Monitoring the internal structure behaviour of alkali-activated slag paste: effect of the curing mode

Petr Nápravník; Dalibor Kocáb; Vlastimil Bílek, Jr.; Dominik Lisztwan; Barbara Kucharczyková

doi:10.14311/AP.2023.63.0411

Authors

Petr Nápravník Brno University of Technology, Faculty of Civil Engineering, Institute of Building Testing, Veveří 331/95, 602 00 Brno, Czech Republic https://orcid.org/0000-0001-6602-5735
Dalibor Kocáb Brno University of Technology, Faculty of Civil Engineering, Institute of Building Testing, Veveří 331/95, 602 00 Brno, Czech Republic https://orcid.org/0000-0002-8273-4571
Vlastimil Bílek, Jr. Brno University of Technology, Faculty of Chemistry, Institute of Materials Science, Purkyňova 464/118, 612 00 Brno, Czech Republic https://orcid.org/0000-0002-4026-3150
Dominik Lisztwan Brno University of Technology, Faculty of Civil Engineering, Institute of Building Testing, Veveří 331/95, 602 00 Brno, Czech Republic https://orcid.org/0000-0002-5002-353X
Barbara Kucharczyková Brno University of Technology, Faculty of Civil Engineering, Institute of Building Testing, Veveří 331/95, 602 00 Brno, Czech Republic https://orcid.org/0000-0002-7123-5099

DOI:

https://doi.org/10.14311/AP.2023.63.0411

Keywords:

alkali-activated slag, resonance method, resonant frequency, curing mode, flexural strength, crack

Abstract

This paper deals with the monitoring of the internal structure behaviour of an alkaliactivated slag (AAS) paste. The slag was activated with a 4M solution of sodium hydroxide. The behaviour of the internal structure of the paste was regularly monitored through the changes in the resonant frequency and the mechanical properties, until the paste reached the age of 90 days. The main aim of the article is to show the long-term maturation and degradation process of an AAS paste under different curing modes. The results obtained suggest that the curing mode of the specimens has a significant effect on the behaviour of the internal structure of the paste based on the AAS. The development of both the dynamic properties and the flexural strength indicates the occurrence of a higher porosity in the internal structure of the paste, especially when the free drying process is started earlier. Insufficient hydration of the binder system is also a likely cause of cracks. The reduction in the relative dynamic moduli values ranging from 50 % to 80 % was observed for drying specimens at the age of 90 days. What is very interesting is that the occurrence of cracks was not prevented even by intensive moist curing of the paste as, between the 21st and the 28th day of maturing, there was a significant decrease of about 20 % in the relative dynamic modulus of elasticity and also a 50 % reduction in the flexural strength.

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