Industrial Waste in 3D Printed Concrete (2025-09)¶

Sustainable 3D printed concrete (3DPC) offers a promising solution to reduce cement consumption and utilise industrial waste in digital construction. This review examines the roles of metallurgical slags (GGBFS, steel slag) and mining tailings (antimony, bauxite, copper) in affecting the fresh-state performance of 3DPC. A comparative analysis is conducted to evaluate the influence of different industrial waste on key fresh properties, e.g., pumpability, extrudability, buildability, and open time. A dual mechanistic framework is proposed, separating reaction-controlled structuration from packing-controlled rheology. The results show that GGBFS provides the most balanced effect: it lowers yield stress and improves flowability in OPC mixes, while accelerating structuration in alkali-activated binders. Steel slag mainly contributes to packing effects but requires activation or blending with more reactive SCMs. Antimony and bauxite tailings exhibit moderate pozzolanic activity, enhancing buildability and thixotropy at suitable dosages. In contrast, copper tailings act largely as inert fillers, improving pumpability but reducing interlayer bonding at high contents. Beyond these mechanisms, the review highlights environmental and economic benefits. The use of slags and tailings can replace up to 40% of clinker, leading to CO2 emission reductions of about 2-8% depending on the binder system, and lowering raw material costs by approximately 10-20% compared with conventional mixes. Future directions include standardising fresh-state test methods, applying machine learning to mix optimisation, and validating performance at the field scale to ensure reliable and sustainable application.