MOCK UP TEST FOR LARGE CONCRETE POURS - TEMPERATURE MONITORING

Mass concrete is defined as "any volume of concrete with dimensions large enough to require that measures be taken to cope with the generation of heat from hydration of cement and attendant volume change to minimize cracking."^[ (ACI Committee 207–Mass and Thermally Controlled Concrete)

Mass concreting can result in high temperatures in concrete core during hydration process. Which can result thermal cracking of concrete in a severe way. Basically the temperature variance (in different locations of the concreted element) or the temperature gradient will cause the thermal cracking.

Maximum Limits

Maximum temperature - 78 'C
Maximum temperature variance - 27 'C

Hence it is a good practice to do a temperature monitoring mockup in order for the better understanding of the maximum temperature rise, maximum core temperature of the concrete.

A sample mockup test is shown below with Grade 40 concrete mass concreting work.

Details of the Test Block

A wooden box was used with polystyrene based insulation to simulate the maximum temperature rise as well as the maximum temperature differential.

The selected size of the Test Block is 1.5 m × 1.5 m × 1.5 m.

All the vertical and Horizontal surfaces was insulated with a layer of 25mm thick rig foam sheets in order to prevent heat loss as the interior part of the raft foundation in actual conditions. Top surface was covered with 25 mm thick sand layer.

The arrangement of thermocouples to monitor the core and surface temperatures is also shown in figure No: 01. Additional thermocouple was used to monitor the ambient temperature. Two data loggers were used to record the temperature at the selected locations at 10 & 15 minutes time intervals. Temperature monitoring was carried out for a period of 7 days to obtain the following information.

1. Maximum temperature rise

2. Maximum temperature differential