The Use of Geopolymers for Stabilising Expansive Soils

Daley, Dylan Craig (2019) The Use of Geopolymers for Stabilising Expansive Soils. [USQ Project]

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Abstract

Expansive soils are common around the world and are characterised by their non-linear shrink-swell behaviour with changes in water content. Expansive soils create problems for engineers by damaging structures, pavements and foundations with this unpredictable movement. Along with these shrink-swell variations, expansive soils exhibit very low bearing capacities and strengths when moisture contents are high. Expansive soils vary in performance and identifying these soils can be difficult.

Lime stabilisation is the most common method for stabilising expansive soils in Australia. Lime stabilisation decreases plasticity, reduces shrink-swell, increases bearing capacity and shear strength of subgrade soils. Lime has disadvantages, namely the high financial and carbon cost of lime. Australia has an abundance of fly ash, a waste product from the production of electricity using coal. Fly ash can be used as a geopolymer binder when combined with sodium hydroxide and sodium silicate. These geopolymers can achieve the same results as lime and cement-based stabilisers, at a fraction of the carbon cost, and making use of waste fly ash that would otherwise go to landfill.

The most reliable methods of identifying expansive soils were examined and a series of laboratory tests were conducted to determine the characteristics of an expansive soil found in the South East Queensland region. A geopolymer treatment option was found using past research and applied to the expansive soil. The laboratory tests were repeated and the changes to the soil were recorded. These performance changes were examined and compared with the standards for subgrades as determined by Austroads pavement design guidelines. Pavements were then designed using these standards to determine if geopolymer soil stabilisation is viable from a technical performance perspective using the current Australian design guides for pavements. A cost analysis was also conducted to see if geopolymer stabilisation was viable from a financial perspective.

The research found that alkali activated fly ash geopolymers were effective at improving the engineering characteristics of expansive soils. The results obtained met the requirements for Austroads standards for bearing capacity and reductions in plasticity index, meaning that it was viable alternative from a technical perspective. Geopolymer stabilisation was found to be far more sustainable, producing roughly 10-20% of the carbon cost of lime stabilisation. Financially, geopolymer stabilisation is still expensive, costing roughly double what lime stabilisation does in Australia.


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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Honours)(Civil)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 -)
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 -)
Supervisors: Nataatmadja, Andreas
Date Deposited: 11 Aug 2021 01:27
Last Modified: 11 Aug 2021 01:27
Uncontrolled Keywords: South East Queensland, expansive soils, geopolymers stabilisation, fly ash, sodium hydroxide, sodium silicate
URI: http://eprints.usq.edu.au/id/eprint/43094

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