What Is Hydraulic Setting?

Hydraulic binders, when mixed with water, set and harden both in air and underwater, making them fundamental building materials.

Examples of hydraulic binders include:

• Hydraulic lime
• All types of Portland cement

Types of Binders

1. Air Binders

These binders gain strength only in the air. When exposed to water, they lose cohesion, soften, and deteriorate.

Most common air binders:

• Building lime (main component: calcium hydroxide)
• Gypsum binders (e.g., building gypsum, spackling gypsum, gypsum plasters, gypsum adhesive)
• Anhydrite binders

2. Hydraulic Binders

These binders harden through chemical reactions with water. The setting and hardening process occurs during hydration. Hydraulic binders are known for their strength and durability, even underwater.

Examples of hydraulic binders:

• General-purpose cement
• Hydraulic lime, Roman cement
• Masonry cement

Composition of Hydraulic Binders

All hydraulic materials contain the following key oxides as fundamental components:

• SiO₂ (Silicon dioxide)
• Al₂O₃ (Aluminum oxide)
• Fe₂O₃ (Iron oxide)

Raw Materials for Cement Production

The main raw materials used in cement manufacturing include:

• Limestone (CaCO₃ - Calcium carbonate)
• Clay (Al₂O₃ - Aluminum oxide)
• Industrial by-products (e.g., blast furnace slag, fly ash, and waste sludges containing CaCO₃)