ASR Mitigation of Cementitious Composites Using Nano-Fibrillated Cellulose (NFC)

Nano-Fibrillated Cellulose (NFC) is a new high-performance biomaterial produced from wood pulp. Recent work has demonstrated that low levels of NFC can dramatically reduce swelling due to the Alkali Silica Reaction (ASR) in concrete. A 92–97% reduction in swelling was observed with just 0.1% addition of NFC (by weight of binder). In previous work, it was demonstrated that very low loadings of NFC in concrete have exceptional abilities to reduce early age shrinkage cracking (through internal curing), reduce corrosion (through pore restructuring), and improve adhesion in repair mortars [2, 12]. Using ASTM C 1260-21, samples containing 0.1 wt % NFC exhibited ~ 97% less expansion than their non-NFC-containing counterparts. It is hypothesized that this pronounced effect is due to the sequestration of alkali ions at the surface of the NFC fibrils, reduced permeability of the concrete matrix leading to reduced alkali transport, as well as through physical restraint of swelling by the nanofibrils. The very high surface area of NFC (~120–150 m2/g), along with the readily available hydroxyl and carboxyl groups on the NFC surface, is expected to contribute to the alkali sequestration effect. These results suggest that, in addition to NFC’s potent crack-reduction, corrosion prevention, and adhesion promotion capabilities, there is also an excellent case for using NFC as a low-cost highly effective additive for mitigation of ASR-induced swelling in cementitious composites.