Using drinking water treatment alum sludge to make greener and more durable concrete

Status

Complete

Partners

• University of South Australia
• SA Water

Outputs

FINAL REPORT

Publications

• Duan, W., et al. (2020). “Utilization of Drinking Water Treatment Sludge as Cement Replacement to Mitigate Alkali–Silica Reaction in Cement Composites.” Journal of Composites Science 4(4).
• Duan, W., et al. (2022). “A ternary blended binder incorporating alum sludge to efficiently resist alkali-silica reaction of recycled glass aggregates.” Journal of Cleaner Production 349.
• Duan, W., et al. (2022). “Mechanical performance and phase analysis of an eco-friendly alkali-activated binder made with sludge waste and blast-furnace slag.” Journal of Cleaner Production 374.
• Duan, W., Zhuge, Y., Chow, C.W.K., Keegan, A., Liu, Y., Merta, I., 2023. Mitigation of alkali-silica reaction in blast-furnace slag-based alkaline activated material through incorporation of alum water treatment residue. Construction and Building Materials 406.
• Duan, W., Zhuge, Y., Liu, Y., Chow, C.W.K., Keegan, A., Jiang, G., 2024. Enhancing acid corrosion resistance in alkaline-activated materials with water treatment residue and blast-furnace slag. Construction and Building Materials 447.
• Huang, B., Zhuge, Y., Rameezdeen, R., Xing, K., Huang, G., Liu, Y., 2024. Integrated carbon assessment for sludge-derived concrete: Modelling and a comparative study. Journal of Cleaner Production 435.
• Duan, W., Liu, Y., Chow, C.W.K., Keegan, A., Zhuge, Y., 2025. Evaluating microbiologically influenced corrosion in alkali-activated materials incorporating alum sludge. Journal of Building Engineering 106.
• Liu, J., Liu, Y., Zeng, J., & Zhuge, Y., 2025. A comprehensive review of mechanisms, techniques, and precursors in enforced carbonation for low-carbon concrete. Journal of Building Engineering, 112.
• Huang, B., Zhuge, Y., Rameezdeen, R., Xing, K., & Liu, Y., 2025. Optimizing resource efficiency in regional industrial symbiosis: Integrated modelling and scenario analysis. Journal of Cleaner Production, 489.
• Liu, J., Liu, Y., Bu, F., Zeng, J., Chow, C.W.K., & Zhuge, Y., 2026. Quality-control metrics for Al-rich calcined alum sludge: linking intrinsic variability, pozzolanic reactivity, and cement hydration performance, submitted to journal.

Videos

Summary

• Researchers explored alum sludge as cement and sand replacements in concrete products.
• They found that alum sludge can be safe to use and can reduce concrete lifecycle emissions by 9%.
• Alum sludge has the potential to improve concrete durability in harsh sewer environments.
• More work is needed to demonstrate alum sludge products in the field.

The industry problem

Australia has around 400 water treatment facilities that produce 2,000 tonnes of the byproduct alum sludge each year (Alum Sludge Reuse Report).

This creates major disposal costs, with one water utility spending $6 million on landfilling alum sludge per year (Alum Sludge Reuse Report).

At the same time, water utilities face high costs repairing and maintaining concrete infrastructure as the harsh conditions inside pipes accelerate their degradation.

Part of what makes this infrastructure expensive to maintain is the high cost and carbon footprint of cement in traditional concrete.

This study explored whether alum sludge could be used in concrete to divert waste from landfill, reduce emissions and produce more durable infrastructure.

The solution

Researchers used alum sludge to produce and test products such as mortar, blocks and precast concrete products.

They found that after pre-treatment, alum sludge can act as cement and sand replacements in concrete.

They also showed that at 10–20% cement replacement, products have equivalent or even improved 28–90-day strength compared to traditional mixes.

Researchers found that alum sludge can improve resistance to the types of chemical reactions and microbial attacks that occur in sewers.

They developed methods to reduce the variability across alum sludge sources, established quality control processes and confirmed safe levels of leaching.

The impact

The researchers’ assessments showed that alum sludge emits around 80% less CO₂ than general purpose cement, with 10% cement replacement reducing concrete life-cycle emissions by about 9%.

With their improved durability, alum sludge products could extend the service life of sewer pipes and deliver significant savings in repairs, maintenance and asset damage for water utilities.

The carbon assessment and supply chain modelling demonstrated the potential CO₂ reductions through transport, logistics, energy use and other supply chain arrangements.

The project also included education and training that builds long-term skills in the materials workforce.

Next steps

This project produced recommendations for further research to turn the quality control framework into formal testing methods.

Recommendations also included further work to understand how alum sludge interacts with admixtures and to develop mix formulations and guidelines.

With most of the data produced in this project coming from laboratory and pilot-scale studies, recommendations highlighted the need to demonstrate the products in long-term field trials.

They also emphasise the importance of industry collaboration to test processing and logistics pathways, and to develop procurement frameworks, standards, and landfill diversion strategies.