10.10 : 대량 콘크리트

When large volumes of concrete are placed, if the temperature of the concrete on the surface and the interior region is different, thermal cracks may occur. 

To mitigate thermal cracking, the concrete mix uses low-heat cement, pozzolans such as fly ash, cooled aggregates with angular particles, and water-reducing admixture.

The ingredients are then mixed using chilled water to produce fresh concrete at a temperature of about 45 degrees Fahrenheit.

Fresh concrete is then placed in formwork made of thermally insulating materials.

Covering the surfaces of the structure with plastic-coated quilts controls the heat loss.

Additionally, cooling pipes can be embedded into the structure to facilitate cooling post-concreting.

To ensure the structure is insulated, thermocouples are positioned at various locations to monitor the concrete's temperature.

The formwork and insulation are kept in place for up to two weeks for sections with thicknesses greater than twenty inches.  

However, for externally restrained large concrete sections, construction should take place in lifts, and movement joints are to be provided at suitable locations to prevent cracking.