Toward 3D Printable Low Carbon Mortar. Method and Application

Because the environmental impact of 3D printable mixtures by weight is often higher than traditional mixtures due to their high clinker content [1], the benefit of material savings through optimization and digital manufacturing may thus be annihilated by the difficulty to formulate printable mixes with low binder content [2]. This paper aims to develop a methodology for designing cementitious materials specifically tailored for large-scale 3D printing of mortar in bi-component printing systems. This method, developed and used in this study, focuses on the packing density of a dry mix because high packing density is one of the key factors for obtaining ultra-high-performance cementitious materials, but packing density also plays a role in the fresh state, influencing various properties of dense suspensions, including rheological properties and stability, which are highly important in 3D printing applications and can be related to the three steps of a 3D printing process: Pumpability, extrudability, buildability [3]. To compute the packing density of futures mixes, the Compressive Packing Model [4, 5] was used. With various sets of raw materials, four different mixes were formulated with this method: a high performance mortar, a PLC (Portland, Limestone, Cement), a low carbon PLC, and a LC3 (Limestone filer, Cement, Calcinated-Clay). These mixes were tested at small scale to validate their rheological properties, particularly the yield stress. Pumpability, extrudability and buildability were evaluated by utilizing these mixtures in different large-scale printing sessions. The compressive strengths of these mixtures is characterized, and the carbon intensity [6] of theses mix is be discussed.