Nano-fly ash and clay for 3D-Printing concrete buildings: A fundamental study of rheological, mechanical and microstructural properties

Abstract

Three-dimensional printing concrete (3DPC) represents a recent innovation in the construction and building research sector and novel approach to building techniques. The focus of this study is to develop an environmentally sustainable cementitious composite optimized for 3D printing applications. The research involved preparing 3D printing mixtures that comprised of 50 % Portland Cement (PC), 50 % Colorobia Clay (CC), and varying contents (0 % 5 %, 10 %, and 15 % by weight of cement) of Nano-Fly Ash (N-FA) under standardized printing parameters. The fresh mixture's properties have been evaluated and the mechanical and microstructural properties of the printed samples were assessed, subsequently. The findings demonstrated that incorporating N-FA into the cementitious mixes enhanced their flowability and workability. Specifically, the mix containing a low N-FA concentration of 5 wt% exhibited superior compressive strength relative to the other formulations. Additionally, flexural strength assessments indicated a minimum increase of 39.4 % across all mixes compared to the control 3D-printed mixture. Microstructural investigations by SEM imaging validated the anticipated formation of hydration products, namely calcium-silicate-hydrate (CSH) and ettringite, facilitated by the synergy between clay and fly ash. The t-statistical analysis further corroborated that the inclusion of N-FA significantly bolstered the strength attributes of the mixes designated for 3D printing. In conclusion, this study underscored the efficacy of integrating clay as a sustainable construction material within 3D printing applications. The utilization of clay-cement mixes, augmented with N-FA, emerged as a viable strategy to enhance the sustainability and reduce the carbon footprint of construction practices.