Water leakage through concrete and mortar joints is a common problem in many houses and buildings. Water seepage not only damages the structure, but also creates unhealthy living conditions. Selecting the right type of cement is crucial for preventing water leakage.
What causes water leakage in concrete?
Water leakage in concrete can occur due to several reasons:
- Cracks in concrete allow water to seep through. Cracks develop over time due to factors like corrosion of reinforcement bars, foundation settlement, temperature changes, structural movements etc.
- Permeability of concrete also plays a role. Standard concrete mixes are porous and allow water to pass through capillary action. Concrete with high porosity leads to dampness and seepage.
- Poor quality concrete is more vulnerable to cracking and water infiltration. Low cement content, high water-cement ratio, poor curing etc. compromise concrete strength and durability.
- Defective construction joints without proper seals/waterstops allow water ingress into the structure.
- Pressure differential across concrete surfaces can drive water through fine cracks and pores.
- In coastal areas, the chloride content in water can damage concrete and increase permeability.
How to select the right cement?
While there are many types of cements available, the most commonly used options for waterproofing concrete are:
Portland Pozzolana Cement (PPC)
- PPC is prepared by blending pozzolanic materials like fly ash with ordinary Portland cement.
- It has improved water resistance and reduced permeability compared to OPC.
- The pozzolanic reaction improves concrete density and impermeability.
- PPC has better workability than OPC and is less prone to cracking.
- It is more environment friendly and economical than OPC.
Portland Slag Cement (PSC)
- PSC is produced by grinding Portland cement clinker with granulated blast furnace slag.
- The slag reacts with cement and improves concrete durability and strength.
- It reduces concrete permeability significantly compared to OPC.
- PSC has better resistance to chlorides and sulfates than OPC.
- It is more workable than OPC.
- However, availability may be limited in some regions.
Sulphate Resistant Cement
- This type of cement is specially designed to resist damage from sulphate attacks.
- It is manufactured by reducing tricalcium aluminate content in cement.
- Sulphate resistant cement has improved water impermeability.
- It is recommended for use in seawater environments and where soil/ground water has high sulphate content.
- It avoids expansion and disruption in concrete exposed to sulphates.
White Cement
- White cement is made from raw materials with very low iron oxide content.
- It has better water resistance than grey cement.
- The lighter color enables detecting cracks and leaks easily.
- It is commonly used for waterproofing swimming pools and water tanks.
- However, it is more expensive than other cement varieties.
How to further improve waterproofing properties of cement?
Some measures that can enhance the water repellent properties of cement are:
- Use plasticizers and superplasticizers – These enhance workability at lower water content and improve concrete density.
- Treat cement with waterproofing compounds – Adding tiny amounts of water-repellent chemicals like fatty acids, metal stearate soaps, silicones etc. to cement makes it hydrophobic.
- Use finely ground cement – Higher fineness improves hydration and reduces voids and pores in concrete, enhancing water tightness.
- Lower water-cement ratio – Denser concrete with lower permeability is obtained by reducing water content.
- Proper compaction and curing – Appropriate consolidation eliminates honeycombing. Adequate moist curing prevents cracks.
Which cement is best for water leakage?
While all common cement types can be used for waterproofing, each has its own merits and demerits. Here is a comparison:
| Cement Type | Waterproofing Ability | Workability | Resistance to Sulfates and Chlorides | Cost |
|---|---|---|---|---|
| OPC | Poor | Low | Low | Low |
| PPC | Good | High | Moderate | Low |
| PSC | Excellent | High | High | Moderate |
| SRC | Good | Moderate | Low | High |
| White Cement | Good | Low | Low | High |
Based on the above comparison, we can conclude that:
- For general construction, PPC is a good choice as it improves water tightness over OPC, without compromising on workability or cost.
- In coastal areas exposed to chlorides, PSC is the best option due to its superior sulfate and chloride resistance.
- Where soils have high sulfates, SRC is preferable despite higher cost.
- For water tanks and pools, white cement is specially suitable.
- However, factors like availability, cost, type of exposure, workability requirement etc. also need to be considered.
- Using suitable admixtures and construction techniques further enhances water resistance of the cement selected.
Conclusion
Water leakage through concrete is a nuisance that can be avoided by selecting appropriate cement. Cements like PPC, PSC, SRC and white cement provide improved waterproofing than conventional OPC. However, the choice depends on site conditions, cost and availability. Employing good construction practices also helps utilize the full waterproofing potential of the cement used. With careful selection and execution, even ordinary cement can be made water-tight for most applications.