Mechanical Properties and Freezing and Thawing Behavior of 3D Printing Concrete containing Recycled Fine Aggregates from Construction and Demolition Waste

This study focuses on evaluating the mechanical, microstructural, and durability properties of 3D printing mortar (3DPM), with a specific emphasis on the influence of incorporating Recycled Fine Aggregates (RFA). These RFA are produced from Construction and Demolition Waste (C&DW) in Belgium and are sieved to a maximum particle size of 2 mm [0.08 in].
Cast and printed samples of mortar containing 100% RFA, with a sand-to-cement ratio of approximately 1:1 and a water-to-cement ratio of 0.29, were subjected to mechanical tests, including flexural, compressive, and tensile strength, at 2, 7, 28, and 56 days. The possible anisotropic behavior of the printed material was also investigated. The results show that using RFA does not significantly affect the mechanical properties of the mortar, and some anisotropic behavior was observed based on the compression test results. The end-goal of the project is to print non-reinforced urban furniture; in order to assess its durability, only freezing and thawing (F-T) behavior was investigated. The F-T behavior were analyzed based on the quantity of spalling particles after 7, 14, 28, 56, and 91 F-T cycles. The results show that up to 91 F-T cycles, no significant surface damage occurred.