Waterproofing concrete helps avoid penetration of waterborne contaminants and chemicals that can cause damage. There are different methods for waterproofing concrete during the construction process including the use of the sheet membrane where a polymer sheet integrated with asphalt achieves waterproofing, use of liquid membranes that can be applied with brush or roller, and use of admixtures to react chemically with the concrete.
Sheet membranes are the most common in concrete waterproofing processes today. However, they present different installation challenges, application limits, and they are also very costly. This has led to more development of better concrete waterproofing methods.
The more recent methods include admixtures, which are integrated into the concrete itself.
Crystalline admixtures have been applied in the construction industry since the 1980s.
In selecting a concrete waterproofing solution, you require an understanding of how they operate. The mechanical methods such as membranes will resist water passage from the positive or exterior side. Modern technology allows the application of waterproofing products that will offer the solution from the negative or interior side.
Integral methods such as the admixtures are more superior because they act from within the concrete after converting the concrete itself to become waterproofing and can therefore block water from all directions.
When selecting a waterproofing solution for your concrete product, efficiency is the number one factor.
Different methods of waterproofing concrete
Admixtures
These are the latest version of waterproofing now being used around the world. They are added into the concrete to react chemically with it and render it waterproofing.
In effect, they do not add a barrier over concrete against water like would other systems such as the polymer sheet method or liquid membranes. Instead, they turn the concrete itself into a waterproof chemically.
The admixtures can be of different types: densifiers, water repellents, or crystalline admixtures.
Densifiers
When water is added during the formation of concrete, it will form calcium hydroxide. This is what the densifiers react with to make the concrete waterproofing. This is because the by-product formed during this reaction will increase the density of concrete and make water slow to migrate into or through it.
To protect the concrete fully from damage by water under hydrostatic pressure, an additional waterproofing method would be needful when densifiers are applied because the latter will not seal cracks and joints like would the repellent-based waterproofing materials.
Water repellents or hydrophobic materials
These are the products that usually come in liquid form, and which repel water and prevent it from penetrating the concrete. They include long-chain fatty acid derivatives such as oils, hydrocarbons, and stearates.
These products are effective when damp-proofing but there need to be additional waterproofing mechanisms especially when water under hydrostatic pressure is to be resisted.
Concrete may experience cracking through which cracks water can pass when there is under induced stress on the material. Hence, whether the repellents are effective and how effective they depend on the concrete itself.
These repellents usually come in liquid form.
Crystalline admixtures
These products or systems come in dry and powdered form although can also be shipped in dissolvable, palpable bags that are thrown into concrete batch during the mixing process. They have hydrophilic characteristics and work or act by forming crystals inside of concrete and these crystals block the paths to effectively prevent the water from entering or penetrating the concrete. These products, instead of repelling water like the hydrophobic versions, will use water to form the crystals inside the concrete.
The concrete will, itself, become waterproofing and will resist water penetration from all sides. These products can be recycled at demolition and they are environment-friendly because they contain no VOCs.
These products are not as labor-intensive and expensive as the membrane-based concrete waterproofing methods. Further, the labor costs are reduced and the construction process sped up by using dissolvable palpable bags thrown into the batch during the mixing process at or off the construction site.
However, these waterproofing products or systems cannot be used on construction processes or systems in constant motion. This is because the crystals, which align in a three-dimensional array, will break when subjected to excessive movement. Waterproofing of concrete used in constructing plaza decks, roof-tops, and other areas that face recurring movements is, therefore, done using other methods.
Liquid applied membranes
These concrete waterproofing membranes can be applied on the positive side of cured concrete using a brush, squeegee, roller, trowel, and spray. However, it is possible to apply them on the negative side of cured concrete due to recent technologies. The solvent base in these products is usually a hot-or cold-applied polymeric asphalt or urethane.
They have high elastomeric properties and the success of their application will require proper thickness and uniform application. However, they require skill and experience to apply.
They also require a clean and dry substrate, which can be very challenging in construction.
You also need a protection layer before backfilling and the concrete requires to be cured properly. The curing helps to avoid problems with adhesion and blistering. It also requires a sub-slab for the case of horizontal applications.
These membrane products are, unfortunately, unable to withstand foot traffic and will be affected negatively when exposed to UV radiation. They are also toxic to the environment because they contain hazardous volatile organic compounds VOCs.
The membranes are also typically used only when prefabricated sheets do not work. However, they also work well on areas with multiple plane transitions and intricate geometric shapes and protrusions.
Sheet membrane systems
These types of concrete waterproofing products are the oldest innovation in this category and still command the concrete waterproofing market in terms of market share today. Some of the benefits over other discussed methods or products include being more durable, tough, and having a higher impact resistance.
The material comprises polymer integrated with asphalt and then attached to a polyethylene sheet. The result is an elastic material that is more viscous and less temperature-sensitive when compared to asphalt alone.
The cold-applied polymer-modified bitumen membrane sheets are self-adhering; hence there will be no need to use adhesive materials as would when using asphalt alone. Hence, they are more environment-friendly because the adhesive materials used when applying asphalt alone contain harmful toxins. Their other beneficial characteristics include a higher tensile strength, self-healing and bondability, better resistance to acidic soils, and resilience.
This does not mean that they are perfect systems. The seams on their corners, edges, and between sheets will need to be sealed, lapped, and finished. This presents an installation challenge. Additionally, voids, honeycombs, and protrusions present installation challenges for these membranes as they cannot be applied to areas with such.
Common problems concrete waterproofing can prevent
Poor waterproofing does fail with time when waterproofing is a critical element for commercial buildings and homes which must preserve their value. While waterproofing accounts only for 2-3% of s building’s total costs, defects arising from poor waterproofing can contribute 80% to all of the building defects when not attended.
Poor waterproofing results in cracks, mold issues, and concrete cancers among other structural defects. Not only can it reduce the value of the property but also cause safety issues. The building may become inhabitable due to things like molds and serious cracks and structural problems.
Further, leaks can damage furniture, carpets, and other items while concrete cancers can make the steel bars and mesh reinforcing the concrete to be exposed to air and hence to corrode. The steel may spall when it expands due to this effect. The expansion will also cause the surrounding concrete to crack. Severe waterproofing failure may result in concrete cancer.
It is important to catch and fix waterproofing issues early
These problems and failures in waterproofing may result from several issues including poor workmanship. Incorrect installation methodology, for instance, can cause leakage issues when waterproofing is damaged. It is imperative to use professionals in waterproofing areas like balconies and windows.
In selecting waterproofing products, sheet membranes require being selected with all the ancillaries. Consider how flexible the membrane is when buying because this will allow building movements. Another characteristic is the membrane’s resistance to UV, chemicals, harsh salt, and root penetrations when green applications are desired.
Other problems associated with poor workmanship in waterproofing include wrong product specifications, improper preparation before application, and insufficient preparation of the substrate. Defective plumbing can also result in leaks and other waterproofing problems.
Waterproofing failures can also result from higher floors for multilevel buildings. When rainwater puddles form on the roof of top floors, waterproofing problems can manifest.
Excessive rain collecting on top flat floors can also leak and finally damage the structure of the floor.
It is important to insist on proper maintenance where the building structures are checked for inconsistencies. It is possible, through consistent maintenance, to fix cracks, leaks, and concrete cancers before they can go too far. Maintenance can also fix leaks on windows, doors, and wall systems. You can also check drainage efficiency on floors when planning for maintenance works.
In some cases, you would require stripping and disposing of old membranes and install new ones during the maintenance practice. Using waterproofing methods that last long helps protect the environment and lower construction and maintenance costs.
