Recycled glass fines as a partial sand replacement in concrete
| Category | Details |
|---|---|
Product |
Concrete specification and demonstration using recycled glass fines |
Material classification |
Glass fines |
Product specifications and standards |
|
Project type |
Research, development and product validation |
Research result |
Demonstrated unwashed glass fines of up to 10% by mass can be used to replace sand in concrete. Amendment to the VicRoads Standard Section 703 General concrete paving. |
Sector |
Roads |
Grant recipient |
University of Melbourne |
Project partners |
Hanson, Department of Transport (VicRoads) and North Western Program Alliance (NWPA) |
SV funding |
$215,000 |
The outcome
University of Melbourne successfully demonstrated that unwashed recycled glass fines (RGF) of up to 10% by mass can be used as a sand replacement in concrete, fulfilling the fine aggregate requirement as per AS (Australian Standards) 2758.1 Concrete aggregates. The light particles and organic contaminants proved to not cause any issues when this amount of glass is used, accelerating the potential uptake of RGF into the infrastructure and construction industries.
The Department of Transport has since updated the relevant standard on the VicRoads website: Section 703 General concrete paving. In this version, Clause 703.05(d) allows the use of up to a maximum of 10% of unwashed fine glass aggregate as a replacement of the total mass of fine aggregate for concrete grades specified in Section 703.
In addition to creating a new use for glass fines, the Department of Transport (formerly VicRoads) is likely to see a reduction in the costs of these construction products, as the unwashed glass will require less processing and may be preferred over more expensive and scarce virgin materials.
The need
While high quality glass and larger pieces of broken glass are processed into new glass products, tiny pieces of contaminated broken glass, called fines, have previously had few end-uses and have been stockpiled or sent to landfill.
At the same time, the concrete industry has been facing a shortage of virgin sand. Recycled glass fines (RGF) can be considered as a partial replacement to sand, due to the similarities between their physical and chemical properties. However, RGF obtained from waste streams contain a lot of contaminants harmful to concrete. Washing the glass fines is not economical for full scale production in industry due to the energy and costs associated with the process.
Developing the solution
This research project investigated the feasibility of replacing 10% by mass, natural sand with unwashed RGF in VR400/40 structural concrete and assessing performance of RGF washed and unwashed in the lab and onsite.
The contaminants in the unwashed RGF were qualified or quantified in the University’s lab to determine whether they exceeded the standard limit for fine aggregate used in concrete according to AS 2758.1
Durability tests were conducted at University of Melbourne’s labs for washed and unwashed RGF as a replacement for sand at 10% by mass, examining a range of key concrete parameters (for example, slump value, setting time, density tests, compressive and flexural strength, and so on).
A demonstration site was constructed on High Street, Reservoir in March 2020. This footpath allowed for onsite tests and casts to be brought back to Hanson’s lab for further analysis. After 28 days, core samples were further tested. Performance differences were minor with some differences in workability.
Environmental risks and assessment of any chemical leaching was successfully completed at University of Melbourne labs where they analysed any types of contaminants to ensure RGF are safe to use in concrete. The testing demonstrated that there were no environmental risks associated with using unwashed RGF as a sand replacement at 10% by mass in concrete.
Lightweight concrete pour at Reservoir Station, March 2020 The partnership
The University of Melbourne delivered this project with the research team responsible for conducting the required tests on the studied concrete in the lab.
North Wesern Program Alliance kindly provided a trial site for pouring the studied concrete, which was used in the construction of the completed Level Crossing Removal Project at Reservoir Station.
Hanson supplied materials, delivered concrete to the site and assisted with testing site samples.
The Department of Transport reviewed and updated the current concrete standards.
Pathway to commercialisation
Based on the outcomes, the Department of Transport updated Section 703 in August 2021 making the aggregate mix ready for broader use. This will allow councils, and building and infrastructure works contractors to use this mix more broadly and increase uptake of RGF and further refine processes for its application. Reference to use of Section 703 can be found on the SV Buy Recycled Service – Standards and Specifications.
Concrete with Recycled Glass Fines being poured to make a new footpath More information
For more about this project, email marketsacceleration@sustainability.vic.gov.au