Transcript Raw Materials Study at Chicago O’Hare Int’l Airport

Impact of Potassium Acetate
Deicing Chemicals on ASR of
Candidate OMP Concrete Materials
Francis B. Nelson III
Leslie J. Struble
January 12, 2006
Overview
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Alkali Silica Reaction
Previous Work
Deicer Background
Tasks
Schedule
Testing Programs
Alkali Silica Reaction
• Chemical reaction between alkali and
hydroxide ions in pore solution and
reactive silica in aggregate
• Reaction produces gel
• Gel adsorbs water and swells, causing
expansion and cracking of aggregate
Highway pavement and
bridge abutment in
Peoria, Illinois
Affected Concretes
Concrete
anchor for
cable-stay
bridge, Royal
Gorge,
Colorado
Effect of Supplemental Cementing
Materials
• Fly ash, slag, silica
fume, metakaolin all
reduce expansion by
replacing cement,
lowering alkali
concentration
• Effective replacement
level must be
determined for specific
material
PCA
To Prevent ASR
• Recognize and avoid
susceptible aggregate
• Use low alkali cement
• Use supplemental
cementing material
Previous Work
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Tech Notes
IDOT work
UIUC Testing
Recommendations to OMP
Tech Notes
• #9 – Freeze Thaw Performance of Coarse
Aggregates
– Recommended Use of IDOT F/T list
• #10 – Summary of IDOT & ASTM Specifications
for Coarse Aggregate Gradation
– Described CA Gradations for Use at OMP
• #20 – FAA Concrete Materials Specification
Evaluation
– Recommended Material Guidelines for OMP
IDOT Working Group Meetings
• Working with Industry to develop ASR specification
• Slowly introduce a statewide specification (June 2006)
– Special provision on job specific basis (Dan Ryan
Project using GGBFS)
• Only District 4 (Peoria) showing evidence in pavements
of ASR currently
– Other districts have reactive aggregates however
• Developing List of Fine Aggregate Producers
– Proposed Four Categories of Aggregate Reactivity
– According to ASTM C 1260 Test Results
• Allowing mitigation according to ASTM C 1567
UIUC ASR Testing
• Aggregates
selected from
Chicago market
0.367%
0.350%
0.3% and above: Deleterious
Sand 1
Sand 2
Sand 3
Sand 4
Sand 5
Man Sand
Ottawa Sand
Pyrex Glass
0.300%
0.250%
Expansion (%)
– 5 natural sands and
1 manufactured
sand
– Ottawa sand and
Pyrex glass
Mortar Bar Expansion (ASTM C 1260)
0.1% to 0.3%:
Potentially
Deleterious
0.200%
0.186%
0.163%
0.150%
0.142%
0.134%
0.1% and below: Innocuous
0.111%
0.100%
0.097%
0.050%
0.022%
0.000%
1
3
5
7
9
Time (days)
11
13
15
UIUC ASR Recommendations
• Two categories of expansion rather than
three (<0.1% and >0.1%)
• No maximum alkali content for cements
(due to potassium in deicer)
• Allow contractors to use ASTM C 1567 to
make a combination of aggregate, cement,
and mineral admixture that yields
expansion less than 0.1%
Mitigating ASR Testing
• Test Mineral Admixtures
– Test for potential combinations to mitigate
against reactive aggregates, use ASTM C
1567 test method.
– Use fine aggregates previously tested and
combine with mitigating materials, such as fly
ash and slag, to test for decreased expansion.
Mitigating Materials Test Program
• ASTM C 1567
– Class F Fly Ash
• 15%, 10%, 5%, +/-
– Class C Fly Ash
• 15%, +/-
– Ground Granulated Blast Furnace Slag
• 20%, 25%, 15%, +/-
– Silica Fume*
• 10%, +/-
– Metakaolin*
• 10%, +/-
Background on Potassium
Acetate Deicer
• Non-chloride based deicer
• Non-toxic, Biodegradable and less
corrosive
o
• Lowers freezing temperature (-76 F)
• Also anti-icing agent (prevents freezing)
• Avoid use with non air entrained concrete,
galvanized metals, and non-watertight
electrical systems
Tasks
1.
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6.
7.
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9.
Conduct literature review
Select representative fine aggregates
Survey/test deicing chemical
Test selected samples for ASR using ASTM C 1260
modified to simulate potassium acetate solution
Test mitigating materials for effective level of
replacement according to ASTM C 1567
Obtain concrete cores from pavement using deicer
Examine cores for possible alkali-silica reaction
Recommend materials for OMP pavements
Write final report at end of project and Technical Notes
as necessary throughout the study.
Schedule
Task Number
1 ( perform literature review)
2 (select aggregates)
3 (survey alkali concentration)
4-5 (test samples)
6 (obtain concrete cores)
7 (test cores)
8 (make recommendations)
9 (write final report)
Month
1
1
1
2-6
3
3-5
6-7
8
Potassium Acetate Studies
• Modified ASTM C 1260 tests
– Work done by Prasad Rangaraju, PhD
• pH and Chemical Composition
Rangaraju et al 2005
Modified ASTM C 1260
• Compare 14 day expansions between NaOH
(left) and PA (right)
Rangaraju et al 2005
Mortar Bars and Concentration
• Concentration of 6.46 M is what is applied to
pavements
• Expansion accelerated so much tests ended due
to severe cracking and warping of mortar bars
Rangaraju et al 2005
Deicer Testing Program
• 5 natural sands tested previously
– Test in deicer solution and compare
expansions
• Test mitigating mixtures from ASTM C
1567 results
– Test in deicer solution and compare
expansions
Assistance from OMP
• Obtaining cores from pavements at
Midway and/or O’Hare
• History and understanding of deicer use
so far in Chicago
• Open for discussion