Influence of Illitic Calcined Clay on Properties of Mixtures for 3D Concrete Printing

This paper focuses on the use of illitic calcined clay (CC) as supple-mentary cementitious material (SCM) partly replacing Portland cement (OPC) in binders for mixtures suitable for 3D Concrete Printing (3DCP). This kind of re-placement would be ecologically and economically feasible and meets a global need to reduce CO2 emission in construction industry. Availability and abun-dance throughout the world, especially of illitic clays, makes CC a potential SCM in concrete technology. Influence of CC additions of two different levels of fineness on properties of mixtures, important from a technological point of view in 3DCP is examined. On fresh concrete mixtures, flow of a Hägermann cone was measured at different CC percentages in the binders. Behaviour of CC in ternary blends with OPC and limestone filler (LF) for mixtures, containing al-so chemical admixtures and fibres was also examined. An experimental mixture from a local producer of dry mixes was used for that purpose. Print of an L-shape wall element with attended measurement of essential printing parameters, flowability, extrudability and buildability was performed. A mixture with a ter-nary blend binder containing OPC-LF-CC in proportion of 50-30-20 was used for Gantry-type 3D concrete printer. It was found that CC additive in ternary blend binders increases water demand of the mixture and has positive influence on strength. From a printing point of view, CC gives extra properties to the mix-tures by improving their extrudability, buildability and shape retention.