Keynote Paper: International Conference on Recent Trends in Concrete Technology and Structures, INCONTEST 2003, 10-11 September, Coimbatore, India. 1 GEOPOLYMER CONCRETE: TURN WASTE INTO ENVIRONMENTALLY FRIENDLY CONCRETE Djwantoro Hardjito, Steenie E. Wallah, Dody M.J. Sumajouw, B.V. Rangan *) Faculty of Engineering and Computing, Curtin University of Technology GPO Box U 1987, Perth, Australia 6845 *) e-mail: v.rangan@curtin.edu.au Abstract Efforts are needed to develop environmentally friendly construction materials in order to reduce the greenhouse gas emissions. This paper presents the development of geopolymer concrete. In geopolymer concrete, the inorganic alumino-silicate polymer gel synthesised from source materials rich in silicon and aluminium, such as low calcium (class F) fly ash, binds the loose coarse and fine aggregates, and other un- reacted materials in the mix. The test results demonstrate the excellent potential of geopolymer concrete to be a material of choice for the future. Introduction The trading of carbon dioxide (CO 2 ) emissions is a critical factor for the industries, including the cement industry. The infrared radiation emitted by the earth due to sun’s rays is absorbed by carbon dioxide released to the atmosphere, and therefore, is prevented from escaping into the space. This situation creates greenhouse effect on the earth, which produces an increase in the global temperature and results in climate changes. The production of cement is increasing about 3% annually (McCaffrey, 2002). As the production of one ton of cement liberates about one ton of CO 2 to the atmosphere, currently the contribution of portland cement production worldwide to the greenhouse gas emission is about 1.35 billion tons annually or about 7% of the total greenhouse gas emissions to the earth’s atmosphere (Malhotra, 2002b). Aside from that, cement is among the most energy-intensive construction materials. Furthermore, it has been reported that the durability of ordinary portland cement (OPC) concrete is under examination, as many concrete structures, especially those built in corrosive environments, start to deteriorate after 20 to 30 years, even though they have been designed for more than 50 years of service life (Mehta and Burrows, 2001). The concrete industry has recognized these issues. For example, the U.S. Concrete Industry has developed plans to address these issues in ‘Vision 2030: A Vision for the U.S. Concrete Industry’. In this document, strategies to retain concrete as a construction material of choice for infrastructure development, and at the same time to make it an environmentally friendly material for the future have been outlined (Mehta, 2001).