# Nanmodified Concrete with Enhanced Characteristics Based on River Snail Shell Powder
###### Abstract
The compressive strength was about equal to or slightly better than controls when replacing part of the cement with 30\% blast furnace slag or 10\% oyster shell powder and 20\% slag” slag” [32]. The use of seashell powder (4-30\% by weight of cement) and natural pozzolan (up to 30% by weight of cement) in solutions significantly reduces the environmental impact while maintaining a similar compressive strength compared to conventional Portland cement [34; 35]. Four types of seashell waste have been used as a replacement for cement (5, 10, 15, 20\% by weight) to make a mixture for masonry and plaster. Due to this, it was possible to reduce water demand and increase the setting time of the solutions. At the same time, the strength remained sufficient, shrinkage and thermal conductivity decreased in comparison with conventional cement. Seashells can be used as a substitute for cement in masonry and plaster mortars, improving their workability [36]. Replacement in the range of 5-15\% reduces strength at an early age and improves mechanical performance after long periods of concrete hardening, reduces concrete workability [37]. Ground seashell has been used as a replacement for 2, 4, 6\% and 8\% cement. The most effective for compressive strength was a dosage of 4\%. Shelled concrete showed a lower compressive strength and elastic modulus compared to conventional concrete, but greater flexural tensile strength and axial tension [38]. An increase in compressive strength after 28 days of concrete hardening was achieved up to 7.5\%, and in axial tensile strength--up to 3.5\%. The optimal replacement ratio is 5\% [39; 40]. \\ \hline \hline \end{tabular}  
* The use of seashell waste without crushing, filled with foam, in foam concrete as a volume replacement for coarse aggregate 0, 20, 50, 80 and 100\% led to a decrease in shrinkage, fresh concrete density, and an increase in fresh concrete fluidity. At the same time,detail [43]. Of no small importance in studies of the possibility of using aquaculture waste in cement composites is the study of the mechanism of \"the effect of such waste on the synthesis, characteristics, and hydration of cement\" [44], as well as the preparation and characterization of CaCO\({}_{3}\) microparticles/polypropylene composites [45]. The \"reuse of shell waste to promote sustainable shellfish aquaculture is also an important task in the studies of many authors\" [46; 47]. One of the most common types of aquaculture waste is the shells of river snails. Such waste is common in water bodies, is a side waste when screening sand for masonry work and concrete work, and thus is a rather urgent environmental problem. The basis of the shells of most mollusks is calcium. The snail is no exception. Also, in the composition of its shells, but in smaller quantities, manganese, zinc and iron are found. It is known that the shells of gastropods consist of three layers:  
1. periostracum--outer thin layer, consisting of a protein--conchiolin;
2. ostracum--the middle layer of the shell, which consists of CaCO\({}_{3}\),
3. hypostracum or mother-of-pearl layer--the inner layer of the shell, consisting of CaCO\({}_{3}\) plates, which are wrapped with conchiolin [37]. Thus, summing up the results of the literature review, it can be summarized that quite a few studies are devoted to improving the properties of concrete by replacing part of the cement with shellfish powder and even less are devoted to freshwater. In general, in most of the studies studied, the mechanical properties of modified concrete only approach those of conventional concrete at certain dosages of powdered waste in the form of shells. In this regard, the main aim of this work was to substantiate the obtaining unmodified concrete with enhanced characteristics on the basis of the powder of snail shells.