Ultra-high-performance cementitious composites with enhanced mechanical and durability characteristics

Concrete is the most widely used construction material. It offers a desirable balance of cost, strength, moisture barrier qualities, and dimensional and chemical stability. The rising costs of aging infrastructure systems, however, point to the need for further improvements in concrete properties. Carbon-based nanomaterials (CBNs) are predicted to have excellent mechanical properties, and so are attractive candidates for addressing these issues. However, the relatively high cost of CBNs, means that only low weight fractions in cement matrices will be economically viable, which presents a significant challenge. The research presented here investigated various surface functionalization techniques for improving the compatibility of carbon nanomaterials (multi-walled carbon nanotubes, carbon nanofiber and graphene nanoplatelets) with cementitious materials in fresh and hardened state. The effects of surface functionalization on the contributions of CBNs to the performance characteristics of ultra-high-performance cementitious matrices (UHPCM) were evaluated. Functionalized multi-walled carbon nanotubes at 0.03% weight fraction increased the flexural strength by 30%, doubled the energy absorption capacity, and tripled the ductility of UHPCM. The moisture barrier qualities, abrasion resistance and toughness characteristics of UHPCM benefited significantly from introduction of CBNs at less than 0.1% weight fraction. This study demonstrates that the low weight fraction of CBNs can effectively enhance the key engineering properties of UHPCM at a viable cost. Thus, this approach has both performance advantages and economic benefits. Article highlights Surface functionalization of multiwalled CNTs improved dispersion in cementitious matrices at low weight fractions. 0.03 wt.% multiwalled CNT addition increased the flexural strength and the flexural toughness of UHPCM. Abrasion resistance and moisture barrier qualities improved. These improvements are achieved at viable cost.