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