Rheological and buildability characterization of PVA fiber-reinforced cementitious composites for additive construction

This paper investigates the rheological and printability characteristics of PVA fiber-reinforced cementitious composites. To fabricate 3D printable strain hardening cementitious mixtures, ordinary Portland cement, fly ash, silica fume, fine sand, water, and a polycarboxylate-based superplasticizer are used. The effects of a modified starch-based viscosity modifying agent and nano clay on the rheological properties of these mixtures are explored. A shear rheometer with a building materials cell and vane motor is used for rheological tests. First, stress-growth tests are conducted to determine the static yield stress evolution curves for the PVA fiber-reinforced cement composites. A constant low shear rate is applied to minimize the viscous contributions to yield stress. Then, structural recovery tests are conducted by applying three different shear rates that mimic initial rest, extrusion, and after deposition conditions of printable mixtures and the change in apparent viscosity is observed. Next, structural build-up of PVA fiber-reinforced cementitious composites is assessed through constant shear rate rheology tests at different rest intervals. Finally, the buildability of the PVA fiber-reinforced cementitious composites is evaluated using a 3D concrete printer equipped with a 15 mm diameter nozzle and screw pump.