Sewage sludge ash: A comparative evaluation with fly ash for potential use as lime-pozzolan binders

Yi fan Zhou, Jiang shan Li, Jian xin Lu, Chris Cheeseman, Chi Sun Poon

Research output: Journal article publicationJournal articleAcademic researchpeer-review

38 Citations (Scopus)


The disposal of sewage sludge ash (SSA) has become an environmental issue due to the limited available landfill space. This study aims at applying the finely-ground sewage sludge ash (FSSA) with quicklime and hydrated lime to develop a new type of lime-pozzolan system and study the effects of different types of lime on the mechanical properties of the systems. A traditional pozzolanic material (i.e. coal fly ash (FA)) was also used to compare with the FSSA. Multiple techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were used to assess the hydration kinetics and microscopic characteristics of the lime-pozzolan systems. The results showed that the quicklime system exhibited lower strength than the hydrated lime system, which was due to its lower reaction degree with the FSSA and the higher porosity caused by the expansion during the vigorous hydration reaction of quicklime. Compared to FA, the FSSA attained higher strength for the whole curing period (up to 90 d) in the lime system due to the highly porous nature of FSSA leading to a lower effective water to binder ratio. However, in the hydrated lime system, due to the higher overall pozzolanic activity of FA, its long-term strength values gradually improved. Besides, calcium phosphate hydrate crystals were detected by XRD in the FSSA; while some clinotobermorite was found in the FA both from XRD and SEM, which might govern the strength gain in the lime-FA system. Overall, the application of FSSA as a pozzolan in the lime-pozzolan system could be a promising option to both relieve the waste disposal pressure and provide a potential sustainable construction material.

Original languageEnglish
Article number118160
JournalConstruction and Building Materials
Publication statusPublished - 10 May 2020


  • Construction material
  • Finely-ground sewage sludge ash (FSSA)
  • Fly ash (FA)
  • Hydration
  • Lime-pozzolan
  • Waste management

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • General Materials Science


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