Impact of Potassium Acetate Deicing Chemicals on ASR of
Candidate OMP Concrete Materials
Francis B. Nelson III
Leslie J. Struble
January 12, 2006
Overview
• 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
Affected ConcretesHighway pavement and bridge abutment in Peoria, Illinois
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
• 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– 5 natural sands and
1 manufactured sand
– Ottawa sand and Pyrex glass
Mortar Bar Expansion (ASTM C 1260)
0.142%
0.111%
0.134%
0.163%
0.186%
0.097%
0.022%
0.367%
0.000%
0.050%
0.100%
0.150%
0.200%
0.250%
0.300%
0.350%
1 3 5 7 9 11 13 15
Time (days)
Exp
an
sio
n (
%)
Sand 1
Sand 2
Sand 3
Sand 4
Sand 5
Man Sand
Ottawa Sand
Pyrex Glass0.1% to 0.3%: Potentially Deleterious
0.3% and above: Deleterious
0.1% and below: Innocuous
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
• Lowers freezing temperature (-76o F)
• Also anti-icing agent (prevents freezing)
• Avoid use with non air entrained concrete, galvanized metals, and non-watertight electrical systems
Tasks
1. Conduct literature review2. Select representative fine aggregates3. Survey/test deicing chemical4. Test selected samples for ASR using ASTM C 1260
modified to simulate potassium acetate solution5. Test mitigating materials for effective level of
replacement according to ASTM C 15676. Obtain concrete cores from pavement using deicer 7. Examine cores for possible alkali-silica reaction8. Recommend materials for OMP pavements9. Write final report at end of project and Technical Notes
as necessary throughout the study.
Schedule
Task Number1 ( 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 111
2-63
3-56-78
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