The effect of photoluminescent powder on the rheological properties of architectural cement composites for 3D printing

The object of research is 3D-printable decorative concrete with added photoluminescent powder. This work aims to obtain cement composite mixtures with photoluminescent properties for construction 3D printing with specified technological properties by varying their component composition in terms of the type of cement matrix, the type of cement, and the dispersion of the photoluminescent powder. Method. The technological characteristics of the resulting mixtures were determined using compression rheometry. The setting kinetics of the mixtures were controlled by the plastic strength indicator, which was determined using a conical plastometer of the author's design. The fluidity of the mixtures was evaluated by the diameter of the mixture flow using the standard method of mechanical creep using the Hegemann cone. The criteria for the plasticity and shape stability of the studied mixtures were determined based on the results of compression tests conducted at a constant deformation rate and a constant loading rate. Results. The dependence of the setting processes of the studied mixtures on the type of cement matrix (micro-grained, fine-grained), the type of cement used (white, gray), and the dispersion of the photoluminescent powder has been established. The setting process is more intense in micro-grained systems with limestone flour. At the same time, systems with white cement have higher plastic strength and lower spread diameter than systems with gray cement, regardless of the type of filler and aggregate. All studied systems show increased plastic strength when photoluminescent powders are added, regardless of particle size. Based on the obtained values of the criteria characteristics of plasticity and form stability, all studied systems are suitable for the 3D-printing process. However, mixtures with the addition of photoluminescent powder PLP2 do not meet the requirements of the 3D-printing process in terms of preserving properties over time, as they are characterized by a rapid increase in plastic strength over time, and mixtures based on gray cement do not meet the requirements for decorative properties. Therefore, it is recommended to use white-cement mixtures with quartz sand and a photoluminescent powder additive (particle size <35 μm) as the cement matrix for creating small architectural forms for decorative purposes.