# High-Performance Concrete Nanomodified with Recycled Rice Straw Biochar
## 3 Results  
### Evaluation of the Microstructure and Chemical Composition of Rice Straw Biochar  
Based on the results of SEM, photographs of the microstructure of biochar samples of rice straw modified by the electromagnetic method were obtained, which are shown in Figure 5.  
A sample of rice straw biochar is a corpuscular porous body, and individual particles of which have ordered cylindrical pores without a bottom of approximately equal size. The material itself can be directly attributed to nanomaterials with a particle size of 10 to 100 nm. The electromagnetic activation method makes it possible to obtain a mesoporous-type nanomaterial from APC waste with a modified surface structure of particles, which can intensify the process of mixing concrete with water. This material optimizes the curing cycle of concrete by reducing the curing time and increasing the class of concrete. In addition, a significant advantage of using an electromagnetically activated additive from rice straw biochar is the long-term absence of microcracks during the operation of a concrete structure due to the homogeneity of the concrete body and the reinforcing effect of biochar. Figure 5: Microstructure photo of rice straw biochar samples: (**a**) with a resolution of 10 nm, (**b**) with a resolution of 3 nm; (**c**) with a resolution of 1 nm; (**d**) regions 1, 2, 3 selected for EDX spectroscopy. Figure 6 shows the EDX spectrum of a rice straw biochar sample. The EDX spectrum covers the presence of C, O, Si, K, Ca, Mg, Na, and Fe in the biochar sample. As can be seen from Figure 6, the chemical composition of the obtained biochar is mainly represented by carbon, the content of which is 78.5%. In addition, the EDX spectrum of the biochar sample shows a small amount of Fe. The presence of iron in the chemical composition of biochar can be explained by its electromagnetic activation carried out at the UAP installation. The sample analysis result--rice straw magnetostriction--is shown in Figure 7.  
Figure 6: EDX spectrum of rice straw biochar samples. Figure 7: Results of thermogravimetric analysis of a sample of rice straw biochar modified by the electromagnetic method: TG—thermogravimetry, obtained by determining the mass loss during heating to high temperatures; DSC—differential scanning calorimetry. Weight loss begins at temperatures above 60 \({}^{\circ}\)C and is 4.2% in the range from 60 \({}^{\circ}\)C to 210 \({}^{\circ}\)C; further weight loss is more intense. The interval 210-510 \({}^{\circ}\)C is accompanied by a loss of 27% of the mass with a complex exothermic effect with maxima at 318 \({}^{\circ}\)C and 420 \({}^{\circ}\)C. In this interval, the decomposition and release of organic substances and the combustion of combustible material probably occur. In the range of 600-670 \({}^{\circ}\)C, a loss of 0.68% of the mass is observed, probably, to the release of chemically bound moisture, as well as a certain amount of organic volatile substances. Residual mass at 950 \({}^{\circ}\)C is 62.85%. At the same time, after 670 \({}^{\circ}\)C, the rate of weight loss is noticeably reduced, which may indicate a possible imminent end of the decomposition process. Phenomenological Model of the Influence of the Dosage of Rice Straw Biedar Addition on the Strength and Deformation Characteristics of Heavy Concrete  
An analysis of the effect of a nanomodifying additive on the strength properties of concrete shows that the additive generates physical and chemical processes that can be conditionally divided into constructive, that is, increasing strength, and destructive, reducing strength. A slight increase in strength is observed with a small amount of nanomodifying additive. Too much amount leads to a decrease in strength.