Development of 3D printed heavyweight concrete (3DPHWC) containing magnetite aggregate.

[Display omitted] • Printable heavyweight mixes with maximum dry density of 3500 kg/m3 were developed. • Mix containing 60% of magnetite aggregate exhibited the highest green strength. • Mixes containing MA displayed an adequate fresh property performances for medium scale printing. • The incorporation of MA gradually increases the flexural and compressive strengths of both cast and printed samples. • A substantial improvement in gamma-ray and neutron shielding was reported in mixes incorporating MA. The main objective of this study is to develop 3D printed heavyweight concrete (3DPHWC) to produce elements with a dry density of up to 3500 kg/m3 by replacing natural aggregate (SA) with magnetite aggregate (MA) up to 100%. A comprehensive systematic study was conducted to thoroughly assess mixtures' mechanical properties, physical proficiency, fresh properties, and printing qualities. The inclusion of MA exhibited the desired fresh properties required for 3D printing and promising physical and mechanical properties. Evaluation of the mechanical properties of designed 3DPHWC indicates that replacing SA with MA increases both cast and printed samples' strengths. The 3D printed M100 sample achieved higher 28 days flexural and compressive strengths by 18 % and 20 %, respectively, compared to printed control mix (M0). Micro-CT study correspondingly demonstrated improvements in the composites' porosity, pore size, and pore morphologies. The linear attenuation coefficients (LACs) and half-value layer (HVLs) for slow neutron and gamma-ray were measured to assess radiation shielding characteristics. A significant performance improvement was obtained for slow neutrons by introducing the magnetite aggregate. Unlike slow neutrons, no significant difference was observed between cast and printed samples against γ-rays. Moreover, the effect of porosity on the shielding performance was discussed. [ABSTRACT FROM AUTHOR]