Sustainable Development – Fly ash

What is sustainable development?A definition widely used is, ‘development which meetsthe needs of the present without compromising the ability of future generations to meet their own needs’. It encompasses a range of issues including environmental,economic and social.

From a cementitious materials perspective sustainability isnot only about preserving natural resources for futuregenerations and minimising energy requirements duringmanufacture through greater efficiency and the use ofrecycled materials, it is also concerned with the effectsthey have on concrete performance in terms of mixdesign, durability, thermal conductivity and recycling.

What is fly ash?Fly ash is the residue product from burning coal in coalfired power stations.

Fly ash utilisationIn Australia we produce over 13 million tonnes per year.Worldwide there are over 750 million tonnes of coalcombustion products produced each year.

The majority of the material that is recycled is used by the premix concrete industry.

Other applications include civil construction, roadstabilisation, agricultural, mining, waste filtration andmineral fillers.

How does fly ash influencesustainable development?There are several ways in which fly ash improves thesustainability of concrete construction.

Preservation of natural resources:

The production of Portland cement requires extraction oflarge amounts of natural resources. Using fly ash as asupplementary cementitious material (SCM) reduces theamount of cement needed in concrete thereby helping topreserve our natural mineral deposits for future generations.

Waste reduction:

There is enormous potential to utilise fly ash for itsbeneficial properties rather than traditionally disposing ofit in landfill or fly ash dams.

Concrete durability:

Fly ash improves a wide range of hardened concreteproperties, enabling concrete structures to betterwithstand chemical attack, physical stress and mechanicalforces. This translates into less maintenance and a longerservice life.

Embodied energy:

The production of Portland cement is an energy intensiveprocess which contributes to atmospheric Carbon Dioxide(CO2) levels. Using fly ash as a supplementarycementitious material (SCM) reduces the amount ofcement needed in concrete which equates to a significantreduction in CO2 output from the cement industry.

Thermal conductivity:

Fly ash can be used to produce lightweight aggregates.With correct use the lower thermal conductivity of theseaggregates can significantly reduce the energy requiredto heat or cool a building.

Recycling:

Concrete containing fly ash can be crushed and reused ina range of civil and structural applications.

Life cycle assessment:

Preservation of natural resources, waste reduction, lowerembodied energy, improved durability, longer service life,improved thermal properties and the ability to berecycled, are all possible with fly ash. These are allimportant factors when evaluating the true environmentalcost of our built environment.

The need for sustainable development has received a great deal of attention in recent years. The built

environment consumes massive amounts of natural resources and energy and understandably there is a

growing focus on the materials and processes used in modern day construction.

Fly ash explainedFly ash is a supplementary cementitious material that delivers improved later-age strength,

workability and enhances the durability performance of concrete.

Its physical composition is a fine grey powder comprised of minute glassy particles, mainly

spherical in shape, produced as a by-product in coal-fired power stations. It is commonly

used as a 20-30% cement replacement in concrete.

In a properly proportioned mix, Fly ash delivers improved late-age strength and workability

and enhances the durability performance of concrete.

Fly ash is used as a single product or may be blended to produce a Fly ash blend cement.

Our Fly ash blend cements exceed the requirements of Type GB cements as specified in

AS 3972. Our fine grade Fly ash also exceeds the requirements specified in Australian

Standard AS3582.1

Unique technology means even better quality

In a properly proportioned mix, Fly ash can improve many of the properties of concreteincluding:

• Control of bleeding and segregation• Lower drying shrinkage and creep• Improved late-age strength growth• Minimisation of thermal induced cracking by lowering the “heat of hydration”• Reduction in porosity and permeability resulting in an improved resistance to sulfate

and chloride environments• Increased resistance to Alkali-Aggregate Reaction• High level of mix design flexibility – ranging from 1 MPa Flowable Fill to high

strength/high performance concretes• Improved pumpability/placeability during concrete pours

Suitable for a wide variety of applications and usesApart from the use in virtually all conventional concrete applications, Fly ash can also beused in:

• Roller compacted concrete• Road stabilisation where extended working time is desired• Flowable fill including back filling• Mass concrete for major engineering projects• Pre-cast applications where high durability and quality off-form finishes are required

Cement Australia Pty LimitedABN 75 104 053 474

Head OfficeLevel 2, 40 McDougall Street, Milton, QLD 4064PO Box 1328, Milton, QLD 4064Tel: 07 3335 3000 Fax: 07 3335 3222

www.cementaustralia.com.au SD FA Revision 2.0 issued 18/03/11