Wang, Ziyan;
Shui, Zhonghe;
Sun, Tao;
Li, Xiaosheng;
Zhang, Mingzhong;
(2022)
Recycling utilization of phosphogypsum in eco excess-sulphate cement: Synergistic effects of metakaolin and slag additives on hydration, strength and microstructure.
Journal of Cleaner Production
, 358
, Article 131901. 10.1016/j.jclepro.2022.131901.
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Abstract
Landfilled phosphogypsum would cause severe environmental issues, but the waste can be recycled for preparing excess-sulphate cement, an eco-friendly alternative to conventional cement. This paper investigates the effect of metakaolin (0–50%) on early hydration, phase assemblages and mechanical properties of the excess-sulphate phosphogypsum cementitious materials (ESPCMs). Results indicate that metakaolin is related to a new exothermic peak and significantly shortens the induction period. Setting time of ESPCM pastes is reduced by 13%–38% with 10%–50% dosage of metakaolin. More ettringite and highly disordered C-(A)-S-H gel are characterised when metakaolin dosage is below 20%, leading to 70% increase in 28-d compressive strength. With above 20% metakaolin dosage, portlandite consumption at early stage is promoted and hydration degree at late state is reduced. It turns out that within 20% metakaolin dosage is efficient to optimise setting time and strength development of ESPCMs, where slag and metakaolin synergistically promote the formation of ettringite and C-(A)-S-H gel to bind the unhydrated cement particles effectively.
| Type: | Article |
|---|---|
| Title: | Recycling utilization of phosphogypsum in eco excess-sulphate cement: Synergistic effects of metakaolin and slag additives on hydration, strength and microstructure |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.jclepro.2022.131901 |
| Publisher version: | https://doi.org/10.1016/j.jclepro.2022.131901 |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher's terms and conditions. |
| Keywords: | Excess-sulphate cement, Phosphogypsum, Metakaolin, Early-age hydration, Microstructure, Strength |
| UCL classification: | UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Civil, Environ and Geomatic Eng UCL > Provost and Vice Provost Offices > UCL BEAMS UCL |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10147421 |
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