presentaion Chemical Admixtures - NJIT.pdfcd

Sika

1. Construction
Sika Corporation
Chemical Admixtures
Presentation by-
Ketan Sompura, Ph.D

2. Construction
Sika Corporation
Admixtures
Admixtures are those ingredients in concrete other than Admixtures are those ingredients in concrete other than
cement, water, and aggregates that are added to the cement, water, and aggregates that are added to the
mixture immediately before or during mixing to give the mixture immediately before or during mixing to give the
concrete special properties. concrete special properties.

3. Construction
Sika Corporation
Reasons For Using Admixtures
SIncrease Strength
SImprove Mix Workability
SImprove early strengths
SControl set time
SReduce Permeability
SControl Efflorescence
SImprove Color Vibrancy
SMeet Durability Requirements
SControl Shrinkage
SImprove mix economics

4. Construction
Sika Corporation
Admixture Types
SWater-Reducers
SAccelerators
SRetarders
SAir Entrainment
SSpecialty
S
Viscosity Modifiers
S
Corrosion Inhibitors
S
Anti Wash-out
S
ASR Controlling
S
Shrinkage Reducers
S
Water-Repellent Admixtures...etc
SManufactured concrete products (MCP) Admixtures

5. Construction
Sika Corporation
ASTM Classification of admixtures SASTM C 494
S
Type A –Water reducer
S
Type B –Retarding admixture
S
Type C –Accelerating admixture
S
Type D –Water reducing and retarding
S
Type E –Water reducing and accelerating
S
Type F –High range water reducer
S
Type G –High range water reducing and
retarding admixture
S
Air entraining admixtures (ASTM C 260)

6. Construction
Sika Corporation
Water Reducers

7. Construction
Sika Corporation
Water Reducers
SDefinition as per ACI 116.R-2:
Admixtures that either increase slump of freshly-mixed
mortar or concrete without increasing water content OR
maintain slump with a reduced amount of water, the effect
being due to factors other than air entrainment.
SBenefits:
S
Increase in strength
S
Increase in workability
S
Cement reduction

8. Construction
Sika Corporation
Water Reducer-

Types SLignosulfonates
SNaphthalene based (SNF)
SMelamine based (SMF)
SVinyl Copolymers
SPolycarboxylatebased

9. Construction
Sika Corporation

10. Construction
Sika Corporation
CEMENT GRAINS
Attractive forces between cement
grains will give flocculation with
LOSS OF FLUIDITY
Water/Cement System Without a Water
Reducing Admixture
Further growth of hydration products
will cause stiffness and LOSS OF
WORKABILITY

11. Construction
Sika Corporation
Cement particles
Dispersion

caused by electrostatic
repulsion
decrease of the W/C ratio
Mechanism of Action for a Conventional
Water Reducing Admixture
Dispersant
molecules

12. Construction
Sika Corporation
Mechanism of Polycarboxylate-
Based Admixtures
SDual mechanism of
SElectrostatic Repulsion
SSteric Hinderence
SThis dual mechanism results in improved dispersion, mix
lubrication and performance

13. Construction
Sika Corporation
Cement particles
Polycarboxylate

dispersant molecules
Dispersion

caused by electrostatic repulsion
and steric

hindrance
decrease of the W/C ratio
Mechanism of Action for a Polycarboxylate
based Water Reducing Admixture

14. Construction
Sika Corporation
2L
Conventional Water
Reducer
Polycarboxylate

Water Reducer

15. Construction
Sika Corporation
Accelerators and Retarders

16. Construction
Sika Corporation
General Definition
Accelerators
▲Increase the rate of hydration of the cement
▲Reduce the set time of concrete
▲Increase the early age strength of concrete
Retarders
▲Slows down the rate of hydration of cement
▲Increases the time of set
▲Slow down the rate of early age strength development

17. Construction
Sika Corporation
Accelerators AcceleratorFaster Set Time
Early strength
Strength/Hardening
Accelerator
Early Strength
Set time
Control
Set Acclr.Str. Acclr.

18. Construction
Sika Corporation
Accelerators
Uses
▲In cold weather, to avoid concrete from freezing when it is
plastic or/and to maintain normal setting behavior and strength
development.
▲To increase productivity (faster stripping of formwork)
▲Compensate for the delay in set or strength gain due to use
of SCMs

such as Fly ash or Slag.
▲Rapid repair of pavement sections
Accelerators need to co nfirm to ASTM C 494 as:
Type C –

Accelerating admixtures and/or
Type E –

Water reducing and accelerating admixtures

19. Construction
Sika Corporation
Accelerator -

Types
▲Soluble Inorganic salts
▲Soluble Organic Compounds
▲Quick setting admixtures
▲Miscellaneous solid admixtures.
Chlorides
Bromides
Fluorides
Carbonates
Thiocynates
Nitrites, Nitrates
Thiosulfates,
Silicates,
Aluminates and
alkali hydroxides
Triethalomine
Calcium
Formate
Urea, Oxalic
acid
Lactic acid
Compounds
of amines
and
formaldehyde
Aluminates
Carbonates
Silicates
Silicates
Carbonates
Cement Compounds: C3S, C2S, C3A, C4AF

20. Construction
Sika Corporation
Calcium Chloride
▲One of the most effective accelerators known.
Disadvantages
▲Potential for corrosion
▲Acceleration of Alkali Silica reaction
▲Reduction in freeze thaw and sulfate resistance
Due to the above Non-

Chloride Accelerators are used for
RCC.

