CON 124 - Session 3 Sulfate Attack O. Tavares

1. CON 124
Basic Concrete Mix Design Proportioning
Session 3
Concrete Durability

2. CON 124 - Session 3
 This session will discuss
 Sulfate Attack
 Corrosion of Steel
 Mechanisms
 Recommendations and solutions

3. Sulfate Attack Mechanism
 Sulfate ions (SO4
-2) react with hydration products
(calcium hydroxide and aluminate hydrates)
 Reaction products result in swelling (mechanism
is uncertain)
 Swelling pressures destroy cement matrix
 Affected by
 Cement type
 Sulfate ion concentration in water or soil
 Permeability of concrete
 Presence water

4. External Sulfate Attack
External to internal
progression of deterioration

5. Mitigation of Sulfate Attack
 Use low w/c
 Use sulfate resistant cement (Type V)
 Use supplementary cementitious materials

6. Test method ASTM C1580 for determining
water-soluble sulfates in soil

7. Table 4.2.1.b Exposure Category S –
Sulfate Exposure
Class Description Water-soluble
sulfate (SO4) in
soil, % by weight
Sulfate (SO4) in
water, ppm
S0 NA < 0.10 < 150
S1 Moderate 0.10 to 0.20 150 to 1500
S2 Severe 0.20 to 2.00 1500 to 10,000
S3 Very Severe > 2.00 >10,000

8. Sulfate
Class
Maximum
w/cm (Normal
wt.), by mass
Minimum f'c,
MPa (psi)
ASTM C150
ASTM
C595
ASTM
C1157
Other
S0 — — — — — —
S1 0.50 28 (4000) II
IP(MS),
IS(<70)
(MS)
MS —
S2 0.45 31 (4500) V — HS
No calcium
chloride
S3 0.45 31 (4500)
V + pozz
or slag
—
HS +
pozz or
slag
No calcium
chloride
Table 4.3.1.b Exposure Category S –
Sulfate Exposure
Cement Types for Sulfate Resistance of various classes of sulfate attack, most
severe sulfate resistance class is S3

9. Exposure Class
Max. Expansion When
Tested Using ASTM C1012
S1 0.10% at 6 months
S2
0.05% at 6 months, or
0.10% at 12 months*
S3
0.10% at 18 months
* 12 month applies when 6 month is not met
Table 4.5.1 Requirements for Establishing Suitability of
Cementitious Materials Combinations When Exposed
to Water-Soluble Sulfate
Exposure Class and maximum expansion according to test
method ASTM C1012

10. ASTM C1012
Standard Test Method ASTM C1012 for testing expansion
due to sulfate solution.

11. ASTM C1012
• Evaluate sulfate
resistance of different
cementitious materials
(cement, pozzolans, slag)
• Use ASTM C109/C109M
mortar mixture
proportions to make
25 x 15 x 185 mm prisms
• Immerse in sodium
sulfate solution
• Measure length change

12. Effect of Cement C3A on
Sulfate Resistance
121110987654
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
C3A
SulfateAttack4Month%Expansion
R-Sq = 0.320
Y = 0.116075 - 3.71E -02X + 5.80E -03X **2

13. Long-term Sulfate Exposure Study
Visual Rating Scale
1.1 2.5 5.0

14. Corrosion of Bridge Structures
 Fulton Road Bridge, Cleveland, Ohio
 Corrosion due to deicing salts used on roadway
 Wooden platform was built underneath concrete arch to protect patrons to
the zoo from falling concrete
 Deck and columns need to be replaced because structurally deficient.
Consulting Engineers trying to save arches and apply cathodic protection

15. Corrosion: How Big a Problem?
“The average bridge deck located in a
snow-belt State with black reinforcing steel
and 40 mm (1.5 in.) of concrete cover has
shown spalling in about 7 to 10 years after
construction and has required construction
and has required rehabilitation in about 20
years after construction.”
Repair / Replacement Cost: ~ $ 20 billion & increasing

16. Marine Corrosion

17. Marine Corrosion – Replacement Bridge

18. Corrosion of Steel in Concrete
High alkalinity of concrete promotes
formation & stabilization of natural
protective oxide layer at steel surface.

19. Corrosion of Steel in Concrete
 Electrochemical process that requires:
 Moisture & Oxygen
 Breakdown of Protective Oxide Layer (the Passive
Layer)

20. 1/2 O2 + H2O + 2e- 2OH-
Water
Oxygen
Chlorides, CO2
iron
OH-
Cathode
Anode
“ionic path”
Electronic Path
Fe 2e- + Fe2+
e-
Corrosion Reaction - Necessary Factors
Corrosion Reaction due to movement of ions

21. Corrosion of Steel in Concrete:
Net Effect
 Corrosion by-product (rust) induces tensile
stresses within matrix…..

22. Sources of Chloride
 De-icing Salts for
Snow & Ice Removal
 Groundwater
 Brackish Water
 Seawater &
Airborne
 Mixture design

23. Sources of Chloride
 De-icing Salts for
Snow & Ice Removal
 Groundwater
 Brackish Water
 Seawater &
Airborne
 Mixture design

24. Sources of Chloride
 De-icing Salts for
Snow & Ice Removal
 Groundwater
 Brackish Water
 Seawater &
Airborne
 Mixture design

25. Sources of Chloride
 De-icing Salts for
Snow & Ice Removal
 Groundwater
 Brackish Water
 Seawater &
Airborne
 Mixture design

26. Rule #1 for Corrosion Protection of
Steel in Concrete
Good Concreting Practices
 Good quality concrete
 Low water-cementitious materials ratio
 High-range water-reducing admixture
 Proper placement & consolidation
 Good Curing !!!

27. ACI 318 Classes for Corrosion Exposure
Category
Category Severity Class Condition
C
Corrosion
Protection of
Reinforcement
Not Applicable C0 Concrete dry or protected
from moisture
Moderate C1 Concrete exposed to moisture
but not to external sources of
chlorides
Severe C2 Concrete exposed to moisture
and an external source of
chlorides from deicing
chemicals, salt, brackish
water, seawater, or spray from
these sources

28. ACI 318 Requirements for Concrete for
Corrosion Exposure Category
Exposure
Class
Max.w
/cm
Min.f’
c
(psi)
Additional Minimum Requirements
Max Water-Soluble Chloride Ion
(Cl-) Content in Concrete (percent
by weight of cement) Related
Provisions
Reinforced
Concrete
Prestressed
Concrete
C0 n/a 2,500 1.00 0.06 None
C1 n/a 2,500 0.30 0.06
C2 0.40 5,000 0.15 0.06 7.7.6, 18.16

29. Please return to Blackboard and watch
the following videos:
 Video 1: Concrete Durability Freezing-Thawing
Freethaw.mpg

30. Questions?
Email cemtek@netzero.net