Characteristics of Mass Concrete

Mass concrete is made with solid structures (> 80 cm). These structures frequently contain a greater volume. It signifies that large volumes of concrete should be set up in a short time. It needs highly well-organized planning and competent methods.

Mass concrete is applied for:

 Foundations for large loads
 Foundations for buoyancy control
 Solid walls (e.g. radiation protection)
 Infill concrete

The following major issues are formed with these enormous structures:

 Extreme internal and external temperature discrepancies throughout setting and hardening
 Excessive maximum temperatures
 High internal and external temperature deviations and as a result forced shrinkage
 Secondary consolidation (settling) of the concrete and as a result cracking occurs over the top reinforcement layers and also settlement under the reinforcement bars

Riska: All of these issues can lead to cracks and cement matrix defects assumed to be “skin or surface cracks” which may happen if the external/internal temperature variation is more than 15 °C or the outer layers can contract because of their initial drying out. Usually, the depth of skin cracks is few centimeters and can close again later.

Proper Measurement:

 Utilize cements with low heat development
 Low water content (curtailment in w/c ratio)
 Biggest possible maximum particle size (e.g. 0–50 rather than 0–32)
 If required, chill the aggregates to have a low initial fresh concrete temperature
 Set the concrete in layers (layer thickness < 80 cm)
 Restrain the bottom layers to make sure that the entire section is recompacted as soon as the top layer is set
 Start curing by applying thermal insulation methods
 Make sure the proper design and circulation of joints and concreting sections, so that heat can be dissipated and the temperature developments and deviations can be adjusted

Characteristics of Mass Concrete