4.1 The temperature of the air in the vicinity of the mixing
slab, the dry cement, molds, and base plates shall be maintained
between 20 and 27.5°C (68 and 81.5°F). The temperature
of the mixing water and of the moist closet or moist room
shall not vary from 23°C (73.4°F) by more than 6 1.7°C (3°F).