Civil engineering is often a complex, multifaceted process that requires the application of mathematical, physical and engineering principles. A variable of particular importance for many civil engineering projects is heat of hydration, which has direct and indirect effects on the overall success of a project.
This article provides an overview of the concept of hydration, its applications, and how it can be controlled and measured to ensure project success.
Heat of hydration is the heat released during hydration reactions. This heat comes from the chemical reaction between water and cement that creates calcium hydroxide. This can cause problems in many civil engineering projects as it can cause an increase in the temperature of the concrete, which can cause cracks and other structural damage.
The heat of hydration can also cause problems for the environment, as rising temperatures can lead to evaporation and condensation, which in turn can lead to air pollution and water shortages.
Concrete hydration reaction
The main components of cement are as follows.
| Components | percent after Weight |
chemical formula | |
| C 3 S | tricalcium silicate | 50% | 3Ca0SiO2 |
| C 2 S | Dicalcium silicate | 25% | 2Ca0SiO2 |
| C 3 A | tricalcium aluminate | 10% | 3Ca0Al2O3 |
| C 4 AF | Tetracalcium aluminum ferrite | 10% | 4Ca0Al2Fe2O3 |
| plaster | 5% | CaSO4 H2O |
The strongest component of concrete is calcium silicate. Most of the initial resistance is caused by tricalcium silicates (first seven days). In the later stages, the initial dicalcium silicate hydrates formed more slowly contribute to the reinforcement of the concrete.
The heat created by the reaction of water and Portland cement is called the heat of hydration. The percentage of C 3 S E C 3 A in the cement has the greatest influence on the heat of hydration, although this is also influenced by the water-cement ratio, fineness and curing temperature.
Typically, heat release is greatest in the first 24 hours and heat development is strongest in the first three days. For most concrete components, such as sidewalks, long-term heat development is not a problem because this heat is released into the environment.
Special Notes on Heat of Hydration
There are two ways to control the heat of hydration : using a lower water-cement ratio or using a plasticizer. A lower water cement ratio results in concrete that is less prone to cracking and hydration damage. A plasticizer can be used to give concrete flexibility, which also helps prevent cracking.
The heat of hydration can be measured with a calorimeter. This device measures the heat released during the hydration reaction. The calorimeter is placed in the center of the concrete mass and the temperature is monitored over a period of time. The result of calorimetry is used to calculate the heat of reaction.
