Measurement of Asphalt Concrete Temperatures during Transport with the use of an Instrumented Probe System

Recently, so-called warm technologies have provided the paving industry with a considerable amount of versatility by increasing the options available to perform a given project. The ability to mix at traditional hot-mix temperatures and to compact at warm-mix temperatures is one of these options, because doing so can allow for long-haul distances. Warm technologies are fairly new to the United States, and documentation of their use on long-haul-distance projects is not abundant. This paper presents successful full-scale use of an instrumented probe system developed to simultaneously measure temperature at multiple locations within an asphalt mix while it was hauled for an extended period of time (10 h+). The data collected spanned haul distances far beyond those needed for any conceivable conventional application and likely exceeded distances needed for any emergency application. Probe temperature measurements appeared to be as reliable as well-accepted temperature measurement with asphalt thermometers. For representation of most of the mix in a truck with cooler material near the edges, a laboratory short-term aging protocol was recommended for long hauls of 6 h or less that held mixes at 15°C to 20°C below their mixing temperature for all but the last few minutes before they were progressively cooled to the desired compaction temperature. Additional findings illustrated the significant amount of time that most of a truck's asphalt could retain heat and provide temperature gradient measurements from just inside the truck bed to near the center of the truck bed.