Effectiveness of Western U.S. High-Lime Fly Ash for Use in Concrete

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Title: Effectiveness of Western U.S. High-Lime Fly Ash for Use in Concrete

Author(s): Oscar E. Manz and Gregory J. McCarthy

Publication: Special Publication

Volume: 91

Issue:

Appears on pages(s): 347-366

Keywords: admixtures; compressive strength; concretes; fly ash; freeze-thaw durability; lignite; lime; sulfate resistance,

Date: 2/1/1986

Abstract:
Western U.S. lignite and subbituminous fly ashes have higher CaO + MgO + SO3 and lower Al203 + SiO2 than bituminous ashes. They also have lower loss on ignition and greater proportions of crystalline material. No more than one-third of the total lime is free lime. Several chemically, physically, and mineralogically different lignite and subbituminous fly ashes were used in varying substitutions for portland cement. The following data were obtained: compressive strength, effect of admixtures, freeze-thaw durability, and resistance to sulfate solutions. Depending on the mix proportions, a high lime fly ash may not contribute more to compressive strength than one that has 50 per-cent less lime, and is coarser. High lime fly ashes produce excellent freeze-thaw durability. With certain high lime fly ashes, similar strengths are obtained by either 25 or 75 percent substitution for cement. Extremely low expansions of several high lime fly ash concrete specimens soaking in 10 percent Na2S04 for up to 3 years have indicated that the R factor, (CaO-5)/Fe203, for sulfate resistance is not totally valid. Concretes using high lime fly ashes produce higher early strengths than low lime bituminous ashes.