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MONITORING THERMAL PROPERTIES AND VOLUME CHANGES OF ALKALIACTIVATED MATERIALS BY USING ADVANCED EXPERIMENTAL TECHNIQUES

par Lacante, Maïté ;Delsaute, Brice ;Staquet, Stéphanie
Référence RILEM 2026 Spring Convention(2026-04-15: Gent, Belgium), RILEM Conference on Innovative Construction Materials and Processes for Sustainable Buildings and Infrastructure, page (289)
Publication Publié, 2026-04-14

Abstract de conférence

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Résumé :

As autogenous and thermal strains are significantly high in alkali-activated pastes, it isnecessary to investigate ways to reduce these. This research studies how the volume changes of pastesmade from slag activated by alkalis can be mitigated by substituting part of the slag with limestonefiller or metakaolin and how this impacts the early age behaviour of the material with a focus on theautogenous shrinkage and the thermal expansion coefficient by using a customized AutoShrink devicedeveloped at ULB for that purpose.When slag is partially substituted by limestone filler at substitution rates of 15% and 30%, amaximal reduction in the compressive strength of 23% has been obtained. Isothermal calorimetryrevealed that the limestone filler was not entirely inert and showed the effect of dilution which islinked to the increase in the solution-to-binder ratio when the substitution rate increases. Theautogenous shrinkage magnitude decreased when substituting 15% of the slag while higherautogenous shrinkage magnitude was obtained when 30% was substituted. The coefficient of thermalexpansion was slightly reduced and delayed when slag was substituted with limestone filler.When slag is partially substituted by metakaolin, its effect on the autogenous shrinkage andthe coefficient of thermal expansion were found to depend on both the type and concentration of thealkaline activator. The swelling was increased at 10% substitution followed by constant shrinkage incase of NaOH-activation. Shrinkage was mitigated with Na2SiO3 activation. Higher substitutions with 8M NaOH resulted in a significant increase in the shrinkage rate and thermal expansion coefficient (CTE).A 10% substitution delayed the CTE increase but resulted in higher later-age values (dilutioneffect). The 20% substitution led to a similar final CTE value at 300 h, while 30% substitutionresulted in a decrease in CTE after the initial increase.