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 %.

The paper presents the results of a study of the physical-mechanical and operational properties of high-strength lightweight concrete and the influence of nanoscale modifier on these properties. The nano-modifier and its method of application to improve the properties of lightweight concrete with hollow microspheres at 10-25% are proposed. The method to control structure formation processes by the nano-modification is shown. The nanoscale modifier is grafted onto the surface of the hollow filler and interacts with cement and its hydration products (calcium hydroxide). This local activation of the hydration of Portland cement and the formation of an additional amount of calcium hydrosilicates at the phase boundary leads to the increasing of the strength of the concrete. This provides growth of operational properties. The high-strength lightweight concrete with an average density less than 1500 kg/m 3 is characterized by a strength more than 40 MPa (specific strength R sp > 30 MPa). The optimum range of concentrations of the precursor for preparation of nano-modifier is defined to be 1.25 ≤ [Na + ]/[Cl − ] ≤ 2.5. We can conclude that the developed composition has a dense and strong structure which can resist intense cracking. Application of nanoscale modifier enables an increase of the elastic modulus of 13-36% (equal to 6.2-8.5 GPa depending on the average density), a decrease of water absorption (to 1%) and an improvement of the water resistance (coefficient of water resistance is more than 0.95) and freeze-thaw resistance (up to F300). The nano-modified high-strength lightweight concrete has beneficial values of heat-conduction coefficient (0.48-0.70 W/(m Á C)), temperature conductivity coefficient ((3.43-4.04)Á 10 −7 m 2 /s) and specific heat capacity (1080-1175 J/(kg Á C)). It allows us to consider this concrete as a multifunctional material with both structural and thermal insulation properties. K E Y W O R D Snanotechnology, nanoscale modifier, high-strength lightweight concrete, structural lightweight concrete, strength, hollow microspheres | INTRODUCTIONThe application of nano-sized modifiers to improve the quality of building materials has spread in various directions. [1][2][3] The various carbon nanoparticles, nano-oxides, sols and gels have been studied by authors from different countries. [4][5][6][7][8][9] Use of these additives to modify the materials in the entire volume of the structure leads to achievement of desired operational properties in different areas of application. However, some unresolved problems 10,11 still complicate the use of such modifiers in practice (for example, there is an aggregation of powdered carbon nanoparticles). Colloidal solutions are most promising in this area because the particle distributions in volume will depend on the properties of the carrier media, stability of the system and physico-chemical properties of the substance. That is why the resolutions for the identified difficulties are achieved at the design stage of such modifiers when taking into account the ...

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This paper presents research into the deformation properties of high-strength lightweight concrete (HSLC) containing hollow aluminosilicate microspheres. A method of increasing the fracture toughness of the HSLC by using a modifier as a coupling agent on the surface of the microparticles of aggregate is proposed. Use of the hollow microspheres is μ Poisson's ratio ρ average density σ load equal to 0•3R pr Advances in Cement Research A method for the reduction of deformation of high-strength lightweight cement concrete Inozemtcev and Korolev