8 June 2016

Making a sustainable, more durable cement

By Associate Professor Ir Dr Dominic Ong

Concrete is one of the most widely used synthetic materials in the world. A simple material, concrete is made from Portland cement, the most common type in general use around the world, mixed with gravel, sand and water. The production of cement, however, releases carbon dioxide – from mining it and especially while heating it at over 1,400°C in a kiln, often using fossil fuels in what is called the clinker process. The International Energy Agency estimates that for every ton of cement produced, one ton of carbon dioxide is released into the atmosphere.

Be that as it may, the demand for cement is only expected to increase. The 2015 ASEAN Construction Summit opened on the note that the infrastructure market is expected to show higher growth in the coming years, providing opportunities for the construction industry. While building infrastructure is necessary, thus increasing the need for cement, we cannot ignore the implications. Experts at the Summit reached a consensus that green construction has to play a bigger role in shaping demand and delivering green solutions as best practices.

Today, researchers and innovators continue to look into making breakthroughs with cement. Can we find alternatives? What can we use instead of the clinker process, and how can we make concrete greener are some of the questions at the top of their minds.

Sarawak is transforming under the government’s initiative to become an economic region. The state, with abundant natural resources, especially water, clean energy can be harnessed on an industrial scale by developing hydropower to attract operators of ferroalloy production plants. Beside hydropower, the State is investing in coal-fired power stations as an alternative source of energy. The by-product of coal combustion is fly-ash, a very fine grey ash particle that “flies” in the furnace. In 2014, the US Environmental Protection Agency labelled the release of fly-ash into the atmosphere as a health hazard, and industries are therefore required to capture and store it.

For the last two decades, construction companies have been adding fly-ash into their cement to reap the obvious benefits, namely, making conventional concrete stronger and more durable against fire and salt attacks. The “industrial waste” is readily available, slightly cheaper and has the potential to substitute cement in parts or wholly. This green cement is termed “geopolymer”. When it is substituted wholly, it is named “fly ash geopolymer”.

In recent years, Swinburne Sarawak has discovered just how instrumental fly-ash can be in making green cement. The chemical composition of fly-ash is broadly similar to that of cement although they react differently. With the addition of water, hydration of cement occurs via pozzolanic reaction to form a super binder. On the other hand, for geopolymer to form, the fly-ash is activated to become a binder by adding alkali activators to create an alkaline environment, conducive for its geopolymerisation process to take place.

Collaboration in developing the geopolymer has been taking place between Swinburne Sarawak and its home campus in Melbourne, Australia, where there are a large number of researchers working on the subject. The advanced equipment at Swinburne’s home location could perform complex mechanical and analytical tests which are vital for high-end research. The other advantages of the collaboration are that the two campuses could then contribute to a bigger knowledge pool, and could compare their research findings.

A comparative analysis of Sarawak fly-ash against the famous Australian Gladstone fly-ash, known for its good compressive strength, has shown that the former is capable of achieving commendable performance. The novel outcomes of the research has been published in some of the field’s top international journals such as the UK’s Royal Society of Chemistry “Advances”, Elsevier’s “Construction and Building Materials” and “Ceramics International”.

The fly-ash geopolymer shows it has good potential to be the green cement of the future as it is more resistant to fire, acid attack and corrosive sea-water compared to ordinary cement, making it ideal for the construction of hydropower dams and sea-ports. Steps are being made to further improve its mechanical properties, strength and ease of use on construction sites.

While this is an exciting development, how it can be produced and applied on an industrial scale is another matter. Apart from the challenge of sourcing materials there is the hurdle of getting contractors on board the idea, since it would mean making changes to their machineries and sourcing of materials. More importantly, regulations on building standards would also need to be revisited since the current international standards on building regulations require a certain amount of Portland cement in concrete to meet safety standards. With new technologies and techniques being made, statutory regulations may have to be amended one day.

Associate Professor Ir Dr Dominic Ong is the Director of the Swinburne Sarawak Research Centre for Sustainable Technologies at Swinburne University of Technology Sarawak Campus. He is contactable via elong@swinburne.edu.my