Development and Characterization of a Printable Concrete Made with Construction and Demolition Waste Aggregates

To address the environmental challenges associated with Construction and Demolition Wastes (CDW) disposal and the depletion of natural sand resources by the construction industry, this paper investigates the potential use of fine aggregates from CDW as a complete replacement for natural sand in concrete formulations tailored for 3D printing applications. The study begins by physically characterizing fine aggregates produced by crushing and sieving CDW from concrete and fired clay brick residues. This stage includes water content and water absorption capacity tests, specific gravity tests and unit weight tests, and particle size analysis. Then, a 3D printable concrete mix formulated entirely with CDW fine aggregates, replacing 100% of natural sand, is developed using mortar flow and rotational rheology tests. This formulation is validated by printing a medium-sized wall using a 3D printing system developed in-house. Finally, compression tests are performed on printed filaments to examine mechanical properties such as compressive strength and modulus of elasticity. Fresh-state and hardened-state properties are compared with control concrete samples made with natural sand (0% of CDW fine aggregates). The study demonstrates the feasibility of formulating printable concretes with a total replacement of sand by CDW for real-size applications. However, special attention must be given in large-scale projects to the rate of workability loss caused by the high water absorption capacity of CDW fine aggregates. The research findings offer valuable insights into the potential and performance of CDW aggregates in 3D-printed concrete applications within the context of a circular economy.