O’Hare Modernization Program 2.2 Raw Materials Leslie J. Struble Francis Nelson and Li Ai OMP Program Meeting, September 21, 2006

Accomplishments in 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

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 ( 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%

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

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)

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)

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

Expansion of Local Sands

Expansion with Mitigating Materials

Expansion in Deicing Solution

Expansion of Fused Silica in Deicing Solution