Geopolymers target Portland cement monopoly
Khai Trung Le talks to Róisín Hyde as she prepares to take her geopolymer research from Ireland to the USA.
Geopolymers have found a home in high-concept applications including space travel, but Róisín Hyde, architect and doctoral researcher at Queen’s University Belfast, UK, hopes to convince the construction sector of their qualities with a cement-free geopolymer concrete. However, to do that, Hyde will have to persuade the industry to move away from the ubiquity of Portland cement.
Hyde is developing an alternative to the conventional Portland cement concrete sandwich panel, used in retrofitting cladding of existing buildings, with a geopolymer panel using industrial by-products and waste materials. Principally, the cement will be replaced with an alkali geopolymer mix. This will comprise a flexible aluminosilicate – potential materials include kaolinite clay, coal fly ash, rice husk ash, and lunar regolith – and an alkali activator.
Initial factory tests of a 2.40m x 2.17m prototype panel enabled a reduction in thickness to almost 33% of the depth of a conventional panel, and lowering the weight by 25% while retaining the same degree of thermal performance and durability. Her work is detailed in the conference paper, Manufacture and assembly of a thin, lightweight, low impact, prototype precast geopolymer sandwich panel for the retrofit cladding of existing buildings.
Hyde told Clay Technology, ‘As an architect, I’ve seen a lot of fashionable materials, such as hempcrete, come and go. They are attractive but have limited application, and their performance is not equal to conventional materials. Whereas these alkali-activated geopolymers are high-performance and superior to current standards.’
Hyde received a Fulbright Irish Award, and will work with the University of North Carolina, USA, to develop a large-scale panel. She said, ‘I’ll be making everything bigger – the traditional reason Europeans go to America.’
Fight the power
According to Hyde, the popularisation of Portland cement is embedded in regulations across most of the world. ‘Portland became mainstream,’ she said. ‘Regulations in America, Europe and Africa specify a certain percent of Portland cement content because it is reliable and known quantity, taking a lot of guesswork out of things. It’s a powerful industry.’
Hyde noted that in Australia regulations are performance-based. She said, ‘Because Australian regulations specify degrees of strength, flexibility and durability, the country has moved forward with geopolymer research. Australia also has one of the world’s first geopolymer concrete buildings, the Global Change Institute.’
Taking on Portland cement is a gargantuan task, but Hyde, who won the Best Poster Award at the 2016 IOM3 Cement and Concrete Science Conference, is unfazed. She argues that the impact on the construction sector would be minimal. ‘Particularly for the guys on the ground, the process is almost identical,’ se said. ‘There is more involved in the chemistry, but that would be two guys in the factory performing simple tests such as X-ray defraction to determine its chemical composition and reactivity.’
The potential of geopolymers has been recognised for high-end applications, including by NASA as a possible material for building lunar and Martian habitats. But there remains nervousness around a wider adoption of geopolymers within industry. ‘People are averse to change. The Portland cement model has been used for as long as 3,000 years. Unless there is a tariff on Portland cement, it will be hard to get people to move over purely on sustainable reasons,’ said Hyde. ‘But fundamentally, because Portland cement is so environmentally unsustainable, there is pressure to create more sustainable materials.’