A team of researchers from Huaiyin Institute of Technology in China has determined that bottom ash, which is a finely ground residue from incinerated municipal solid waste, could be used as a filler material in cement.

To make this determination, the team examined micronized powder recycled from bottom ash, testing its chemical composition and performance when used as an ingredient in mortar — which is the combination of cement, sand and water used in construction.

While typically landfilled, bottom ash features important cement-related minerals — silicon dioxide, calcium oxide, aluminum oxide and iron oxide, specifically. The team discovered that once it is milled to a particle size of under 100 micrometers, bottom ash can be used in cement hydration, which is the chemical process that enables cement to harden.

The team discovered that replacing more than 30% of cement with incinerator bottom ash significantly reduced strength after 28 days. However, longer curing times improved performance. As such, the team recommends lower replacement levels for most construction and reserving higher amounts for applications such as pavement bases.

The material is detailed in the article, “Hydration and mortar properties of municipal solid waste incineration bottom ash as a cement substitute,” which appears in the International Journal of Environmental Engineering.