Researchers from the University of South Australia (UniSA) have developed an innovative construction material that could redefine sewage infrastructure through a more sustainable and durable alternative to conventional concrete. This new material not only addresses the chronic issue of corrosion in sewer pipes but also supports circular design by repurposing industrial waste.

Rethinking Concrete for Infrastructure

Traditional concrete, while widely used for sewer systems due to its strength and cost-effectiveness, has a significant flaw: it is vulnerable to acid attack and microbial corrosion. These conditions are common in sewage networks and often lead to cracking, structural failure, and expensive repairs. In Australia alone, the maintenance and repair of such damaged pipes cost taxpayers an estimated $70 billion each year. South Australia’s sewage network alone spans over 9,300 kilometres, while globally, sewage infrastructure stretches far beyond, highlighting the vast scale—and vulnerability—of these systems.

A Material Innovation: Sludge and Slag Synergy

The new material developed by UniSA engineers combines two waste products: alum-based water treatment sludge (AWTS), a byproduct of drinking water purification typically sent to landfill, and ground granulated blast-furnace slag (GGBS), a common cement replacement derived from steel production. These materials are chemically activated to form alkali-activated materials (AAMs), offering a promising alternative to Portland cement in sewer pipe manufacturing.

The resulting composite demonstrated impressive performance in laboratory tests. Samples containing 20 to 40 percent AWTS exhibited more than 50 percent higher compressive strength compared to those made with GGBS alone. The material also resisted sulphur-oxidising bacterial penetration and acid-induced degradation, both key factors in sewer pipe deterioration. These attributes suggest significantly improved longevity and structural resilience for future sewage systems.

Closing the Loop: Environmental and Circular Benefits

This development carries substantial environmental benefits, particularly for architects, landscape designers, and civil engineers working with sustainable materials. By redirecting AWTS from landfill, the solution reduces greenhouse gas emissions associated with waste disposal and transportation. Moreover, replacing cement—a material responsible for a large share of construction-related CO₂ emissions—with industrial byproducts helps reduce the carbon footprint of infrastructure projects.

Weiwei Duan, a PhD candidate at UniSA and lead researcher on the project, noted the environmental importance of finding new uses for sludge. Typically viewed as a disposal problem, the sludge now becomes a valuable resource in construction. His efforts were recognised nationally when he received the 2025 Australian Water Association’s Student Water Prize, the first UniSA student to win the award in six decades.

Opportunities for Designers and Material Innovators

The innovation has far-reaching implications for designers across multiple disciplines. Architects and urban planners focused on sustainable infrastructure can benefit from more durable and eco-friendly sewage systems. Landscape architects involved in designing public infrastructure may consider integrating similar materials into water-sensitive urban design projects. Furthermore, the potential for using alkali-activated materials in other applications—such as modular urban components or street furniture—may appeal to product designers interested in circular and biobased innovation.

As the construction industry continues to grapple with the challenge of reducing emissions and waste, such developments underscore the critical role of materials research in achieving environmental targets. This project demonstrates how rethinking waste streams and embracing material circularity can lead to stronger, greener infrastructure.

Source & image: University of South Australia