Technical Note #32 Energy Efficient Technologies - Dematerialisation

Fired bricks
Green bricks

Dematerialisation is the reduction of total material and energy throughput of any product, thus limiting its environmental impact. One of the identified methods to implement dematerialisation in clay brick production is to change from solid to perforated bricks.

This case study therefore focuses on the reduction of material required to firstly produce a clay brick, and secondly on the subsequent reduction in energy required to fire the clay brick.

Perforating a clay brick is the act of extruding the 3 dimensional clay body such that there are voided areas or holes within the clay body. It is estimated that >30% of clay bricks manufactured in South Africa are perforated, meaning that there is much experience to draw from. An imbalanced die may lead to invisible drying cracking which would only become apparent after firing via an increase in fired waste. Clay preparation, green strength, green brick handling etc. are some of the issues that may also have to be addressed.

Nature of benefits

The shift to perforations provides a range of benefits, with the obvious one being a direct reduction in raw materials used, being either clay or a combination of clay and internal carbon. A total perforation ratio of 20% is an immediate 20% reduction in materials.

The drying of product is one of the foremost challenges faced by brick makers, and any introduction of perforations which means lower mass, less water and an increase in surface area, leads to a direct reduction in time and energy required for the drying of product.

The lower mass of product being fired requires a proportionate reduction in firing energy, and also usually has the added benefit of a more “even” burn due to each unit having a higher surface area and improved oxygen availability. Each individual unit also has a reduced “mass” that needs to be cored. Firing times are usually reduced as an added benefit.

A reduction in fired brick mass also allows for larger loads to be transported adding to the competitiveness of a cored product versus a solid product.