1. CON 122
Concrete Admixtures
Session 4
Water Reducing Admixtures &
Set Controlling Admixtures

2. Standard Specification for Chemical
Admixtures for Concrete ASTM C494
 Type A - Water Reducing
 Type B - Retarding
 Type C - Accelerating
NOTE: Type B & C provide no water reduction
 Type D - Water-Reducing & Retarding
 Type E - Water-Reducing & Accelerating
 Type F - High-Range Water Reducing (HRWR)
 Type G - HRWR & Retarding

3. Standard Specification for Chemical
Admixtures for Concrete ASTM C494
Type Description
Type A Water Reducing
Type B* Retarding
Type C* Accelerating
Type D Water-Reducing & Retarding
Type E Water-Reducing & Accelerating
Type F High-Range Water Reducing (HRWR)
Type G HRWR & Retarding
*Note: Types B & C provide no water reduction

4. Liquid Admixture Dispenser
 Liquid admixture
dispenser at a ready
mix plant provides
accurate volumetric
measurement of
admixtures.

5. Set-Control Admixtures
 Modify the setting and strength
development characteristics of
concrete
 Accelerators
 Retarders

6. Effect of Cool Temperatures
on Time of Set
Temperature Approximate Time of Setting
100 F (38 C) 2 hours
90 F (32 C) 3 hours
80 F (27 C) 4 hours
70 F (21 C) 6 hours
60 F (16 C) 8 hours
50 F (10 C) 11 hours
40 F (4 C) 14 hours
20 F (-7 C) Set does not occur
(concrete will freeze)

7. Accelerating Admixtures
ASTM C 494 or AASHTO M 194, Type C
Accelerate the rate of:
 Hydration (setting)
 Early-age strength gain
Calcium chloride accelerators:
 Increase drying shrinkage, potential
reinforcement corrosion, potential scaling
 Darken concrete

8. ACI 306R – Cold Weather Concreting
 1.3.1 ... ―The degree of saturation of newly placed
concrete will be reduced as the concrete hardens
and water is combined in the hydration process.‖
 ―Under such conditions, the time at which the
degree of saturation becomes reduced below a
level which would cause damage by freezing,
corresponds roughly with the time at which the
concrete attains a compressive strength of 500 psi
(3.5 MPa).‖
 ―At temperatures of 50 ºF (10 ºC), most well
proportioned concrete will reach this strength
during the second day.‖

9. Accelerating Admixtures
ASTM C 494 Physical Requirements
Compressive Strength;
Minimum % of Control
Type C Type E
1 day -- --
3 days 125 125
7 days 100 110
28 days 100 110
90 days n/a n/a
6 months 90 100
1 year 90 100

10. Maximum Chloride-Ion Content
Maximum water soluble
Type of member
chloride-ion (CI¯) in concrete
Pre-stressed concrete 0.06
Reinforced concrete ex-
posed to chloride in 0.15
service
Reinforced concrete that
will be dry or protected 1.00
from moisture in service
Other reinforced concrete
0.30
construction

11. Four Classes of Accelerating Admixtures
 Calcium Chloride
 Accelerating admixtures containing
calcium chloride
 Non-chloride accelerating admixtures
 Non-chloride accelerating admixtures for
use in concrete placed in sub-freezing
temperatures

12. Accelerating Admixtures
 Non-chloride
 Non-corrosive
 Dosage rates of up to 60 fl oz/cwt (3.9
L/m3)

13. Hot Weather as Defined in ACI 305R
 "Any combination of high ambient
temperature, high concrete temperature,
low relative humidity, wind velocity, and
solar radiation that impair quality of
concrete by accelerating the rates of
moisture loss and cement hydration”

14. Potential Problems:
Freshly Mixed Concrete in Hot Weather
 Increased:
 water demand
 rate of slump loss
 potential for jobsite
re-tempering
 potential plastic shrinkage
cracking
 potential for cold joints
 Fast setting
 Placing, consolidation &
finishing problems
 Control of air entrainment

15. Plastic Shrinkage Cracking
Wind

16. Potential Problems for Hardened
Concrete in Hot Weather
 Increased
 Drying shrinkage and thermal cracking
 Permeability
 Decreased
 28-day and later age strength
 Durability

