Become Concrete Master - Concrete Mix Designing

[Dnyan Deshmukh]

Concrete is a material which is a basic for any project.

I will be helping you out by sharing my experience with all of you (You too can help me in learning new tech's in this field by sharing your experience through doing post on forum).

After reading all posts you will be in position to say yourself as Master in Concrete (Provided you have basic knowledge about thinks which i am posting here).

Concrete is not a subject which can be taught in one post or page, i will be posting daily here as i get time to do.

I will be covering all the parts from selection of materials till its end of life.

This thread will be locked so you cant post your questions on it at here.

You can ask your questions regarding this thread at Help Thread

Do like my posts if they really helps you and make sense.


Update: - now you can download a concrete mix design program made in excel sheet, from below link.

- Concrete Mix Design: Concrete Mix Design Excel Program up to M85 Grade

 

[Dnyan Deshmukh]

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.

 

[Dnyan Deshmukh]

Concrete is made from following materials

• Cement
• Fine Aggregates
• Coarse aggregates
• Water
• Mineral Admixtures
• Chemical Admixtures
• Bio Admixtures (New funda will become common in coming days)
• Other Addons

 

[Dnyan Deshmukh]

Concrete and Cement History

Oldest surviving concrete is found in Yugoslavia which was laid around 5600 BC

The first major users were Egyptians around 2500 BC and Romans from 300 BC

Romans mixed materials from "Pozzuoli" a pink sand with lime mortar and built their structures.

This is nothing but the Volcanic Ash and they produced the first "Pozzolanic" Cement

OPC - Ordinary Portland Cement

Mr. JOSEPH ASPDIN

• 21st Oct 1824
• The product resemble natural rock in PORTLAND - EGLAND

In INDIA - in 1902 (South India Structural)

 

[Dnyan Deshmukh]

How Cement is Made

Cement is made from Limestone and Clay / Shale

It goes from Quarrying, crushing, mixing together, Heating, Clinker formation.

Clinker then finally grinded with Gypsum and Other additives as per the Max % allowed for mix in Creation of finest powder of cement As per the limits specified in The Indian Standard Codes (Please refer to relevant codes for cement specification in your Country).

I am not writing here in detail about the cement manufacturing.

To know more in cement manufacturing process Click Here To see the Process with Photographs

 

[Dnyan Deshmukh]

Cement

Types:

Following Types are listed in IS 456-2000 you can check clause number 5.1 for easy reference.

The cement used shall be any of the following and the type selected should be appropriate for the intended use:

• OPC 33 Grade ordinary Portland cement conforming to IS 269 - 2015
• OPC 43 Grade ordinary Portland cement conforming to IS 269 - 2015 (old code IS 8112)
• OPC 43S Grade ordinary Portland cement conforming to IS 269 - 2015 (old code IS 8112)
• OPC 53 Grade ordinary Portland cement conforming to IS 269 - 2015 (old code IS 12269)
• OPC 53S Grade ordinary Portland cement conforming to IS 269 - 2015 (old code IS 12269)
• Rapid hardening Portland cement conforming to IS 8041
• Portland slag cement conforming to IS 455
• Portland pozzolana cement (fly ash based) conforming to IS 1489 (part 1)
• Portland pozzolana cement (calcined clay based) conforming IS 1489 (part 2)
• Hydrophobic cement conforming to IS 8043
• Low heat Portland cement conforming to IS 12600
• Sulphate resisting Portland cement conforming to IS 12330.

Other combinations of Portland cement with mineral admixtures like Fly ash, Silica fume, Rice husk ash, Metakaolin and GGBS of quality confirming with relevant Indian standards may also be used in the manufacture of concrete provided that there are satisfactory data on their suitability, such as performance test on concrete containing them.

Low heat Portland cement conforming to IS 12600 shall be used with adequate precautions with regard to removal of form work, etc,

High alumina cement conforming to IS 6452 or Supersulphated cement conforming to IS 6909 may be used under special circumstances with prior approval of Engineer-in-charge. Specialist literature may be consulted for guidance regarding the use of these types of cements.

 

[Dnyan Deshmukh]

Physical 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​
Fineness m2/Kg Minimum​	225​	225​	370​	225​	370​	225​	300​	225​
Initial Setting Time(Not less than)​	30​	30​	30​	30​	30​	30​	30​	30​
Final Setting Time ( Not more than)​	600​	600​	600​	600​	600​	600​	600​	600​
Soundness by Le Chatelier (mm)​	10​	10​	5​	10​	5​	10​	10​	10​
Soundness by Autoclave (%)​	0.8​	0.8​	0.8​	0.8​	0.8​	0.8​	0.8​	0.8​
Compressive strength in MPA Minimum	​	​	​	​	​	​	​	​
72 +/- 1 Hour​	16​	22​	23​	27​	27​	16​	16​	16​
168 +/- 2 Hours​	22​	33​	37.5​	37​	37.5​	22​	22​	22​
672 +/- 2 Hours​	33​	43​	43​	53​	53​	33​	33​	33​
672 +/- 2 Hours Max​	48​	58​	-​	-​	-​	-​	-​	-​
Drying shrinkage (max %)​	-​	-​	-​	-​	-​	-​	0.15​	-​

​

 

[Dnyan Deshmukh]

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.

