Dry Mixtures Strength and Elastic-Deformative Characteristics Determination for Construction 3D Gypsum and Cement Printing

A new technique for dry mixtures strength and elastic-deformative characteristics determination for construction 3D gypsum, cement and mixed printing is described. It is shown that the standard testing methods of concretes and mortars used in construction practice for fine-grained concretes and mortars are inapplicable: firstly, due to the scale factor, and secondly, due to the significant voidness of the printed samples, which also varies widely. The developed technique is based on the method for determining the grouting mixtures characteristics on small cross-section samples. A new formwork mold consisting of several cylindrical links (in metal or polymer), allowing the samples molding and subsequent exposure directly during 3D printing, has been developed and tested in pilot industrial conditions. The samples made according to the proposed method were tested on a universal testing machine and their results made it possible to determine with sufficient reliability the dry mixes basic strength and elastic-deformative characteristics for construction 3D printing, such as compressive strength, prism strength, elasticity modulus, transverse deformation coefficient and to construct a full-scale stress–relative deformation curve.