Ageing and Cooling of Hot-Mix-Asphalt during Hauling and Paving—A Laboratory and Site Study

Abstract

In road construction, it can happen that, for different reasons, the time between hot-mix asphalt (HMA) production and paving is extended to some hours. This can be reflected in several problems such as mix cooling and temperature segregation, but also in an extremely severe bitumen ageing due to its prolonged exposure to high temperatures. This paper deals with the investigation of these phenomena both in the laboratory and on site. In particular, the first part of the research aimed at observing the influence of the conditioning time, when the loose HMA is kept in the oven at a high temperature, on the mix properties. The second part focused on the ageing/cooling that happens on site during HMA hauling, as a function of time and type of truck. Temperatures were monitored using a thermal camera and different probes, and gyratory compactor specimens were produced by sampling some HMA from the trucks every 1 h for 3 h. The results showed that HMA stiffness rises if the time when the loose mix stays in the laboratory oven before compaction increases. However, on site, the HMA volumetric and mechanical properties do not change with hauling time up to 3 h, probably because the external material in the truck bed protects the HMA core from the access of oxygen, hindering bitumen oxidation and loss of volatiles. The temperature monitoring highlighted that temperature segregation, after 3 h hauling, can be higher than 30 °C but it can be reduced using insulated truck beds.

Effects of Environment-Friendly Rejuvenator on the Rheological Properties and Microstructure of Aged Asphalt

“…Compared with the original asphalt, the four absorption peaks representing aromatic molecules at 727–868 cm −1 in the spectrum of aged asphalt gradually become smaller, indicating that the light components such as aromatics in aged asphalt are reduced, which is also the internal reason for the change of rheological properties of asphalt during aging. This is consistent with the findings of previous studies ( 47 , 48 ). This is mainly since the light component of asphalt is gradually transformed into heavy components such as asphaltene during the ageing process; at the same time, in the aging environment of higher temperature, the light components in asphalt have volatilization.…”

A Review on Bitumen Aging and Rejuvenation Chemistry: Processes, Materials and Analyses

“…The evaporation of saturated and aromatic components has been also reported as an aging mechanism of bitumen. In particular, this phenomenon is mainly related to shortterm aging, as it depends on the temperature to which the bitumen is subjected during the mixing and installation phases [72]. It has been quantified that the loss of volatiles can be double for a temperature increase of 10 • C during HMA manufacturing at the plant [73].…”

Recyclability Potential of Induction-Healable Porous Asphalt Mixtures

“…The induction heating technique has been used with RA to know its behavior when the mixture is aged due to weather conditions [22]; however, its recycling performance, including the re-use of residual metallic particles inside the RA, and the addition of a rejuvenator, have not been deeply analyzed. Although the aging process depends on a lot of parameters [23], induction-healable PA mixes was artificially aged according to the AASHTO R 30-02 to be used as RA in new induction healable PA mixes.…”