21. Construction
Sika Corporation
Hardening Accelerator /
Strength Accelerator Advantages:
SIncreases high early strength, but may not significantly
influence the time of set.
SEnables addition of accelerator at the plant rather than
addition at site

22. Construction
Sika Corporation
Factors influencing accelerator
performance ▲Ambient temperature
▲Concrete temperature
▲Requirements of early set and strength
▲Accelerator dosage
▲Cement content, Cement Type, SCM
▲W/Cm
▲Testing method

23. Construction
Sika Corporation
Retarders
Uses
▲Reduces faster slump loss during hot weather.
▲Enables longer haul times
▲Delays set time, allows ti me for finishing operations
▲Reduces temperature of concrete at early stages
▲Slows down the rate of hydration of cement
▲Increases the time of set

24. Construction
Sika Corporation
Retarders
RetardationDelayed Set Time
Longer slump life Slump Retention

25. Construction
Sika Corporation
Retarders -

Types
▲Sugar derivatives
▲Hydroxycarboxylic

acid
▲Lignosulphonates
▲Tartaric acid and salts
Retarders need to confirm to ASTM C 494 as:
Type B –

Retarding admixtures and/or
Type D –

Water reducing and retarding admixtures

26. Construction
Sika Corporation
Hydration Control admixture SCan completely stop the hydration process of cement up to
several hours or days
SOnce set, strength development continues just as regular
concrete
SApplications:
S
High retardation or long slump life
S
Returned concrete

27. Construction
Sika Corporation
Factors influencing performance of
retarders ▲Ambient temperature
▲Concrete temperature
▲Control concrete (slump)
▲Cement content, Cement type, SCM
▲W/Cm

28. Construction
Sika Corporation
Air Entraining Admixtures

29. Construction
Sika Corporation
Why do we use Air Entraining
Admixtures (AEA’s) ? SFreeze Thaw durability
SResistance against deicer scaling
SWorkability and placing

30. Construction
Sika Corporation
QUIZ QUESTION : SWhat happens to water when freezes
and what is causing concrete damage
during freezing cycle?

31. Construction
Sika Corporation
ANSWER : SDuring freezing process,
water increases its
volume up to 9%.
SPressure developed
during this volume
change reaches up to
200MPa (29 000psi)

32. Construction
Sika Corporation
Freeze thaw conditions Freezing temperatures are not always detrimental for
concrete. To observe freeze thaw damage,
following two conditions must be fulfilled.
SConcrete pore saturation must be higher than
91.7%
STemperatures must be low enough to cause water
to freeze.
⇓
PRESSURE

33. Construction
Sika Corporation
How do AEA’s

work?
SWhen temperatures surrounding concrete decreases below
the freezing point of water, water present in pores and
capillaries of concrete starts to freeze and expand.
SAEA entrain minute size air bubbles uniformly throughout the
concrete
SAir entrained voids acts as small reservoirs for freezing
water, which can freely freeze and expand without building
up the pressure within the concrete.
SProperly air entrained concrete should provide enough voids
to accommodate all the water contained within the concrete.

34. Construction
Sika Corporation
What does entrained air voids do in
concrete? SIf air content increases 1%, then compressive
strength decreases about 5%
SIf air content decreases 1%, then yield will
decrease about 1/4 cubic foot per cubic yard
SIf air content decreases 1%, then slump
decreases about 1/2 inch
SIf air content decreases 1%, then durability
decreases about 10%

35. Construction
Sika Corporation
Specialty Admixtures and
Specialty Concrete Products

36. Construction
Sika Corporation
Specialty products SAnti-washout and viscosity modifying
admixture
SShrinkage Reducing admixture
SCorrosion inhibitors
SASR mitigation admixture
SAdmixture for Pervious Concrete
SFlowableFill admixture (CLSM)
SSurface Retarder
SFinishing Aid

37. Construction
Sika Corporation
Anti-

Washout Admixtures &
Viscosity Modifying Admixtures
How they work:
SWater soluble cellulose ether or acrylic type polymers
SThey increase the viscosity of water in the mix.
SThis results in increased thixotropy and improved resistance
to segregation
Applications:
SUnder water concreting
SSelf Compacting concrete
SIncrease cohesion in case of gap graded aggregate mixes.

