Development of a concrete mixture composition utilizing a nanostructuring additive for 3D printing of small architectural forms

Introduction. Currently, additive technologies are widely used across various fields. Their application in construction addresses several critical challenges. In the 3D printing process of small architectural forms, it is very important to choose the right composition of the materials from which they will be made. Materials and methods. We used for composition development: synthesized aluminosilicates as a nanomodifying additive, Portland cement without additives 52.5N as a binder, fine filler quartz sand from the Ukhtinsky and Chaadaevsky deposits, complex additive Sika Antifreeze N9, and superplasticizers Axton and C-3. The water retention capacity of formulations using a nanomodifying additive was determined by the amount of water in the test composition before and after the tests. The kinetics of water absorption of the compositions was determined in accordance with the methodology presented in GOST 5802. Porosity was determined by the content of free and chemically bound water in the cement stone. The change in the normal density and setting time was determined using the Vic device. The intergranular voidness of the sand was calculated from the values of the true and bulk densities of the fine aggregate. The true density was determined using the Le Chatelier device. The bulk density of materials was determined using the methodology established by GOST 9758. Results and discussion. It was revealed that the presence of a nanomodifying additive in the composition, with a dispersion of Sud = 0.69 m2/g and Sud = 1.03 m2/g, increases the strength of the compositions compared with the control ones (without additives) from 7% to 17.8%, respectively. That is, there is an inverse relationship between the dispersion of the introduced additive and the change in the strength of the samples. The high dispersion value of the introduced additive ensures optimal conditions for the hardening of compounds, which is confirmed by studies on the water absorption of compounds. During the research, the influence of the amount of the studied additive on the setting time of cement, changes in the normal density of cement dough and porosity of cement systems were evaluated. In order to reduce cement consumption and increase the mobility of the mixture composition, a fine filler is introduced – sand with a mixed grain composition. In the process of selecting the composition of the concrete mix for 3D printing of small architectural forms, their technological properties were taken into account. Four compositions of a concrete mix for 3D printing with different amounts of nanostructuring additive, sand, and cement were studied. Conclusion. Compositions with optimal characteristics have been identified for further research in the field of selection and development of concrete mixtures for 3D printing of small architectural forms.