The principal cementing chemical compound used in cement is calcium aluminate.
Cement, particularly Portland cement, is a complex mixture of various chemical compounds that react when mixed with water to form a hardened paste. While several substances are present, one stands out as the primary agent responsible for the cement's binding properties.
Based on the composition detailed in the reference:
- Cement contains 35 to 40 percent lime.
- It includes 40 to 50 percent alumina.
- Up to 15 percent iron oxides are present.
- Preferably not more than about 6 percent silica is included.
However, the core binder, the compound that forms the strong structure upon hydration, is specifically identified.
The Principal Cementing Compound
According to the provided reference, the principal cementing compound is calcium aluminate (CaO · Al2O3). This compound plays a crucial role in the early strength development of the cement paste after mixing with water.
Here's a breakdown of the main components and the principal compound mentioned:
| Component/Compound | Chemical Formula | Approximate Percentage (from Reference) | Role |
|---|---|---|---|
| Lime | CaO | 35 - 40% | Key clinker component |
| Alumina | Al₂O₃ | 40 - 50% | Key clinker component |
| Iron Oxides | Fe₂O₃, Fe₃O₄ | Up to 15% | Contributes to strength |
| Silica | SiO₂ | Not more than about 6% | Key clinker component |
| Calcium Aluminate | CaO · Al₂O₃ | Principal Compound | Main cementing agent |
Note: The percentages listed for lime, alumina, iron oxides, and silica represent the raw material components or clinker phases, while calcium aluminate is highlighted as the specific compound responsible for the primary cementing action.
Understanding the chemical composition is essential to appreciating how cement transforms from a dry powder into a durable construction material. The precise ratios and interactions between these chemicals, particularly the hydration reactions of calcium aluminate and other phases, determine the final properties of the hardened concrete.
