## 2 State of the Art
By increasing the proportion of rice husk ash from 0 to 5%, the penetration decreased slightly, and when the proportion was 10% and 15%, the penetration decreased even more. The ductility of the uncured modified bituminous binder decreased slightly with an RHA content of 2-10% and significantly decreased when the RHA content was 15%. The application of SBS/RHA increased the viscosity of the base bituminous binder, and the viscosity increased with the increase in the proportion of RHA. The cycle factor decreased with increasing temperature, and the decreasing trend became slower when the test temperature was higher than 64 \({}^{\circ}\)C. The addition of SBS/RHA slightly reduced the resistance to the action of water and the appearance of cracks at low temperatures. The tensile strength ratio (ITSR) of the control and modified bituminous mixture meets the prescribed conditions. It was determined that the ash content of rice husks should not exceed 15%. The conclusions of the test results [11] are that an increase in the proportion of rice husk ash (RHA) in bitumen causes an increase in the softening point (RB method) and a decrease in the penetration value of bitumen, which indicates that there is an increase in hardness with the bituminous binder. The addition of RHA increases the viscosity of the bituminous binder, improves the penetration index (PI), and lowers the temperature sensitivity of the bitumen. The rheological changes of the bitumen binder with RHA cause an improvement in the physical-mechanical properties of the asphalt mixture (hot mix asphalt--HMA). Bituminous binder with up to 20% RHA increases the stability of the asphalt mixture and also the Marshall quotient (MQ); both are indicators of resistance to putting. The stiffness modulus of the RHA of the modified asphalt mixtures achieves higher values than those of the standard control mixtures. The fatigue test results of asphalt mixes with RHA confirm an extended service life, which can be attributed to a lower proportion of voids in the mix and/or improved adhesion between aggregate and bitumen. Based on the data obtained in [12], it was concluded that the value of bitumen penetration decreases if the addition of black rice husk ash (BRHA) is used when compared to the penetration of classic bitumen. The softening point (RB method) increases with increasing BRHA content, and the bitumen becomes more viscous when 6% BRHA is added to it. A PI penetration index of 0.25 indicates high resistance to cracking at low temperatures and the formation of permanent deformation in the form of rutting. A group of authors [13] investigated the role of fillers in improving the properties of asphalt concrete pavements (ACPs) in resistance to the occurrence of rutting caused by temperature rises, as well as the economic profitability of construction costs. Rock dust of a carbonate composition is usually used as a filler in ACP. This study carried out experimental tests on asphalt concrete containing bagasse ash as a filler. As a reference, the properties of asphalt concrete with stone dust as a filler were taken. Subsequently, samples of asphalt concrete with the addition of 5% bagasse ash in the filler and a stone aggregate with 4.3% of a 60/70 type bitumen binder were tested. During the research, it was established that the use of bagasse ash does not affect the granulometric composition of the asphalt mixture. The measured rutting depths of the asphalt mix with bagasse filler confirm better rutting resistance. Additionally, asphalt pavement using bagasse ash has a lower price of about 0.1% per m\({}^{3}\) than conventional pavement. Based on the results obtained in [14], the efficiency of using fly ash as a substitute for mineral filler in porous bituminous mixtures was evaluated. Modified porous bituminous mixtures with fly ash have a slightly lower content of bituminous binder compared to the controlled versions that use a classic mineral filler. The porous asphalt mix with ash is more resistant to binder leaching than the control mix.