Recycling drinking water treatment sludge into eco-concrete blocks with CO2 curing: Durability and leachability

• Published in: The Science of the total environment Vol. 746; p. 141182
• Main Authors: Liu, Yue, Zhuge, Yan, Chow, Christopher W.K., Keegan, Alexandra, Pham, Phuong Ngoc, Li, Danda, Qian, Gujie, Wang, Lei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-12-2020
• Subjects: Accelerated carbonation; Drinking water treatment sludge; Leaching behaviour; Stabilisation and solidification; Sulfate attack resistance; Value-added recycling; CB-X1-X2; Value-added recycling; LOI; XCT; Leaching behaviour; Stabilisation and solidification; Accelerated carbonation; Sulfate attack resistance; DWTS; TCLP; SEM; CLSM; CB; Drinking water treatment sludge
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.141182

Drinking water treatment sludge (DWTS) can be recycled into low-strength concrete blocks for construction use. The sodium sulfate resistance and leaching behaviours of the DWTS-derived blocks are investigated in this study. The experimental results show that the addition of DWTS degrades the sodium sulfate resistance of the concrete blocks, however CO2 curing compensates for such property, especially in the case of blocks incorporating 30% DWTS. The improvement can be attributed to the formation of crystalline CaCO3 during CO2 curing for microstructure refinement evidenced by X-ray Computed Tomography and Scanning Electron Microscopy. Leaching analyses show that Cu and Al concentrations increased with increasing DWTS content, and CO2 curing adversely increased the leachability of metals due to the decrease of pH, especially at early leaching stage. Nevertheless, the total leaching concentrations of Cu and Al after 60-day test is far below the prescribed limitations, regardless of samples subject to air curing or CO2 curing. In summary, sludge-derived blocks exposed to CO2 curing are safe and behave well in aggressive environments. Therefore, this study showcases a green technology that successfully recycling DWTS into value-added and durable concrete blocks with low environmental impacts.
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•Drinking water sludge was recycled as a substitute for natural sand.•Drinking water treatment sludge deteriorates sulfate resistance of concrete blocks.•CO2 curing improves sulfate resistance of sludge-derived concrete blocks.•Leaching behaviour of sludge-derived concrete blocks fulfilled the standard.