cement and chemical admixtures effect of fresh and hard concrete

Chemical Admixture and their Effect on Fresh and Harden Concrete

Muzafar

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Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

CementLime CaO

(60 - 65 )%

A cement is a binder, a substance that sets and hardens and can bind other materials together

Silica SiO2

(17 – 25 )%

Alumina Al2O3

(3 - 8)% (0.5 – 0.6 )%

Iron oxide Fe2O3

Sulphur trioxide SO3

(1- 2 )%

Magnesia MgO

(0.5 - 4 )%(0.5 – 1.3 )%

Na2O + K2O

Tricalcium Silicate (Alite) C3S 25-50%

Dicalcium Silicate (Belite) C2S 20--45%

Tricalcium Aluminate (Clite) C3A 5-12%

Tetracalcium Alumino Ferrite (Flite) C4AF 6-12%

33 grade 2250 cm2 /g 43 grade 3400+ cm2 /g 53 grade 3400++>> cm2 /g

58(3) 104(90) 122 (13) Cal/g

12 (3) 42(90) 59 (13) Cal/g

212(3) 311(90) 324 (13) Cal/g

69(3) 98(90) 102 (13) Cal/g

Initial strengthFlashflahset

Early Strength

Later Strength(Reaction after 7 days)

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

ADMIXTURE Admixture are formulated chemical compounds that are used to modify certain properties of concrete.

Admixtures are the material, other than

Cement

Water

Aggregates

Chemical Admixture

These admixture are added to concrete mix before or during mixing of concrete

ADMIXTURE

CHEMICAL

MINERAL

Chemical Admixtures

•Accelerating admixtures•Retarding admixtures•Air-entraining admixtures•Water Reducing admixture/plasticizers•Grouting admixtures•Air detraining admixtures•Gas forming admixtures•Corrosion inhibiting admixtures•Permeability reducing admixtures•Bonding admixtures•Shrinkage Reducing Admixtures•Colouring admixtures•`Fungicidal ,germicidal and insecticidal admixtures

To speed up the rate of development of strength. To keep concrete workable for long time(Enhance workability). To decrease the weight of concrete per cubic meter. To increase the strength of concrete by reducing the water content

To inhibit the corrosion.

To increase the resistance to chemical attack

To enhance the bond between old and new concrete

To produce coloured concrete

Functions of Admixtures

To reduce the cost of concrete construction To achieve certain properties in concrete

To maintain the quality of concrete during the stages of mixing, transporting, placing, and curing To overcome certain emergencies during concreting operations

Reasons for using admixtures are

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Coloring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

AcceleratorAccelerating admixtures are added to concrete to increase the rate of early strength development in concrete

Accelerating admixtures also used to speed up the initial set of concrete

C3S + (x)CATALYST(Admixture) = XC3S

XC3S + (Y) = C3S2H3 + (x) + (z)

Accelerator cause a more rapid dissolution of compounds of cement

Mechanism of action is catalytic in nature

The compounds of Accelerating Admixture :

Calcium Chloride CaCl2 ( Most commonly used for plain concrete) Is 7861-1981 maximum 1.5% by mass of cement

Calcium Formate Ca(HCOO)2 (fine powder,less effective than cacl2 and less corrosion to steel)

Fluro silicates and Trietholamine (Remains plastic for less than 10 min, not exceeding 0.2% by mass)

sodium hydroxide (NaOH) and potassium hydroxide (KoH)

Sodium sulfate (Na2So4),

Sodium Chloride (Nacl)

potassium sulfate(K2SO4)

Why Accelerators ?

Earlier removal of formwork.

Reduction of required period of curing

Early placement of structure in service.

Partially compensate for the retarding effect of low

temperature during cold weather concreting.

In emergency repair work.

The Chernobyl disaster (Ukrainian)

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Retarder AdmixtureA retarder is an admixture that slows down the (Initial) chemical process of hydration so that concrete remains plastic and Workable for a longer time.

Delay the setting of cement

Cement particle

Thin coating of Retarding Admixture

Thus slowing down Cement particle reaction with water

Not allowing cement particles to react with each other

Thus slowing downing the chemical reaction

The compounds Retarder Admixtures Gypsum CaSo4 2H2O (Calcium sulphate) Most commonly used

Water solible Sugar (C12H22O11)

Starch and dextrin (0.05 to 0.1)%

Zinc

lead

calcium borate

Why Retarders ?

Very useful when concrete has to be place in very difficult conditions and delay may occur in transporting and placing.

Retarders are used to overcome the accelerating effect of high temperature on setting properties of concrete in hot weather concreting.

