60 • May 2017 www.concreteproducts.com
TECHNICAL TALK
BY CLAUDIO ARATO
The decline in coal for energy has reduced available fly ash supply to
the concrete industry and generated a significant increase in finished
product variability, which has led to a sharp rise in material costs for
high profile projects such as One World Trade Center, New York City.
The increase in coal combustion residuals (CCR) variability and
decline in production has resulted in a shortfall in excess of 100
million tons of high quality coal ash stock.
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Anecdotal stories abound
about CCR imported from Asia to meet U.S. market demands over the
last year. The American Coal Ash Association (ACAA) is now taking
steps to quantify U.S. coal ash imports by commissioning an indus-
try-wide survey with the results due this September. Why is there a
need for CCR imports when there are nearly two billion tons in storage
plus annual production?
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The answer, simply, is consistency.
Over the last several decades, there has been a consistent increase
in the demand to beneficiate ash generated from coal-fired power
plants. Simultaneously, there has been a steep decline in global
coal-derived energy, from greater than 50 percent to less than 30
percent.
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The coal-fired power industry has made excellent progress
in quantifying and mitigating the perception of risk associated with
CCR, generically "coal ash," as a pozzolanic high quality material for
the production of high performance concrete (HPC). This is seen in
the dramatic rise in the use of CCR in North America as the product
Uniform particle size coal ash: Essential for future concrete applications
At the heart of the SonoAsh process is the Sonicator, which enables
the extraction and gradation of ASTM C618 fly ash from previously
landfill- or impoundment-grade coal combustion residuals.