Waterproofing – What, Where and How? Application, Details, and Methodology

Samir Surlaker, MC-Bauchemie India Private Limited, Mumbai

Sunny Surlaker, MC-Bauchemie India Private Limited, Mumbai

Introduction

Waterproofing is important in protecting the structure and ensuring that the structure is usable over its entire service life. The forces exerted by water are enormous and its effects are unpredictable. Water enters the structure through the weakest route.Due to extreme requirements we put on speed, economy and construction practices, the durability of concrete is severely affected. Due to construction and/or material problems, concrete structures both above and below ground are susceptible to water ingress, due to porous structural elements. Dampness entering the living space (especially through walls and ceilings) is an indication that the concrete structure has failed its durability and that structural elements have already begun deteriorating.

Waterproofing is an art as much as it is a science and needs to be addressed as such. The main principle in waterproofing is "Keep the Outside water Out and/or Keep the Inside water In". This principle is applicable to walls, basements, roofs/terraces, R.C.C structural elements where we want to keep outside water out and to structures such as swimming pools, water tanks, bathrooms, etc. where we want to keep the water in.

The most successful waterproofing systems to date are the ones that put as many barriers as possible between the water and the structure we are attempting to protect. Again no single material can claim to be a complete waterproofing solution. The best solutions are the optimum combination of an excellent Material, Skilled Manpower to apply it, and use of the right Machinery and tools. This 3 M practice of waterproofing, is the approach we should follow because, doing a waterproofing treatment with "Predetermined" Material, Method or Manpower would more often than not lead to failures. Each waterproofing application is unique and should be treated on its merits and demerits before specifying any particular system. While designing the waterproofing system, actual service conditions should be considered for selection of the material.

That being said the following system or approach can be taken to maximize benefits of waterproofing:
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1. Provision of impermeable / waterproof concrete
2. Correct joint detailing
3. Provision of Liquid Applied or sheet membranes
4. System Detailing
5. Correct Application

Provision of Impermeable / Waterproof Concrete

With high demands on durability, the thought process should turn to preventing water ingress through the concrete, either by provision of an external membrane or by manipulating the properties of concrete itself. This method ensures that the concrete is protected against water and aggressive media and the structure is protected from failure through its design life. This approach also follows the logic that "Waterproofing can only be as good as the Base Concrete". Figure 1 shows a graphic to that effect.

For any kind of structure and especially for structural elements like foundations, slabs and shear walls,the main aim of waterproofing is to prevent the passage of water through the concrete. Quite simply this can be achieved by blocking the capillaries in concrete.

Figure 1:

Blocking pores/capillaries in the concrete can be done using the following methods:

1. Using New Generation PCE polymers
2. Use of materials like Silica-fume or Aluminosilicate slurries in concrete
3. Use of highly specialized latest generation Integral waterproofing compounds that work on process of Dynamic SynCrystallization® (DySC) technology.

Using PCE Polymers

Figure 2:

It is well-known that using PCE polymers, give excellent water reduction as compared to normal plasticizers. These materials also aid placing and compaction much more as compared to older generation admixtures (e.g. application in Self- consolidating concrete). This helps to reduce the w/c ratios and optimize cement contents, even in normal concretes. Lower the w/c ratio, lower are the number of capillaries in concrete. PCE based admixtures do not have the side effects of retardation often seen with normal retarding super-plasticizers. This is beneficial as workability time of concrete can be controlled but the setting of concrete will proceed unhindered. This ensures that any subsequent vibration to concrete after initial set will not open up capillaries, thereby rendering concrete relatively waterproof. Figure 2 shows the structure and functioning of the latest PCE Polymer molecules.

Use of Alumino silicates as Supplementary Cementitious Material in concrete

Again it is well-known that Aluminosilicates are extremely fine materials that function both as microfillers as well as pozzolanic materials that hydrate in the presence of the Calcium Hydroxide in Concrete. The combined effect of these materials as microfillers and hydrating materials help close capillaries in concrete, thereby rendering it waterproof.

Using Integral Waterproofing Compounds working by Dynamic SynCrystallization

To complete the waterproof concrete system, the last component would be to use the latest generationof Integral waterproofing compounds working on the principle of Dynamic SynCrystallization® (DySC) and Hydrophobic Pore Blocking. The ease-of-use and relative economy of this material makes it ideal to convert normal concretes to high performance waterproof concretes.

Figure 3:

Use of special latent hydraulic and pozzolanic Nanoparticles in integral waterprrofing additives cause the cement matrix to be compacted and hardened by DySC®. The strength of a cement-based material is based on the hydration of cement. The C-S-H gel so formed along with interlocked hydration crystals form a dense, impenetrable cement matrix. Specialized Nanoparticles in the additive act as additional crystallization seeds that lead to new C-S-H gel and crystal formation thus completing mineralization of the cavity structure,in presence of water. Over time the structure of the matrix becomes more refined, overall porosity decreases, micro-cracks are sealed and pore size distribution is optimised. Thus DySC® technology reduces pore content of the concrete making it water tight.