Amount used and effects

Admixture addition litres/ 50 kgs.

Setting time hrs.W : C ratio

Compressive Strength MPa

Initial

Final

3 days

7 days

28 days

0 4.5 9 0.68 20 28 37

0.14 8.0 13 0.61 28 36 470.21 11.5 16 0.58 30 40 50

0.28 16.0 21 0.58 30 42 54

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Air-Entraining admixturesAir entraining admixtures help to incorporate a controlled amount of air in the form of millions of minute non coalescing bubbles distributed throughout the body of concrete.

Anionic surfactants

Reducing surface tension and enable the water to Entrain Air

The components used for Air entrainment are

Natural wood resins containing abietic and pimeric acid

Some animal and vegetable fats and oils such as tallow olive oil

Fatty acids such as stearic and oleic acid

Salts of sulphonated hydrocarbons used for harsh concrete(sand deficient in fines)

Neutralized vinsol resin is used in mass concrete

Why Air-Entraining admixtures ?

Replacement of fine aggregate as small bubbles of Air

It also modifies the properties of hardened concrete regarding its resistance to frost action and permeability.

These incorporated millions of non-coalescing air bubbles(5 microns to 80 microns distributed evenly ), which will act as flexible ball bearings and will modify the properties of plastic concrete regarding workability, segregation, bleeding and finishing quality of concrete.

The Effect of Air Entrainment on the Properties of Concrete

Increased resistance to freezing and thawing.

Improvement in workability.

Reduction in strength.

Reduces the tendencies of segregation.

Reduces the bleeding and laitance.

Decreases the permeability.

Increases the resistance to chemical attack.

Permits reduction in sand content.

Improves place ability, and early finishing.

Reduces the cement content, cost, and heat of hydration.

Reduces the unit weight.

Permits reduction in water content.

Reduces the modulus of elasticity.

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Water Reducing Admixtures/plasticizersWater Reducing Admixtures allow a reduction in water content for the given workability, or give a higher workability at the same water content, are termed as water reducing Admixtures / plasticizing admixtures

Normal water reducer (reduces the water (5-10)%

Mid water reducer (reduces the water (10-15)%

High range water reducer (reduces the water (20-40)%

Depending upon degree of water reduction the Water reducers are categorized as

The Water reducing compounds such as

Anionic surfactants such as lignosulphonates and their modifications and derivatives, salts of sulphonates hydrocarbons. Non ionic surfactants, such as polyglycol esters, acid of hydroxylated carboxylic

acids and their modifications and derivatives. Sulphonated malanie-formaldehyde condensates (SMF) Sulphonated naphthalene-formaldehyde condensates (SNF) Modified lignosulphonates (MLS)

superPlasticizers(High range water reducers) Amount used

Permits reduction of water content about 30%+ without reducing the workability

It is possible to use w/c ratio as low as 0.25 or even lower and yet to make flowing concrete to obtain strength of order 120 Mpa or more.

Results - benefits

• Based on various types of superplasticizers different amount is used.

• Lignosulphonates – not more than 0.25%

• Carboxylic acids – 0.1%

• Sulphonated malanie-formaldehyde condensates (SMF) – 0.5 to 3%

• Sulphonated naphthalene-formaldehyde condensates (SNF) – 05 to 3%

SuperPlasticizers(High range water reducers) Used at Superplasticizer is practiced for

Production of flowing, self levelling, self compacting concrete

Production of high strength and high performance concrete.

45

Shanghai tower 61 000 m3 of concrete 30 hours

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Grout is a mixture of cementitious material and water with or without fine Aggregate

Grouting materials can be broadly classified into tow categories

1. Free flow grout for use in machine foundations foundation bolts and fixing crane etc

2. Injection grouting to fill up small cracks and is normally accomplished under pressure.

Grouting Admixture

Admixture are use for grouting are

A. Accelerators(ex:plugging)

B. Retarders(Deep penetration,cracks)

C. gas forming agents (machine bases,it expands and set)

D. Plasticizers (for effective flowability and high strength)

Generally used admixtures are gels,clays,pregelatinized starch and methylcellulose

300 tons of grouth ground too soft

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Air detraining admixtures

Remove a part of the entrained air from a concrete mixture

• Tributyl phosphate• Dibutylphathalate• Water insoluble alcohols • silicones

• There are some cases where aggregates have released gas into or excessive air entrainment in concrete.

The compounds such as

Dissipate excess air or other gases

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Gas forming admixtures

A gas forming agent reacts with hydroxide of cement to produce minute bubble of Gas.

