Auckland University of Technology (AUT) received funding of $80,420 from the Waka Kotahi NZ Transport Agency Hoe ki angitū Innovation Fund to investigate the use of waste glass in the alkali-activation process for stabilising pumice soils.
The project was funded in response to one of the Fund’s Round One challenges - Accelerating the use of recycled materials and sustainable practices.
The project’s objective was to deliver insights into a possible new and sustainable approach to soil stabilisation for road construction in pumice soils, which are widespread in the central North Island. Pumice soils have a low strength meaning they are easily crushed and more subject to erosion than other soil types. They need to be stabilised as part of the road building process. There is an existing body of literature that suggests that reclaimed glass could have a role in stabilising these types of soils.
The project focused on comparing the environmental impact of soil stabilisation using waste reclaimed glass and comparing it against current soil stabilisation methods using cement and lime to see if carbon dioxide emissions from soil stabilisation could be reduced. It conducted an experimental investigation into the strength characteristics of soil samples stabilised with alkali-activated reclaimed glass in a laboratory setting. It then studied the underlying mechanisms of the stabilised soil using microstructural analysis. It also conducted a life cycle assessment to compare the developed binder with traditional stabilisers.
The research identified that utilising reclaimed glass as a cement substitute and soil stabiliser in pumice soils is feasible. It found mortar mix designs, especially those with an activator/precursor ratio greater than 0.3, showed impressive strengths exceeding 35 MPa. The assessment highlighted that the proposed soil stabilisation approach using reclaimed glass could results in lower carbon dioxide emissions than cement (21%) and lime (15%). This finding paves the way for more environmentally friendly construction methods, and justifies more work, including for scaling up to pilot field tests. Such expansion would help validate the preliminary results at a larger scale and could also provide data that would be beneficial to other parts of the construction sector.
The project also identified that the existing testing and approval frameworks for new road building techniques did not specifically include using alkali-activated materials as soil stabiliser. This created challenges to demonstrating the viability of their innovative technique.
The applicants now plan to work with industry stakeholders, regulatory bodies, and academic institutions, to ensure knowledge transfer and to further promote the adoption of alkali-activated materials.
Read the full report here:
| Kalatehjari R., & Asadi A. (2023). A Sustainable Method for Stabilisation of Pumice Soil in Road [PDF, 3 MB]. Auckland University of Technology. |
