Hot bitumen mastic with a complex modifier for underground main pipelines in the Arctic

The article considers improvement of bitumen materials used as anticorrosive protection of underground main pipelines in the Arctic. It proposes modification of bitumen mastic with a complex modifier, including citric acid and polyethylene wax. A twofactor experiment was planned with secondorder central composite scheme, during which the effect of varying concentrations of modifier components on various bitumen properties was evaluated. Based on the data obtained, the most relevant composition was selected, enabling increase in softening temperature from 75 °C to 87 °C, decrease in needle penetration depth at 25 °C from 23 to 15 (0.1 mm), decrease in brittleness temperature to 12 °C, as well as increase in adhesion strength to metal. It has been established that combined introduction of modifying components contributes to the formation of a spatial structural grid in bitumen and to adhesion improvement. The developed bitumen mastic can be used in protective coatings operated at low temperatures and increased mechanical stress.