Mechanical Properties of a 3D-Printed Wall Segment Made with an Earthen Mixture

Abstract

This study provides a contribution to the research field of 3D-printed earthen buildings, focusing, for the first time, on the load-bearing capacity of these structures. The study involves the entire production and testing process of the earthen elements, from the design, to the preparation of the mixture and the 3D printing, up to the uniaxial compression test on a wall segment. The results indicate that 3D-printed earthen elements have a compressive strength of 2.32 MPa, comparable to that of rammed earth structures. The experimental data also made it possible to draw conclusions on the action of the infill, which seems to have the function of stopping the propagation of cracks. This has a positive effect on the overall behavior of 3D-printed earthen elements, since it avoids the onset of dilative behavior in the final stages of the load test and maintains ultimate load values higher than 50% of the maximum load.

Rice-Husk Shredding as a Means of Increasing the Long-Term Mechanical Properties of Earthen Mixtures for 3D Printing

“…This does not affect the validity of the results obtained. In fact, the extensibility of the results obtained for specimens with hand compaction to the behavior of the 3D-printed solids derives from the comparison between the results of this paper (Section 4) and its complementary experimentation on a 3D-printed wall segment made with the LT mix [7]. The earthen wall segment of [7] is partially visible behind the cubic specimens in Figure 2: in the fresh state (the day of 3D printing) in Figure 2a, and in the hardened state in Figure 2b.…”

“…In fact, the extensibility of the results obtained for specimens with hand compaction to the behavior of the 3D-printed solids derives from the comparison between the results of this paper (Section 4) and its complementary experimentation on a 3D-printed wall segment made with the LT mix [7]. The earthen wall segment of [7] is partially visible behind the cubic specimens in Figure 2: in the fresh state (the day of 3D printing) in Figure 2a, and in the hardened state in Figure 2b. To allow for the comparison between the experimental results of the two complementary studies, the 3D printing of the wall segment took place on the same day, and with the same mixture, as the casting of the LT cubic specimens.…”

“…The present work is part of the second line of research undertaken by the WASP (the World's Advanced Saving Project) with the collaboration of the Department of Civil, Environmental and Materials Engineering of the University of Bologna (Italy), which deals with the mechanical characterization of the earthen mixes for 3D printing (Section 1.3). Since extrudability, buildability, and workability are topics of the WASP's first line of research (Section 1.3)-from which the mixtures used in the present experimental program derive-they will not be further investigated in this work, as they are established data [7]. In fact, these are mixtures already being used to print full-size prototypes.…”

“…To this end, we performed uniaxial compression tests on cubic specimens made with shredded rice husk-the vegetable fiber of the mixture-and compared the results with those of cubic specimens made with nonshredded rice husk, with all components and dosages being equal (Section 3.1). This work is actually the first part of a wider experimental campaign, which includes the mechanical characterization of a 3D-printed wall segment, made with one of the mixtures of this first part [7]. Since the two parts of the experimental campaign are complimentary, where necessary, we will discuss the results of this first part with reference to the findings of [7].…”

“…This work is actually the first part of a wider experimental campaign, which includes the mechanical characterization of a 3D-printed wall segment, made with one of the mixtures of this first part [7]. Since the two parts of the experimental campaign are complimentary, where necessary, we will discuss the results of this first part with reference to the findings of [7]. Since the experimental campaign is the result of a long period of study of the traditional earthen construction techniques, on the one hand, and of the physical-mechanical properties of earthen mixtures for manual construction and 3D printing, on the other hand, this introductive section includes some subsections in order to provide a comprehensive overview of the knowledge and motivations behind the experimental campaign.…”