Reducing the negative environmental impact of a widely spread building material such as concrete is possible by decreasing the amount of cement in this composite material, especially when specific waste is included as a substitution for the binder. Another important environmental issue is accumulated aquaculture waste. This work justifies the possibility of achieving modified concrete with improved properties based on sea mussel shell powder (MSP). An improved environmentally friendly concrete was obtained and modified with MSP as a result of experimental studies. The dosage of MSP in the amount of 6% instead of part of the cement turned out to be optimal and most effective. Because of the modification, it was possible to increase the strength properties: the increments were up to 12% for the compressive strength (CS), up to 13% for the axial CS, up to 14% for the tensile strength (TS) in bending, and up to 12% for the axial TS. The ultimate strains under axial compression and tension decreased to 9% and 12%, respectively, and the elastic modulus increased to 15%. SEM analysis showed a more integral microstructure without voids and cracks in this composite with a modifier content of 6% compared with the sample of the ordinary composition. Economic efficiency is expressed in reducing the total cost of new concrete compared to traditional ones by about 17% and the cost of building construction by up to 15% due to a decrease in the percentage of defects.

One main global problem is the accumulation of a large amount of agricultural waste. This problem causes environmental pollution and requires an immediate comprehensive solution. The purpose of this study was scientific substantiation and experimental testing, at the micro- and macro levels, of the joint influence of electromagnetic activation of cement paste and nano-modification by rice straw biochar on the strength and strain properties of concrete. In addition to standard methods, the methods of electromagnetic activation, scanning electron microscopy, and energy dispersive spectrometry were used. The results of the joint influence of electro-magnetic activation and nano-modification by rice straw biochar on the strength and strain characteristics of concrete were experimentally verified and confirmed by microstructure analysis. Electromagnetic treatment of the cement paste increased the compressive strength, axial compressive strength, tensile strength in bending, and axial tensile strength of concrete. The best performance was demonstrated by electromagnetically-activated concrete containing 5 wt.% rice straw biochar. Strength characteristics increased from 23% to 28% depending on the type of strength, ultimate tensile strains decreased by 14%, and ultimate compressive strains by 8% in comparison with the control concrete composition. Replacing part of the cement with 10 wt.% and 15 wt.% rice straw biochar led to a strong drop in strength characteristics from 14 to 34% and an increase in strain characteristics from 9 to 21%. Scanning electron microscopy showed a denser and more uniform structure of electromagnetically activated samples.

The utilization of aquaculture waste, such as snail shells, is a severe issue. These shells are common in water-sources and are a by-product of sifting sand for masonry and concrete work. Calcium-rich river shells are of great interest for cement building materials. In this regard, the purpose of this article was to develop a nanomodified concrete with improved characteristics based on the powder of snail shells. Experimental studies have confirmed the effectiveness of the use of river shells in concrete without a decrease in strength characteristics and deterioration of other properties. It has been found that the optimal replacement by the snail shell powder that replaced cement is in the amount of 6%. By the nanomodification of concrete with the powdered shells of river snails, it was possible to achieve an increase in compressive strength up to 12%, axial compressive strength—up to 8%, tensile strength in bending—up to 9%, axial tensile strength—up to 11%, elastic modulus—up to 8%. Concrete nanomodification with snail shell powder in the amount of 6% contributed to a reduction of deformations of up to 7%. The study of the microstructure of concrete samples nanomodified with snail shell powder confirmed the obtained dependences of the cement’s properties on the nanomodifier dosage, as well as the most effective dosage of snail shell powder.

Polymer composite reinforcement (PCR) and its use to produce high-quality concrete with the right design and technological and formulation solutions can demonstrate the results obtained with the steel rebars. This article discusses the synergistic effect from the combined reinforcement of concrete with traditional polymer rods and dispersed fiber, which, as a result, lead to an increase in strength and deformation characteristics and an improvement in the performance of compressed and bent structural elements. The synergistic effect of the joint work of polymer rods and dispersed reinforcement is considered in the context of relative indicators (structural quality factor CSQ), showing the relationship between strength characteristics and concrete density. The behavior of glass fiber in a cement matrix and the nature of its deformation during fracture were studied by scanning electron microscopy. It is shown that the use of PCR and dispersed reinforcement makes it possible to increase the strength characteristics of concrete in bending. In quantitative terms, the achieved results demonstrated that the CSQ values of a beam reinforced with a PCR frame with the addition of glass fiber were 3.4 times higher compared to the CSQ of a beam reinforced with steel reinforcement frames. In addition, for a beam reinforced with a PCR frame with no fiber addition, the CSQ values were three times higher.

At present, the load-bearing enclosing structures of buildings and structures are designed and built considering the increasing requirements for energy efficiency and energy saving of such structures. This is due to the need for a thrifty attitude to the energy consumed and the need to strive for the greening of construction and increase the energy efficiency of buildings and structures. In this regard, one of the most effective and proven building materials is cellular concrete. The purpose of this study was to study the influence of some prescription factors on the structure formation and properties of non-autoclaved aerated concrete with improved characteristics. Standard test methods were used, as well as SEM analysis of the structure of aerated concrete. Non-autoclaved aerated concrete with the replacement of part of the cement with microsilica in an amount from 4% to 16% MS showed higher strength characteristics compared to aerated concrete, where part of the cement was replaced by the addition of granulated blast-furnace slag and a complex additive. The maximum value of compressive strength was recorded for aerated concrete with 16% MS addition. The largest increase in the coefficients of constructive quality was observed in compositions of aerated concrete with the addition of silica fume from 11% to 46% compared with the control composition. The addition of microsilica makes it possible to achieve an improvement in the thermal conductivity characteristics of non-autoclaved aerated concrete (up to 10%). Replacing part of the cement with slag and complex additives does not have a significant effect on thermal conductivity. The obtained dependencies were confirmed by the analysis of the structure formation of the studied aerated concrete at the micro level. An improvement in the microstructure of aerated concrete with the addition of microsilica in comparison with samples of the control composition has been proven.

The widespread use of aerated concrete in construction has led to the emergence of many types and compositions. However, additional research should fill theoretical gaps in the phenomenon of gas release during the formation of the structure of aerated concrete. Based on theoretical analysis and experimental studies, the article proposes a mathematical model of the swelling process based on the physicochemical laws of convection and molecular diffusion of hydrogen from a mixture and the conditions of swelling, precipitation, and stabilization of the mixture. An improved method for the manufacture of aerated concrete is proposed, which consists of introducing cement pre-hydrated for 20–30 min into the composition of the aerated concrete mixture and providing improved gas-holding capacity and increased swelling of the mixture, reducing the average density of aerated concrete up to 29% and improving heat-shielding properties up to 31%. At the same time, the small dynamics of a decrease in the strength properties of aerated concrete were observed, which is confirmed by an increased structural quality factor (CSQ) of up to 13%. As a result, aerated concrete has been obtained that meets the requirements of environmental friendliness and has improved mechanical and physical characteristics. Economic efficiency is to reduce the cost of production of aerated concrete and construction in general by about 15%.