NSF Award
1142455
This Small Business Innovation Research Phase I project will make complementary use of relatively low-cost graphite nanomaterials and conventional microfibers to realize balanced gains in diverse engineering properties of high-performance concrete. The targeted nanomaterials offer most of the geometric and performance advantages of carbon nanotubes at substantially reduced cost; they also provide a relatively high concentration of surface functional groups, which facilitate their dispersion and interfacial interactions in concrete. The peculiarities of concrete structure and construction practices impose unique challenges for the effective use of nano-scale reinforcement. These challenges will be addressed through refinement of the particle size distribution of cementitious materials, reduction of the capillary pore size and content, lowering the presence of micro-scale crystalline products among cement hydrates, and modification of nanomaterial surfaces using polyelectrolytes and high-molecular-weight surfactants. These measures employ economically viable materials and methods commonly used with high-performance concrete and nanomaterials. The proposed project will: (i) identify complementary selections, surface modification conditions and dosages of nano- and micro-scale reinforcement, and concrete mix designs which are cost-effective; (ii) develop a theoretical framework to explain the reinforcing action of nanomaterials in concrete; and (iii) assess the commercial merits and priority applications of high-performance concrete nanocomposites.<br/><br/>The broader impact/commercial potential of this project draws upon major gains in the safety (under explosion, fire and earthquake), structural performance and durability (weathering and abrasion/erosion resistance, and fatigue life) of the concrete-based infrastructure resulting from the use of economically viable nano-scale and hybrid reinforcement systems. The benefits rendered to concrete by the new reinforcement system far surpass those of conventional (micro-scale) fibers in terms of both the extent of improvements and the range of properties impacted. The high reinforcement efficiency and the relatively low cost and industrial-scale availability of the selected nanomaterials make them highly cost-competitive against conventional fibers. The new hybrid reinforcement offers pronounced gains in a wide range of qualities, and performance-to-cost ratios surpassing those rendered by each reinforcement system alone. The unprecedented balance of qualities provided by high-performance concrete materials with hybrid reinforcement helps expand their markets beyond those of conventional fibers, impacting broader markets for concrete admixtures (including fibers). Examples of priority applications for high-performance concrete nanocomposites include mission-critical infrastructure systems (protective shelters, hazardous/nuclear waste containment systems, nuclear power plants), key components of the transportation infrastructure (bridges, tunnels), and critical elements of the hydraulic and sewer infrastructure.
