o’hare modernization program 2.2 raw materials leslie j. struble francis b. nelson kickoff...

O’Hare Modernization Program2.2 Raw Materials

Leslie J. Struble

Francis B. Nelson

Kickoff Meeting, October 28, 2004

Proposed Objectives

• Assess and test suitability of materials– Aggregates

• Properties required for mix design• Properties required for durability

– Cementitious materials• Suitability in combination with other materials

– Admixtures• Suitability in combination with other materials

• Provide database of properties • Make recommendations concerning materials

Aggregates

• Geometric properties– Size distribution

• Physical properties– Adsorption capacity– Hardness

• Durability – Freezing and thawing– Alkali-silica reaction– Alkali-carbonate reaction

Testing Procedures

• Gradation– ASTM C136– ASTM C33

• Adsorption Capacity• Bulk Density

– ASTM C29

• Abrasion Resistance– ASTM C535

• Analysis– X-ray fluoresence– X-ray diffraction– Optical Microscopy

Freezing and Thawing

• Freezing when saturated causes expansion and cracking (D-cracking)

• Expansion affected by– Porosity– Permeability– Degree of saturation– Size

• Mitigation– No mitigation is possible,

avoid susceptible aggregate

Testing Procedures

• ASTM C 666– Procedure A – freeze and thaw in water– Procedure B – freeze in air, thaw in water– Measure ultrasonic resonance frequency

• IDOT Modified Method– Procedure B using length change

Alkali-Silica Reaction

• Chemical reaction– Alkalies in cement and

silica in aggregate – Reaction forms a gel

that adsorbs water and expands

– Expansion causes severe cracking

• Mitigation– Mineral admixtures– Low-alkali cement

Micrograph courtesy of D. Cong, WJE

Testing Procedures

• Petrographic analysis

• ASTM C289– Quick chemical method (24 hours), useful for

quality control

• ASTM C1260– Accelerated mortar-bar method (16 days)

• ASTM C1293– Concrete test (1 year), most reliable

IDOT Experience with Chicago Quarries

• Extensive database of quarries with approved sources

• Freeze/thaw performance, excellent durability

• ASR performance, low expansion

Work Done during Fall 2004

• Reviewed IDOT aggregate database

• Learned IDOT F/T testing procedure

Work Planned for 2004-05

• Select 5 quarries based on IDOT database to avoid deterioration due to F/T, ASR

• Measure properties needed for mix design

• Test aggregates for F/T, ASR – If ASR possible, select and test cements and

mineral admixtures– If F/T possible, reject quarry

Possible Work in Year 2

• If aggregate alkali-reactive, identify suitable cements and mineral admixtures

• Based on recommended mix proportions, identify suitable cements and chemical admixtures

• Test cement-admixture combinations for performance, robustness