Transforming waterworks sludge into controlled low-strength material: Bench-scale optimization and field test validation

Xiaoliang Fang, Lei Wang, Chi Sun Poon, Kitae Baek, Daniel C.W. Tsang, Sui Ki Kwok

Research output: Journal article publicationJournal articleAcademic researchpeer-review

8 Citations (Scopus)


In order to reduce landfill disposal of waterworks sludge (alum sludge) and incinerated sewage sludge ash (ISSA), this study proposed an innovative approach for upcycling them into value-added controlled low-strength materials (CLSM). Waterworks sludge interfered with cement hydration reaction and delayed the stiffening time of CLSM (>10 h) due to its high organics content (5%). The addition of triethanolamine (TEA) with a dosage of 0.1 wt% of binder effectively shortened the stiffening time to 4.5 h. The lab-scale results suggested that the optimal CLSM design (6% cement, 14% ISSA, 8% sludge, and 72% recycled fine aggregate at a water/binder ratio of 1.2) complied with the standard requirement of flowability (>200 mm), stiffening time (<5 h), and compressive strength (0.3–2.1 MPa). The pilot-scale field tests further confirmed that the sludge-incorporated CLSM achieved a high flowability (220 mm), short stiffening time (4 h), low compressive strength (1.38 MPa), and easy re-excavatability after 3 months. This study demonstrated that waterworks sludge can be potentially transformed into sustainable construction materials for urban development.

Original languageEnglish
Pages (from-to)254-263
Number of pages10
JournalJournal of Environmental Management
Publication statusPublished - 15 Feb 2019


  • Biomass waste recycling
  • Green/sustainable remediation
  • Incinerated sewage sludge ash
  • Stabilization/solidification
  • Waste valorization
  • Waterworks sludge

ASJC Scopus subject areas

  • Environmental Engineering
  • Waste Management and Disposal
  • Management, Monitoring, Policy and Law

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