Become Concrete Master - Concrete Mix Designing

[Prakash Joshi]

The article is very informative for the civil engineers.In my opinion some modifications are required at some places.
1) for cement testing sieve test is replaced by air permeability test
2) for concrete mix design charts are ready which can be referred to.
Over all article is good.

 

[Consoles]

Thanks a lot mr dnyan deshmukh for your posts on concrete mix designs

 

[Pk27feb]

Chemical Requirements of Cement as per IS Codes

Types of Cements	OPC 33 Grade	OPC 43 Grade	OPC 43S Grade	OPC 53 Grade	OPC 53S Grade	SRC	PPC (Flyash​ Based)	PSC
IS Code​	269​	269​	269​	269​	269​	12330​	1489 part 1​	455​
Ratio of percentage of lime to percentage of silica , aluminium and iron oxide, when calculated by formula Cao - 0.7 SO[SUB]3[/SUB] --------------------------------------------- 2.8 SiO[SUB]2 [/SUB]+ 1.2 Al2O[SUB]3[/SUB] + 0.65 FeO[SUB]3[/SUB]	0.66 to 1.02​	0.66 to 1.02​	0.80 to 1.02​	0.80 to 1.02​	0.80 to 1.02​	0.66 to 1.02​	-​	-​
Ratio of percentage of Aluminium to that of iron oxide, Min	0.66​	0.66​	0.66​	0.66​	0.66​	-​	-​	​
Insoluble residue, percentage by mass, Max	5​	5​	2​	5​	2​	4​	4 (100-x) -------------- x + 100​	4​
Magnesia, percentage by mass, Max	6​	6​	5​	6​	5​	6​	6​	8​
Total sulphar content calculated as sulphuric acnhydride (SO3). Percentage by mass, Max.	3.5​	3.5​	3.5​	3.5​	3.5​	2.5​	3​	3​
Loss on ignition, percentage by mass, max	5​	5​	4​	4​	4​	5​	5​	5​
Chloride content, percentage by mass, Max	0.1​	0.1​	0.1​	0.1​	0.1​	​	​	​
Chloride content, percentage by mass, Max (for prestress structures)	0.05​	0.05​	0.05​	0.05​	0.05​	​	​	​

​

where “ x” is the fly ash content used in the production of cement

Note in IS code for Alkali Content
Alkali aggregate reaction have been noticed in aggregates in some parts of region. On large and important jobs where the concrete is likely to be exposed to humid atmosphere or wetting action, it is advisable that the aggregate be tested for alkali aggregate reaction. in the case of reactive aggregates, the use of cement with alkali content below 0.6 percent expressed as sodium oxide (Na[SUB]2[/SUB]O + 0.658 K[SUB]2[/SUB]O), is recommended. where, however such cements are not available, use of alternative means me be resorted to for which a reference may be made to appropriate provisions on durability in the concrete codes. If desired by the purchaser, the manufacturer should carry out the test for alkali content.

Sir I don't understand about what is alkali reaction. Please explain in easy way. And how does it work .

 

[Dnyan Deshmukh]

Sir I don't understand about what is alkali reaction. Please explain in easy way. And how does it work .

I do not have much idea about how chemical reactions do form but below article might help you in understanding it in more better way.

Alkali-Aggregate Reaction

Alkali-Aggregate Reaction

www.cement.org

 

[Pk27feb]

Aggregates

In general aggregates we use in concrete are inert and do not play in role in gaining strength for produced concrete.

It contribute to more than 75% of volume in normal concrete mixes (Special type may have less aggregates depends on their use and other properties)

From durability point of view the Quality of aggregate plays important role and one should not ignore it.

As per the IS 383, aggregates are classified into 3 categories base on their size.

Fine Aggregates : Aggregates which passe through 4.75mm sieve and contains less amount of coarse as specified in code are said to be Fine Aggregates.

For Fine aggregates IS code classified them further into 4 Zones, Specifications are given in Table No 4, Clause 4.3

We can find the FA (Fine Aggregates) belongs to which Zone by doing the sieve analysis.
To analyze the zone of FA, we should check the Cumulative % passing of 600 micron sieve and compare it with the zone table (You cant find this info anywhere else, its required close observation on things to determine, now open code and do observe table closely to understand it)

FA can be any of following as per IS Code

Natural Sand - FA resulting from natural disintegration of rock and which has been deposited by streams or glacial agencies.