17. Retarding Admixtures
 An admixture that causes a decrease in the
rate of hydration of the hydraulic cement,
and lengthens the time of setting (ACI 116)
 ASTM C 494/C 494M (AASHTO M 194)
Classifications
 Type B: Retarding
 Type D: Water-Reducing & Retarding
 Type G: Water-Reducing, High-Range &
Retarding

18. Retarding Admixtures
ASTM C 494 Physical Requirements
Type B Type D
Min. Water Reduction, % -- 5
Initial Time of Set*:
At Least……….. 1:00 later 1:00 later
Not More Than….. 3:30 later 3:30 later
Final Time of Set*:
At Least……….. -- --
Not More Than….. 3:30 later 3:30 later

19. Retarding Admixtures
ASTM C 494 Physical Requirements
Compressive Strength;
Minimum % of Control
Type B Type D
1 day -- --
3 days 90 110
7 days 90 110
28 days 90 100
90 days n/a n/a
6 months 90 100
1 year 90 100

20. Retarding Admixtures
ASTM C 494 Physical Requirements
Flexural Strength;
Minimum % of Control
Type B Type D
1 day -- --
3 days 90 100
7 days 90 100
28 days 90 100

21. Types of Retarding Admixtures
 Conventional Retarders
 Extended-Set Control (ESC) Admixtures
 Extended-Set Control Admixtures are very
potent retarders that facilitate long hauls,
and effective management of returned
concrete.

22. Effect of Retarders on Time of Set
Penetration Resistance, MPa
40
35
30
25
20 No Admix, 32°C
15 No Admix, 23°C
Retarder, 32°C
10 Retarder, 23°C
5
0
2 3 4 5 6 7 8 9 10 11
Time, Hours

23. Effect of Retarders on Strength
7000
Compressive Strength, psi
6000
5000
4000
3000
2000 Plain
Retarder @ 3 fl oz/cwt
1000 Retarder @ 4 fl oz/cwt
Retarder @ 5 fl oz/cwt
0
1 7 28
Time, Days

24. Benefits of Retarders
 Minimize potential for cold joints
 Provide sufficient time for finishing
operations in hot weather
 Permit full form deflection before initial set
of concrete

25. Potential Issues with Retarders
 Over-retardation
 Rapid stiffening & slump loss with some
cements
Time of Set should be determined from trial
mixtures using local materials

26. Retarding Admixtures
…DOT Applications
 Retard set time:
 Hot Weather Concreting
 Deck Pours
 Long Hauls
 Particularly, with Extended-Set Control Admixtures
 Slump retention & control of temperature rise

27. Water Reducing Admixtures
ASTM C 494 or AASHTO M 194
 Type A ―
 reduces water content at least 5%
 tends to retard ― accelerator often added
 Type D ―
 reduces water content 5% min.
 retards set
 Type E ―
 reduces water content 5% min.
 accelerates set

28. What are Water-Reducing
Admixtures?
―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.‖ (ACI 116R)
28

29. In Short…
 Water-reducing admixtures increase the
slump and workability of concrete without
an increase in water-cementitious
materials ratio.

30. Benefits of Water Reduction
 Improved Slump &
Workability
 Without reducing water
content
 Increased Strength
 by reducing total mix Strength
water content while
maintaining slump &
workability
 Economy
 by lowering cement &
water contents

31. Example: Reference Concrete
Cement = 500 lb/yd3
Water = 300 lb/yd3 Slump = 5 in.
Water 300 lb =
Cement
=
500 lb
0.60
Strength = 3500 psi

32. Add Water Reducer & Increase Slump
Cement = 500 lb/yd3 Water = 300 lb/yd3 Slump = 7 in.
Water 300 lb =
Cement
=
500 lb
0.60
Strength = 3500+ psi

33. Reduce Water Content to Maintain Slump
Adjust
agg.
to yield
Cement = 500 lb/yd3 Water = 280 lb/yd3 Slump = 5 in.
again
Water 280 lb =
Cement
=
500 lb
0.56
Strength = 4000+ psi

34. Reduce Cement & Water Contents: COST
Adjust
agg.
to yield
Cement = 467 lb/yd3 Water = 280 lb/yd3 Slump = 5 in.
again
Water 280 lb =
Cement
=
467 lb
0.60
Strength = 3500+ psi

