What temperature difference is noted between the mid-point and the bottom of the asphalt layer?

The 30°F temperature difference between the mid-point and the bottom of the asphalt layer can be attributed to several factors in the thermal behavior of asphalt during the paving process. When asphalt is laid down, the top layer experiences direct exposure to ambient conditions, leading to quicker cooling. In contrast, the layers beneath remain insulated by the layer above them, leading to a significant retention of heat.

Typically, during the laying of asphalt, the temperature gradient is established due to the combined effects of heat loss to the environment and thermal conductivity, which influences how quickly heat dissipates through the material. A 30°F difference is a realistic figure that reflects both the physical characteristics of asphalt and the typical conditions seen in the field, illustrating the importance of monitoring temperature gradients to ensure proper compaction and bonding of layers. This temperature differential is critical for evaluating the quality and durability of the asphalt pavement, as improper cooling can lead to premature failures or defects.