38. Construction
Sika Corporation
Anti-

Washout Admixtures &
Viscosity Modifying Admixtures
Under water concreting
Self compacting concrete

39. Construction
Sika Corporation
Shrinkage Reducing Admixtures (SRA)
What do SRA’s

do:
SMinimizes volume changes due to
Drying Shrinkage cracking.
SDrying Shrinkage:
SLoss of moisture from
hardened concrete surface
SVolume of concrete reduces
and it shrinks
SWater in capillary exerts
forces on capillary wall
How Shrinkage reducing admixtures work:
SReduces surface tension of the liquid
SForces on the wall are reduced
SLess Shrinkage
Concrete

40. Construction
Sika Corporation
Corrosion Inhibitors types SCalcium Nitrite based
SMigration corrosion inhibitors ( based on a
combination of Amino alcohol and Organic
and inorganic inhibitors)

41. Construction
Sika Corporation
Calcium Nitrite based SA layer of Ferric oxide protects the steel from corrosion in
concrete
SThis layer can be damaged by carbonation or chloride
ingress, which can lead to corrosion.
SCalcium nitrite admixture fortifies the ferric oxide passivating
layer
SThereby protects steel from corroding
2 Fe
++

+ 2 OH + 2 NO
2
2 NO + Fe
2
O
3
+ H
2

O
S
Dosages: 10 – 30 liters per m3.

42. Construction
Sika Corporation
Migratory corrosion inhibitors SDual mechanism
S
Migrating inhibitor – Penetrates through the concrete to
the steel reinforcement and gets absorbed on the surface
S
Displaces chloride ions from steel surface and forms a
continuous film
SHence reduces overall corrosive activity
SDosages : 10 – 15 liters per m3

43. Construction
Sika Corporation
z
What is ASR?
Alkali’s (Na, K from
Cement)
+ Reactive Silica
(Aggregates)
ASR Gel
ASR Gel+

MoistureExpansive ASR Gel Cracks Concrete
Alkali silica reaction mitigating
admixture
Lithium Nitrate based admixture

44. Construction
Sika Corporation
ASR mitigating admixture

45. Construction
Sika Corporation
Pervious concrete
A concrete
-

that contains little or no sand
-

which forms a system of highly
permeable and interconnected voids
-

allows 3-8 gallons of water per
minute to pass through 1 sq.ft
Typical Properties:
Compressive strength –

500 –

4000 psi
Voids –

15 to 25%
Unit weight –

100 to 125 pcf
Permeability –

3 to 8 gallons/ minute per
sf.ft

46. Construction
Sika Corporation
Pervious concrete admixture
S
Polymer based liquid admixture
Benefits:
SImproves aggregate to cement paste bond
SImproves Strength and workability
SAids discharge from truck, easy to place
SReduces bleeding and improves cohesion
SDosage : 10 – 25 liter / m3
Other admixtures for pervious concrete
SWater reducers
SRetarders
SViscosity modifiers

47. Construction
Sika Corporation
Flowable

fill admixture Uses:
STo produce controlled low strength materials (CLSM)
used as flow able fill
Application:
SUse 454 gram bag (1 lb) to produce 0.77 m3 (1 cyd)
of CLSM
SAdd all mix ingredients and mix for 5-7 minutes.
SMaterial volume increases by 25 to 35%.

48. Construction
Sika Corporation
Surface Retarding admixture
S
Retards the set of concrete surface
Applications:
SExposed aggregate surface for architectural purposes
SUsed when concreting done in layers to improve mechanical
key

49. Construction
Sika Corporation
Finishing aid admixture Benefits:
SEnhances finish on concrete flatwork
SEliminates addition of water to aid finishing
SPrevents plastic shrinkage cracking

50. Construction
Sika Corporation
Admixtures for Manufactured Admixtures for Manufactured
concrete products concrete products

51. Construction
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SMCP Market Segment

52. Construction
Sika Corporation
MCP Applications
SStandard Gray Block

53. Construction
Sika Corporation
MCP Applications S
Architectural Split-Face Block

54. Construction
Sika Corporation
MCP Applications SConcrete Pipe

55. Construction
Sika Corporation
MCP Applications
S
Segmental Retaining Walls
(SRW’s)

56. Construction
Sika Corporation
MCP Applications
S
Concrete Pavers

57. Construction
Sika Corporation
MCP Applications
S
Concrete Roof Tile

58. Construction
Sika Corporation
MCP Applications
S
Extruded Hollow-Core Plank

59. Construction
Sika Corporation
Why use admixtures for MCP products?
SProduce Desired Texture
SSpeed Production Rate
SImprove Edge Definition
SIncrease Strength
SReduce Absorption
SControl Efflorescence
SWater Repellency
SImprove Color Vibrancy
SMeet Durability Requirements
SIncrease Profitability

60. Construction
Sika Corporation
MCP Admixtures SPlasticizers
SAccelerating Plasticizers
SAccelerators
SWater-Repellent
Admixtures
SEfflorescence-Controlling

61. Construction
Sika Corporation
Thank you...............