Reader Response Draft #3
The
NaturalBlaze.com article, "Researchers Turn Waste from Coal Power Plants
into Concrete" (2019), reports that researchers from Drexel University
have discovered that recycling coal ash is a sustainable solution to protect
the natural environment and improve the built environment. Millions of tons of
coal ash, a less harmful by-product of coal-fired power plants, end up in
landfills each year. The article also states that by turning the waste product
into a special additive, and adding it to a concrete mixture, will improve the
resulting concrete’s durability and quality (as cited in the journal “Cement
and Concrete Composites”). The article also asserts that proper mixing and
curing is required to use concrete without any drawbacks. Hence, the special
concrete additive will shorten the time for concrete to harden. Using this
method will reduce the amount of coal ash in landfills and benefit the concrete
industry.
Based on the article,
turning coal bottom ash into an additive for concrete mixture has many
environmental benefits such as reducing the amount of coal bottom ash in
landfills, and is also advantageous to the concrete industry in creating a
durable concrete . However, the article fails to address the disadvantages of using
coal bottom ash as a concrete additive.
One of the
disadvantages of using coal bottom ash in concrete is that it increases the
water absorption rate in concrete. According to the article, “Potential Use of
Malaysian Thermal Power Plants Coal Bottom Ash in Construction” (2012), as coal
bottom ash has a high water absorption rate, it requires higher water content
to achieve the “degree of lubrication” for a workable mix. As the strength of
concrete depends on the water-cement ratio, this would mean that the higher the
water-cement ratio, the lower the strength of the concrete. If the concrete
mixture absorbs too much water content, it will adversely affect the strength
of the concrete.
From the article,
“Researchers Turn Waste from Coal Power Plants into Concrete" (2019), it is
stated that concrete requires the exact amount of moisture inside it as once
the powder and aggregates form a strong
“cementing matrix”, it becomes difficult for moisture to penetrate once
it begins to dry. As coal bottom ash is used as an internal curing for
concrete, it requires the right amount of water content in order for it to
effectively cure the concrete from the inside. This mixture also needs a high
percentage of water in order for the coal bottom ash to be able to mix with the
cement mixture.
Another
disadvantage is the resulting lower compressive and flexural strength.
According to a study, “Use of Bottom Ash as Fine Aggregate in Concrete: A
Review” (2016), it was found that the compressive strength of bottom ash
concrete is “lower than the control concrete specimens at all the ages”.
Different amount of coal bottom ash was added to test if the different amounts
will affect the compressive and flexural strength of concrete. As noted by
Adbus Salaam Cadersa et.al(2014), the result shows that with the increasing
bottom ash content, the strength decreases proportionately. It is also noted
that coal bottom ash concrete gains strength slowly and only starts to increase
rapidly after 28 days. The study also stated that coal bottom ash concrete’s flexural
strength is lesser than that of the controlled concrete.
Using
coal bottom ash as a special concrete additive is a possible solution for
environmental preservation and is beneficial to the concrete industry. However,
the disadvantages of using the additive must also be considered before it could
be implemented in the industry.
References:
Abubakar, A, U., Baharudin, K, S. (2012). Potential use of Malaysian
thermal power plans coal bottom ash in construction. International Journal of Sustainable Construction Engineering &
Technology.
Received November 11, 2012, from https://publisher.uthm.edu.my/ojs/index.php/IJSCET/article/view/429/362
Ahady, S., Gupta, S. (2016). Use of bottom ash as fine aggregate
in concrete: a review.
Retrieved February 28, 2020, from
Balapour, M., Zhao, W. J., Garboczi, E. J., Oo, N. Y., Spatari,
S., Hsuan, G. Y., Billien, P., Farnam, Y. (2019). Potential use of lightweight
aggregate (LWA) produced from bottom coal ash for internal curing of concrete
systems.
Retrieved October 1, 2019, from https://www.sciencedirect.com/science/article/pii/S0958946519301593?via%3Dihub
Natural Blaze. (2019). Researchers turn waste from coal
power plants into concrete.
Retrieved October 29, 2019, from
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