Digital Fabrication of ‘Just-Add-Water’ Geopolymers: Effects of Curing Condition and Print-Time Interval

Abstract

A 3D-printable one-part geopolymer concrete has recently been developed by the authors of this study for construction automation applications. Instead of large amounts of alkaline solutions, a small amount of sodium metasilicate powder as the solid activator was used to formulate the ‘just-add-water’ geopolymer binder. Development of such 3D-printable concrete tackles the challenges associated with handling of hazardous activator solutions and enhances the commercial viability of using geopolymer as a sustainable binder for 3D-printable concretes. This paper presents the effects of curing conditions (i.e. curing temperature and curing time) and the print-time interval on the properties of the developed printable concrete. Workability, setting time, static yield stress evolution of the mixture were measured. In addition, compressive strength and flexural strength in different loading directions, as well as the inter-layer strength of the printed specimens were measured. According to the results, the compressive and flexural strengths of the specimens printed with different delay times were comparable in all loading directions. In addition, the compressive and flexural strengths of the printed specimens subjected to 28 days of ambient temperature curing were higher than those of the counterpart heat cured specimens. Furthermore, the static yield stress of the fresh mixture increased linearly for up to 60 min of rest time.