New insights on the basic creep mechanism of one-part alkali activated slag and fly ash paste

In this paper, basic creep mechanism of ambient cured one-part alkali activated slag-fly ash (AASF) paste is examined at the microscopic level. A special mini creep rig is constructed enabling in-situ monitoring of water redistribution over time between high- and low-density (HD, LD) gel pores within the loaded paste specimens using 1 H NMR relaxometry. The results suggest that the contraction of C-(N)-A-S-H particles is accompanied by the reduction of water content in HD gel for loaded AASF paste. In contrast, in the loaded OPC paste a noticeable decrease of water residing in LD rather than HD C-S-H gel was observed, implying the presence of a distinct creep mechanism. In addition to the different water environment, the more crosslinked bonding structure of AASF could partially account for its lower creep response supported by 29 Si NMR measurement. The findings of this study provide evidence in understanding underlying basic creep mechanism of AASF. • Basic creep mechanisms of one-part activated slag-fly ash paste are examined. • A mini creep rig is designed for use with proton nuclear magnetic resonance testing. • In-situ monitoring of changes in water redistribution over time between gel pores • A greater crosslinked material structure may lead to lower creep.