Installation of Geopolymer concrete pavement at Wyndham Street for City of Sydney: interim report

Building materials Geopolymer concrete Roads Sydney

It has been calculated that cement production is responsible for about six percent of total greenhouse gas (GHG) emissions and, while considerable effort has been undertaken by Australian industry to reduce emissions due to the energy input, which is considerable, process emissions represent about 56 per cent of the total. To date, schemes such as carbon-capture-storage-utilisation have yet to make significant inroads into reducing the release of these process emissions with environmentally harmful gasses released to the atmosphere.

This project represents the third and final stage of a seven-year program by the CRC for Low Carbon Living for the mainstreaming of non-traditional concrete and its delivery to practice; more specifically Geopolymer concrete (GPC). It was identified in the first stage of this project that although research in Australia on GPC began almost three decades ago, a lack of codes of practice and design and construction specifications have led to significant roadblocks in transference from university and industry research laboratories to practice. This was addressed in stage two, which continues, with the development of “Handbook for Design of Geopolymer and Alkali Activated Binder Concrete Structures”, by the CRC and Standards Australia.

This third, and final, stage of the CRC low carbon materials project is the transfer the work undertaken in earlier projects to reality and to deliver the CRCs goal of moving GPC from a specialised product to mainstream construction.

GPC addresses two major issues of our time – climate change and the sustainable use of resources. GPC uses blended fly ash and GGBFS (slag) as the binder; all of which are by-products of industry. The development and use of “no-cement” concrete is one of several initiatives in the construction sector to a reduce its the carbon footprint.

In Australia alone, more than 30 million cubic meters of concrete is placed annually and is estimated to release between 8 and 12 million tonnes of CO2-e emissions. Whether 8 million or 12 million tonnes, the contribution to Australian environmental CO2 emissions released to the atmosphere by concrete is considerable and cannot be ignored if the goal is to reduce such emissions.

Pavements, slabs on ground and mass concrete elements represent about 70 per cent of all concrete supplied to end users and, thus, are a large component of the embedded carbon in concrete construction. A successful, monitored, demonstration of GPC pavement under high volume traffic loads provides councils, government, business enterprises, public utility companies, owners and architects, as well as suppliers and specifiers, confidence in product delivery and placement, as well as its long-term performance. It is the aim of this study to provide the evidence needed for designers and specifiers to build pavements of non-traditional concrete and for stepped change in the concrete supply industry.

The field trail in this study took place on Wyndham Street, near the junction of Bourke Road, Alexandria, in the City of Sydney. City of Sydney constructs many thousands of square metres of pavement each year and, with a zero emissions goal, led the project in the planning and identifying the site, in providing the needed approvals to close the roadway for a 45-hour period and in contracting of the construction crew. UNSW, the Ash Development Association of Australia (ADAA) and Australasian (iron & steel) Slag Association provided the technical expertise for the project and Wagners provided the Geopolymer concrete. Both the Geopolymer and OPC concrete roadways were constructed by contractors Sydney Civil, with the Geopolymer concrete pavement constructed first and the OPC concrete pavement one week later.

Two sections of road were placed (each 3m x 15m), one of GPC and one of conventional concrete. The pavements are located one after the other and subjected to the same, high-volume, traffic conditions. Due to the high-traffic volumes and importance of the road to the local traffic network, construction was undertaken on Saturday and the pavement opened 5:00 am Monday morning, just 37 hours after the completion of works.

The project showcases the potential for green construction materials through delivery by a major Australian Council, and Industry Partner the City of Sydney, in the adoption of Geopolymer concrete as “conventional” practice. The project further demonstrates the capacity to deliver on the council’s stated objectives for the use of “Sustainable Materials in Concrete”.

This interim report details the installation of the pavements, the GPC materials properties, the installation of gauges and initial surface scanning undertaken for monitoring of long-term performance. The project will be on-going over the next five and more years to evaluate performance under high volume and heavy vehicle traffic loading.

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