Using non-hydraulic cement is fundamentally different from using common hydraulic cements like Portland cement. Unlike hydraulic cement, which hardens when water is added, non-hydraulic cement does not require water to set and cure.
Based on the provided information, the core requirement for using non-hydraulic cement is:
- Dry Conditions: It will not set when wet conditions exist. The environment must be dry.
- Presence of Carbon Dioxide (CO₂): This is the key element that triggers the setting and curing process.
Essentially, to use non-hydraulic cement, you need to ensure the mix is placed in a dry environment where it can react with atmospheric carbon dioxide.
Key Differences from Hydraulic Cement
Understanding the primary difference is crucial:
| Feature | Hydraulic Cement (e.g., Portland) | Non-Hydraulic Cement (e.g., Lime) |
|---|---|---|
| Hardening Agent | Water (Hydration) | Carbon Dioxide (Carbonation) |
| Environment | Can set under water | Requires dry conditions |
How to Apply Non-Hydraulic Cement
While specific applications may vary depending on the exact type of non-hydraulic cement (like traditional lime-based mortars or plasters), the general principle derived from the requirement is to ensure:
- Mixing: The non-hydraulic cement powder is mixed with aggregate (like sand) and a minimal amount of water to achieve a workable consistency. This water is primarily for workability, not for the chemical setting reaction itself.
- Application: Apply the mixture to the desired location (e.g., for mortar joints, plaster coats).
- Curing Conditions: This is the most critical step. The material must be exposed to dry conditions and carbon dioxide (CO₂) in the air.
- Ensure good ventilation to allow fresh air (containing CO₂) to reach the surface.
- Protect the work from rain or excessive moisture during the curing period.
- The curing process (called carbonation) can be slow, especially in thick applications.
Examples of Use (General)
Non-hydraulic cements, such as traditional lime cements, have historically been used in various applications, including:
- Mortar for brick and stone masonry in historic buildings
- Traditional wall plasters and renders
- Lime washes
In these uses, the material hardens over time by reacting with the CO₂ in the atmosphere, forming calcium carbonate.
In summary, to use non-hydraulic cement, you prepare it and then expose it to dry conditions and carbon dioxide to allow it to set and cure through the process of carbonation. It fundamentally relies on the air, not water, for its long-term strength development.
