Outdoor Engineering
Fly ash proves
key to
sustainable
concrete
As the concrete industry focuses
on responsible sourcing and
improving resource efficiency,
fly ash is set to play a vital role
in boosting the sustainability of
concrete. Here, Dr. Robert Carroll,
Technical Director at UKQAA,
explores what this means for the
users and producers of fly ash
and the concrete industry as a
whole.
The Concrete Industry’s 7th Sustainability Performance Report is a key indicator of
the progress that is being made to improve the sustainability of concrete across the
sector. Not only does it report that the CO2 of concrete has reduced by 22 per cent
since 1990 but it also explores the variety of ways in which the sector is seeking to
sustain this success in the future.
Aligned with Green Construction Board goals, the report shows that the sustainability
of concrete is improving thanks in part to a rise in responsible sourcing and the
industry’s steady use of additional cementious materials - low-carbon alternatives to
primary raw materials - such as fly ash.
SUSTAINABLE SOURCING
As the report indicates, within the concrete industry there is a growing trend to
demonstrate responsible sourcing. Indeed, the certification of responsibly sourced
concrete products has increased to above 90 per cent, and it’s expected that the
report’s 2020 target of 95 per cent will also soon be met.
A readily available and easily accessible material, fly ash is often a constituent
of responsibly sourced concrete. It is produced in abundance as a by-product of
coal-fired power generation and, sourced direct from stations, it reduces reliance on
the resource-intensive process of extracting primary raw materials. The use of fly
ash in the manufacturer of concrete can therefore provide opportunities to improve
sustainability.
THE RISE OF ADDITIONAL CEMENTIOUS MATERIALS
According to the report’s figures, additional cementious materials such as fly ash
already constitute almost 30 per cent of cementious products - a figure which has
remained broadly consistent since 2008. Responsibly sourced and resource efficient
to manufacture as part of a cementious mix, fly ash is well known to significantly
lower the embodied carbon of concrete products. For example, while Portland
cement has around 900kg/tonne of embodied CO2, a typical fly ash cement has
around 670kg/tonne. That it can also improve the performance and versatility of its
applications, only adds to its enduring appeal as a sustainable addition to concrete.
To both improve and future-proof the sustainability of concrete, the report
recommends increasing the amount of additional cementious materials as a
proportion of total cementious materials to 35 per cent by 2020. This will increase
the sustainability of a composite concrete mix and reduce the industry’s reliance
on primary raw materials. This is welcome news to the user and producers of fly
ash and an encouraging sign that the concrete industry is continuing to diversify its
supplier base.
The message from the report is clear - the market for sustainable additional
cementious materials is set to grow and the opportunity to enhance the sustainability
of concrete will increase. It’s now down to the specifiers and manufacturers of
concrete to continue to make the sustainable choice.
UK QUALITY ASH ASSOCIATION
TEL: 01902 373365
WWW.UKQAA.ORG.UK
READER ENQUIRY NO: 33
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