Nanotechnology for Concrete with Low Carbon Footprint (ACI Spring 2023, San Francisco, CA) Carbon Nano Fibers used to produce Ultra High-Performance Concrete (UHPC) is revolutionizing the concrete industry. This technology yields safe, simple, and sustainable UHPC for use in the infrastructure, building construction and other design applications where its low shrinkage and creep, superior bond strength and tensile performance are an asset. It has the unique, sustainability benefit of using CO2 captured from waste streams as the feedstock for producing the required nano fibers used in the mix. This presentation will describe the nanoporomechanical structure of the matrix, fundamental characteristics of the nano technology and give concrete examples of applications where this material is being used today. It will explain why UHPC is an ideal material for use in resilient/sustainable design and how engineers and concrete professionals can leverage this material for longer lasting projects with smaller environmental footprints than traditional applications.

Novel Developments in the Use of Advanced Fiber Reinforced Concretes (ACI Spring 2023, San Francisco, CA)This study investigates the durability of cement mortar incorporating cellulose nanofibers against MgSO4 and Na2SO4 based sulfate attack and alkali silica reaction (ASR). Two different types of cellulose nanofibers namely lignified cellulose nanofibers (LCNF) and delignified cellulose nanofibers (DCNF) were used. Three different dosages of cellulose nanofibers (0.05%, 0.1% and 0.3%) were considered to prepare mortar specimens. The resistance to sulfate attack by incorporating were evaluated by exposing the mortar specimens to 5% MgSO4 and 5% Na2SO4 to mimic the sulfate attack for 6 months. The effect of sulfate attack was measured by evaluating the length change and change in compressive strength. The microstructural evaluations in paste samples were also carried out by X-ray diffraction technique (XRD), Thermal gravimetric analysis (TGA), X-ray Fluorescence (XRF) and Mercury Intrusion Porosimetry (MIP). The results showed that both LCNF and DCNF containing samples showed higher (42% ~ 52%) residual strength and lower expansion compared to the control batch when exposed to 5% Na2SO4 up to 6 months.