Nano-engineered ultra-high performance concrete for controlled autogenous shrinkage using nanocellulose

Abstract

For its superior mechanical strength and durability aspects, ultra–high performance concrete (UHPC) offers an advanced construction solution for resilient concrete infrastructures. Nonetheless, one major handicap of UHPC is autogenous shrinkage, particularly for insitu casting. This study proposes nanoengineering using nanoscale cellulose filaments as a novel approach for controlling autogenous shrinkage of UHPC. A typical UHPC mix was redesigned by incorporating cellulose filaments at 0–0.30% by mass of cement while varying silica fume content from 25 to 15%. Results indicate that cellulose filaments can significantly mitigate autogenous shrinkage by a twofold mechanism. The first is an internal curing effect leading to characteristic volumetric expansions at very-early-ages, thereby significantly attenuating autogenous shrinkage. Thus, reduction in autogenous shrinkage of 45–75%, 22–53%, and 20–40% were achieved at 24 hours, 7 days, and 14 days, respectively. The second mechanism pertains to a nanoreinforcing effect leading to matrix bridging, thereby improving volumetric stability. On the other hand, while adjusting silica fume content from 25 to 15% does not affect early-age autogenous shrinkage (~0–4% reduction at 1 day), this measure can allow reducing 7-days autogenous shrinkage by up to 28%. However, given the remarkable role of silica fume in the mechanical performance of UHPC, mixtures with 15% silica fume recorded 21–25% drop in flexural capacity. Interestingly, nanoengineering UHPC with cellulose filaments enabled obtaining UHPCs with 25% silica fume exhibiting as low autogenous shrinkage as UHPCs with 15% silica fume while maintaining the enhanced flexural strength offered at 25% silica fume content.