Hnatenko R. Improvement of crack curing technology in asphalt wearing course with bitumen-polymer sealing materials

The thesis covers solving of important scientific and practical task which implies the increase of durability of flexible road pavements by means of crack sealing in asphalt concrete pavement with bitumen-polymer sealing materials of increased heat resistance, frost resistance and strength of adhesion to asphalt concrete surface in zone of crack as well as the use of sustainable design and technological solutions during curing. Distress such as cracks appear in asphalt concrete pavement courses of motor roads under the influence of traffic loads and external climatic factors at different stages of the service period. Cracks in asphalt pavement courses result in intensive reduction of the whole structure rigidity due to penetration of water through it to the courses of unbound materials and subgrade soil. Analysis of foreign experience of repair of cracks in asphalt concrete pavements indicates that crack sealing with hot applied bitumen-polymer materials is the most wide spread technique in Europe. Possibility of formation of structure providing both high frost resistance, elasticity, service heat resistance and strength of adhesion of hot-applied bitumen-polymer sealing materials to crack walls of road pavement asphalt concrete has been theoretically substantiated. It has been proved that formation of two interpenetrative spatial structures from macromolecules of thermoplastic elastomers and macromolecules of cationic latex in bitumen volume is possible to be reached by their sequenced combining with plasticized oxidized maltenes high content road bitumen. Evaluation methodology of strength of thermoplastic bitumen-polymer sealing material adhesion to the surface of asphalt concrete in crack has been developed, which allows studying the influence pattern of temperature regimen of their combining effect on adhesion strength between them. Influence patterns of content and viscosity of oxidized petroleum road bitumen, concentration of thermoplastic elastomers, plasticizer and various fillers on properties of hot-applied bitumen-polymer sealing materials have been experimentally studied. Decrease of brittle point and flexibility of bitumen-polymer sealing materials at low temperatures due to increase of plasticizing component amount in initial matrix bitumen has been found. Increase of thermoplastic elastomer and cationic latex content in plasticized matrix bitumen demonstrated the increase of elasticity and heat resistance of bitumen-polymer sealant by softening point criterion. It has been determined that increase of concentration of mineral fillers in bitumen-polymer sealing material results in increase of its softening point, brittle point and flexibility at low temperatures, and decrease of needle penetration, ductility and elasticity. Introduction of polymers to matrix bitumen has been proved to provide higher increase of heat resistance by softening point criterion as compared to introduction of fine fillers. Regular increase of strength of bitumen-polymer sealing material adhesion to asphalt concrete crack surface when decreasing test temperature has been determined by the results of the experimental research. It has been found that the value of asphalt concrete pavement temperature during crack sealing has significant influence on absolute values of pull-off load and strength of adhesion of sealing material to asphalt concrete surface. Increase of filler content in hot-applied bitumen-polymer mastic composition has been shown to cause decrease of its strength of adhesion to asphalt concrete surface. Heating of asphalt concrete surface in zone of crack, immediately prior to its sealing, gives rise to stronger adhesive bonds between the surface and the sealant.