| dc.description | The application of additive manufacturing technologies for construction has evidenced
potential economic, social, and environmental benefits compared to conventional
casting procedures. 3D printing for construction is a disruptive technology with the
potential for rapid and massive applications making it a feasible alternative for social
housing, temporary shelters after disasters, and, recently, extraterrestrial habitats.
In this line, this thesis presents the development of earthen-based and cement-based
matrices with fresh properties, hardening, and hardened-state properties compatible
with this new construction process. First, a medium-scale 3D printing prototype was
designed and validated for additive construction applications. The revision of state of
the art helps us to define the key properties to design printable matrices: flowability,
extrudability, open time, and buildability. Based on these key properties, together with
a mechanical evaluation and shrinkage cracking monitoring, printable earthen-based
and cement-based matrices were developed. First, the printable capabilities of ecofriendly
earthen-based matrices which use potato starch as a natural stabilizer for raw
soil mortars aim to obtain 3D printed filaments with adequate fresh and hardenedstates
properties. The results indicate that printable earthen-based matrices reinforced
with 1 % of sisal fibers by weight of soil and stabilized with aqueous starch gels with
concentrations up to 5 % (w/w) showed improved workability and minor cracking and
can be used for 3D printing. Then, the thesis presents a methodology based on a set of
low-cost experimental tests for the development of cement-based matrices suitable for
layer-by-layer deposition. The results of the systematic experimental campaign
indicate that yield strength obtained by shear vane tests is a good reference value for
proportioning extrudable, pumpable, and buildable concretes. However, special
attention has to be given to the binder/fine aggregate weight ratio as low binder
contents can lead to clogging of the pumping system. The current research shows four
formulations with good printing capabilities obtained after shear vane tests, filament
printing tests, and stacking tests. Finally, two medium-scale section walls have been
additively manufactured using the optimum concrete validating the proposed
methodology. | |