35. Water Reducers are Dispersants
 Water Reducers (all types)
 belong to a group of chemical compounds
known as dispersants

36. Dispersants
Dispersant (Dispersing Agent): Material added to a
solid in liquid suspension to prevent the individually suspended particles
from flocculating.
Dispersant
Shear
Flocculated State Dispersed State
36

37. Water Reducer Chemistries
(categorized by primary ingredients)
1. Lignosulfonic acids & their salts (tree &
pulping)
2. Hydroxylated polymers/carbohydrates (corn
syrup)
3. Hydroxylated carboxylic acids & their salts
4. Sulfonated melamine (MSFC) and
naphthalene formaldehyde (NSFC)
condensates
5. Polyether-polycarboxylates (engineered
comb-shaped polymers)

38. How Water Reducers Work
+ +
+
Water
+ Cement
+
+ +
Charged Cement Particles Cling
Together and Form Flocs
that Trap Water

39. Floc Busting Action of Water Reducers
Dispersant (water reducer) molecules imparts negative charge on surface of cement
particles when absorbed, causing the particles to repel each other
(ELECTROSTATIC REPULSION)
Water Reducer
Freed Water
Cement
Water reducers separates flocs into individual grains. Thus, trapped water is released
and the grains slip by each other like ball bearings, improving the workability of the
concrete.

40. Benefits of Dispersion
 Better dispersion of cement grains results
in increased workability.
 Increased dispersion results in more
efficient hydration which increases
compressive strength.
 Increased dispersion maximizes benefits
of reduced water-cementitious materials
ratio.

41. Benefits of Water Reducers
 Fresh Concrete properties:
 Lower water-cementitious materials ratio
 Improved workability, flowability, pumpability,
and placeability
 Influence time of setting
 Improved finishing

42. Benefits of Water Reducers
 Hardened Concrete properties:
 Increased strength
 Improved durability

43. Water Reducer Types
 Conventional
 Mid-Range
 High-Range (superplasticizers)
Water-reducing admixtures are used
in most concretes produced today !

44. Conventional Water-Reducing
Admixtures
 Effects of Increasing Dosage...
 Diminishing returns.
 Excessive retardation / bleeding.
 Increased air content (lignins).
 Slow strength development.
44

45. Water-Reducing Admixtures
ASTM C 494 Physical Requirements
Compressive Strength;
Minimum % of Control
Type A Type F
1 day -- 140
3 days 110 125
7 days 110 115
110 110
28 days
(120) (120)
90 days (117) (117)
100 100
6 months
(113) (113)
1 year 100 100

46. Mid-Range Water-Reducing
Admixtures
 First Introduced in 1986*
 Dosages of 3-15 fl oz/cwt (175-975
mL/100 kg)
 Most Widely Used Water-Reducer Type
 Based on lignosulfonate salts,
polycarboxylate ether, other with set-,
strength-, & finishability- enhancing
ingredients

47. Mid-Range Water-Reducing
Admixtures
 Provide mid-range water reduction (6-
12%)
 Used in production of concrete with slump
between 5 - 8 in. (125 - 200 mm).
 Used in concretes with moderate w/cm.
 Also used in combination with HRWR at
low w/cm.

48. Benefits of Mid-Range Water Reducers
 True Mid-Range
Performance
 Excellent Finishability
Characteristics
 Fly Ash, Slag Cement,
Silica Fume Mixtures
 Lean & Harsh Mixtures
(Manufactured Sands)
 Flatwork, Curb & Gutter,
etc.

49. Water Reducer and Slump Loss
 Slump loss at 23 C
(73 F) in concretes
containing
conventional water
reducers (ASTM C 494
and AASHTO M 194
Type D) compared
with a control mix.

50. Retardation (Initial Set)
 Retardation of set in
cement-reduced
mixtures relative to
control mixture.
Concretes L and H
contain conventional
water reducer,
concretes N, M, B,
and X contain high-
range water reducer.

51. Retardation (Final Set)
 Retardation of set in
cement-reduced
mixtures relative to
control mixture.
Concretes L and H
contain conventional
water reducer,
concretes N, M, B,
and X contain high-
range water reducer.