Crush Stone Sand - It is produced by crushing hard stones.

Crush Gravel Sand - produced by crushing natural gravels.

Coarse Aggregates (CA) : Aggregates most of which retained on 4.75mm IS Sieve and contains finer materials allowed as per IS Code are termed as Coarse Aggregates.

Coarse aggregates may be described as

Uncrushed gravels or stone which results from natural disintegration of rock.

Crush gravel or stone when it result from crushing of gravels or hard stone.

partial crushed gravels or stone, when it is product of above 2.

All in Aggregates :

It is composed of fine aggregates and coarse aggregate.

State the order of IS SIEVE for fine and course aggragete. And also the limit ℅ of sieve analysis of 10mm and 20mm. In what order will sieve be placed.

 

[Pk27feb]

Admixtures

Admixtures are added to modify one or more of the properties of concrete in the plastic and hardened states. Admixtures used in concrete should satisfy the requirement of IS 9103.

Admixtures are of four types:

1. Accelerating admixtures

2. Retarding admixtures

3. Water reducing admixture and

4. Air entraining admixtures

Dear sir,Admixture content limit ℅ in concrete according to IS CODE ?

 

[Pk27feb]

Admixtures

Accelerating admixture or Accelerator

An admixture when added to concrete, mortar or grout, increases the rate of hydration of a hydraulic cement, shortens the time of set, or increases the rate of hardening or strength development.

Retarding admixture or retarders

An admixture which delays the setting of cement paste, and hence the mixtures , such as mortar or concrete containing cement.


Water reducing admixture or workability aid:

An admixture which either increases workability of freshly mixed mortar or concrete without increasing water content or maintains workability with a reduced amount of water.

Air entraining admixture:

An admixture for concrete or mortar which causes air to be incorporated in the form of minute bubbles in the concrete or mortar during mixing, usually to increase workability and resistance to freezing and thawing and disruptive action of de-icing salts.

Super plasticizing admixture :

An admixture for mortar or concrete which imparts very high workability or allows large decrease in water content for a given workability.

Retarding super plasticizing admixture :

Super plasticizing admixture that imparts prolonged workability retention and retards setting.

Sir addmixture company name and some test limit?

 

[Dnyan Deshmukh]

Dear sir,Admixture content limit ℅ in concrete according to IS CODE ?

Normally the maximum admixture dosage are taken as per the manufacturer specifications.

It can be up to 2% max.

While doing mix design, trials also need to be conducted for checking the behavior of concrete at higher dosage.

 

[Pk27feb]

Normally the maximum admixture dosage are taken as per the manufacturer specifications.

It can be up to 2% max.

While doing mix design, trials also need to be conducted for checking the behavior of concrete at higher dosage.

Sir but I read dosing liMit min 0.2℅ to max 5℅....?

 

[Pk27feb]

Sir but I read dosing liMit min 0.2℅ to max 5℅....?

Yeah when I doing trial I will start 1.0 then 1.1 and 1.2 ℅ for cementenius material.

 

[Dnyan Deshmukh]

State the order of IS SIEVE for fine and course aggragete. And also the limit ℅ of sieve analysis of 10mm and 20mm. In what order will sieve be placed.

Refer to this article

Gradation of Aggregates and its importance in Mix Designing - Civil4M

Concrete mix designing is a vital part of any construction activity. Why we do mix design when proportions for material are listed in IS codes for various grades? The listed mixes have more cement content than required and have fix properties like workability, retention time etc. In order to...

civil4m.com

it have combine gradation and individual gradation report along with limits and sieve orders.

For fine aggregates there are 4 limits prescribed in IS code named as Zone.
You can see it in below table, Zone is confirmed as per passing % on 600 micron sieve as it only had passing percentage which is not overlapped in any other zone (highlighted in red box).

 

[Dnyan Deshmukh]

Yeah when I doing trial I will start 1.0 then 1.1 and 1.2 ℅ for cementenius material.

You need to first decide on which admixture to use.
Then call admixture representative and define them you requirement.

They will workout on it base on there previous experience with brand of cements and mixes.
If they had product suitable to you, they will supply the samples and provide you dosage limits to start.
If they do not had any product matching your requirement, they will formulate it and do the experiment.

