Research in the International Journal of Environmental Engineering has demonstrated that bottom ash from incinerated municipal solid waste could be used below a certain concentration as a filler in cement without loss of material strength in construction materials.
The researchers studied micronised powder recycled from bottom ash, a finely ground residue from waste incineration. They tested its chemical composition and performance as a component of mortar, a cement, sand, and water mixture used in construction.
Municipal waste incineration reduces landfill demand and can generate energy but produces large quantities of ash residues. In China’s major cities more than 200 million tonnes of municipal waste are incinerated annually, while almost 20 million tonnes are sent to landfill.
The IJEE paper discusses how bottom ash contains key cement-related minerals, including silicon dioxide, calcium oxide, aluminium oxide and iron oxide. After milling to a particle size of less than 100 micrometres, this material can be used in cement hydration, the chemical process that takes place allowing cement to harden.
However, replacing any more than 30% of the cement with this material reduces the 28-day compressive strength by half and flexural strength by more than a quarter. That said, a longer curing period did eventually see an increase in both compressive and flexural strength.
The researchers recommend lower replacement levels for general construction, with higher proportions reserved for applications such as pavement bases where bending resistance is important. The findings highlight the potential of recycling incineration residues while identifying barriers to wider use.
Cheng, Y. and Mu, W. (2026) ‘Hydration and mortar properties of municipal solid waste incineration bottom ash as a cement substitute’, Int. J. Environmental Engineering, Vol. 14, No. 2, pp.183–198.
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