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Early Age Characterization of Viscoelastic Properties of Alkali-Activated Binders

par Naqi, Ali
Président du jury Deraemaeker, Arnaud
Promoteur Staquet, Stéphanie
Publication Non publié, 2023-12-22

Thèse de doctorat

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Résumé :

With the global population on the rise, the construction industry has experienced significant growth in the last two decades. Cement, a key component in concrete production, contributes up to 8% of total CO2 emissions. This underscores the demand for concrete solutions that are durable, cost-effective, and environmentally friendly. Alkali-activated materials (AAMs) present a promising alternative to traditional cements, contributing to more eco-friendly concrete production. In this research, twelve mixture compositions are explored, incorporating various combinations of precursors (slag, fly ash) and activators (sodium hydroxide and sodium silicate). Different alkali dosages and solution-to-binder ratios are also considered. The independent and combined effects of these parameters are observed on the development of main binder properties through specific experimental equipment. The first part focuses on characterizing the setting behavior of these novel binders. Continuous non-destructive tests, including ultrasonic pulse velocity (UPV) measurements and isothermal calorimetry tests, are combined with traditional tests such as slump flow, Vicat, and uniaxial compressive strength tests. For characterizing viscoelastic behavior post-setting, a novel technique involving repeated short-term creep tests is employed. This approach allows continuous monitoring, facilitating the characterization of early-age elastic stiffness and creep properties. To model short-term creep behavior, a power-law creep function is utilized. For long-term creep, a logarithmic creep function is applied. Furthermore, a logarithmic trend is observed in the development of specific creep over an extended duration of loading. An adapted version of the Model Code 2010 is employed to fit the experimental data, showing good agreement in modeling the specific creep of slag-based mortar samples.