Modification on the chloride binding capacity of alkali activated slag by applying calcium and aluminium containing phases

Modification on the chloride binding capacity of alkali activated slag by applying calcium and aluminium containing phases

Yang, Tingli (Wuhan University of Technology)
Fan, Xiaochun (Wuhan University of Technology)
Gao, Xu (Wuhan University of Technology)
Gu, Qian (Wuhan University of Technology)
Xu, S. (TU Delft Materials and Environment; Wuhan University of Technology)
Shui, Zhonghe (Wuhan University of Technology)

2022

In this study, a modified alkali activated slag system is designed by introducing additional calcium and aluminum containing phases in the binder, aiming at promote the formation of Friedel's salt (Fs) within the reaction products and therefore achieve a better chloride binding capacity. The effect of calcium and alumina contents on phase composition, chloride binding behavior, pore structure and mechanical properties of alkali activated slag are investigated. The results show that the addition of Ca(OH)₂ and nano γ-Al₂O₃ (CH and NA) results in the residual CH within the reaction products, but when in present of chloride, all residual CH transformed into Fs or other phases. The chloride binding capacity of the binder is obviously enhanced by CH and NA addition, owing to the increased ability to chemically bind chloride through Fs formation. There also exists an optimum Ca/Al ratio of the starting material regarding the chloride binding capacity. Adding CH coarsen the pore structure of the hydrated matrix by increase the amount of pores with the sizes larger than 200 nm, while NA exhibits a contrary effect. The chloride chemically binding behavior, namely the formation of Fs, slightly reduced the porosity of the binder. The strength results illustrate the negative effect of CH on compressive strength, and NA presents a positive effect, the modified binding system is able to provide a comparable mechanical property when compared with the reference alkali activated mixture.

Alkali-activated materials
Chloride binding capacity
Friedel's salt
Hydration products
Thermodynamic modelling

http://resolver.tudelft.nl/uuid:454cc846-2e3b-46a6-97b3-c09d0a2605f6

https://doi.org/10.1016/j.conbuildmat.2022.129427

2023-07-01

0950-0618

Construction and Building Materials, 358

Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2022 Tingli Yang, Xiaochun Fan, Xu Gao, Qian Gu, S. Xu, Zhonghe Shui