Evaluation of thermal stability of adhesion additives

Abstract

High adhesive properties of bituminous road binders are the key to satisfactory water resistance of asphalt pavements and their durability. Petroleum bitumen, which is currently used in the road industry in Ukraine, is usually characterized by low adhesion to the surface of stone materials. The most common method to improve the adhesive properties of road bitumen is to modify them with adhesive additives. One of the main requirements for additives is their thermal stability, which is determined by the change in the adhesive properties of the modified bitumen after its aging by the method of short-term aging. The study aims to evaluate the effect of the short-term aging method on the thermal stability of bitumen binders modified with adhesive additives. To achieve this goal, we compared the adhesion values of bitumen modified with various adhesive additives aged by the RTFOT method and the domestic method, which is analogous to the TFOT method. For the study, road bitumen modified with adhesive additives used in the road industry of Ukraine was used. Based on the experimental data, it was found that the aging method has almost no effect on the adhesion of the original bitumen used for modification with adhesive additives - the difference in adhesion to the glass surface of bitumen prepared by the RTFOT method and the TFOT method is on average 6.8 %. At the same time, the adhesion of binders modified with adhesive additives, after curing by the RTFOT method, is on average 1.2 times higher than the adhesion of binders cured by the TFOT analog method, and the maximum difference in adhesion values reaches 2.5 times. Based on this, it was found that one of the main factors in reducing the thermal stability of adhesive additives used to modify road bitumen is the duration of the binder's exposure to high process temperatures. Given this, it is advisable to introduce a requirement to determine the adhesion of bitumen modified with adhesive additives after curing by the TFOT method in SOU 45.2-00018112-067 and DSTU 9187. In addition, it is desirable to amend the requirements that establish the minimum permissible adhesion values of bitumen modified with adhesive additives, which are given in SOU 45.2-00018112-067.