Utilisation of Carbon-Rich Waste in the Production of Clay Bricks
Jing Xu*, Takafumi Numata, Cathy Inglis, and Phil Morey
Brickworks Building Products, 738-780 Wallgrove Road, Horsley Park, NSW 2175,
Australia;
*Email: jing.xu@brickworks.com.au
Carbon-rich waste materials from the timber and coal industry have the potential to
provide beneficial outcomes when they are added to clay bricks as an on-board fuel.
Such waste materials can provide economical benefits, such as reduced energy
requirements for the firing process, owing to their high calorific values and extended
lifespan of the clay reserve. They also can provide environmental benefits, such as
diversion of waste materials from landfill and reduced usage of non-renewable fuels.
However, there are issues that must be considered when these waste materials are
introduced into the clay brick manufacturing process. Firstly, adding an excessive
amount of the waste material may result in bloating or deformation of the clay bricks,
which occurs owing to the entrapment of gases formed by decomposition of the
waste materials within the vitrified brick body during the firing process. Secondly, the
presence of excess carbon in the brick body can deplete the available oxygen,
leading to the reduction of red-coloured haematite (Fe2O3) in the clay to darkcoloured magnetite (Fe3O4) or wüstite (FeO). This causes an aesthetic issue in
which the surface shows an undesirable non-uniform finish called hearting. To
overcome these issues, optimisation of the manufacturing parameters, including
particle sizes of the waste materials, rates of addition, and production speeds, is
required. A balance between the benefits and the potential risks and drawbacks of
introducing carbon-rich waste materials must be evaluated in order to enhance the
utilisation of these materials.