# High-Performance Concrete Nanomodified with Recycled Rice Straw Biochar
In Norway, the R&D program--VOW (Turning Organic Waste into Environmentally Friendly Products for Cleaning Polluted Water, Soil and Air)--is conducting research on the possibilities of biochar, the purpose of which is to use biological waste to create sustainable products for cleaning soil, air, and wastewater [32]. Rice husk ash is used as pozzolan, which is a finely dispersed material that, in the presence of water, reacts with calcium hydroxide released during the hydration of Portland cement to form calcium silicate hydrate and other binders [10]. Different options for using rice husk ash as a pozzolan and a cement component were considered in [11] and [12]. When rice husks are burned \"below the silica crystallization temperature, ash is formed, which has a predominantly amorphous character\" [13; 14] with its reactivity due mainly to \"the inner surface of microporous particles. Quickly cooled ash has the maximum amount of silanol groups, which are important for the pozzolanic additive in cement\" [15], and the pozzolanic activity increases during grinding [16]. The setting of concrete increases with \"increasing ash content, and when used in masonry concrete, rice husk ash provides good strength and durability\" [17]. In addition, the inclusion of 20-30% rice husk ash improves resistance to sulfates, acids, and chlorides [13], \"while 20% Portland cement can be replaced with rice husk ash without adversely affecting its strength\" [18]. The water requirement for rice husk ash when used as a partial replacement for cement can be controlled by mixing with clinker during cement production or by mixing it with cement at the point of use. Rice husk ash fixes free lime released during the hydration of clinker silicates, and amorphous silica reacts with Ca(OH)\({}_{2}\) in a secondary hydration reaction to form a porous structure with a large specific surface area, which increases the strength and durability of concrete\" [19]. The possibility of using rice husk ash in recycled concrete aggregate (RCA) is considered in [33; 34]. Compared to other additives, rice husk ash has shown superior performance in terms of the mechanical properties of RCA [33]. In addition, rice hull ash can be used as a partial replacement for cement to mitigate the poor performance of RCA concrete and improve the bond between concrete and fibers [34]. Works [35; 36; 37; 38] are devoted to the issue of using various types of waste. The effect of compaction state and dry-wet cycles on crack propagation in biochar soils was examined by performing multiple regression analysis and developing a multiple regression model to estimate crack intensity in biochar soils based on soil and biochar properties. Woody biochar had a higher resistance to crack propagation compared to hog manure biochar. The proposed method provided preliminary qualitative information about the intensity of cracks in the samples when the main properties of the soil are known [35]. The use of cellulose fiber as a reinforcing material in polymer matrices is considered in [36]. Composites reinforced with cellulose fiber are sufficiently strong, light, harmless to human health and the environment, and biodegradable, so they can be used in various fields as structural components of cars, aerospace structures, structures, etc. Aspects of fiber processing to improve the mechanical properties of composites, production methods, characteristics of hybrid composites, the effect of laminate configuration, and many different applications of natural fiber composites are highlighted [36]. The creation of ecological materials from green resources based on nanocellulose materials is considered in [37]. Cellulosic nanomaterials have environmentally sustainable characteristics such as biodegradability, biocompatibility, and potential availability in abundance at a lower cost.