Waterproofing: The need and importance:
Waterproofing is a very common word used in day to day life. Most of us know and understand the pain of leaking roofs, walls, and bathrooms. The damage done by such leakage is not only limited to aesthetics but many times compromises the safety of users and inhabitants. Dampness on interiors may lead to many issues like fungus growth, foul order, and spalling of plasterwork. Water ingress may result in damage to electrical fittings, potentially exposing people to various hazards such as fire and electrical shock.
Why does concrete require protection? The simple reasons are the porosity, cracks, and potential to react with atmospheric gases such as CO2. Apart from that, the structures have various joints and connections which need to be considered and given extra protection.
Some important areas for providing waterproofing are basements, exterior walls, and roof.
Integral approach:
It is very clear that waterproofing is not just about the single system or section of construction. Careful analyses need to be done to understand and design the waterproofing system, which will take care of the entire building envelope. The integral approach considers all materials, sections, and factors such as the environment, final use, and critical areas. This approach begins at the stage of conceptualization of a project. There are various places and sources from where water can enter a structure. This could be groundwater (which depends on the water table), rainwater, and water associated with damp areas, and plumbing works. Various products and systems such as sheet membranes, liquid waterproof coating, crystalline systems, water repellants, and integral waterproofing agents are available in the market.
Types of system available:
A number of systems are available for waterproofing of the complete building envelope as well as infrastructure. Each system has its own advantages and disadvantages. Table 1, shows some of these systems.
Liquid applied to waterproof
The term means, any system applied in a liquid state and then transforms to a solid-state or integrates itself to effectively waterproof the application area. This mainly includes flexible cementitious slurries, acrylic, EVA or SBR based elastomeric coatings, Polyurea, Polyaspartic, Polyurethane, Hybrids, thermoplastic acrylates, epoxy-based coatings, and membranes, etc.
Crystalline and penetrating treatments are also applied in liquid form but their action is not through sealing but through penetration into the concrete and reaction with hydration products.
The effectiveness of each system depends on application methods, substrate conditions, exposure/usage conditions, thickness applied, and subsequent maintenance. Differentiation can be made depending on the following factors,
1. Whether applied Internally or Externally
2. Covered or Exposed
3. Contact of water is continuous or intermittent
4. Trafficked or Non-Trafficked
5. Exposure to other chemicals except for water and CO2
6. Access to the area in the future, if re-application or repair is necessary
7. Underground (Below Grade) or above ground (Above Grade)
8. Expected Movements
9. Primary or Secondary system
10. Other specific requirements as per user needs or Exposure conditions.
Some standards & specifications:
Some of the standards used to test and evaluate the performance of waterproofing systems are mentioned in table 2.
There are more standards and a lot of effective test methods to verify and ensure that the waterproofing product being used would serve its purpose and last for the specified lifetime.
For elastomeric coatings following properties assume utmost importance,
1. Tensile Strength, Elongation and recovery after extension. (ASTM D 638)
2. Crack bridging ability (ASTM C 1305)
3. Tear Strength (ASTM D 624)
4. Adhesion in wet and dry conditions (ASTM D 7234, 719 & 794)
5. Water vapor Permeability (ASTM E 96 )
6. UV Resistance (ASTM D 4587, 5894, 6695)
Application Procedures
As for any coating or liquid applied system, surface preparation holds the key. Proper surface preparation will ensure good adhesion, uniformity of coating thickness, proper curing or drying, as well as the development of performance properties such as tensile, tear strength, and hardness.
Some systems require a primer, some are self-priming, whether to use the primer or not always remains a tricky question. As a general rule, all smooth surfaces such as glass and metal require a primer. Surface with poor strength and high porosity would also need priming/sealing. Various primer systems including epoxy, moisture curing PU, silane / Siloxane based primers, and latex-based products are widely available in the market. Proper primer shall be decided from the manufacturer's literature and project specifications.
Application methods may vary from brush application to multi-component spraying. Uniformity and proper thickness will only be achieved, with the use of suitable equipment and method. After application, care has to be taken to protect the application area, until the applied product dries completely. In traffic areas, the traffic shall only be allowed after the applied product cures to attain minimum performance criteria
