Ultralightweight foamed concrete reinforced with natural fibers compatible with 3D printing

Concrete is one of the world’s most produced and widely applied materials. Its versatility has drawn the attention of the construction industry, making it the number one material for building houses, buildings, facilities, and even civil works worldwide. Unfortunately, due to its fabrication processes, energy consumption, and elevated expenditure on raw materials, concrete has become one of the most pollutant materials. Taking into consideration the environmental impact of the material, this research focuses on four well-known strategies to improve concrete’s sustainability, the reduction of the amount of binder, the implementation of secondary materials to the cementitious matrix, the diminution of energy consumption during the material’s lifetime, and the efficiency improvement of the construction process. The reduction of the amount of binder occurs due to the presence of the foaming agent that creates a microporous matrix reducing the amount of cement in terms of volume of the material considerably. This characteristic contributes to reducing the energy consumption in buildings as well because the air bubbles found in the matrix reduce the thermal conductivity. The implementation of sheep wool fiber reinforcement not only contributes to the material’s mechanical properties but also gives a second life to a widespread and pollutant secondary-material that would otherwise be disposed of. The studied material possesses the ability to develop green strength; therefore, it can be applied to automated construction processes that lead to material, time, and cost savings in construction. The present research studied the effects of the incorporation of sheep wool fiber reinforcement into extrudable foamed concrete and performed several laboratory experiments to determine the most suitable fiber characteristics for this type of concrete. The research divides into two parts. The first aims to determine the most performant fiber-treatments (non-treated, salt-treated, lime-treated, NaOH-treated, and surfactant-treated fibers), fiber-length (6, 12, and 20mm), and fiber/cement ratio (2,5, 5, and 10%) for ultralightweight extrudable foamed concrete in terms of mechanical strength. The second part consisted of applying the fiber characteristics outlined in the first experimental campaign to ultralightweight cement pastes with 100, 300, and 500 kg/m³ target densities to evaluate the influence of fiber-addition in diverse lightweight conditions. In this part, each admixture was analyzed in terms of its rheology, density variation, microstructure, compressive and flexural strength, and thermal conductivity. The studied material can be applied to both traditional and automated construction. In addition, its application can occur onsite and as part of a prefabrication process. Its main application is thermal insulation, leading to the improvement of the energy efficiency of a building. Finally, in a 3D concrete printing context, its application can occur by inserting the insulating material inside a 3D printed structural shell acting as formwork or extruding it with a multi-material process. For this last option to be possible, further experimental research should lead to determine the effective extrudability and printability capabilities of extrudable ultralightweight foamed concrete reinforced with sheep wool fibers, as expressed in the last chapter of this thesis in addition to the final experimental considerations.