Title: Early-Age Mechanical Performance of Fiber-Reinforced Mortars Used in 3-D Printed Concrete Construction

Author(s): Liberato Ferrara, Marta Fioretti, Kasyapa Sriram Kompella, Laura Esposito, Costantino Menna, Francesco Lo Monte

Publication: Web Session

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Date: 6/1/2020

Abstract:
The digital fabrication with cement-based materials requires to pay specific attention to the rheological and mechanical material properties in both fresh and hardened state. For the layered extrusion process, the cement-based material needs to satisfy the so called “printability” requirement. Generally, printable mortars exhibit a brittle mechanical behavior due to the absence of physical reinforcement; to overcome this issue, many different strategies can be implemented. Among them, the addition of short fibers in the mortar represent a first step towards the development of robust materials for 3-D printing in construction. In this context, the paper focuses on the early stage properties of fiber reinforced cement-based material to be used in the layered extrusion process. The embedment of discrete fibers in a printable mix is expected to improve the fresh and hardened mechanical behavior but, at the same time, it implicates a loss of workability in the mix, which could lead to problems during the printing process (in terms of extrudability and pumpability of the mix). In particular, the mechanical response under direct tensile and shear load conditions are investigated as a function of the type/concentration of fibers as well as the mortar resting time. Furthermore, the effect of varying the amount of the superplasticizer to guarantee the printability requirement of the printable mortar is also investigated. In a quality control framework, the development of tensile and shear fracture properties, in the considered production time frame, is fundamental to discriminate about the printability of the mix, with reference not only to the quality of the finishing but also to the speed of the printing process.