h i g h l i g h t sWe evaluated a foamed 50/70 pen bitumen modified with Fischer-Tropsch wax. The additive reduced the dynamic viscosity of the binder above 100°C. The foam expansion ratio increased linearly with additive dosage. The foam half-life increased linearly with additive dosage. The foam index increased with the increase of FT wax concentration. a b s t r a c tThe aim of the research was to evaluate the properties of foamed bitumen, produced from a FischerTropsch synthetic wax modified 50/70 penetration grade bitumen for use as a binder in road construction layers. The binders were subjected to conventional tests (including penetration, softening point, Fraass breaking point and dynamic viscosity) as well as bitumen-foam-specific testing (including expansion ratio, half-life and foam index at different foaming water contents). Optimum amounts of foaming water and Fischer-Tropsch wax were identified and the binders were classified as relevant for different low-energy bitumen mix production techniques.

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To ensure the standard properties of half-warm asphalt (HWA) mixes produced with foamed bitumen, the binder needs to have the best possible characteristics. One way to attain this is to modify the bitumen before it is foamed. The 50/70 penetration bitumen used in this study, was modified with a surface active agent (SAA) at different rates (0.2%, 0.4%, and 0.6% by wt.). The effect of the modifier on the bitumen properties (penetration, softening point, the Fraass breaking point, dynamic viscosity at 60 °C, 90 °C, and 135 °C) and on the binder foaming parameters (expansion ratio - ER, half-life - HL, foam index - FI) was investigated and the optimum quantity of foaming water was determined. Statistical analysis of the results showed that the addition of 0.6% SAA had the most beneficial effect on the set of 50/70 bitumen standard properties and foaming characteristics.

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This paper presents findings of a study concerning the influence of binder type on the mechanical properties of road base in the cold recycling technology. The principal aim of this investigation was to evaluate the mixes in scope of susceptibility to moisture and low-temperatures. In the comparative research foamed bitumen and bitumen emulsion were used in four different concentrations (2.0%, 2.5%, 3.0%, 3.5%). The materials used in the study were reclaimed from an existing road construction layers: reclaimed aggregate from the road base and reclaimed asphalt pavement obtained by milling the surface and binder course. Portland cement in 2.0% concentration was used as a hydraulic binder. The evaluated parameters were: indirect tensile strengths, tensile strength retained and indirect tensile stiffness modulus at 25 °C. These tests were complemented by an evaluation of susceptibility to moisture and frost according to modified procedures implemented by American researchers: Tunnicliff, Root and Lottman. Moreover, tests for low-temperature cracking were conducted according to Finnish standard. The investigations showed that the use of foamed bitumen for road base layer produced in the cold recycling technology results in better mechanical properties and resistance to moisture and frost compared to using bitumen emulsion. The use of 2.5% of foamed bitumen and 2.0% of Portland cement in the recycled road base allowed to meet the established criteria.