Investigating the early-age diffusion of chloride ions in hardening slag-blended mortars on the light of their hydration progress. (20th November 2019)

• Record Type: Journal Article
• Authors: Ben Fraj, Amor; Bonnet, Stéphanie; Leklou, Nordine; Khelidj, Abdelhafid
• Is Part Of: Construction & building materials. Volume 225(2019)
• Page Start: 485
• Page End: 495
• Publication Date: 2019-11-20
• Subjects: Chloride diffusion -- Slag-blended mortar -- Early age -- Hydration -- Chemical shrinkage -- Microstructure; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2019.07.185
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: A slow hydration promotes the chloride ingress in slag-blended mortars at early age. The hydrates gradually develop within the hardening microstructure. In long term, the chloride ingress decreases drastically for slag-blended matrices. Abstract: The present work seeks to investigate the ingress of chlorides during the hardening of slag-blended mortars that may have been exposed to chlorides since an early age. In order to correlate chloride ingress with the microstructure development, both the hydration reaction and chemical shrinkage of the investigated mixtures are monitored, and their microstructure is characterized through SEM observations. Results indicate a slow hydration reaction in the presence of slag, which decelerates the formation of hydrates and the filling of capillary pores. Despite the decrease in chemical shrinkage, chloride ingress still increases, thus amplifying the risk of corrosion in slag-blended matrices. The hydrates gradually develop within the hardening microstructure and obstruct the chloride diffusion paths, resulting in a lower chloride diffusion coefficient. The apparent chloride-diffusion coefficient measured after 28 days of exposure is 12 × 10 −12 m 2 /s, 14.2 × 10 −12 m 2 /s and 14 × 10 −12 m 2 /s for hardening mortars, with respectively 0%, 30% and 60% of slag. These coefficients are respectively 2 times, 2.8 times and 4.7 times higher than those of hardened mortars.