Project Status: Complete
Project Participants: Alcoa, ANSTO, Curtin University of Technology, Orica, Rocla
Project Leader: Arie van Riessen (Curtin University of Technology)
This project's overall aims were to develop the necessary chemical and structural understanding of geopolymers made from waste products. This information could then be used to capture a significant share of the ready-mixed and precast concrete market for a given industrial region. Research assessed the suitability of silica-bearing waste streams generated in any one geographical region, and helped determine the role that secondary metal ion constituents in the geopolymer process play on the kinetics of formation and resulting microstructure of geopolymers.
The project had a number of streams of work, including demonstrations of geopolymer concrete products, which are described below.
The fundamental science project aims to support the demonstration projects and provide a resource base for the Geopolymer Alliance. PhD research work essentially underpins this project and generates publications. This work is ongoing for the life of CSRP and running in parallel with, and feeding into, the demonstration projects.
An important aspect of the work was developing robust techniques to enable determination of the reactive component of precursor materials such as fly ash. A number of PhD students contributed to this by investigating the chemical reactivity of fly ash and determining the reactive component via x-ray techniques:
1) “Premix” geopolymer concrete
This project was divided into two stages. The first stage was the laying of a path using an existing formulation to ascertain that the logistics of scale up from laboratory to field trial are feasible; to have a visible geopolymer product that could be used for promotion purposes; and finally to enable key factors to be monitored so that the curing, aging and durability of a geopolymer product could be determined. The second stage of this project was development of a geopolymer formulation using local fly ash and then laying an additional path using this new formulation. The same regime of assessment was then then undertaken for this path.
The second geopolymer concrete path was cast in November 2009 using a blend of two Australian fly ashes. As with Path 1, a number of hurdles were encountered but in the end the exercise was successful. Overall this was a very successful demonstration benefitting from the effective collaboration between CSRP Participants CSIRO and Curtin, with strong support from Boral.
2) High performance geopolymer concrete railway sleepers
This project investigated the design of high-performance, low-profile geopolymer railway sleepers suitable for use as a replacement for wood sleepers. The work continued the previous joint efforts of CSIRO and Rocla in developing pre-stressed geopolymer sleepers as a replacement for ordinary Portland cement sleepers. CSIRO had previously worked on developing a geopolymer formulation to meet the critical demands of a low-profile railway sleeper. Rocla provided the necessary specifications for the sleepers and made the pre-stressed sleepers from the new formulation.
Benchmarking the mechanical properties of a revised geopolymer mixture was provided by Rocla. Kaolite (clay) fly ash was used in a series of trials but the properties did not meet the target values – so the decision was made to revert to fly ash from the Bayswater power station in New South Wales. Mix optimisation using the Bayswater fly ash was completed however variations in the fly ash composition delivered inconsistent results – which did not meet the target material requirements for railway sleeper design specifications. An ongoing partnership between Rocla and CSIRO after the term of CSRP will re-evaluate the materials requirements for future railway sleeper production trials.
3) Thermal properties of geopolymers
Geopolymers are sufficiently durable and stable at high temperatures to be used in building fireproofing applications however using geopolymer fireproofing coatings on steel have not yet been exploited. This project developed fire-resistant geopolymer coatings that could potential be introduced into the market place.
The team developed a geopolymer composition that proved to be suitable for spray coating in terms of flow and spray-ability. To improve the fire-resistance performance of the mixture, a 10 weight percent (concentration) of vermiculite was added – a natural clay-like mineral that expands with the application of heat. Two size fractions were trialled, those below 63 microns and those over 63 microns. Adding vermiculite required extra water to maintain the spray-ability. Several papers and a book chapter have been published based on this work.
4) Bayer residue geopolymers
Geopolymers with impressive physical properties have been successfully manufactured from Bayer residue at laboratory-scale. This new source material opens up opportunities for utilisation of significant amounts of industry by-product. Since the completion of major project work with Bayer residue based geopolymer, there has been an investigation into granulation of the material with international companies. Some experimental work was completed during 2008/09 and further work was then undertaken as part of CSRP project "Fundamentals of Bayer-based Geopolymer" (132).
The Geopolymer Alliance aims to enhance the sustainability of the mining and power industries by promoting the uptake of geopolymer technology within existing industries such as the building and construction industry. The Alliance has been set up as a resource centre to provide support to industry and to ensure standards and regulations are available for alkali activated cements and concretes. In addition, the Alliance will conduct workshops and coordinate conferences to assist in promoting geopolymers.
The Foundation constitution and Alliance By-laws were finalised and approved by the CSRP Board. Geopolymer Foundation Ltd has been formally established to manage the Alliance. The first meeting of the Foundation's Board was held on 17 February 2010. The Alliance prospectus was sent to potential members and now has 13 organisations as founding members. The inaugural meeting of the founding members was held in Perth on 4 May.
The Alliance is a member of RILEM and their Technical Committee on Alkali Activated Materials. This committee is charged with the responsibility of setting up European standards, test methods and codes of practice for AAM's (geopolymers). The most recent meeting was held in Jinan, China on 9 May 2010.
The Alliance is also part of the Concrete Institute of Australia's committee set up to prepare a Current Practice Note on Geopolymer Concrete. This note is currently being drafted with considerable input from the Alliance and is expected to be published in December 2010. Following the recent resignation of the Chairperson, the Alliance's offer to chair the committee has been accepted. Dr Natalie Lloyd from Curtin University has been invited to join the committee and has agreed to write the chapter on Engineering Design Issues.
A symposium on geopolymer concrete was organised as part of the CIA's Concrete 09 conference. A full Geopolymer Alliance conference is planned for 2011/12.
This project aimed to compare selected sustainable development metrics for geopolymer concretes with Portland cement concretes using a versatile reusable sustainability metric calculator. The Calculator clearly demonstrates that the source of alkali solutions and transport dominates the price, energy and carbon dioxide produced for geopolymer concrete.