Development of a Functional Cementitious Mixture with Expanded Graphite for Automated Spray Construction

Abstract

Spray-based three-dimensional (3D) concrete printing is an innovative method to automatically construct structures on vertical and overhead surfaces, which contributes to less labor investment and construction time. On the other hand, expanded graphite is widely known for its high thermal and electrical conductivity as a lightweight ingredient, and thus its potential in functional cementitious materials has been gradually realized in recent years. In this study, a lightweight cementitious material containing expanded graphite has been developed specifically for spray-based 3D concrete printing with added values. Through the characterization and overall evaluation of densities, mechanical and rheological properties, and Joule-heating performance, the appropriate expanded graphite content was determined as 1% by weight of cement. Afterward, silica fume was introduced into the matrix to tailor the rheological properties of the mixtures. The subsequent spray-based printing showed that the tailored mixture had significant improvements in the building capacity and spray quality. On the other hand, it also possessed superior Joule-heating performance than the control mixture without expanded graphite. The potential engineering applications of the developed material include deicing and structural health monitoring, and the compatibility with spray-based 3D concrete printing provides extra values of higher construction efficiency and adaptivity to the structures of complex contours.