Nanotechnology Applied To High Volume Fly Ash Concrete And Its Resistance To Freeze Thaw Damage

Download or read book Nanotechnology Applied to High Volume Fly Ash Concrete and Its Resistance to Freeze/Thaw Damage written by Sen Du and published by . This book was released on 2020 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: Partially replacing cement with fly ash in concrete is an effective approach for reusing fly ash. High-volume fly ash (HVFA) concrete contains more fly ash than cement and exhibits many advantages including low hydration heat, low shrinkage, and reduced production cost. In this context, HVFA concrete has been successfully used in the field, such as mass concrete and structural concrete. However, some drawbacks are hindering its wider acceptance, including low early-age strengths and low freezing-thawing (F-T) resistance.This dissertation firstly optimizes the mix design of HVFA mortar through a statistical design of experiment, aimed at obtaining the best performance in the mechanical properties. In the HVFA system that adopted the optimized mix design, a hypothesis is proposed that approaches that can improve the transport properties, matrix's microstructure properties, and the interfacial transition zone (ITZ) properties could finally benefit the F-T resistance of HVFA concrete. Nanotechnology, including nanoscience and nanoengineering, is applied to investigate the hydration characteristics of fly ash and modify the F-T durability of HVFA concrete.For transport properties, some chemical admixtures are admixed into HVFA mortars, the dosages of which are optimized based on the performance of water sorptivity and mechanical properties. Pore structure at nanoscale and microscale are investigated based on its close relationship with transport properties. Graphene oxide (GO), as a promising nanomaterial in cement-based material, is added into HVFA concrete to enhance its microstructure. The modification mechanisms of GO on HVFA mixture are studied. Focusing on the ITZ, GO and nanosilica (NS)-contained paste slurry are applied to coat the coarse aggregate. The effectiveness of this approach is verified through images analysis. HVFA concretes with the best performance in the aforementioned three sections are subjected to further F-T testing. A four-phase sphere model is proposed for HVFA concrete to predict the change in dynamic modulus of elasticity during F-T cycles. Future research may include the life-cycle assessment of HVFA concrete in the context of employing nanotechnology. Besides, the F-T durability of HVFA concrete in the presence of deicers should be researched given the fact that more deicers are applied on concrete infrastructures.