Design optimization and characterization of a green product by combined geopolymerization of sewage sludge ash with metakaolin

Zhen Chen, Chi Sun Poon, Jiang Shan Li, Qiang Xue

Research output: Journal article publicationJournal articleAcademic researchpeer-review

Abstract

This study aimed at developing sewage sludge ash (SSA) as a green binding material through geopolymerization for saving natural resources and reducing problems with the waste disposal. Geopolymer pastes based on a precursor comprising 25 wt% of metakaolin (MK) and 75 wt% of SSA were synthesized using the dry-mixed method. Compressive strength tests of the specimens revealed that geopolymers produced from mixes with a Na2O/SiO2 molar ratio of 0.30 and a SiO2/Al2O3 molar ratio in the range of 3.00 to 3.60 achieved the highest compressive strength after 28 days of curing, regardless of temperature. The microstructural analyses showed the formation of N-A-S-H gels in the specimens. The initial curing temperature had a significant influence on the compressive strength of the geopolymers. Specimens initially cured at 40 °C for 7 days and then stored at room temperature showed progressive gain in compressive strength with time. However, raising the initial curing temperature from 40 °C to 60 °C resulted in the formation of cracks in the matrix and new mineral of zeolite P (Na) which caused a notable loss of late-age strength. Leaching toxicity tests showed that the concentrations of heavy metal(loid)s in leachates did not exceed the specified limits.

Original languageEnglish
Article number106271
JournalApplied Clay Science
Volume214
DOIs
Publication statusPublished - 15 Nov 2021

Keywords

  • Geopolymer paste
  • Initial curing temperature
  • Metakaolin
  • Molar ratio
  • Sewage sludge ash

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

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