ASSESSING THE MATERIAL PROPERTIES OF MORTAR CONTAINING GROUND GRANULATED BLAST-FURNACE SLAG FOR 3D PRINTING PURPOSES

Abstract

Construction 3D Printing is one of the technologies identified in BCA’s R&D Roadmap to help improve the productivity of Singapore’s construction industry. Literature has shown that the replacement of cement with Ground Granulated Blast-Furnace Slag (GGBS) in a mortar mix can reduce the amount of CO2 generated from cement production. This paper investigates the material properties of GGBS mortar for Construction 3D Printing. Workability and buildability of GGBS mortar for 3D printing purposes were analysed to propose a suitable percentage of replacement of cement with GGBS. Jump Table Test was performed to evaluate the workability of GGBS mortar. It was discovered that the replacement of Portland cement with GGBS in the mortar resulted in higher workability. However, the dosage of viscosity modifying agent (VMA) and superplasticiser (SP) in GGBS mortar mixes can be adjusted to achieve similar workability as a printable control mix. Uniaxial Unconfined Compression Test (UUCT) was then carried out to analyse the buildability of GGBS mortar. The results from UUCT shows that GGBS mortars have a lower green strength and stiffness as compared to a printable control mix. Mortar containing 50% of GGBS as the binder was unable to support its self-weight at t = 60min. GGBS mortar containing 30% of GGBS as the binder had a lower green strength of 30.515KPa at t = 90min as compared to 56.496KPa of the printable control mix. Based on the results, the maximum replacement level of cement with GGBS for 3D printing is up to 30%.