O. Tavares

1. CON 124
Basic Concrete Mix Design Proportioning
Session 7
Concrete Durability

2. Session Topics
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Dicers
Mass Concrete
Carbonation
Abrasion Resistance
Special Aggregate Reaction
Mechanisms
Curing Measures

3. De-Icers

4. 
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De-icing Salts for Snow & Ice Removal
Mixture design

5. 
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De-icing Salts for Snow & Ice Removal
Mixture design

6. De-Icing Chemicals Exposure
Cementitious
materials
Fly ash (Class C up to
35%) and natural
pozzolans
Slag
Silica fume
Total of fly ash, slag,
silica fume and
natural pozzolans
Maximum
replacement , %
25
50
10
50
Cementitious
Materials
Requirements for
Concrete Exposed
to Deicing
Chemicals (Ref
ACI 318)

7. Fly Ash and Natural Pozzolans
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Reduced Permeability & Diffusivity
Resistance to ASR
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Consumption of Ca(OH)2
Reduction in water mobility
Resistance to Sulfate (Low CaO pozzolans)
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Dilution of C3A
Consumption of Ca(OH)2

8. Blast Furnace Slag
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Reduced Permeability & Diffusivity
Resistance to ASR (>35%)
Resistance to Sulfate
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Dilution of C3A

9. De-Icing Chemicals
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Sodium Chloride
Calcium Chloride
Both in combination
Magnesium Chloride
Urea
All of the above in solution or salts form

10. Disintegration Mechanism
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Surface disintegration in the form of pitting or
scaling
High degree of saturation in the concrete is
mainly responsible for their detrimental effect
due to lower vapor pressure
Development of disruptive osmotic and hydraulic
pressures during freezing, principally in the paste
Concentrations (3 to 4%) of deicing solutions
most severe

11. Recommended Solutions
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Benefit from entrained air in concrete
exposure same as frost action
Concrete surface should have received some
drying, and minimum strength level specified
and concrete cover
Do not use in pre-stressed concrete or where
steel reinforcement has been used due to
corrosion effect

12. Mass Concrete
Mass concrete requires
minimizing heat
generation in massive
elements or structures
such as very thick
bridge supports, and
dams.

13. Mass Concrete
Hoover dam, shown
here, used a Type IV
cement to control
temperature rise.

14. Mass Concrete Heat Generation
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Control the generation of heat and resultant
volume change within the mass will require
consideration of temperature control
measures
Concrete temperature rise of 10 to 15 F per
100 lb of Portland cement/yd3 in 18 to 72
hours
Temperature rise of the concrete mass creates
thermal gradient causing Cracking

15. Thermal Cracking
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May reduce the service life of a structure by
promoting early deterioration or excessive
maintenance
Selection of proper mixture proportions is
only one means of controlling temperature
rise
Additional aspects of the concrete work
should be studied and incorporated into the
design and construction requirements

16. Nominal Maximum Size Aggregate
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Mass concrete is not necessarily larger aggregate
concrete
The minimum cross sectional dimensions of a
solid concrete member approach or exceed 2 to 3
ft or when cement contents above 600 lb/yd3 are
being used
Larger aggregate provides less surface area to be
coated by cement paste, a reduction in the
quantity of cement and water can be realized for
the same water-cement ratio

17. Nominal Maximum Size Aggregate
ACI Recommendation

18. Cementitious Materials Impact
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Reduction of heat of hydration, improved
workability, improved strength and/or
improved durability
Fly ash, natural pozzolans meeting ASTM C
618
Slag cement meeting ASTM C 989

19. Portland Cement Impact
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Fineness of cement is an important factor affecting rate
of heat liberation, particularly at early ages
ASTM C150 contains optional limits for the heat of
hydration for Type IV and also includes Type II (MH)
moderate heat cement that limits the C3S and C3A
content
Chemical optional requirements are less restrictive in
ASTM C150, as compared to the optional Physical
requirement when evoked; 60.cal/g is the maximum
permitted for a Type V cement (7 days) or 70 cal/g (28
days)

20. Principle Phases of Portland Cement
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Tricalcium aluminate (C3A) releases most of its
heat in the first day or so
Tricalcium silicate (C3S) in the first week
Dicalcium silicate (C2S) and calcium
aluminoferrite (C4AF) hydrate more slowly

21. Blended Cement Impact
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Blended cements have lower heats of hydration
than Portland cements
Generally, most slag cements, fly ashes, and
natural pozzolans will hydrate after 28-day thus
lowering the maximum heat peak of a concrete
mixture
The volume occupy by supplementary materials
like slag cement, fly ashes, and natural pozzolans
is typically less than Portland cement.

22. Carbonation Affects
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Carbon dioxide causes a reaction producing
carbonates accompanied by shrinkage
Carbonation during production can improve
the strength, hardness, and dimensional
stability of concrete products
Carbonation can result in deterioration and a
decrease in the pH of the cement paste
leading to corrosion of reinforcement near the
surface

23. Exposure to Carbon Dioxide (CO2)
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During the hardening process can affect the
finished surface of slabs, leaving a soft,
dusting, less wear-resistant surface
During the hardening process, the use of
unvented heaters or exposure to exhaust
fumes from equipment or other sources can
produce a highly porous surface subject to
further chemical attack

24. Dusting Surface
Dusting of
surface caused
by the use of
unvented
heaters

25. Crazing Surface
Crazing surface due
to premature drying,
shrinkage of
concrete surface
caused by exhaust
fumes of heating
equipment in an
enclosed area

