3 days they will give result of these tests
1.     Chemical Analysis of water
2.     Petrographic examination of course aggregate
3.     Chemical analysis of course aggregate
4.     Organic impurities in fine aggregate
5.     Potential alkali reactivity chemical test method on course aggregate
6.      Potential alkali reactivity chemical test method on course aggregate
3.     Determination of maximum size of aggregate
You are making design you first determine that which will be the maximum size of aggregate. The maximum size of aggregate depends upon three factors
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
So you calculate this by yourself and your project manager will also help you in determining of maximum size of Aggregate.


4.     Determination of Slump
The third main important point in concrete mix design is determination of slump.


So this is the required list of slump according to your structure you will take the value of slump from this table. Suppose you structure is Reinforced foundation wall and footing in this case required slump is 75 mm. So when you will make trail in your lab in this case you see one point

That how much is the distance between from your concrete batching plant and bridge or building. If distance is of 30 minutes so when you will make trail in laboratory in concrete mixture you must bring 75mm slump after 30 minutes. So in future when your concrete mixture will go from batching plant to Bridge it will com 75mm.
 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.


5.     Water/cement ratio

During trial in lab slump can be control by water to cement ratio. You start
Your trail from w/c  0.35 w/c
If you are making trial in lab after 30 minutes slump is coming 50 mm in this case you have to increase water to cement ratio to 0.36 if in 0.36 again slump is coming 65mm. now you have to increase your w/c 0.37 upto 0.45 or more. When you achieve slump 75mm then at this point you take simple of concrete for compressive strength for 3, 7 and 28 days. So if after 28 days strength is coming .
      When you achieve slump 75mm then at this point you take simple of concrete     for compressive strength for 3, 7 and 28 days. So if after 28 days strength is coming 100% Then you can submit your design for approval in consultant.
6.     Calculation of Concrete mix Design
For this step I will give a practical concrete mix design excel sheet which we have made in our lab so that it will give to reader a great help when he will make practical.
We will explain only one trail other trail you can do by yourself easily.

So you calculate by yourself with calculator 
These are five sheets of calculation  which excel format you can take also from me or you can take from your company Material Engineer.

Calculation Sheet No 1
In this we calculate
1. w/c ratio .
2. Water which we will get by multiplying cement with w/c ratio


















Calculation Sheet No 2
In this sheet we will so calculation of
1. Estimated Strength
2. Air Content Percentage
3. Dry Rodded unit Volume of Course Aggregate
4. And weight of course Aggregate



Calculation Sheet No 3
In this sheet we will do calculation for to determine volume of
1. Cement
2. Water
3. Absolute Volume of Course Aggregate
4. Volume of Air
5. Volume of Admixture
6. Absolute Volume of Fine Aggregate
5.  Weight of Fine Aggregate



In this sheet we will adjust weight of
1. Course Aggregate
2. Fine Aggregate
3. Water
  Note ( We will adjust weight because in Aggregates has moisture and absorption so we will take value of this all after this we will get accurate weight of Course and Fine Aggregate and Water

4. At last we will get the Final weight  from aur above calculation
Cement
Water
3/4 " Size
3/8 " Size
Fine Aggregate
Admixture


     







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