The Influence of Hydrated Lime on IT-CY Stiffness Modulus of Foam-Based Asphalt Concrete Compacted at 95 °C

Abstract

For a number of years worldwide, the road construction industry has been seeking new technologies for producing energy-saving asphalt mixtures in order to meet new environmental requirements and laws. Some of these techniques include new classes of mixtures characterized by reduced processing temperatures compared to the conventional Hot Mix Asphalt (HMA) production temperature of 165 °C and paving temperature of approximately 145 °C. These techniques include Half Warm Mix Asphalt (HWMA) mineral mixtures produced with the use of foamed bitumen as a binder at temperatures of about 100 °C and paved at 95 °C. Although generally HWMA mixes are comparable to HMA, depending on the mix, they may suffer from decreased mechanical parameters resulting in a reduced service life of the asphalt pavement. The implemented research program investigated asphalt concrete (AC 8) with foamed bitumen (HWMA) compacted at 95 °C and the control HMA sample produced and compacted at a regular temperature. A typical 50/70 road paving bitumen modified with 0.6% surface active agent SAA (fatty acid amide) was used as the foamed binder, dosed at 5.6% and 6.2% by weight to the mixture. Mineral filler replacement with hydrated lime at 15% and 30% by weight was evaluated. The content of voids in the asphalt mixture was examined. The indirect tensile stiffness modulus (IT-CY) characterizing the durability of the mixture was measured at -10 °C, 0 °C, 10 °C, 20 °C and 25 °C. The results of statistical analysis showed significant correlations between the mix production technology used and the content of foamed bitumen and hydrated lime in terms of the temperature of stiffness modulus testing. As confirmed by the stiffness modulus values, the application of hydrated lime provided the half-warm mix asphalt concrete AC8 produced with foamed bitumen with mechanical properties comparable to those of the HMA mix.