Вестник МГСУ Научно-технический журнал по строительству и архитектуре

The technology of 3D printing in construction causes great interest by increasing the speed and accuracy of building structures, reducing labor costs, construction waste and risks to human health. Today, the principles of 3D-printing actually are interpretations of the existing monolithic or prefabricated technology. This requires the development of high-performance materials for the extrusion of functional structures. The paper shows the example of the effectiveness application of high-strength lightweight fiber-reinforced concrete with a complex of structural and thermal insulation properties in 3D-printing technology. It has been established that the use of high-strength lightweight fiber-reinforced concrete for 3D-printing provides an increase in the useful space by 1.1...5.4 %, a reduction in the material consumption of wall structures by 6.1...19.1 % and a reduction in the number of machine hours by 29.6...37.4 %. The total technical and economic efficiency of using such a material for a standard or optimized wall section is 30.8...50.4 %.

In the global information space there is a positive trend in the number of publications devoted to the technology of building 3D-printing. As functional additive for internal care of concrete superabsorbent polymer (SAP) can be used. It was found that the mobility of high-strength lightweight concrete mixtures with SAP is decreased in contrast to cement pastes. The decrease of the spread diameter of the concrete mixture with an increase of the SAP content to 2.3 % by weight of Portland cement is to 20 %. The SAP content of less than 1.5 % by weight of Portland cement provides the required mobility of the concrete mixture and the average density of high-strength lightweight concrete. Taking into account the requirements for the strength of the studied concrete, the optimal content of SAP is 1.0-1.5 % by weight of Portland cement. The efficiency of the use of solutions of superabsorbent polymers for reducing shrinkage deformations of the concrete in contrast to granular SAPs is proved. This is especially actual for concrete used in adverse hardening conditions of Portland cement, for example in 3D-printing in construction. It was shown that the concentration of SAP less than 1.5% by weight of Portland cement allows to ensure the mobility of the mixtures and preservation of concrete strength.

The knowledge of cement concretes and the availability of raw materials allows them to be used for 3D-printing technology in construction. One of the ways to increase the strength and reduce the shrinkage of the extruded layers is the introduction of reinforcing fibers into the mixture. An important task is the selection of effective types and concentrations of fiber. In this work, research on the selection of such fibers for compositions of high-strength lightweight concrete on hollow microspheres has been carried out. The optimal content of fiber which provides an acceptable decrease in mobility and the greatest strength of concrete is 1.25…1.5 % of the mass of Portland cement. It was found that the studied concretes on hollow microspheres have a reliable connection at the «steel-concrete» interface. The adhesion strength to metal reinforcement with a diameter of 8…12 mm is 6.1… 10.1 MPa with a relative deformation of 0.097…0.025 mm/mm. High-strength lightweight fiber-reinforced concrete has low air permeability parameters, corresponding to the high water permeability grade W20. Such concrete with an average density of 1400 kg/m³ has high frost resistance F₁800.

The paper shows the study of the possibilities, limitations in the design of structures made of high-strength lightweight fiber-reinforced concrete and its use in the construction of a high-rise building using the LIRA SAPR software package. The calculations of the finite-element spatial model show that compared to heavy concrete, using high-strength lightweight fiber-reinforced concrete in the multi-storey buildings construction provides a large number of advantages, such as: reducing deflection of the building from its own weight up to 44.0%, from effect to wind loads - by 2,4 … 2.6% with a decrease in the period of the first 3 vibrations of the building structure by 11.3%; an increase in the number of storeys to 7 floors without changing foundation bearing capacity; increasing specific usable area per 1 m² of building land by 26.6%; reducing consumption of materials for the foundation while maintaining the number of storeys of the building or the possibility of construction in weak soils. At the same time, the technology of high-strength lightweight fiber-reinforced concrete, combining low average density and high strength, is associated with an increase in the cost of the material, therefore, the existing limitations can be identified: the dependence of economic efficiency on the structural features of a particular building, construction conditions and local resources used for concrete production.