Waterproofing – The Quality Factor, Materials and Detailing

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Waterproofing is a basic requirement for all types of structures irrespective of the fact whether they are residential, commercial or industrial buildings. The simplest definition of waterproofing is to:

1. Keep the unwanted water out of dry living areas (living rooms, basements, bedrooms, terraces, walls, etc.) and
2. Keep the water inside the wet areas (bathrooms, kitchens, water tanks, swimming pools, sanitary areas, etc.

In fact the word waterproofing should be used with limitations as it is practically not possible to remove all water out of concrete and it is advisable to have some quantities of water in the concrete for continued hydration in one form or other. In fact most of the cases of waterproofing we refer to are of dampproofing.

Implications of Water Entering the Living Areas

It is essential to note that the passage of water through the structure not only results in peeling of plaster or paints but it has wider implications. The passage of water through concrete leads to corrosion of the embedded reinforcement leading to the structural failures. In addition, the water can carry with it chlorides and sulphates accelerating the deterioration. The ingress of water in the water tanks, etc. can give rise to health hazards on account of microbial pollutions. The dampness can decay the wood in the buildings. Lack of waterproofing or improper treatments not only pose health hazards, but also have a lasting implication on the durability, structural stability and sustainability of the constructed structures. An early treatment will not only provide longevity to the structures but will also save the financial resources.

The Steps

Basically there are two types of waterproofing depending upon the time of application, i.e., either new waterproofing or repairs of old waterproofing. Once again the treatments can be carried out at two stages, i.e., while concreting by use of integral waterproofing compounds or surface coatings after the concrete is hardened. All waterproofing treatments should consider knowing the client's requirements, investigation, diagnosis, design and specifications for waterproofing system, selection of materials, application, supervision and maintenance. These stages are important and negligence at any step mentioned above can lead to the failure of the waterproofing treatment.

Most of the failures are due to the combination in errors at different stages. In all the above stages the human factor is involved and therefore it would be worthwhile to have third party supervision to ensure proper application of the materials in conformity with the specification laid down.

While making the specifications, the properties of materials should be given due weightage and alternatives should be provided for encouraging the use of materials of new technology. The final evaluation of contractor should not only depend upon the lowest quotation but also factors like expertise, technical ability and integrity of the contractor.

The Materials and Detailing

When any concrete structure is constructed, we are certain about the materials of construction, viz., cement, aggregates, sand, water and the reinforcement. But when it comes to the waterproofing, there are several materials from which the choice is to be made. This is due to the fact that the process of waterproofing is quite complicated and the system of waterproofing has to withstand different parameters, which differ from case to case. It is evident that the waterproofing system cannot be better than the materials used.

While selecting the materials for waterproofing systems one has to consider several conditions at the site jointly and individually. The materials for waterproofing in effect should have properties like water-tightness, flexibility, crack-bridging ability, bonding strength, breathability, resistance to UV radiations, microbial attacks, fungus growth, mechanical stresses, insulation characteristics and above all the cost effectiveness.

However, it is clear that it is quite difficult to have all the above properties in one material and therefore a judicious combination of materials has to be used to suit individual requirements. Faced with several proprietary formulations the engineer may get confused, but one should exercise caution before final selection. The selection will be easier if the decision maker knows the limitations rather than the advantages, of individual materials. Some of these materials and their properties are discussed in this section.

Integral Waterproofing Compounds working by Dynamic SynCrystallization

Use of special latent hydraulic and pozzolanic Nanoparticles in Specialized Integral Waterproofing additives causes the cement matrix to be compacted and hardened by a process called Dynamic SynCrystallization® (DySC®).

Testing showed that the selected nano-pozzolan reacts with the free lime in concrete, to form a very dense, foil-like Calcium Silicate Hydrate (C-S-H phase) or Calcium Alumino-Silicate Hydrate (C-A-S-H). These phases are much denser than the C-S-H phases formed due to hydration of normal OPC. This dense C-S-H and C-A-S-H phase formation also strengthens the transition zone between the cement matrix and inert aggregates. It leads to formation of concrete structure, more resistant to aggressive media and water. In addition, this type of nano-pozzolan has a much higher reactivity with free lime in the concrete's cement matrix. Testing showed that 1g of the nano-pozzolan reacts with over 1000mg of free lime to form dense C-S-H and C-A-S-H phases. Thus DySC® technology reduces pore content of the concrete making it water tight. In addition to the DySC®, special additives in the integral waterproofing compounds cause a contraction of capillaries and hydro-phobise open capillaries in the concrete. A combination of these material properties can ensure watertight concrete.

Secondary Barriers using Integral Additives

Special integral waterproofing additives should be incorporated into the mortars during masonry laying, or selected pre-bagged waterproof mortars can be used. When used in conjunction with good quality concrete blocks, this system would provide excellent watertightness. Special consideration and care should be given to interface of masonry and RCC elements. These interfaces can be sealed with high quality polymer mortar and the edges treated with good quality, Flexible Coatings or PU based joint sealants. The last barrier is the plaster, which is also a porous medium and allows water ingress. The best possible solution here is to use an integral waterproofing additive in the plaster for secondary protection.

