Strategies for Reducing the Environmental Footprint of Additive Manufacturing via Sprayed Concrete (2022-06)¶

Lately, the construction industry has been trying to reduce its environmental footprint with the help of an additive manufacturing. This emerging technique allows for an automated construction of free-of-form structural elements. This, in turn, enables optimization ofgeometrical dimensions during design. However, the 3D concrete printing (3DCP) based on extrusion of material requires high amount of Portland cement, additives, and consumes an already scarce fine sand. On the other hand, the additive manufacturing using spraying (S-3DCP) offers larger flexibility in material composition, allowing for further reduction of the carbon footprint. It also facilitates implementation of larger aggregates, which improve material mechanical stability during manufacturing process and ameliorate its flexural strength in the hardened state. In this work, strategies related to the circular economy and the reduction of CO2 emissions through the concrete recipe optimization are assessed and demonstrated. The first strategy is based on the use oflow-CO2 cement,which can reduce CO2 emissions by about 40% compared to using CEM II. The second strategy is based on the design of elements, which is to reduce the thickness while satisfying all mechanical constraints, that is, to reduce the concrete by approximately 25%. Finally, this paper will show the possibility of using demolition waste to replace 45% of aggregate (i.e., 35% of 0–4 mm sand and 10% of 48 mm aggregate) and the potential circular economy of S-3DCP. Due to the use of high-speed spraying (shotcrete) as the material placement method, continuous and isotropic elements with a low environmental footprint are produced.