Ordinary Portland Cement (OPC) is a widely used binding material in construction, but it comes with certain drawbacks that limit its application and raise environmental concerns.
Here are the primary disadvantages associated with using OPC, based on common knowledge and the provided reference:
Key Drawbacks of OPC Cement
While OPC offers excellent strength and versatility for many construction projects, several limitations should be considered:
1. Susceptibility to Chemical and Sulphate Attacks
OPC is not resistant to chemical and sulphate attacks. This means that in environments where concrete is exposed to sulphates (common in soils, groundwater, and seawater) or other aggressive chemicals, the concrete made with OPC can degrade over time. The reaction between sulphates and components of the hardened cement paste leads to expansion, cracking, and loss of strength.
- Practical Insight: For structures exposed to harsh chemical environments or sulphate-rich soils, alternative cement types like Sulphate-Resisting Portland Cement (SRPC) or blended cements (using fly ash or slag) are often preferred to enhance durability.
2. Higher Cost Compared to Alternatives
It is costlier in comparison to other cement types, particularly blended cements that incorporate supplementary cementitious materials (SCMs) like fly ash, slag, or calcined clay. While OPC is the standard, the raw materials and energy required for its production can make it more expensive per unit weight than cements where a portion of the clinker is replaced by cheaper by-products.
- Solution: Using blended cements can often provide similar performance for certain applications at a lower material cost while also offering environmental benefits.
3. Limitations in Underwater Construction
OPC cannot be used for underwater construction without special precautions or modifications. The nature of OPC setting relies on hydration, which is significantly disrupted or prevented when mixed or placed directly in flowing or stagnant water bodies without protective measures. The cement particles can wash away before adequate hydration occurs, leading to poor strength development and durability.
- Note: Specialized underwater concretes or construction techniques are required for submerged structures, often involving anti-washout admixtures or tremie methods, but standard OPC mixtures are not suitable without these.
4. Significant Environmental Impact
The production of Portland cement is energy-intensive and generates a large amount of carbon dioxide, which can contribute to climate change. The process of calcining limestone, a key raw material, releases embodied CO2, and the high temperatures required for clinker production consume substantial energy, often derived from fossil fuels. Cement production is a major source of global CO2 emissions.
- Environmental Concern: The large carbon footprint of OPC production is a significant driver for the development and adoption of lower-carbon cements and sustainable construction practices.
Summary of Disadvantages
| Disadvantage | Description | Implication |
|---|---|---|
| Chemical/Sulphate Attack | Not resistant to aggressive chemicals and sulphates. | Reduced durability in harsh environments. |
| Higher Cost | Generally more expensive than blended cements. | Can increase project costs. |
| Underwater Use | Not suitable for direct underwater placement without special measures. | Limits application in aquatic environments. |
| Environmental Impact | Energy-intensive production releases significant CO2. | Contributes to climate change. |
Understanding these limitations is crucial for selecting the appropriate cement type for a given construction project, ensuring both structural integrity and consideration for environmental sustainability.
