Optimising sodium incorporation into potassium-activated metakaolin-based alkali-activated materials

Chaerun, R. I.; Sato, Junya; Hiraki, Yoshihisa; Yoshida, Yukihiko; Sato, Tsutomu*; Osugi, Takeshi

Construction and Building Materials, 500, p.144270_1 - 144270_10, 2025/11

https://doi.org/10.1016/j.conbuildmat.2025.144270

Alkali-activated materials (AAMs), particularly those derived from metakaolin, have gained significant attention as sustainable binders for hazardous waste immobilisation, owing to their dense microstructure and chemical durability. Their amorphous aluminosilicate framework enables effective encapsulation of hazardous materials and reduces environmental risks. However, maintaining the stability of this amorphous network is challenging, particularly when sodium (Na)-rich precursors are used, as excess Na) promotes crystallisation and compromises matrix integrity. This study systematically investigates the influence of Na) concentration on the structural stability of metakaolin-based AAMs activated primarily with potassium (K)). The objective is to identify the threshold Na incorporation level that preserves the amorphous structure and maintains chemical stability. Transmission electron microscopy (TEM), Raman spectroscopy, and thermodynamic modelling were employed to examine the structural evolution of K-AAMs across a range of Na:K molar ratios. The results reveal that higher Na:K ratios induce nanopore formation and early crystallisation of Na-rich zeolitic phases, which can reduce matrix stability. In contrast, an optimal Na:K ratio was identified that maintains the amorphous network and preserves the aluminosilicate framework. These findings provide valuable insights into optimising K-AAMs for advanced, durable waste encapsulation technologies.

Design and characterisation of different characteristics of metakaolin-based geopolymer for fuel debris removal, 3; Application potential of domestic metakaolin products

Kikuchi, Ryosuke*; Takeuchi, Nozomi*; Elakneswaran, Y.*; Niu, X.*; Osugi, Takeshi; Sato, Junya; Hiraki, Yoshihisa; Chaerun, R. I.

no journal, , 

Technologies are required to stabilise and solidify fuel debris and contaminated water present inside the Primary Containment Vessel (PCV) of the Fukushima Daiichi Nuclear Power Plant. In this study, metakaolin, a representative reactive filler, was investigated by comparing the specifications and properties of commercially available products before and after hardening. In addition, with consideration of a stable supply of raw materials, domestically produced metakaolin was manufactured and its properties were systematically evaluated.

Design and characterisation of different characteristics of metakaolin-based geopolymer for fuel debris removal, 4; Characteristics and Hydrogen Generation of Potassium-based Geopolymers Containing Simulated Wastes

Hiraki, Yoshihisa; Sato, Junya; Chaerun, R. I.; Niu, X.*; Kikuchi, Ryosuke*; Elakneswaran, Y.*; Yoshida, Yukihiko; Osugi, Takeshi

no journal, , 

no abstracts in English

Effect of boric acid addition on potassium-based Alkali-Activated Materials

Hiraki, Yoshihisa; Sato, Junya; Chaerun, R. I.; Niu, X.*; Elakneswaran, Y.*; Yoshida, Yukihiko; Osugi, Takeshi

no journal, ,