In addition to the Dynamic SynCrystallization, special additives in the integral waterproofing compounds cause a contraction of capillaries and also convert the water-absorbing capillary forces into water repellant capillary forces by hydrophobic effect. A combination of these two materials properties can ensure watertight concrete. Figure 3 shows the crystallization process under a high resolution Microscope. However, some precautions need to be addressed with waterproof concrete:

1. Requires adequate quality control
2. Even if waterproof concrete is used, joints become the weakest link in entry of water and should be adequately treated.
3. Apart from the material itself, good waterproof concrete is also subject to proper designing of mix, manufacturing, placing, compaction, finishing and curing practices and adequate care must be taken in these areas.

Good waterproof concrete is a cost-effective measure, especially for structural elements as it prevents future deterioration and repair cycles. It is recommended to characterize the material added to concrete with respect to the properties it imparts. Table 1 shows comparative testing for an integral waterproofing compound incorporating the Dynamic SynCrystallization and Hydrophobic Pore Blocking Mechanisms used at 2 percent dosage.

Correct Joint Detailing

This is one of the most important tasks in waterproofing, as Joints are normally the weakest link in a system that water tends to breach easily. Some of the methods available today include swellable water-stops, injection hoses, high-performace PU and acylic resin injection systems. Based on actual site conditions, one or a combination of systems can be used to best advantage. A wide range of available flexible cementitious membrane systems and joint tapes can also supplement these systems. Finally maximum number of barriers we can put between water and structure, higher the rate of success in waterproofing systems.

Provision of Liquid Applied or Sheet Membranes and Detailing

After the waterproof concrete and joint detailing, the next step incorporates use of 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 either by capillary action or hydrostatic pressures.

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, some points to remember in use of Liquid Applied Membranes are:

1. The surface applied barrier materials are no substitute to joint sealants, which are to be applied in the third dimension.
2. The performance of barrier materials for waterproofing and damp proofing should also be checked for exposure to aggressive soil contaminants.
3. 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.

Since several options are available, the choice of waterproofing material should be carefully evaluated. Built up bituminous or polymer waterproofing membranes were very popular few years back and they were bonded to the surface either by self-adhesion, cold application or heat welding. Major difficulty in the application of bituminous or polymeric bituminous membranes was the geometry of the structure as well as overlapping joints and moisture sensitive adhesives. These joints act as avenues for water-entry rendering the system ineffective. Some other limitations are UV resistance, breathability, less easy application as well as excessive detailing.

Liquid applied membranes became more popular in the last decade on account of their ease of application and mouldability to form seamless membranes over any curvature. Polymer modified bituminous emulsions with low VOCs are popular for basement waterproofing especially in aggressive soil conditions. Liquid applied membrane should be of breathable type able to avoid blisters and craters with an eventually effect 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 environmental-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.

Figure 4:	Figure 5:

The main point to remember while using a liquid applied membrane is the detailing of joints, waterstops and interfaces (covings) between horizontal and vertical surfaces. Figures 4, 5 and 6 show waterproofing details for different applications.

Some Additional properties of Liquid applied Membrane Forming Systems include:

• Crack bridging
• Thermal resistance
• Water tightness
• Easy application to both dry and moist surfaces
• Good bonding to the substrate
• Resistant to aggressive waters

Application

The success of waterproofing system depends not only on the materials alone, but also more on application and understanding limitations of the materials in question. Rather than asking for Guarantees from applicators, which has not stopped failures, the adherence to Quality Assurance systems should be reverted to.

Figure 6:

Guarantees can only be asked from bonafide, qualified and authorized applicators. There are quasi-governmental institutions abroad, e.g. BZB in Germany, which issues IRP certificates to trained, qualified applicators. Such qualifications should form a part of specifications. Technical Prequalification of the applicator, followed by referrals and successful application works executed should form part of specification.

Since Construction Chemical Companies are the experts in materials, specifiers and owners should work with all parties involved (Material Manufacturers, Applicators, Machinery Providers, Site Managers) to finalize waterproofing systems. Finally, we have to take the approach of "Do it once, Do it Right" when it comes to waterproofing.

Conclusion

Today's specifier or constructor has innumerable materials at his disposal, each claiming to be the best. Most of these materials are submitted by its generic properties. Unfortunately our existing codes of practice only focus on testing the properties of materials. These tests are suitable for Quality Control to produce batch certificates, but do not address the waterproofing system as a whole. The best waterproofing system is made of Good Base, Good Material, and Good Application. The waterproofing system is susceptible to failure, if either of the elements as mentioned above is defective

Finally, it is the best practices to be followed in construction, which will ensure that the longevity of the structure is maintained and the structure is cost effective over its design life.{/akeebasubs}

NBMCW April 2013