Unless you take special precautions, laying masonry when the weather is too hot can adversely affect both the quality of the masonry work and the productivity of masonry workers. How hot is too hot? ACI 530.1-92/ASCE 6-92/TMS 602-92 Specifications for Masonry Structures requires masonry contractors to submit hot-weather procedures when the temperature exceeds 100 degrees Fahrenheit, or 90 degrees Fahrenheit with a wind velocity greater than 8 miles per hour. The most serious problem occurs when the mortar becomes too hot. It loses water so rapidly that the cement doesn't have the chance to fully hydrate. In the field, this condition is know as "dry-out." If noticed soon enough, the condition can be remedied after the fact by damp-curing the wall. Mortar can be revitalized by fogging the wall with a light water spray.

Mortar Selection
Select a mortar with higher water retentivity when possible. Because higher temperatures can cause flash set of the cement, maintain the mortar temperature between 70 and 120 degrees Fahrenheit. To do so, keep materials as cool as possible. The best way to keep materials cool is to provide shade. Cold water should be used to mix the mortar, and to cool down metal equipment and wood mortar boards.

Worker Comfort and Productivity
In long periods of very hot weather, schedule construction early in the day to avoid peak mid-afternoon temperatures. Encourage workers to drink plenty of water to prevent dehydration.Hot weather can be tough on workers and materials. But by following the requirements of ACI 530.1 and adopting the preceding recommendations when appropriate, contractors can minimize their problems.