10.11 : 暑い天候でのコンクリート打設

In dry and hot conditions, placing fresh concrete at high temperatures accelerates the setting and leads to rapid evaporation of water from the concrete, which can cause cracking.

Preferably, the concrete's temperature in hot weather conditions should not exceed 60 degrees Fahrenheit.

This is achieved by reducing the cement content, using Sulfate-free aggregates with less moisture absorption, incorporating set-retarding admixture, adding ice to the mixing water, and ensuring its complete melting before the concrete mixing is completed.

Additionally, on hot weather sites, precautions include shading the aggregate stockpiles from direct sunlight, spraying them with water to facilitate cooling by evaporation, burying the water pipes, and painting concrete handling equipment and tanks white to reflect sunlight.

Formwork is sprayed with water before the concrete is placed, and the placement is done during the cooler evening hours.

After placement, the concrete may be covered with white-colored plastic sheeting to protect it from the sun and rapid evaporation.

Lastly, in dry weather conditions, wetting the concrete and allowing evaporation of water facilitates good curing and cooling.