Abstract
In the course of manufacturing, transport and installation, road bitumens and asphalt mixtures can be exposed to the impact of elevated process temperatures exceeding 240 °C. This mainly applies to the mixtures used for road pavements and bridge deck insulation during adverse weather conditions. The heating process should not change the basic and rheological properties of binders and the asphalt mixtures that to a degree cause the degradation of asphalt pavement durability. The work involved analyzing the properties of non-modified bitumens and SBS polymer modified bitumens, heated at temperatures of 200 °C, 250 °C and 300 °C for 1 h. Next, the asphalt mixtures were heated in the same temperatures. Based on the developed Overheating Degradation Index (ODI) it was demonstrated that polymer-modified bitumens were characterized by higher overheating sensitivity A(ODI) than non-modified bitumens, which was confirmed by mixture test results. Overheating limit temperatures T(ODI) were determined, which in the case of polymer-modified bitumens are up to 20 °C lower than for non-modified bitumens. When the temperature increases above T(ODI), loss of viscoelastic properties occurs in the material which causes, among other effects, a loss of resistance to fatigue cracking.
Highlights
Bituminous binders and asphalt mixtures during technological processes can be exposed to high temperatures, greatly exceeding the permissible temperature determined by a binder manufacturer or in the domestic technical documentation
The test results presented in the article confirm that the process of overheating binders and asphalt mixtures causes adverse changes in their properties, which can significantly decrease pavement durability
Based on the literature study there are different opinions regarding the limit temperature, which can be achieved by non-modified and polymer-modified road bitumens through heating, without deteriorating pavement durability
Summary
Bituminous binders and asphalt mixtures during technological processes (production, transport, application) can be exposed to high temperatures, greatly exceeding the permissible temperature determined by a binder manufacturer or in the domestic technical documentation. Decreased workability of mastic asphalt compared to other asphalt mixtures and the need to conduct the work in adverse weather and process conditions (wind, thin layer, bridge pavement layer cooling from the top and bottom), make it possible for the mastic asphalt during transport and maturation in boilers to maintain workability and to be heated for over 1 h, even at a temperature of 240 ◦ C. The phenomenon of overheating occurs in the case of other asphalt mixtures, such as asphalt concrete (AC) and stone mastic asphalt (SMA), the application of which in the case of bridges is common. Another reason for overheating of bitumen may be an emergency situation, for example a bridge fire, fire in a tunnel or a car on fire standing on an asphalt pavement. The third possible reason for overheating may be excessive heating of the pavement during renovation works in hot technology (e.g., operation of radiators, heaters, etc.)
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