Development of 3d printing mixes based on portland cement and additions of metakaolin, microsilica, and calcium carbonate

This article focuses on the utilization of additions such as microsilica (MS), metakaolin (MK), and calcium carbonate (CaCO3)for the design of cementitious materials based on ordinary Portland cement (OPC) suitable for 3D printing (additive manufacturing). The additions were incorpora-ted into the mixes as replacements for OPC in quantities of 5-10% (MS), 5-15% (MK), and 5-15% (CaCO3).The effect of the additions on the fresh and hardened state properties of the mixes was evaluated. The properties studied included extrusion capability, workability (mini slump), flowabi- lity (flow table test), setting time, open time, and printability. Additionally, microscopic inspection of the 3D printing mixes was conducted using scanning electron microscopy (SEM), and physi-cal-mechanical characterization was performed through tests for density, absorption, porosity, flexural strength, and compressive strength. The results demonstrated that the additions directly influence the aforementioned properties. It was concluded that the mix 90%OPC-5%MS-5%Ca- CO3 (mixture 1) and the mix 90%OPC-5%MS-5%MK (mixture 2) exhibited the most suitable set of characteristics to be implemented as 3D printing cementitious materials. From these mixes, it was possible to 3D print beam-type specimens (160 x 40 x 40 mm), achieving flexural streng- th values at 28 days of 3.4 MPa (mixture 1) and 4.0 MPa (mixture 2), and compressive strength values of 44 MPa (mixture 1) and 50 MPa (mixture 2). These results are considered as a starting point for future research related to the use of these types of additions in 3D printing of OPC-ba-sed cementitious materials.