Exploring Fresh and Hardened Properties of Sustainable 3D-Printed Lightweight Cementitious Mixtures

This study investigates using lightweight concrete in 3D printing to reduce transportation costs and maintain structural strength. Normal-weight river (RS) sand was replaced with pumice and expanded glass at 50% and 100% volumes to decrease the material density. This substitution reduced the weight of various mixes up to 25.1%, with apparent porosity ranging from 11.37% to 27.9%. This study found that aggregate characteristics, including the shape, size, and absorption capacity, influenced printability. Rounded aggregates like expanded glass flowed better and required less water than irregular pumice. Lightweight aggregates had finer textures and higher porosity, needing more water. According to the extrudability results, the best print quality was achieved using 100% expanded glass, incorporating methylcellulose (MC) and polyethylene (PE) fibers. Moreover, the buildability outcomes highlighted a reliance on the printing speed and the water-to-binder (W/B) ratio. Comparing cast and 3D printed specimens, cast concrete reached a maximum compressive strength of 65.6 MPa, while 3D printed concrete achieved a maximum strength of 43.4 MPa. RS had the highest strength (65.6 MPa), while expanded glass showed the lowest (17.5 MPa) in both cast and 3D printed specimens. Adding PE and MC enhanced the print quality and increased the compressive strength due to the fibers' bridging capacity.