Fibers of various origins are of great importance for the manufacture of new generation cement composites. The use of modified composite binders allows these highly efficient building materials to be used for 3D-printing of structures for various functional purposes. In this article, changes in building codes are proposed, in particular, the concept of the rheological technological index (RTI) mixtures is introduced, the hardware and method for determining which will reproduce the key features of real processes. An instrument was developed to determine a RTI value. The mixes based on composite binders and combined steel and polypropylene fibers were created. The optimally designed composition made it possible to obtain composites with a compressive strength of 93 MPa and a tensile strength of 11 MPa. At the same time, improved durability characteristics were achieved, such as water absorption of 2.5% and the F300 frost resistance grade. The obtained fine-grained fiber-reinforced concrete composite is characterized by high adhesion strength of the fiber with the cement paste. The microstructure of the developed composite, and especially the interfacial transition zone, has a denser structure compared to traditional concrete. The obtained materials, due to their high strength characteristics due to the use of a composite binder and combined fiber, can be recommended for use in high-rise construction.
A large amount of research publications and analytical data, concerning gypsum-bearing wastes (GSW) gives an understanding of their huge volumes in many countries, as well as the urgent need to find solutions and opportunities that open up in the development and implementation of effective technologies for the disposal of GSW in various areas of the construction industry. In this paper, the review of actual technological approaches for recycling of GSW in the framework of such field of utilization as a gypsum binder production. It was found, that application of traditional technologies of synthesis of binders, containing natural raw materials is not reasonable for GSW-bearing binders due to variation in component composition, high concentration of impurities, and high dispersion. For this reason, the most advanced technologies proposed by various researchers provide for measures to correct these shortcomings or involve the synthesis of the final product - a high-quality gypsum binder, which is based on different principles - growing crystals of the desired geometry and properties in salt and acid solutions. These technologies are characterized by complexity, a negative impact on equipment, and personnel. In addition, they lead to the formation of secondary waste, which reduces the attractiveness of their practical implementation. Synthesis of GSW-bearing binders using the method of calcining is the simplest technologically and organizationally, but the binders are characterized by unsatisfactory physical and mechanical properties. The desired way to increase their profitability and investment attractiveness is the possibility of providing comprehensive processing of raw materials, where the final product will be not only binders but also other conditioned products, taking into account the minimum formation of secondary waste. The development of such technology of GSW recycling and its implementation on a commercial scale will allow increasing the volume of GSW recycling as well as to solve the ecological aspects and to expand the raw materials source base in regions where this problem is actual
non-autoclaved aerated concrete is the only real alternative to gas silicate in the organization of its release on the basis of regional production of small and medium capacity. This will help improve the competitive environment in the building materials market and optimize the cost of construction. Of particular interest is the possibility of expanding the field of application of this material due to a significant increase in strength characteristics, while maintaining its average density in acceptable, in terms of thermal insulation properties, limits - not more than 1000 ... 1100 kg/m3. At a strength level of 10 MPa and above, in combination with dispersed reinforcement or the use of traditional non-metallic reinforcing elements, such aerated concrete can be used as a lightweight structural material for creating power elements of low-rise buildings, including in promising construction printing technologies; devices distributing the load belts; non-removable formwork; porous, stiffening, filling thin-walled tubular structures. The paper presents an assessment of the effectiveness of traditional ways to increase the strength of non-autoclaved aerated concrete. New solutions for the purposeful formation of the pore space structure are proposed and tested due to the creation and use of a gas generator with normalized gas evolution, which allows the creation of pores of a given volume. The key to the economic effectiveness of the proposed solutions is the transition from traditional portland cement to composite binders based on it. The substantiated choice of the amount and composition of the mineral additive makes it possible to optimize the properties of the binder under the particularity of the problem being solved, and to minimize the consumption of cement and chemical modifiers, increase the speed of durability and the final indices of non-autoclaved aerated concrete.
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