Cellulose nanofibres mitigate chloride ion ingress in cement-based systems. (November 2020)

• Record Type: Journal Article
• Authors: Goncalves, Jose; Boluk, Yaman; Bindiganavile, Vivek
• Is Part Of: Cement & concrete composites. Volume 114(2020)
• Publication Date: 2020-11
• Subjects: Cellulose nanofibre -- Chloride penetration -- Colorimetry -- Cementitious system -- Carboxyl group -- pH; Composite-reinforced concrete -- Periodicals; Concrete -- Periodicals; Composite materials -- Periodicals; Composites de ciment -- Périodiques; Béton -- Périodiques; Composites -- Périodiques; Béton léger -- Périodiques; Cement composites; Composite materials; Composite-reinforced concrete; Concrete; Lightweight concrete; Periodicals; Electronic journals; 620.135
• DOI: 10.1016/j.cemconcomp.2020.103780
• Languages: English
• ISSNs: 0958-9465

Abstract

Abstract: This study pioneers the use of cellulose nanofibres (CNF) as a means to restricting the chloride-ion ingress in cement based systems. Three CNF variants, differing in their carboxylate content from 0.13 to 1.13 mmol/g of the nanofibre, were introduced to paste and mortar mixtures alike, at up to 1.2% by volume fraction of the dry nanofibre. The reference mixture was a plain system, prepared with CSA Type GU Portland cement. The ingress of chloride ions was investigated per the Rapid Chloride Penetration Test (ASTM C1202 ) and further assessed by colorimetry. Companion studies were conducted to measure changes to the air-void network and the pH environment within. The results demonstrate that adding CNF significantly impedes chloride-ion penetration, most likely due to a lower porosity in the 10 nm–140 nm range. Higher amounts of carboxyl groups, [ C O O H ], uniformly led to higher CNF efficiency, both for easy workability and for restricting the chloride ingress. So that, for 0.50% fibre volume fraction, and the CNF variant grafted with 1.13 mmol of carboxylate/g, the mortar witnessed a 50% drop in the measured electrical charge as well as in the depth of chloride penetration. The study indicates that the [ C O O H ] groups scavenge the soluble calcium cations C a 2 +, from the aqueous phase of the cement paste without, however, altering the pH therein.