Massachusetts Construction Supervisor License (CSL) Practice Test

What is the chemical process that occurs between water and Portland cement to initiate hardening?

1. Setting reaction

2. Heat of hydration

3. Calorimetry reaction

4. Chemical bonding

The correct answer is: Heat of hydration

The correct answer is the heat of hydration. This process is essential to understanding how Portland cement hardens when mixed with water. When water is added to Portland cement, it reacts chemically with the compounds in the cement, primarily the calcium silicates, leading to the formation of various hydration products, such as calcium silicate hydrate (C-S-H), which contribute to the strength and durability of the concrete. During this reaction, a significant amount of heat is released, known as the heat of hydration. This process not only initiates the hardening of the cement but also plays a crucial role in the temperature increase of the concrete mass as it sets. This temperature rise can influence the properties of the concrete, such as workability and strength development over time. Understanding the heat of hydration is vital for construction supervisors as it impacts how concrete should be mixed, poured, and cured to ensure optimal performance in various environmental conditions.