26. Reaction of Hydrated Portland Cement
with CO2
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Highly dependent on the relative humidity of
the environment, temperature, permeability
of the concrete, and concentration of CO2
Highest rates of carbonation occur when the
relative humidity is maintained between 50%
and 75%
Below 25% relative humidity, the degree of
carbonation that takes place is considered
insignificant

27. Absorption of Ambient CO2
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CO2 absorbed by rain enters the groundwater as
carbonic acid
CO2, together with humic, carbonic, acid, can be
dissolved from decaying vegetation, resulting in
high levels of free CO2
The rate of attack, similar to that by CO2 in the
atmosphere, is dependent upon the properties of
the concrete and concentration of the aggressive
CO2

28. Abrasion Resistance
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“Ability of a surface to resist being worn away
by rubbing and friction”
Abrasion resistance of concrete is a
progressive phenomenon
Closely related to compressive strength at the
wearing surface
degradation that is related to aggregate-topaste

29. Concrete Mixture Quality
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Avoiding segregation;
Eliminating bleeding;
Properly timed finishing;
Minimizing surface w/cm (forbidding any
water addition to the surface to aid finishing);
Hard toweling of the surface; and
Proper curing procedures.

30. Abrasion Damage
Wear of
concrete
surface,
abrasion

31. Abrasion Damage
Abrasion
damage due
to concrete
baffle
blocks and
floor area of
Dam
sluiceway

32. Special Aggregates
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Addition of high-quality quartz
Traprock, or emery aggregates
A blend of metallic aggregate
Use of two-course floors using a high-strength
topping is generally limited to floors where
both abrasion and impact are destructive
effects at the surface

33. Pavement Abrasion Resistance
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Adequate texture and skid resistance for
proper vehicular control
Related to concrete’s compressive strength
and to the type of aggregate in the concrete;
harder aggregates resist wear better than
softer aggregates
Wear of pavement surfaces occurs due to the
rubbing action from the wheels of vehicular
traffic

34. Pavement Abrasion
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Production Operations, or foot or vehicular
traffic
Wind or waterborne particles can also abrade
concrete surfaces
Abrasion is of little concern structurally, yet
there may be a dusting problem that can be
quite objectionable in some kinds of service
Abrasion resistance of concrete is a
progressive phenomenon

35. Wind Abated Surface
Wind Abated
Surface more
potential for
dusting

36. Testing for Abrasion Resistance
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Los Angeles (LA) abrasion test (rattler method)
performed in accordance with ASTM C 131 or
ASTM C 535 / AASHTO T 96
ASTM C 418 subjects the concrete surface to airdriven silica sand, and the loss of volume of
concrete is determined
ASTM C 779, three procedures simulate different
abrasion conditions
ASTM C 944, a rotating cutter abrades the surface
of the concrete under load

37. Alkali-carbonate rock reaction
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Detrimental reactions are usually associated
with argillaceous dolomitic limestones that
have somewhat unusual textural
characteristics
Some carbonate rocks occurs in which the
peripheral zones of the aggregate particles in
contact with cement paste are modified and
develop prominent rims within the particle

38. Alkali-Carbonate Reactivity
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Brucite [Mg(OH)2], dedolomitization of
Magnesium
Feature is different from alkali-silica reactivity,
in which the alkali is combined in the reaction
product as the reaction proceeds
Presence of clay minerals appears significant

39. Affected Concrete Characteristics
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A network of pattern or map cracks
Typically where the concrete has a constantly
renewable supply of moisture
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Waterline in piers
Earth behind retaining walls wick action in posts
or columns
General absence of silica- gel exuding from cracks.

40. Map Cracking

41. Evaluation of Affected Concrete
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Damage can be the result of:
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Poor Design
Faulty Workmanship
Mechanical Abrasive Action
Cavitation Or Erosion From Hydraulic Action
Leaching
Chemical Attack
Chemical Reaction Inherent In The Concrete Mixture
Exposure To Deicing Agents
Corrosion Of Embedded Metal Or
Another Lengthy Exposure To An Unfavorable Environment
Guidance for examining and sampling hardened concrete in
construction is found in ASTM C 823

42. D-Cracking Deterioration
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D-cracking is damage that occurs in concrete
due to expansive freezing of water in some
aggregate particles
The damage normally starts near joints to
form a characteristic D-shaped crack

43. D-Cracking

44. D-Cracking Reduction
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Selecting aggregates that are less susceptible
to freeze-thaw deterioration
Reducing the maximum aggregate size for
marginal aggregates are used
Providing drainage for carrying water away
from the base may prevent saturation of the
pavement

45. D- Cracking Aggregates Characteristics
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Aggregate particles with coarse pore structure
may be susceptible to freeze-thaw damage
Particles become saturated and the water
freezes, expanding water trapped in the pores
cannot get out
Aggregate particles cannot accom-modate the
pressure from the expanding water; the
particles crack and deteriorate

46. Identifying D-Cracking
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Closely spaced cracks parallel to transverse
and longitudinal joints
Location where aggregate is most likely to
become saturated
Cracks multiply outward from the joints
toward the center of the pavement slab

47. D-Cracking Corrective Measures
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Designing a mixture it is critical to select
aggregates that are not susceptible to freezethaw deterioration
If marginal aggregates must be used, you may
be able to reduce D-cracking susceptibility by
reducing the maximum particle size
Providing good drain-age for carrying water
away from the pavement base

48. Please return to Blackboard and watch
the following videos:
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Video 1: Maximum Size
Video 2: Minimum Size

49. Questions?
Email cemtek@netzero.net