Liquid Applied Membranes

After using waterproof concrete, waterproof mortars and plasters, the final stand against water would be a physical barrier to ensure the water does not enter the building envelope and deteriorate structural or cosmetic elements. The main function of these barriers is to arrest the passage of water through the body of concrete.

Physical Waterproofing barriers can be of preformed membranes or they can be liquid applied membranes. Whilst having many advantages, preformed membranes have the inherent limitations such as overlapping joints and the difficulty of application across change in geometry of the structure. Liquid Applied Membranes help in overcoming these limitations. However, detailing of waterproofing coats is of utmost importance. The waterproofing materials should as far as possible provide a seamless membrane across the entire building envelope surface.

Liquid applied membranes are more advantageous on account of their ease of application and mouldability to form seamless membranes over any curvature. Liquid applied membrane should be of breathable type capable to avoid blisters and craters which can eventually affect the barrier performance. These membranes have crack bridging properties in addition to adaptability to complex geometric shapes. These systems are compatible with moist surfaces. These materials are environment–friendly, free from solvents and harmful chemicals, all the essentials needed for today's green buildings. These products are also easy to apply, can be hand applied and require little or no mixing, making it perfectly suitable for applications in difficult, space-limited sites.

Some Liquid Applied Membranes available, incorporating the latest technology are:

1. Polymer Modified Rigid Crystalli- zation Based Coatings
2. Polymer Modified Flexible Coatings
3. Liquid Applied Bituminous Membra- nes
4. Coatings for extreme exposures like pH 3.5 to 14
5. Thin Layer Anti-Carbonation, Water- proof Coating Systems

In addition to membranes, in wet areas it is imperative we use additional barriers like waterproof tile adhesives. A detail incorporating this waterproof tile adhesive of course prevents water from entering the bathroom space, but also proves effective in stopping passage of water through the walls into the living space. In the long run, this approach provides much more efficiency over the sand-bed cement slurry method. Of course, the tile grouts, especially around room edges and around fittings should be polymer modified ones (not only white cement) to provide a better seal against water. This detail is shown in Figures ____.

Waterproofing as System

It is a myth that waterproofing treatment can be carried out by application of single material on new or existing treatments. Most of the failures in the waterproofing treatments are on account of this misconception. The only way to assure reliable treatment is by considering the waterproofing treatment as a system. System for waterproofing can be defined as combination of materials, preparation of specifications, application technique designed by taking into considerations the requirement of the client or home owner, which would provide efficient, reliable and long term protection to concrete structures with minimum maintenance costs and operations. The system should be so designed as to provide waterproofing and damp-proofing to the structure under worst set of conditions and combinations thereof by taking into consideration not only the present stress conditions but also conditions that may arise in near future as per the basic principles of civil engineering and chemistry.

Quality Assurance

It is a common practice in the field of waterproofing to ask the guarantees and equally common for the contractors to give the same. If one thinks conceptually about the whole matter, whether asking and giving guarantees have prevented the failures? The answer would be in negative rather this concept has introduced more sub standard contractors, who gain the contracts by virtue of giving guarantees to satisfy the homeowners leading to more failures. It is a common knowledge that guarantees are given and not always honored.

Also the tendencies to spend minimum amount on waterproofing have led many a genuine contractors to lower the quality of waterproofing involuntarily to fit a given system in the home owners' budget and to secure the contract. A better approach would definitely be to have quality assurance system for waterproofing in the interest of both the owner as well as the contractor. The quality assurance system can create a trust between the homeowners, architects, engineers and the contractors to achieve a common goal of quality waterproofing treatment. The applications are to be carried out by skilled craftsmen knowing to apply the materials of new knowhow and final testing of the system as required by client. It is the quality assurance system and not the guarantees that can ensure a satisfactory waterproofing treatment.

Conclusion

Concrete structures are popular on account of their economy. The economy is derived from the long life considerations that are of the durability. It has been proved beyond doubt that the durability is a direct function of permeability of concrete. The aim of waterproofing or dampproofing should be to prevent or retard the ingress of water into the body of concrete, so that the structure remains safe from deteriorating influences.

Before assigning the job of waterproofing to any party, the engineer concerned or the homeowner should establish the parameters and the reasons for such waterproofing. It should be clearly understood that the cost of waterproofing is not only the initial capital cost but also recurring maintenance cost. It is a myth that waterproofing or dampproofing systems are permanent and maintenance free.

A waterproofing system should be chosen, in which the maintenance costs even after guarantee period are of minor nature. Waterproofing requires sound knowledge of civil engineering as well as chemistry. Therefore the advice of an expert is always beneficial. It is only through timely and proper waterproofing the house owner can be assured that the property is protected and shall withstand all the conditions up to the designed life. Quality waterproofing assures the durability of the structures.