Bridges

Increased worldwide production of Portland cement in recent decades, meet the demands of the construction industry, has led to alarming increases in CO2 emission into the atmosphere. Global interest in the mitigation of global warming has led to innovations in concrete technology to reduce the use of Portland cement in Concrete. An important innovation concerns development of geopolymer concrete, which does not employ Portland cement but binders which incorporate industrial by-products. Unlike Portland cement, geopolymer binders have variable compositions due to the large variety of materials and activators that are used for geopolymer binders. This, and the little history of application, and lack of long-term performance data, are the main barriers to the general acceptance of geopolymer concretes..

Nevertheless, some proprietary geopolymer concretes have had some degree of success in field applications, particularly in Australia, although such compositions are confidential. In order to generate open, transparent information on geopolymer concrete, Austroads supported a project through ARRB, while the first author was Chief Scientist and was responsible for this project. The research utilised precursor materials, mainly fly ash (FA), blast furnace slag (Slag) and alkali activators to develop geopolymer concrete mixes, appropriate for use in bridge structures. They were subjected to various durability and mechanical tests, and the best performing mixes were selected for comparative performance testing. The results of durability and mechanical tests showed that the performance of geopolymer concretes that contained a blend of FA + slag was generally superior to that of Portland cement concrete, particularly under aggressive marine conditions. These mixes developed well above 50 MPa strength and are considers suitable for field application. Geopolymers based on 100% slag showed deficiencies in strength and durability properties and may not be suitable.