Article Dans Une Revue Cement and Concrete Composites Année : 2024

Changes in the structure of alkali activated slag mortars subjected to accelerated leaching

Résumé

The chemically induced degradation of alkali-activated materials exposed to the surrounding environment is a critical concern for durability. In this study, the leaching of alkali activated slag mortars (AASs) subjected to a 6M NH4NO3 solution was investigated by integrating techniques including ICP-OES, XRD/QXRD, TGA/DSC, ATR-FTIR, and 29Si MAS-NMR. The results revealed that the main leachable elements from the AASs and their leaching rates decreased in the following order: Na, K, Ca, and Mg. In contrast, Si and Al, the key elements in the C-A-S-H gel, displayed a remarkable resistance to leaching. Upon NH4NO3 attack, the primary phase (C-A-S-H) becomes more siliceous and has a greater mean chain length through decalcification and dealumination. The second phase, Mg, Al-layered double hydroxide (Mg, Al-LDH, or hydrotalcite), incorporated nitrate from the surrounding solution, sulfate from precursor dissolution, and Ca from gel decalcification to form nitrate/sulfate-bearing Ca, Al-LDH phases. Remarkably, the water-to-binder ratio exerted a nuanced influence, dictating the pace of element leaching, while exhibiting a relatively modest impact on the stability of the solid phases after 28 days of exposure. This work proposes a leaching mechanism for understanding the leaching process occurring in AASs based on an in-depth experimental exploration of mineralogical alterations.

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Dates et versions

hal-04698465 , version 1 (16-09-2024)

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Thi Nhan Nguyen, Quoc Tri Phung, Diederik Jacques, Lander Frederickx, Ziyou Yu, et al.. Changes in the structure of alkali activated slag mortars subjected to accelerated leaching. Cement and Concrete Composites, 2024, 154, pp.105755. ⟨10.1016/j.cemconcomp.2024.105755⟩. ⟨hal-04698465⟩
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