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1
OHare Modernization Program2.2 Raw Materials

• Leslie J. Struble
• Francis Nelson and Li Ai

OMP Program Meeting, September 21, 2006
2
Accomplishments in 2004-6

• Recommendations to avoid freeze-thaw and ASR
  deterioration (Tech Notes)
• Tested mortars containing candidate sands and
  mitigating materials
• Tested mortars in potassium acetate deicing
  solution

3
Recommendations (Tech Notes)

• Recommended specifications for aggregates to
  prevent freeze-thaw deterioration (TN 9)
• Summarized aggregate gradation specifications (TN
  10)
• Recommended specifications to prevent ASR
  deterioration (TN 20)
• Two categories of expansion rather than three
  (lt0.1 and gt0.1)
• 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

4
Tests of Candidate Sands and Mitigating Materials

• Demonstrated that most local sands potentially
  deleterious
• Showed levels of mineral admixtures needed to
  prevent deleterious expansion
• 10 fly ash
• 30 slag
• 10 silica fume

5
Tests with Deicing Solution

• Showed that substantial expansion of glass on
  immersion in deicing solution (verified results
  reported by Rangaraju)
• Showed that pH of deicing solution increased on
  exposure to reacting mortar and to calcium
  hydroxide (preliminary experiments)
• Showed that local sands have low expansion on
  immersion in potassium acetate deicing solution
  (unexpected result, need to understand better
  before making recommendations for specifications)

6
Work Underway During Remainder of 2006

• Analyze cores from Midway of concrete exposed to
  potassium acetate deicing solution (when cores
  are available)
• Complete MS thesis (Francis Nelson)
• Prepare technical note on mitigating ASR with fly
  ash (based on Francis thesis)
• Prepare technical note on effects of potassium
  acetate deicing solution (based on Francis
  thesis)
• Continue preliminary experiments on chemistry of
  interaction between reacting mortar and deicing
  solution (Li Ai)

7
Work Proposed During 2007

• Objective to understand interaction between
  reacting mortar and potassium acetate deicing
  solution
• To provide basis for materials recommendations
• Study chemistry of reaction of mortar in deicing
  solution
• What produces rise in pH?
• Does pH rise depend on aggregate reactivity?
• Does pH rise depends on cement composition?
• Verify that chert is resistant to deleterious
  effects of deicing solution
• Explore whether mitigating materials (fly ash,
  slag) are effective in preventing ASR due to
  deicing solution

8
Expansion of Local Sands
9
Expansion with Mitigating Materials
10
Expansion in Deicing Solution
11
Expansion of Fused Silica in Deicing Solution