Comparison of reinforcement fibers in 3D printing mortars using multi-criteria analysis

3D concrete printing (3DCP) has developed rapidly in recent years, with a relatively high amount of mortars emerging apt for 3D printing. Some of these mortars include fibers to improve their strength. Despite mechanical properties having been quite well studied, there still is missing information on cost, printability, and environmental impacts. The objective of this research is to select the best mortars with fibers considering four criteria: printability, mechanical strength, and economic and environmental impact applying a multi-criteria decision-making analysis (MCDMA). Seven types of fibers with different dosages were assessed in the reinforced mortars: zylon, aramid, carbon, glass, cellulose, textile, and polypropylene. AHP method and equal weights were used as ponderation techniques of the criteria while WASPAS and TOPSIS methods were used to calculate the rankings of the MCDMA. Printability was measured through rheological tests using a rotational rheometer, mechanical strength through flexural tests at 28 days based on EN 196–1, and cost just considering the materials and environmental impact through a life cycle assessment (LCA). The results showed that 13-mm-long glass fibers with a content of 0.1% were the best alternative, closely followed by the mortar with 6 mm cellulose fibers with a content of 0.05%. For the best option (G13;0.1), the increments in the printability index, flexural strength, cost, and LCA were − 14.37%, 16.70%, 5.88%, and 2.86%, respectively. It can also be concluded that high elastic modulus fibers (zylon and aramid), although able to increase significantly the flexural strength (up to 30% in the case of zylon), prevent them from being an optimal solution due to their high cost.