Ex light weight concrete

The compounds such as

Aluminium powder (0.005 to 0.02)% Zinc Magnesium powder Hydrogen peroxide H2O2

Ca(OH)2 + 2 Al + 6 H2O → Ca[Al(OH)4]2 + 3 H2. (GAS)

Effect of temperature : Hot wether : too quick reaction (30 min) : ordinary temperature 1 to 4 hours

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Corrosion inhibiting Admixtures

Corrosion inhibiting admixtures are used to slow down corrosion of steel reinforcement in concrete

These are used as a defensive strategy for concrete structures constructed in

Marinen, highway, industrial environment.

Where cement concrete is exposed to high concentrations of chlorides

The compounds such as

Sodium benzoate (2% with water,10% slurry paint) Sodium nitrate

Fe(s) + 3 Cl2(g) → 2 FeCl3(s Fe(OH)2 FeO +  ⇌ H2O

Fe(OH)3 FeO(OH) +  ⇌ H2O

2 FeO(OH) Fe⇌ 2O3 +  H2O

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Permeability Reducing /Damp proofing Admixtures

Types of Water percolation

Water under pressure and in contact with one surface of concrete, can be forced through the channels between the two surface [permeability Reducer]

Water can also pass though the action of capillary (absorption). [Damp proofers]

The compounds such as

Chemical which react with hydration products of cement = Liquid fatty acids: vegetable and animal fats Chemical which coalesce (Fuse) on contact with hydration product = Fine divided wax emulsions Finely divided hydrophobic materials = Calcium stearate and Aluminium stearate

Admixture prevent percolation of water by forming hydrophobic layers (Water repelling agent)

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Bonding AdmixturesBonding admixtures is used to join two Surfaces

This admixture increases the bond strength between the old and new concrete

Major uses are overlay on an existing pavement and repair works

There are two types of bonding Admixtures:

Bonding is accomplished by a metallic Aggregate = Iron oxide Bonding is accomplished by Synthetic latex = polyvinyl chloride

Metallic Aggregate like Fine cast iron particles reacts chemically causes rapid oxidize results in expansion and form bond

New surface

Old surfaceAdmixture

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Shrinkage Reducing Admixtures

The shrinkage reducing also known as expansion producing admixtures

Introducing self stress in the concrete

Useful in avoiding cracking in large surface area concrete structures

Such as continuous bridge deck,large parking area and large slabs etc

The compounds such as

Granulated iron (oxidation of Iron with ca(oh)2 take place form iron oxide(expands)) Anhydrous sulphoaluminate

Either expand themselves or react with other constituents of concrete results in expansion

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Colouring Admixtures

Pigments are the admixtures added to produce coloured cements

• Apply concrete paint after the concrete surface has been neutralized (by neutralizing agent like zink sulphate)

• Integrating colour into the surface of concrete while it is still fresh.

The chief pigments used in concrete are

Black ( carbon black) Blue (Barium manganite) Green (Chromium oxide) Red (Iron) Yellow (Hydroxides of iron)

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

These Admixture impart Fungicidal, germicidal or insecticidal properties to the hardened concrete (Fungicidal, germicidal or insecticidal Repelling property)

Fungicidal ,Germicidal and Insecticidal Admixtures

The compounds such as

Polyhalogenated phenols Dieledren emulsions Copper compounds

Cement

Admixture

Accelerating admixtures

Retarding admixtures

Air-Entraining admixtures

Water Reducing admixture/plasticizers

Grouting admixtures

Air detraining admixtures

Gas forming admixtures

Corrosion inhibiting admixtures

Permeability reducing admixtures

Bonding admixtures

Shrinkage Reducing Admixtures

Colouring admixtures

`Fungicidal ,germicidal and insecticidal admixtures

Can we use Chemical Admixture ?

PASS THROUGH 4.75MM TO 75 MICRON RETAIN

DEPENDSIZESHAPEBULKING SANDSTRENGTHGRADING UNIFORM,WELL GRADED,GAPGRADED

Retained on 4.75mm Pass 80 mm

Shape angular flaky

Size StrengthGrading

Properties(characteristics and behavior) of Material which influence the properties of concrete

Ph not less than 6 is 456-2000

Quantity of waterw/c ratioType of waterSea,lake,pond,well

Grades of Cementfineness

Type of cement

Concrete Technology, Theory and Practice, by M. S. Shetty, S. Chand Company Ltd. Publication

References

Wikipedia and Google

Concrete TechnologyM L Ghambir

Thank youPresnted by

Pathan Muzafar ali khanFB id : Muzafar.alikhan15@gmail.comContact no : +91 9701471253