For naphthalene base admixture dosage normally starts at 0.8% and can go up to 2%
For PCE base it can start at 05.% and workout at max 1.2%

PCE provides longer retention in workability for longer time without dropping.
Naphthalene base provide retention for smaller time and had reduction effect in workability every minute depending on its formulation.

 

[Dnyan Deshmukh]

Yeah when I doing trial I will start 1.0 then 1.1 and 1.2 ℅ for cementenius material.

You need to first decide on which admixture to use.
Then call admixture representative and define them you requirement.

They will workout on it base on there previous experience with brand of cements and mixes.
If they had product suitable to you, they will supply the samples and provide you dosage limits to start.
If they do not had any product matching your requirement, they will formulate it and do the experiment.

For naphthalene base admixture dosage normally starts at 0.8% and can go up to 2%
For PCE base it can start at 05.% and workout at max 1.2%

PCE provides longer retention in workability for longer time without dropping.
Naphthalene base provide retention for smaller time and had reduction effect in workability every minute depending on its formulation.

 

[Pk27feb]

FLY ASH
Chemical requirements

When tested according to IS 1727 fly ash to confirm the following requirements (As specified in IS 3812 Part I, Table 1, Clause 5.1 and 6.1).
View attachment 531

Physical requirements of fly ash (As specified in IS 3812 Part I, Table 1, Clause 5.1 and 6.1).

View attachment 532

NOTE — Fly ash of fineness 250 m2/kg, Min is also permitted to be used in manufacture of Portland pozzolana cement by intergrinding it with Portland cement clinker if the fly ash when ground to fineness of 320 m2/kg or to the fineness of the resultant Portland pozzolana cement, whichever is lower.

NOTE — Fly ash in general classified as “ Class C” & “Class F”. as per ASTM. Fly ash of Class C is obtained from power plant where Lignite is used as fuel and Class F obtained from power plants where bituminous coal is used as fuel.

.

 

[Pk27feb]

Advantages of using fly ash in concrete

In plastic state concrete:

Improved workability:
Fly ash is spherical in shape it produces a paste with superior plasticity and reduces the amount of water needed in a mix.

Reduced Segregation:
The improved cohesiveness of Fly ash concrete provides added body to plastic state concrete which resist segregation.

Reduces Bleed water:
The lower water content required for workability in fly ash concrete reduces bleeding.

Increased pumpability:
The spherical shape of fly ash acts like a tiny ball bearing, reducing internal friction, thereby producing a mix that is easier to pump.

Reduces Equipment wear:
Fly ash concrete reduces wear on delivery and plant equipment because of the reduction of friction attributed to the spherical nature fly ash.

Long Term advantages of fly ash :

Increases concrete strengths:
Fly ash concrete will continue to gain strength past the age of 28 days. With improved workability and a reduction in water needed , fly ash concrete provides a lower water / cementitous ratio there by producing superior strengths and longer life.

Reduces drying shrinkage:
By providing as much as 10 % water reduction in its plastic state, fly ash concrete maintains workability and reduces drying shrinkage.

Reduced permeability:
The packing effect of the spherical fly ash particles helps to reduce permeability. The chemical reaction between fly ash and lime forms additional (C-S-H) bonds that block bleed channels and fill pore space.

Resistance to Sulphate attack:
Fly ash combines with free calcium hydroxide making it unavailable to react with sulphates. In producing a less permeable structure there is increased resistance to aggressive soluble sulphate solutions resulting in longer life.

Mitigates alkali aggregate:
Fly ash reacts with available alkalis in the hardened cement matrix making them less likely to react with the aggregate.

Reduces heat of hydration:
Large masses of concrete typically produce high internal temperature and thermal cracking. Fly ash concrete produces appreciably less heat than portland cement concrete.

To know the effects of Fly Ash on properties of concrete in details Click Here.

Thank you sir .

 

[Pk27feb]

FLY ASH
Chemical requirements

When tested according to IS 1727 fly ash to confirm the following requirements (As specified in IS 3812 Part I, Table 1, Clause 5.1 and 6.1).
View attachment 531

Physical requirements of fly ash (As specified in IS 3812 Part I, Table 1, Clause 5.1 and 6.1).

View attachment 532

NOTE — Fly ash of fineness 250 m2/kg, Min is also permitted to be used in manufacture of Portland pozzolana cement by intergrinding it with Portland cement clinker if the fly ash when ground to fineness of 320 m2/kg or to the fineness of the resultant Portland pozzolana cement, whichever is lower.

