Influence of the production process on the selected properties of asphalt concrete

Abstract

The paper investigates the influence of the concentration of synthetic wax modification of bitumen on the properties of asphalt concrete produced and compacted at 95°C and at 115°C. In both types of mixes the bitumen was modified with 1,0% to 2,5% concentrations of synthetic wax in 0,5% steps. Nowadays, the most widely adopted classification of asphalt production techniques is the one based on production temperatures. According to this classification, the investigated production methods are regarded as Warm Mix Asphalt, where the production temperatures range from 110°C to 135°C and as Half-Warm Mix Asphalt with production temperatures ranging from 60°C to 100°C. Both methods are subjects of increasing attention due to their significant economic and environmental benefits. In the production of Warm Mix Asphalt mixes, a 35/50 bitumen modified with F-T wax was used as a binder. To achieve production temperatures below 100°C, additionally the binder was foamed prior to mixing – using the method most commonly used in production of CMA foamed bitumen mixes. The experimental work was separated into two stages: the first included assessment of the properties of the 35/50 F-T synthetic wax modified binder and the properties of foamed bitumen. In the second stage, the properties of AC 22W asphalt concrete were investigated, which included: air void content (Vm), resistance to moisture and frost damage (ITSR), wheel tracking slope (WTSAIR) and proportional rut depth (PRDAIR). The investigated asphalt concrete was designed as for binder course for moderately trafficked roads (KR 3-4). The conducted research allowed to assess the minimum amount of synthetic wax which results in the mix fulfilling the binding requirements (for both WMA and HWMA mixes).