Assessment of Degradation of Alkali-Activated Blast Furnace Slag Progress Using the Mercury Intrusion Porosimetry

abstract

English

Alkali-activated systems (AAS) represent a low-carbon inorganic binder as an alternative to Ordinary Portland cement. The main benefits of AAS are the lower carbon foot-print and economic demands along with the superior durability in aggressive environments contrary to the OPC. The techniques like the determination of compressive and flexural strength are usually used for characterization of degradation processes since their realization is accompanied by the deterioration of these properties. The phenolphthalein technique or advanced instrumental techniques (SEM, XRD) can be used as well. This paper study the possibility of utilization of the mercury Intrusion porosimetry (MIP) to characterize the degradation of alkali-activated blast furnace slag. The degradation processes are dependent on the porosity or permeability of the material, as the penetration of the aggressive media into the internal structure is a key for the reaction to take place. The MIP is a suitable method for the characterization of material porosity, thus it can indicate which material will be more susceptible to degradation than the others. Moreover, it can characterize the changes taking place since the reactions like the decalcification are associated by the increase of the total porosity. Various alkaline activators (sodium water glass, sodium hydroxide, sodium carbonate) were used for alkali-activation of blast furnace slag in the same activator dosage (6 % Na2O by the slag weight). A binder based on common cement (CEM III) was also prepared for comparison. Water to binder ratio was kept the same (w/b = 0.45). After the initial 28 days of hydration in water the testing samples (mortars with 3 : 1 sand : binder ratio) were immersed in various aggressive environments (CH3COOH, MgSO4, Na2SO4, NaCl, NH4NO3 and water for 84 days). Then the changes in porosity were characterized with the dependence on the time of degradation. It was found out that immersion in solutions of acetic acid (pH = 3) and ammonium nitrate (6M) had the most significant effect to both total porosity and the pore size distribution. Immersion in other environments did not cause any relevant changes.

Alkali-activated Blast Furnace Slag, Mercury Intrusion Porosimetry, alkaline activator

HAJZLER, J.; HRUBÝ, P.; BÍLEK, V.; TOPOLÁŘ, L.

26. 11. 2021

Vysoké učení technické v Brně, Fakulta chemická

Brno

978-80-214-6002-7

Studentská konference CHEMIE JE ŽIVOT

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75

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https://www.fch.vut.cz/vav/konference/sok/vystupy/sbornik-konference-2021-abstrakty-a5-pdf-p213391