The Effect of MSWI Fly Ash on Mortar Workability

Management of fly ash from municipal solid waste incineration (MSWI) is problematic, due to the fly ash toxicity and leaching. The ash could potentially serve as a partial cement substitute, similarly to fly ash from coal incineration. In this work, the potential of two different MSWI fly ashes as partial cement substitutes were analysed by testing the ashes effect on the workability.

This was achieved by investigating the variations in consistency (ease of flow), caused by increasing fly ash substitution, immediately after mixing and after 30 minutes, on mortar mixes containing 5, 10 and 20% cement replacement. The first fly ash had little impact on the consistency, except at 10% substitution where the flow was reduced by 30% compared to a reference.

The second reduced the flow by 16, 29 and 70% with increasing substitution. With the addition of superplasticizer, a consistency similar to the reference was achieved. Samples with high amounts of cement replaced by ash had a higher reduction in flow after 30 minutes compared to a reference. The addition of superplasticizer reduced the flow loss after 30 minutes except for a 20% substitution.