Measurement of the pore size distribution of limestone aggregates in concrete pavement cores : phase I.
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2012-04-01
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Edition:Final report; April 2011-Nov. 2011.
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Abstract:Freeze-thaw damage is one of the common forms of distress for concrete pavements in Kansas. D-Cracking is a form of
freeze-thaw damage caused by aggregates with poor freeze-thaw durability. It is believed that pores in the aggregates below
10 μm in diameter contribute to this poor durability. In this Phase I study, a methodology for preparing limestone coarse
aggregates taken from concrete cores for examination by scanning electron microscopy (SEM) was developed. Software was
developed to quantify the aggregate pore size distribution from the SEM images. The procedure was used on cores from two
concrete pavements with different field performance. The aggregates from one of the pavements studied, pavement B, had a
larger total area of pores and larger number of pores below 1.5 μm2 in area. The aggregates from the other pavement,
pavement A, had a smaller total area and smaller number of pores below 1.5 μm2 in area, but a higher percentage of the
pores were in this smaller pore size range. Cores from the two pavements were also tested for potential alkali-aggregate
reactivity by measuring their length change after soaking in 1N NaOH solution at 80°C. It was found that the aggregates in
pavement B showed much more potential for expansion from alkali-aggregate reaction than pavement A with approximately
0.2% expansion at 28 days for pavement B vs. 0.04% expansion for pavement A.
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