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

The object of research is a 3D-printable decorative concrete with an addition of 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 kinetics of the mixtures' setting was 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. It has been established that the setting processes are more intense in micro-grained systems with limestone flour. At the same time, systems with white cement have higher values of plastic strength and lower values of the spread diameter systems with gray cement, regardless of the type of filler and aggregate. All the studied systems exhibit an increase in plastic strength when photoluminescent powders are added, regardless of the size of the powder particles. According to the obtained values of the criteria characteristics of plasticity and form-stability, all the 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 the preservation of 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 of decorative properties. Taking this into account, it is recommended to use cement mixtures based on white cement with quartz sand and an additive of photoluminescent powder with a particle size of no more than 35 microns as cement matrices for creating small architectural forms for decorative purposes.

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