Additive Manufacturing for Earth-Based Materials: An Experimental Investigation

The achievement of sustainable development goals should be driven not only by environmental policies but also considering societal constraints, such as the valorisation of local traditions, especially in emerging countries. In the field of construction engineering, 3D printing can be seen as a modern technique which allows reproducing traditional constructions, such as those made in adobe and cob, using local and natural materials, e.g. soils, and even recycled ones, thus reducing the impacts related to the production and transport of the raw materials. The environmental and economic advantages of additive manufacturing are widely recognized for several applications: 3D printing does not require molds and allows to save material, obtaining complex shapes easily. The main advantages are linked to save money, time, handwork and properly reducing the environmental impact of structures. In this paper the results of an experimental campaign aimed at selecting earth-based sustainable mixes for 3D printing are shown. At the beginning of the experimental campaign, 18 mixes were prepared varying the dosage and the components: among them, we selected locally available soil, silica sand, hydraulic lime binder, unaltered rice husk, shredded rice husk, marble waste dust, municipal solid waste incinerator bottom ash and fibres. Each mixture has been evaluated in terms of printability, then mechanical tests were performed at 28 days of curing. Finally, an efficiency evaluation of mixture is carried out considering compressive strength, price and embodied carbon as affecting parameters.