What is a condition under which a mixture should not be placed?

A mixture should not be placed when the subgrade or base course is frozen because freezing conditions can severely impact the integrity and performance of the mixture. When the subgrade is frozen, it creates an unstable foundation that can lead to improper compaction, which is crucial for the longevity and durability of the roadway. A properly compacted subgrade ensures even distribution of loads and affects the overall structural capacity of the road. If the subgrade or base course is not in a suitable condition, the mixture may not bond effectively, resulting in cracking, deformation, or even failure of the pavement over time.

Other conditions, such as outside temperatures dropping below 32°F, could also affect the mixture placement, but the critical concern in this case is the condition of the supporting layers. Additionally, while other projects ongoing on the same road might present logistical challenges, they do not directly compromise the quality and stability of the mixture itself.