Influence of Electromagnetic Activation of Cement Paste and Nano-Modification by Rice Straw Biochar on the Structure and Characteristics of Concrete

Abstract

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.