An investigation on effects of cotton and sunflower stalk biochar on bitumen modification

The employ of agricultural waste materials has recently drawn interest from researchers in a variety of fields, including the building of highways. This study examined bitumen modification using biochar made from cotton and sunflower stalks. At concentrations of 13%, 15%, and 17% by total weight, the biochars produced by pyrolysis at 500°C were added to bitumen binder. Ash content analysis and scanning electron microscopy (SEM) described the chemical and morphological characteristics of the biochars. Physical tests, such as softening point and penetration, showed that the amount of biochar increased the binder's stiffness. For example, the B-17BCS softening point rose from 48.5°C to 55.8°C, but the penetration value dropped from 62 dmm (base bitumen) to 42 dmm. These modifications show improved stiffness and heat resistance, which are primarily attributable to cotton stalk biochar's higher fixed carbon content (60.1%) and porous, fibrous structure. Rheological tests validated the improved high-temperature performance; for B-17BCS, the performance grade increased from PG 64-Y (base) to PG 76-Y. Tests of frequency sweep and rotational viscosity confirmed the improved consistency and resistance to time-dependent deformation. According to the results of the LAS test, B-17BCS had a fatigue life improvement of about 25% at 5% strain. Because of their high carbon content and morphological features, the study demonstrates that biochars, particularly those made from cotton stalks, can effectively improve binder stiffness and high-temperature performance.