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