NOTE — Fly ash in general classified as “ Class C” & “Class F”. as per ASTM. Fly ash of Class C is obtained from power plant where Lignite is used as fuel and Class F obtained from power plants where bituminous coal is used as fuel.

(Fly ash of fineness 250 m2/kg, Min is also permitted to be used in manufacture of Portland pozzolana cement by intergrinding it with Portland cement clinker if the fly ash when ground to fineness of 320 m2/kg or to the fineness of the resultant Portland pozzolana cement, whichever is lower)....You can explain this part again in simple way??.

 

[Niraj Sharma]

Nice, detailed information for Mix design of Concrete.

 

[Er.Deepak Kumar]

In This thread i will be covering following

1. Materials Used in Concrete
2. Testing of Materials
3. Acceptance and Storage of Materials
4. Properties of Concrete and Testing
5. Concrete Mix Designing
6. Production and Transport of Concrete
7. Pouring Concrete in situ and its leveling & Compaction
8. Finishing of Concrete
9. Curing of Concrete and Its Protection.
10. Defects in Concrete.
11. Do's and Do Not's for Formwork and Reinforcement.
12. Repairing of Concrete
13. Advancement in Concrete Field
14. Some questions on Concrete - If you answer correctly then you are Concrete Master!

It will be going to be interesting for you.
Do bookmark this thread to check new updates.

Please send me Excel format

 

[TJ007]

Aggregates

They are further classified as per their shape.

Rounded : Fully water worn or completely shaped by attrition (e.g. – River or Seashore gravel, desert, seashore and windblown sands.

Irregular or partly rounded : Naturally irregular, or partly shaped by attrition and having rounded edges. (e.g. Pit sands and gravel , land or dug flints , cuboid rock

Angular : Possessing well-defined edges formed at the inter-section of roughly Planar faces. (e.g. Crushed rocks of all types, talus, screes)

Flaky : Material usually angular, of which the thickness is small relative to the width and / or length ( e.g. Laminated rocks)

Elongated : Material usually angular, of which the length is more relative to the width and / or Thickness ( e.g. Laminated rocks)

Cubical : This is special production made by crushing rock under vertical shaft impact crusher which forms a cubical shape aggregates.

how much percentage difference of strength can be there due to flaky and elongated aggregates?

 

[TJ007]

Advantages of using fly ash in concrete

In plastic state concrete:

Improved workability:
Fly ash is spherical in shape it produces a paste with superior plasticity and reduces the amount of water needed in a mix.

Reduced Segregation:
The improved cohesiveness of Fly ash concrete provides added body to plastic state concrete which resist segregation.

Reduces Bleed water:
The lower water content required for workability in fly ash concrete reduces bleeding.

Increased pumpability:
The spherical shape of fly ash acts like a tiny ball bearing, reducing internal friction, thereby producing a mix that is easier to pump.

Reduces Equipment wear:
Fly ash concrete reduces wear on delivery and plant equipment because of the reduction of friction attributed to the spherical nature fly ash.

Long Term advantages of fly ash :

Increases concrete strengths:
Fly ash concrete will continue to gain strength past the age of 28 days. With improved workability and a reduction in water needed , fly ash concrete provides a lower water / cementitous ratio there by producing superior strengths and longer life.

Reduces drying shrinkage:
By providing as much as 10 % water reduction in its plastic state, fly ash concrete maintains workability and reduces drying shrinkage.

Reduced permeability:
The packing effect of the spherical fly ash particles helps to reduce permeability. The chemical reaction between fly ash and lime forms additional (C-S-H) bonds that block bleed channels and fill pore space.

Resistance to Sulphate attack:
Fly ash combines with free calcium hydroxide making it unavailable to react with sulphates. In producing a less permeable structure there is increased resistance to aggressive soluble sulphate solutions resulting in longer life.

Mitigates alkali aggregate:
Fly ash reacts with available alkalis in the hardened cement matrix making them less likely to react with the aggregate.

Reduces heat of hydration:
Large masses of concrete typically produce high internal temperature and thermal cracking. Fly ash concrete produces appreciably less heat than portland cement concrete.

To know the effects of Fly Ash on properties of concrete in details Click Here.

but fly ash content in concrete can slower rate of gain of strength in concrete so how come use of fly ash is legitimate for high strength concrete?