Proper understanding of the causes behind water leakage in concrete is necessary for designers and site engineers to incorporate the preventive measures. Several factors, like the use of poor-graded aggregate, overdose of admixtures, deviations from designated mix, improper concrete placement, impurities in aggregates, etc. are responsible for water leakage in concrete.
Examples of some structures prone to water leakage are water tanks, building basements, roof slabs, floor slabs, balconies, swimming pools, concrete-lined stormwater channels, etc. The leakage of water causes corrosion of steel and deterioration of concrete structure if not repaired at an early stage.
Causes of Water Leakage in Concrete and How to Prevent it
1. Coarse Aggregate
Coarse aggregate could be one of the factors to cause leakage in concrete if it is poorly graded, contains dirt materials, or its size is larger than required. These factors usually increase voids in concrete, thereby increasing concrete permeability and, finally, resulting in water leakage.
Make sure to use well-graded aggregate by using sieve analysis for each lot and wash the aggregate to remove impurities to eliminate coarse aggregate issues.
2. Fine Aggregate
The presence of impurities in fine aggregate and improper fineness modulus of fine aggregate can lead to water leakage in concrete.
Like coarse aggregate, wash fine aggregate if pollutants are present and consider using fine aggregate with minimum fineness modulus for producing concrete.
Both coarse and fine aggregate should be moistened to saturated surface dry (SSD) conditions before the mixing process.
3. Reinforcement Bars
Use of rusty steel bars, presence of shutter oil and cement mortar over steel bars, and over reinforcing concrete may cause water leakage. Therefore, avoid bars coated with shutter oil and cement mortar and prevent the placement of rusty steel.
A small amount of rust can improve the bond between concrete and steel bars. Over-reinforcement can create steel congestions that make concrete placement extremely difficult and may result in honeycombing.
4. Admixtures
Various factors related to admixtures, such as expired admixture, improper dosage, and mixing inappropriate admixture types with concrete may cause leakage in concrete.
Add admixtures to the concrete according to the mix design specifications and location of applications. Changing the type and dosage of admixtures should be prevented unless an experienced engineer is consulted.
5. Cement Type and Mixing Water
The use of an improper type of cement and water that contains organic materials and salinity can be the reason behind the leakage of water in concrete.
Therefore, use pure water to make concrete and consider using the right cement grade to eliminate possibilities of water leakage due to water and cement.
6. Deviation from Designed Mix Ratio
Deviation from the designated mix design by using a higher quantity of water and incorrect aggregate quantity can cause leakage in concrete. Therefore, the specified mix proportions should be strictly followed to avoid such a problem.
Use superplasticizer, instead of water, to achieve the required workability as the latter increases the possibility of water leakage in concrete. The addition of a superplasticizer should be according to the manufacturer's guidelines and instructions of an experienced engineer.
Carry out the slump test for each batch coming out of the transit mixer to make sure that the concrete has the right workability.
7. Concrete Placement Issues
Segregation and bleeding of concrete are major concrete placement problems that can cause leakage in concrete. The possibilities of segregation and bleeding are higher when concrete is pumped.
Therefore, the mix design should be prepared keeping in mind that the concrete may need to be pumped. Prevent concrete placement from height as it can lead to segregation and bleeding of concrete and, consequently, water leakage issues.
8. Workmanship Quality
Problems related to workmanship like poor mixing of concrete, poor formwork installation, insufficient clear cover, improper compaction of concrete, improper curing of concrete, and plumbing failure can lead to water leakage in concrete.
Uniform mixing of concrete should be ensured. If machines are used to mix concrete constituents, inspect concrete visually to see whether the mixture is uniform or not. The concrete should be placed before it loses its workability. Use retarder to increase the time frame in which the concrete is placed, compacted, and finished.
The formwork should be sealed adequately to prevent the escape of water from the fresh concrete; otherwise, the risk of honeycomb formation would be high. Prevent the use of polythene sheet to seal formworks as it may cause a separator effect on concrete.
Improper concrete cover and inadequate curing of concrete can cause crack development, and finally, leakage of water could occur. Check concrete cover before concrete placement to ensure adequate concrete cover thickness is provided and start the curing process immediately after concrete hardening. Keep the concrete in a moist condition for a specified curing period.
Finally, use high-quality pipes, watertight joints, and proper plumbing layout to avoid possible water leakage of plumbing joints, breakage of pipes, and blockage in pipes that may result in dampness in concrete later on.
9. Extreme Weather Condition
The exposure of concrete to extreme weather conditions may initiate concrete cracking and water leakage in concrete. Roof slabs are commonly exposed to high temperatures during summer and fall in temperatures and rainfall in winter.
The variations of temperature can develop cracks; hence the cracked concrete roof may allow the passage of moisture. The use of fiber reinforcement can tackle the cracking problem of the roof slab.
Water drippings, damp patches, paint peeling-off, rust stains on the ceiling are signs of water leakage in concrete roofs and floors.
10. Cold Joints
Another cause of leakage of water in the concrete is the presence of cold joints. The application of shear key or chemical additives to potentially leakage prone joints of concrete members can significantly tackle the problem, see Figure-4.
11. Honeycomb
The presence of honeycomb in structurally crucial elements such as reinforced concrete walls, columns, beams, and slabs (see Figure-5) can lead to water leakage. The honeycomb should be treated immediately after removing formworks.
12. Earthquakes
Earthquake forces could be another factor that can cause leakage in concrete structures. There are areas that are vulnerable to earthquakes, and the concrete buildings there may suffer from different damages, and consequently, leakage of water may occur.
FAQs
1. Poorly-graded aggregate
2. Deviation from mix ratio
3. Honeycomb
4. Cold joints
5. Saline water and incorrect cement grade
6. Extreme weather conditions
7. Workmanship quality
8. Concrete placement problems
9. Dirty and rusty reinforcement
10. Overdose of admixtures
If leakage of concrete slab is left alone and not repaired, it would cause steel corrosion and deterioration of concrete.
1. Water tank
2. Concrete roof and floor slabs
3. Concrete-lined water storm pipes
4. Swimming pool
5. Balconies
6. Basements
Read More
Concrete Waterproofing- Types, Steps, and Advantages