Sewage sludge ash-based mortar as construction material: Mechanical studies, macrofouling, and marine toxicity

Arun Kumar Prabhakar, Padmaja Krishnan, Serina Siew Chen Lee, Chin Sing Lim, Anjaneya Dixit, Babu Cadiam Mohan, Jia Heng Teoh, Sze Dai Pang, Daniel C.W. Tsang, Serena Lay Ming Teo, Chi Hwa Wang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

Abstract

Incinerated sewage sludge ash is tested here as a cement and aggregate substitute in mortar blocks. It can be used at various percentages to reduce the overall cost of production and promote ash recycling. The compressive strength of the cast blocks was tested at 28 days to determine the optimal combination of ball milled ash (replacing cement) and sewage sludge ash (replacing sand). This was compared with a control block made of cement and sand only. The cast blocks with the optimal ash formulation were tested for their flexural strength and other properties such as surface functional groups, constituent phases and porosity. The control and ash mortars exhibited similar properties. A potential application of these blocks is to use them as part of seawalls. These blocks were thus suspended in the sea for 6 months. Marine organism attachment was observed over time in both control and ash mortar blocks. There was no significant difference between the mortars after 6 months. The mortar blocks were also subjected to leaching tests (NEN-7345). The leachates did not exhibit toxicity to microalgae. In contrast, mild toxicity was observed in the sea urchin embryo development assay. Overall, the study suggests that sewage sludge ash is a potential material to be used for seawall construction as it has the desirable mechanical properties. However, there remain some residual marine toxicity concerns that need to be further addressed.

Original languageEnglish
Article number153768
JournalScience of the Total Environment
Volume824
DOIs
Publication statusPublished - 10 Jun 2022

Keywords

  • Cement & aggregate substitute
  • Macrofouling
  • Marine toxicity
  • Mortar
  • Sewage sludge ash

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

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