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

Yue Liu; Yan Zhuge; Christopher W K Chow; Alexandra Keegan; Phuong Ngoc Pham; Danda Li; Gujie Qian; Lei Wang

doi:10.1016/j.scitotenv.2020.141182

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

Sci Total Environ. 2020 Dec 1:746:141182. doi: 10.1016/j.scitotenv.2020.141182. Epub 2020 Jul 23.

Authors

Yue Liu¹, Yan Zhuge², Christopher W K Chow³, Alexandra Keegan⁴, Phuong Ngoc Pham⁵, Danda Li¹, Gujie Qian⁶, Lei Wang⁷

Affiliations

¹ STEM, University of South Australia, Mawson Lakes, SA 5095, Australia.
² STEM, University of South Australia, Mawson Lakes, SA 5095, Australia. Electronic address: Yan.Zhuge@unisa.edu.au.
³ STEM, University of South Australia, Mawson Lakes, SA 5095, Australia; Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.
⁴ South Australian Water Corporation, Adelaide, SA 5000, Australia.
⁵ STEM, University of South Australia, Mawson Lakes, SA 5095, Australia; Faculty of Bridge and Road Engineering, The University of Danang-University of Science and Technology, 54 Nguyen Luong Bang Str., Da Nang, Viet Nam.
⁶ College of Science and Engineering, Flinders University, Bedford Park, SA 5042, Australia.
⁷ Institute of Construction Materials, Technische Universität Dresden, 01062 Dresden, Germany. Electronic address: lei.wang1@mailbox.tu-dresden.de.

PMID: 32768782
DOI: 10.1016/j.scitotenv.2020.141182

Abstract

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.

Keywords: Accelerated carbonation; Drinking water treatment sludge; Leaching behaviour; Stabilisation and solidification; Sulfate attack resistance; Value-added recycling.