What are "low-temperature cracking" and its causes?

Low-temperature cracking refers to the formation of fissures in asphalt pavement that occurs when the material contracts in response to cold temperatures. This phenomenon is largely influenced by the properties of the asphalt binder, the temperature at which the pavement is exposed, and the stresses imposed on the material during the cooling process.

When the temperature drops, asphalt undergoes thermal contraction. If the temperature decreases significantly, or if the asphalt binder doesn't possess sufficient flexibility or ductility at those lower temperatures, the tension within the pavement can lead to crack formation. Low-temperature cracking is particularly critical in climates that experience wide temperature fluctuations because asphalt must be formulated to withstand these environmental stresses.

The other options describe different forms of damage. Cracks caused by excessive heat pertain to thermal cracking under high temperatures, while moisture damage relates to issues like stripping and rutting resulting from water infiltration. Cracks during periods of heavy usage would typically be attributed to fatigue cracking or loading stresses rather than specifically to low-temperature conditions. Thus, option B correctly identifies the specific cause of low-temperature cracking in the context of asphalt pavement.