Low field NMR relaxation as a probe to study the effect of activators and retarders on the alkali-activated GGBFS setting process

Xinyu Cong, Wei Zhou, Xiangri Geng, Mohamed Elchalakani

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Low field nuclear magnetic resonance relaxometry (LF-NMR) was used to study the setting process of alkali-activated GGBFS (AA-GGBFS) paste during the early curing hours. LF-NMR measurements were carried out from fresh paste casting until hardening (generally no more than 8 h). The transverse relaxation time T2 was used as a probe to assess the setting process. Combined with Vicat penetration and temperature monitoring, an important threshold indicator was defined as the deadline for paste casting (DPC). The physical meaning of the DPC is a threshold point where the developing micro pores make loss of movable water attain a certain level so that the semi-solid paste has slight strength. Moreover, several periods related to AA-GGBFS early-hour paste development are proposed: (1) dissolution; (2) setting; (3) acceleration; and (4) hardening. By analysing each period during the early hours, it was found that the hybrid retarder of zinc nitrate and sodium gluconate works for the AA-GGBFS system.

Original languageEnglish
Article number103399
JournalCement and Concrete Composites
Volume104
DOIs
Publication statusPublished - 1 Nov 2019

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