Researchers from RMIT University created an eco-friendly, zero cement concrete made from by-products that eliminate corrosion. The team says there has been a large gap in developing eco-friendly materials to protect sewers. Their project is a first step in the right direction.

Concrete corrosion and fatbergs are a major problem in sewer systems. Fatbergs are globs of congealed mass clogging sewers made of fat, grease, oil and nonbiodegradable junk that can grow up to 200 meters long and weigh tons. Fatbergs and general corrosion can cost billions in repairs and replacements over time.

Image comparing highly corroded ordinary Portland cement (left) with cement-free concrete (right). Source: RMIT University

The team's new concrete can withstand the environment of sewer pipes, reduce lime leeching and stop contributing to fatbergs. It eliminates free lime, a chemical compound that promotes corrosion and fatbergs. It is more durable than ordinary cement, making it perfect for major infrastructure.

By-products of the manufacturing industry are key ingredients in the new cement-less concrete. The composite is made of nano-silica, fly ash, slag and hydrated lime. This composite blend significantly improved the concrete’s longevity. The new concrete surpassed sewage pipe strength standards that were set by ASTM International. Using by-products supports a circular economy.

Replacing underground concrete pipe is a tedious and expensive effort. It also has a ripple effect on the city, including prolonged traffic delays and neighborhood nuisances. The Water Services Association Australia has estimated that Australia's sewage network costs $15 million per year and billions around the world. In Portland, Victoria, the cost of concrete pipe replacement cost about 5 percent of the world’s greenhouse emissions.

The team’s study proves that certain manufacturing byproducts are up for the job, which lowers the effect that it has on the environment. With further development, the team believes that the concrete could be made totally resistant to acid corrosions.

A paper on the new concrete was published in Resources, Conservation and Recycling.