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

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Published By
Rajib Dey
www.constructioncost.co
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