Final answer:
Mortar must be used sometimes when temperatures are 80 degrees or higher, with precautions taken to ensure proper hydration and strength due to the increased evaporation rate.
Step-by-step explanation:
When the air temperature is 80 degrees or higher, mortar must be used sometimes, depending on certain conditions.
High temperatures can cause the water in the mortar to evaporate too quickly, leading to rapid drying, which can weaken the mortar due to insufficient hydration.
It is essential to follow industry guidelines for hot weather masonry.
These often include measures such as using cool materials, scheduling work during cooler times of the day, erecting shade structures, or using set control admixtures to ensure the quality and longevity of the masonry work.