Printable properties of cementitious material containing copper tailings for extrusion based 3D printing

3D printing for cementitious material is an innovative and promising construction method that is rapidly gaining ground in recent years. Utilizing waste or recyclable materials as the primary raw material to produce cementitious material for 3D printing can greatly promote the 3D printing to reach its maximum cost-effective potentials. This paper proposes an environmental friendly cementitious mixture that is compatible with an extrusion based printing process. In this study, six replacement ratio of tailing to sand from 0% to 50% are investigated. A single nozzle printing system is developed and the operational process is illustrated. Experimental tests are performed to determine the printable properties of mixtures containing various content of tailings, including the extrudability, buildability, flowability, open time, fresh and hardened properties, etc. Based on the measurements, the optimal mixture is determined as substituting natural sand with 30% mass ratio of mining tailings, which enables structures achieve a favorable buildability and a relatively high mechanical strength. In particular, the critical value of controlling parameters to achieve sufficient printability are specified. And the compressive and flexural strength of the printed and the casted samples are measured and compared. To conclude the present research, extrudability and buildability coefficients are proposed for optimizing design. (C) 2017 Elsevier Ltd. All rights reserved.