## 2 State of the Art
Amounts of SCBA, ranging from 0.1 to 0.5% by weight of filler, with an optimum asphalt content (OAC) of 5.63%, were tested. The established results showed that modified bituminous mixtures containing SCBA were effective in increasing Marshall stability by 0.6%, deformation by 4.9%, and stiffness modulus by 17.4% when compared to classic, hot-mixed asphalts (HMA). The proportion of voids in the bituminous mixture is higher when compared to unmodified mixtures and has an impact on better resistance to rutting. In order to increase the resistance to rutting, the modified asphalt sample has an optimal void ratio of 4.94%. The use of SCBA as a filler in HMA as an alternative material resulted in better pavement management. Based on the analysis [19], it was concluded that the physicochemical composition of the filler has a significant influence on bituminous mixtures. Mixtures prepared with red mud (RM), rice straw ash (RSA), glass powder (GP), and carbide lime (CL) fillers, which have higher porosity than conventional stone dust (SD), were found to have a higher optimum bitumen content (OAC). A modified bituminous mix with a copper tailings (CTs)filler has the lowest OAC because this type of filler has the lowest porosity. Good resistance to cracking and rutting was confirmed for all bituminous mixtures except with an RSA filler. Mixtures with fillers made from smaller particles (RM, CT, CL, and GP) have a higher modulus of rigidity and greater resistance to cracking. The mineralogical composition of the filler affects the adhesion of aggregates and bitumen, which results in good resistance to the action of water. After the tests of all 16 combinations, the best results were obtained with the RM filler and then with the CL, CT, SD, GP, and RSA fillers. Regarding the incorporation of biomass ash as a filler for bituminous mixtures, based on [20], it was determined that biomass ash has acceptable chemical and physical properties for use as a filler. The biomass bottom ash leachate test showed a low concentration in the leachate of heavy metals, as well as carbon and sulfur. The use of biomass ash as a filler in bitumen mixtures with bitumen emulsion develops a mastic that improves tensile strength, improves behavior to plastic deformations, enables greater absorption of bitumen, and has physical properties similar to traditional mixtures. The result of the use of waste ash from biomass in bituminous mixtures is a reduction in landfills and in the need for new raw materials for asphalt pavement constructions. In [21], the physical, chemical, and ecological properties of biomass ash for use as a bituminous mixture filler were tested. The main chemical compounds in biomass ash are silicates, potassium carbonate, sylvite, and arcanite. An examination of the pollution of leachate from biomass ash showed a lower concentration of polluting chemical elements than the maximum limits prescribed by regulations. The environmental effects studied in this research show that less harmful emissions are produced by processing ash from biomass when compared to cement, lime, or limestone filler. The conclusion is that the use of ash from biomass as a filler in bituminous mixtures is technically possible and that there is a significant reduction in environmental impact when compared to other materials that have been investigated. In 2013, [PERSON] et al. [22] investigated 27 types of bio-ash used as a filler in asphalt mixtures and found that the use of bio-ash in bituminous mixtures is safe for the environment due to the binder coating on the filler particles.