Heat of hydration is the process by which concrete liberates heat. This process is the reason heat is generated while concreting. Excessive heat of hydration may lead to energy loss and crack formation in the concrete. Controlled heat in fresh concrete ensures the quality and desired strength of concrete.
Significance
Heat of hydration is an inevitable process but excessive heat or uncontrolled heat reduces the quality of concrete. This is why in fresh concrete heat of the concrete must be known. Excessive heat generation forms cracks in concrete.
High temperature requires high water content and low temperature leads to slow setting of cement. So controlled temperature of the concrete is required.
Temperature Limits: Generally, temperature must not cross 35 degree Celsius.
Factors Affecting Heat of Hydration
- Cements with higher contents of tricalcium silicate and tricalcium aluminate, as well as a higher fineness, have higher rates of heat generation than other cements.
- Tricalcium silicate and tricalcium aluminate chemically generate more heat.
- Higher fineness provides a greater surface area to be wetted, resulting in an acceleration of the reaction between cement and water. This causes an increase in the rate of heat liberation at early ages.
- Other factors influencing heat development in concrete include the cement content, water-cement ratio, placing and curing temperature, the presence of mineral and chemical admixtures, and the dimensions of the structural element.
Apparatus
Thermometer: To check temperature of concrete.
Time watch: To check the age of the concrete.
Procedure
- Prepare concrete with given mix design.
- Check the temperature of the concrete at the desired time intervals.
- Note down the temperature.
- Compare this temperature with the limit at the given time.
- It should not be too low or too high.