Investigation of the hydrothermal treatment for maximizing the MSWI bottom ash content in fine lightweight aggregates

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Abstract

The recycling of Municipal Solid Waste Incineration Bottom ash (BA) with a size below 4 mm is often difficult, due to its high contmination and porosity. To increase its reuse, the manufacture of lightweight aggregates represents a suitable option, as it takes advantage of the BA porous structure and uses cement for the immobilization of harmful contaminants. For highly contaminated ashes, hydrothermal treatment (HT) is known for further improving the immobilization of some heavy metals in the cementitious matrix. However, not many studies have investigated it as a curing method for pellets. This study addresses the application of highly contaminated BA fines in the production of lightweight aggregates. Firstly, pellets containing up to 80%wt. BA are manufactured and classified as lightweight aggregates, according to EN 13055. In the absence of HT, the formation of Friedel's salt helps the Cl retention, lowering the leaching by 65% compared to theoretical values. After HT, the formation of tobermorite on the pellet surface is beneficial for the flexural strength (+14%). However, the decomposition of phases such as Friedel's salt increases the leaching of Cl, Cu, Mo, and Zn compared to standard cured samples.

Original languageEnglish
Article number116947
Number of pages13
JournalConstruction and Building Materials
Volume230
DOIs
Publication statusPublished - 10 Jan 2020

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Ashes
Coal Ash
Leaching
Waste incineration
Municipal solid waste
Salts
Heavy Metals
Bending strength
Curing
Recycling
Cements
Porosity
Heavy metals
Impurities
Decomposition

Keywords

  • Hydrothermal treatment
  • Leaching assessment
  • Lightweight aggregates
  • MSWI bottom ash
  • Pelletization technique

Cite this

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title = "Investigation of the hydrothermal treatment for maximizing the MSWI bottom ash content in fine lightweight aggregates",
abstract = "The recycling of Municipal Solid Waste Incineration Bottom ash (BA) with a size below 4 mm is often difficult, due to its high contmination and porosity. To increase its reuse, the manufacture of lightweight aggregates represents a suitable option, as it takes advantage of the BA porous structure and uses cement for the immobilization of harmful contaminants. For highly contaminated ashes, hydrothermal treatment (HT) is known for further improving the immobilization of some heavy metals in the cementitious matrix. However, not many studies have investigated it as a curing method for pellets. This study addresses the application of highly contaminated BA fines in the production of lightweight aggregates. Firstly, pellets containing up to 80{\%}wt. BA are manufactured and classified as lightweight aggregates, according to EN 13055. In the absence of HT, the formation of Friedel's salt helps the Cl− retention, lowering the leaching by 65{\%} compared to theoretical values. After HT, the formation of tobermorite on the pellet surface is beneficial for the flexural strength (+14{\%}). However, the decomposition of phases such as Friedel's salt increases the leaching of Cl−, Cu, Mo, and Zn compared to standard cured samples.",
keywords = "Hydrothermal treatment, Leaching assessment, Lightweight aggregates, MSWI bottom ash, Pelletization technique",
author = "V. Caprai and K. Schollbach and M.V.A. Florea and H.J.H. Brouwers",
year = "2020",
month = "1",
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doi = "10.1016/j.conbuildmat.2019.116947",
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AU - Caprai, V.

AU - Schollbach, K.

AU - Florea, M.V.A.

AU - Brouwers, H.J.H.

PY - 2020/1/10

Y1 - 2020/1/10

N2 - The recycling of Municipal Solid Waste Incineration Bottom ash (BA) with a size below 4 mm is often difficult, due to its high contmination and porosity. To increase its reuse, the manufacture of lightweight aggregates represents a suitable option, as it takes advantage of the BA porous structure and uses cement for the immobilization of harmful contaminants. For highly contaminated ashes, hydrothermal treatment (HT) is known for further improving the immobilization of some heavy metals in the cementitious matrix. However, not many studies have investigated it as a curing method for pellets. This study addresses the application of highly contaminated BA fines in the production of lightweight aggregates. Firstly, pellets containing up to 80%wt. BA are manufactured and classified as lightweight aggregates, according to EN 13055. In the absence of HT, the formation of Friedel's salt helps the Cl− retention, lowering the leaching by 65% compared to theoretical values. After HT, the formation of tobermorite on the pellet surface is beneficial for the flexural strength (+14%). However, the decomposition of phases such as Friedel's salt increases the leaching of Cl−, Cu, Mo, and Zn compared to standard cured samples.

AB - The recycling of Municipal Solid Waste Incineration Bottom ash (BA) with a size below 4 mm is often difficult, due to its high contmination and porosity. To increase its reuse, the manufacture of lightweight aggregates represents a suitable option, as it takes advantage of the BA porous structure and uses cement for the immobilization of harmful contaminants. For highly contaminated ashes, hydrothermal treatment (HT) is known for further improving the immobilization of some heavy metals in the cementitious matrix. However, not many studies have investigated it as a curing method for pellets. This study addresses the application of highly contaminated BA fines in the production of lightweight aggregates. Firstly, pellets containing up to 80%wt. BA are manufactured and classified as lightweight aggregates, according to EN 13055. In the absence of HT, the formation of Friedel's salt helps the Cl− retention, lowering the leaching by 65% compared to theoretical values. After HT, the formation of tobermorite on the pellet surface is beneficial for the flexural strength (+14%). However, the decomposition of phases such as Friedel's salt increases the leaching of Cl−, Cu, Mo, and Zn compared to standard cured samples.

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KW - Leaching assessment

KW - Lightweight aggregates

KW - MSWI bottom ash

KW - Pelletization technique

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