Properties of Asphalt Concrete in Half-Warm Technology with a Focus on the Impact of Hydrated Lime and Foamed Bitumen – A Case Study

The priority in road construction is to reduce the energy consumption in the production of mineral-asphalt mixtures used for the upper layers of pavement structures. The most effective approach in this regard is production of such a mixture in the half warm technology (HWMA) with water-foamed bitumen. It is produced at a temperature 50 ℃ to 70 ℃ lower than that required for the production of traditional mineral-asphalt mixtures. In the research, AC 8S asphalt concrete was used, made with foamed 50/70 grade bitumen. High values for the foamed parameters of the binder were obtained by adding a surface active agent at a rate of 0.6 wt.% in relation to the bitumen before foaming. In order to ensure the high-quality properties of AC 8S asphalt concrete in the HWMA technology, hydrated lime was used as a substitute for part of the mineral filler. Its influence on the physical (air void content) and mechanical properties (indirect tensile strength, moisture and frost resistance, stiffness modulus, low temperature cracking resistance) of AC 8S asphalt concrete produced in the HWMA technology was studied. Using Harrington's utility function, the optimal content of hydrated lime and foamed bitumen was determined. A comprehensive evaluation of the results demonstrated synergy between hydrated lime and 50/70 asphalt with the addition of 0.6% surface active agent, ensuring that the HWMA AC 8S mixture meets all the normative requirements.