Building Blocks

A QUANTUM OF SCIENCE

Geopolymers turn industrial wastes into energy-efficient super-building materials

Ordinary Portland Cement (OPC) is among the most common building materials on earth. Originating in the early British Industrial Revolution, it is used today in concrete, mortar, stucco and grout. An estimated 2.6 billion tons of it are made worldwide every year. Portland cement manufacture is a highly energy-intensive process involving high-temperature kilns, uses vast amounts of natural resources such as limestone, and produces not only considerable environmental damage in the form of alkaline run-off but also 5-8% of the total carbon emissions worldwide. But is there an alternative for this critical industrial material?

Geopolymers might just be that alternative. This new branch of industrial science explores methods for turning industrial waste products into highly energy-efficient materials with advanced properties. One of those industrial wastes is fly ash, the black powder left over from coal-burning power plants. At present, fly ash disposal is a tremendous industry problem with tremendous environmental impact. Recently, however, scientists have developed ways to use fly ash instead of limestone or other silicas and carbonates for the manufacture of concrete. These materials, known as geopolymers, not only make use of an abundant raw material but also present unique advantages for industrial use. Geopolymer concrete sets much faster than OPC, shows greater mechanical strength, shrinks less, is more resistant to corrosion and can withstand far higher temperatures without breaking down. Perhaps best of all, the production of geopolymer concrete reduces carbon emission by 90% compared to an equivalent amount of OPC.

Geopolymers are poised to provide other advantages as well. The mechanical strength and improved resistance to corrosion and heat make geopolymers ideal for sequestering environmentally harmful compounds such as arsenic, cadmium, chromium, lead, dioxins and even radioactive wastes. Challenges remain, however. Most importantly, long-term durability and stability data has yet to be generated, though ongoing tests suggest favorable performance compared to OPC. There are also existing regulations for OPC-based concrete products that would have to be modified if geopolymers are to gain acceptance and use worldwide, especially in the European Union where such regulations are strict. Still, the prospect of using industrial waste to make one of the most-used building materials on earth with improved characteristics while using less energy and adding less carbon to the planet seems an ideal solution.

For more information:

New Geopolymer Concrete Technology Created (R&D Magazine)

The role of inorganic polymer technology in the development of 'green concrete' (Duxson et al)

Geopolymerisation: A review and prospects for the minerals industry (Komnitsas et al)

Reaction mechanisms in the geopolymeric conversion of inorganic waste to useful products (Van Deventer et al)

Portland Cement (Wikipedia)


© AQOS / P. Smalley (2009)
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