52. High-Range Water-Reducing Admixtures
ASTM C 494 or AASHTO M 194
 Type F― Water Reducing
 Type G ― Water Reducing and
Retarding
 Reduce H2O content 12% -30%
 Reduced W/C produces conc. with:
 Compressive Strength > 70 MPa
 Increased early strength gain
 Reduced Cl ion penetration

53. Why Use High-Range Water Reducers?
Highly workable, non-segregating, very pumpable concrete

54. Benefits of High-Range Water
Reducers
 Significant water reduction
 high-early & high ultimate strengths
 low permeability & increased durability
 more effective use of cementitious materials
 High slump & workability
 faster discharge, pumping & placement
 less consolidation effort

55. Low water to cement ratio
concrete with low chloride
permeability—easily made with
high-range water reducers—is
ideal for bridge decks.

56. Potential Issues with High-
Range Water Reducers
 Segregation potential if dosage & total
water content are out of balance
 Impact on air-void system
 Retardation potential @ high dosages
 Erratic performance* at lower slumps
(Production Nightmare !!!)
* Typically with non-Polycarboxylate Ether chemistries

57. High-Range Water Reducers
…Impact on Air-Void System & Freeze Thaw
 Studies show that freeze-thaw durability is
typically not affected even though spacing
and size of air voids may be altered.

58. High-Range Water Reducer and
Slump Loss
 Slump loss at 23 C
(73 F) in mixtures
containing high-range
water reducers (N, M,
B, and X) compared
with control mixture
(C).

59. HRWR and Air Loss
Final air Percent Rate of air
Initial air content, air loss,
Mixture content, % %* retained %/minute
Control C 5.4 3.0 56 0.020
Water L 7.0 4.7 67 0.038
reducer H 6.2 4.6 74 0.040
High-range N 6.8 4.8 71 0.040
water M 6.4 3.8 59 0.065
reducer B 6.8 5.6 82 0.048
*at point where slump falls below 25 mm
Loss of Air from Cement Reduced Concrete Mixtures
Whiting and Dziedzic 1992.

60. Compressive Strength
Development
 Compressive strength
development in
cement-reduced
concretes: control
mixture (C) and
concretes containing
high-range water
reducers (N, M, and
X).

61. Plasticizers for Flowing Concrete
 Also known as – SUPERPLASTICIZERS
(ASTM C 1017)
 Plasticizers for flowing concrete
 Type 1: Plasticizing
 Plasticizing and Retard
 Essentially High-Range Water Reducer

62. Plasticizers for Flowing Concrete
 Superplasticizers (ASTM C 1017)
 Produce flowing concrete with high slump
(≥ 190 mm [7.5 in.]
 Reduce bleeding
 Extended-slump-life plasticizer reduces
slump loss.

63. Flowing
Concrete
Flowable concrete with a high slump (top) is
easily placed (middle), even in areas of
63
heavy reinforcing steel congestion (bottom)

64. Flowing Concretes and Slump
Loss
 Slump loss at 32 C
(90 F) in flowing
concretes (TN, TM,
TB, and TX)
compared with
control mixture (TC).

65. Retardation of Flowing Concrete
(Initial Set)
 Retardation of set in
flowing concrete with
plasticizers (N, M, B,
and X) relative to
control mixture.

66. Retardation of Flowing Concrete
(Final Set)
 Retardation of set in
flowing concrete with
plasticizers (N, M, B,
and X) relative to
control mixture.

67. Compressive Strength Development
in Flowing Concrete
 Compressive strength
development in
flowing concretes. C
is the control mixture.
Mixtures FN, FM, and
FX contain
plasticizers.

68. Bleeding of Flowing Concrete
 Bleeding of flowing
concretes with
plasticizers (N, M, B,
and X) compared to
control (C).

69. Retarding Admixtures
ASTM C 494 or AASHTO M 194, Type B
 Delay setting or hardening rate for:
 Hot-weather concreting
 Difficult placements
 Special finishing processes

70. Slump Loss at Various
Temperatures
 Slump loss at various
temperatures for
conventional
concretes prepared
with and without set-
retarding admixture.

71. Retarding and Water-Reducing
Admixtures
Please return to Blackboard and watch the
following videos:
 Video 1: Retarding Admixtures
 Video 2: Water-Reducing Admixtures