Comparing the reactivity of different natural clays under thermal and alkali activation

Authors

  • Ahmed Zohair Khalifa Building Materials and Building Technology Section, KU Leuven
  • Yiannis Pontikes KU Leuven, Department of Materials Engineering, Kasteelpark Arenberg 44, 3001 Leuven, Belgium
  • Jan Elsen KU Leuven, Department of Earth and Environmental Sciences, Celestijnenlaan 200C, B-3001 Heverlee, Belgium
  • Özlem Cizer KU Leuven, Department of Civil Engineering, Kasteelpark Arenberg 40, 3001 Leuven, Belgium

DOI:

https://doi.org/10.21809/rilemtechlett.2019.85

Abstract

Metakaolin is one of the most popular solid aluminosilicate precursors for the synthesis of geopolymers. Despite its high reactivity and availability, there is a noticeable move towards the use of other natural clays as alternative precursors, due to their plentiful supply and widespread availability. Natural clays usually consist of a combination of 1:1 and 2:1 layer silicates reactivity of which vary. In this work, four different natural clays (SS, BS, MS and WS) composed of 1:1 and 2:1 clay minerals at different proportions were studied for the synthesis of geopolymers. To increase their reactivity prior to alkali activation, the clays were calcined in a laboratory oven at different temperatures (700, 750, 800, 850, 900 °C) and different holding times (10 seconds to 60 minutes). The reactivity of the calcined clays was assessed by the dissolution test and isothermal conduction calorimetry. NaOH and a mix of NaOH and Na2SiO3 were used as alkaline activators. The results show that the optimum calcination temperature of SS, BS and MS is 800 °C with a holding time of 10 minutes. WS is sufficiently calcined at a higher temperature of 900 °C for 20 minutes. Kaolinite-rich clays (SS) present more reactivity towards alkali activation than clays dominated by smectite or illite.  

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Published

05.11.2019

How to Cite

(1)
Khalifa, A. Z.; Pontikes, Y.; Elsen, J.; Cizer, Özlem. Comparing the Reactivity of Different Natural Clays under Thermal and Alkali Activation. RILEM Tech Lett 2019, 4, 74-80.

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