Knight, Jack (2023) Feasibility of a Partial Replacement of Cement with Millmerran Pond Ash. [USQ Project]
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Abstract
Pond ash is a byproduct of coal fired power plants that is currently unsustainably managed being stored in open ponds that are polluting the surrounding areas. This pond ash could be collected, cleaned, and potentially utilised in concrete as a Supplementary Cementitious Material [SCM]. This would improve the management of waste disposal, and reuse of future waste.
This research project aims to investigate the feasibility of pond ash as an SCM as partial replacement of cement. The main objective of this research project is to comprehensively assess the compressive and flexural properties, along with its workability, of concrete mixes containing varying proportions of pond ash utilising ordinary Portland cement. As higher strength concrete testing utilising pond ash and an SCM was in low quantity, the concrete mix is 40MPa with the mix design being provided by industry for realistic results. Four batches of concrete were planned with a control and a range of replacement percentages of 10%, 20% and 30% by mass.
The results of the slump testing indicated a decrease in workability with the increase in pond ash with a significant decrease at the 20% and above replacements. While largely aesthetic, these samples included voids which introduced some variability in sample density, particularly notable in the 30% pond ash mix. The compressive strengths at 7, 14, 28 and 56 days have been recorded. The mix design yielded higher-than-anticipated strength due to unanticipated shifts in the watercement ratio. The results indicate that the compressive strength reduced as the percentage of pond ash increased with a major reduction at the 30% pond ash replacement. The reduction in compressive strength of the 10% and 20% batches was only 90% and 86.6% of the control strength respectively and both passed the 28 day testing in this mix design. Flexural strength also exhibits a parallel trend of diminishing strength as pond ash replacement percentages rise, with the 30% replacement samples deviating the most from the projected trend due to inadequate aggregate bonding. The 56 day results shows strength growth beyond the typical 28 day testing with the 20% and the 10% replacement achieving the equivalent strength at 56 days.
The results gathered suggest Millmerran Pond Ash as an SCM in concrete is feasible and that a replacement percentage of less than 20% is promising, possibly requiring the use of additives to enhance workability.
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| Item Type: | USQ Project |
|---|---|
| Item Status: | Live Archive |
| Faculty/School / Institute/Centre: | Current – Faculty of Health, Engineering and Sciences - School of Engineering (1 Jan 2022 -) |
| Supervisors: | Lokuge, Weena |
| Qualification: | Bachelor of Civil Engineering Honours (Civil) |
| Date Deposited: | 29 Sep 2025 23:40 |
| Last Modified: | 29 Sep 2025 23:40 |
| Uncontrolled Keywords: | cement; pond ash; Supplementary Cementitious Material [SCM] |
| URI: | https://sear.unisq.edu.au/id/eprint/52963 |
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