Effect of MgO, nitrate intercalated LDH and Calcined-LDH on chloride resistance of alkali-activated fly ash/slag mortar

Tao Liu, Yuxuan Chen, Qingliang Yu, H.J.H. (Jos) Brouwers

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Abstract

Layered double hydroxides (LDHs) are the major secondary reaction products of alkali activated slag. The formation and absorptive performance of LDHs can be affected by factors such as the amount of magnesium oxide (MgO) and the structure of LDHs, making it possible to absorb the chloride ions in alkali activated materials (AAMs). Meanwhile, Calcined layered double hydroxides (CLDHs) have the potential to act as a more effective chloride adsorbent than the original LDHs because of the reconstruction of LDH-like structure in AAMs matrix. The effects of MgO, LDHs-NO3 and CLDHs on mitigating the chloride penetration in alkali activated fly ash and slag blends (AAFS) were investigated in terms of the chloride ingress in AAMs matrix. The objective is to explore the mechanism of LDHs formation with MgO, LDHs and CLDHs addition in alkali-activated materials. In this research, nitrate intercalated Mg–Al layered double hydroxide (Mg-Al-LDH-NO3) was successfully synthesized with the co-precipitation method followed by subsequent washing and aging treatment. Calcined Mg–Al layered double hydroxide was obtained by thermal treatment of MgAl-LDH-NO3 at 500℃ for 3 hours. The results of the rapid chloride migration test (RCM) revealed the ability of the CLDH, LDH and MgO to absorb the chloride ion in mortars. Furthermore, the microstructure of nitrate intercalated LDH and CLDH materials were analyzed by scanning electron microscopy (SEM).
Original languageEnglish
Title of host publicationPROCEEDINGS ICSBM 2019 VOLUME 2-New cementitious binders
Number of pages9
Publication statusPublished - 2019
Event2nd International Conference of Sustainable Building Materials (ICSBM 2019) - Eindhoven , Netherlands
Duration: 12 Aug 201915 Aug 2019

Conference

Conference2nd International Conference of Sustainable Building Materials (ICSBM 2019)
Country/TerritoryNetherlands
CityEindhoven
Period12/08/1915/08/19

Keywords

  • Alkali activated materials
  • LDH
  • MgO
  • Chloride penetration
  • RCM

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