Chemical Admixture and their Effect on Fresh and Harden Concrete
Muzafar
FB id : [email protected] no : +91 9701471253
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 : [email protected] no : +91 9701471253