Issue 50

M. Papachristoforou et alii, Frattura ed Integrità Strutturale, 50 (2019) 526-536; DOI: 10.3221/IGF-ESIS.50.44 526 Focused on the research activities of the Greek Society of Experimental Mechanics of Materials Use of by-products for partial replacement of 3D printed concrete constituents; rheology, strength and shrinkage performance Michail Papachristoforou, Vasilios Mitsopoulos, Maria Stefanidou Laboratory of Building Materials, School of Civil Engineering, Aristotle University of Thessaloniki, Greece papchr@civil.auth.gr, mitsopov@civil.auth.gr, stefan@civil.auth.gr A BSTRACT . In this paper, fly ash, ladle furnace slag and limestone filler were utilized in concrete used as material for additive manufacturing (3D printing). Fly ash and ladle furnace slag were used as a replacement of cement (30% wt.) and limestone filler as a replacement of siliceous aggregates (50% wt.). Work- ability of fresh concretes that contained these by-products was measured 0, 15 and 30 minutes after mixing. Three different workability tests were conducted and compared: flow table, ICAR rheometer and an experimental method that measures the electric power consumption of the motor that rotates the screw extruder. Workability parameters that were measured were evaluated regarding printability of mixtures. Density, ultrasonic pulse velocity, compressive and flexural strength were measured on hardened concrete. Additionally, relative likelihood of cracking of different concrete mixtures was estimated by per- forming restrained shrinkage test (ASTM C1581). Results showed that use of fly ash or ladle furnace slag as binder, and limestone filler as aggregate decreases slightly the mechanical properties of concrete but improve its durability re- garding cracking potential. Monitoring of electric power consumption of screw extruder motor was found to be an effective method for measuring easily real-time workability and define if a mixture is printable or not. K EYWORDS . 3D printing, Concrete; Workability; ASTM C1581; Shrinkage. Citation: Papachristoforou, M., Mitsopoulos, V., Stefanidou, M., Use of by-products for partial replacement of 3D printed concrete constituents; rheology, strength and shrinkage performance, Frattura ed Integrità Strutturale, 50 (2019) 526-536. Received: 12.01.2019 Accepted: 22.05.2019 Published: 01.10.2019 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION -D printing technology is an additive manufacturing technique in which a structure is built layer by layer with various printing materials, based on a three dimensional (3D) model data. The first to introduce this technology in the con- struction industry using concrete as printing material was Khoshnevis who invented the technique of contour crafting [1]. There has been a growing interest over the past decade upon 3D printing for civil engineering applications due to the ad- vantages this method has compared to traditional concrete placing, such as the ability to construct freeform geometry with- out the need of formwork, construction speed and minimization of waste material and labour cost. Today there are many research groups and industries working on the topic with successful applications (Loughborough University [2], D-Shape [3], 3