 

[Dnyan Deshmukh]

Types of Aggregates

Aggregates are classified base on their weight as;

Ultra - Lightweight - is used in architectural / non structural works and allow the user to modify the elements by cutting, nailing etc.

Lightweight - Used for non structural works, can be used in waterproofing, insulation etc.

Normal Weight Aggregates - This is what we used in day to day structural concrete, its most common available material for construction and specifically made from hard rock like basalt, limestone, river gravels etc.

Heavy Weight Aggregates - This are the heavy weight aggregates made from iron ore and other high dense materials. used to make high dense concrete, specifically use where radiations should not go outside of the room area.

 

[Dnyan Deshmukh]

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.

 

[Dnyan Deshmukh]

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.

 

[Dnyan Deshmukh]

Water

Potable water is satisfactory for mixing concrete.
Water should be free from oils, acids, alkalis, salts, sugar and organic materials.
In general , do not use sea water either for mixing or for curing. However IS 456 permits use of sea water for Plain concrete and reinforced concrete permanently immersed in sea water.

The total requirement of water, for all purposes such as mixing, curing, washing of shutters, washing of aggregates , concrete pump /pipe line washing and workmen’s consumption may be estimated on the basis of 350 to 500 litres / m3 of concrete base on site conditions.

 

[Dnyan Deshmukh]

Water
IS 456 –2000 stipulates the permissible limits of solids shall be as follows. (Table 1, Clause 5.4)

In case of doubt regarding the usage of water the same can be tested for setting time and compressive strength test as mentioned below.

1) The average 28 day’s compressive strength of at least three 150 mm concrete cube prepared with water proposed to be used shall not be less than 90 percent of the average of strength of three similar concrete cubes prepared with distilled water.

2) The initial setting time of test block made with the appropriate cement and the water proposed to be used shall not be less than 30 min and shall not differ by + 30 min from the initial setting time of control test block prepared with the same cement and distilled water.

 

[Dnyan Deshmukh]

Water
Apart from the above permissible limits SP 23 specifies the following concentration of some impurities in mixing water which can be considered as tolerable (SP 23, Table No 16, Clause 2.3).



Sea water: Mixing or curing of concrete with sea water is not recommended because of presence of harmful salts in sea water. Under unavoidable circumstances sea water may be used for mixing or curing in plain concrete with no embedded steel after having given due consideration to possible disadvantages and precautions including use of appropriate cement system.

Curing Water: Water used for mixing is suitable for curing concrete. However, water used for curing should not produce any objectionable stain or unsightly deposit on the concrete surface. The presence of tannic acid or iron compounds is objectionable.

 

[Dnyan Deshmukh]

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

 

[Dnyan Deshmukh]

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.

 

[Dnyan Deshmukh]

Mineral admixtures:

IS 456 permits the usage of the following pozzolanic materials confirming the relevant standard specification can be used in concrete as admixtures with the permission of the deciding authorities.

Fly ash (pulverized fuel ash ) confirming IS 3812- Part I

Ground granulated blast furnace slag (GGBFS) manufactured with granules of slag confirming IS 12089

Silica fume confirming IS 15388

Rice husk ash

Metakaoline having fineness between 700 to 900 m2/ kg.

In general fly ash, GGBFS and Silica fume is used depends on project requirement. But fly ash is used in major quantity in concrete making as part replacement to cement.

Now a days GGBFS is also getting priority in many project.

 

[Dnyan Deshmukh]

FLY ASH

Fly ash is the byproduct of coal fired power plants. The ash which is very small in size is collected by the ESP’s. The chemical composition mainly depends up on the type of coal used for firing in the boilers.

The details of requirement of Chemical and Physical properties of Fly ash for use as a pozzolana for part replacement of cement, for use as an admixture is given below.

Designation: As per IS 3812 fly ash is designated as follows

Part I - For use as Pozzolana in cement, cement mortar and concrete. Part II - For use as admixture in cement mortar and concrete

Fly ash is classified in to Siliceous pulverized fuel ash and Calcareous pulverized fuel ash.

Siliceous Pulverized fuel ash: Pulverized fuel ash with reactive calcium oxide less than 10 percent by mass. Such fly ash is normally produced from burning anthracite or bituminous coal and has pozzolanic properties.

Calcareous Pulverized fuel ash: Pulverized fuel ash with reactive calcium oxide not less than

10 percent by mass. Such fly ash is normally produced from lignite or sub-bituminous coal and have both pozzolanic and hydraulic properties.

Types of Fly ash:

Fly ash: Pulverized fuel ash extracted from flue gases by any suitable process such as by cyclone separator or electro-static precipitator.

Bottom ash: Pulverized fuel ash collected from the bottom of boilers by any suitable process

Pond ash: Fly ash or bottom ash or both mixed in any proportion and conveyed in the form of water slurry and deposited dry.

Mound ash: Fly ash or bottom ash or both mixed in any proportion and conveyed or carried in dry form and deposited dry.

 

[Dnyan Deshmukh]

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).


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



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.

 

[Dnyan Deshmukh]

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.