Various permutations and combinations in specifications can avoid such problems; for example, the following options for waterproofing can be considered:
- Give a water-impermeable coating on the finished surface of IPS – Though this method can prove effective on a short-term basis, it may subsequently create problems. It is observed that the coatings based on pure solvent-based polymers, though effective, do not function for a more significant duration due to their requirement for a thoroughly clean and dry surface.
From an economic point of view, these coatings are relatively expensive and, basically being a costly commodity, cannot be given in a more considerable thickness.
These coatings also need to be taken care of for the abuse of UV rays, which involves improvising the formulations knowledgeably with proper UV-absorbent chemical inputs.
2. To take care of the above shortcomings, polymeric cementitious coatings have been preferred worldwide. These systems have better adhesion to the surfaces and can tolerate, to an extent, deficiency of the character, like slight wetness and micro dusting, etc.
These coatings are also 8 to 10 times thicker than pure polymer coatings. However, in this type also, one needs to select the polymer judiciously so that the UV interaction and disintegration due to the same can be avoided.
Though the systems based on the comatrix of polymer and cement are preferred due to their composite properties like adhesion, waterproofing, flexibility, resistance to UV rays, and improved resistance to wear and tear, a discerning specifier has to bear in mind that, after all this system is a film. It is quite possible that the coating itself can get damaged due to any physical damage to the concrete surface underneath the layer.
However, by and large, for inaccessible RCC slabs or terraces above, treatment is proved to be very useful and practical even in high rainfall areas like coastal regions or mountain ranges.
3. Another practical approach is incorporating these water-based polymers into the IPS. This increases the water impermeability of the IPS and, simultaneously, decreases the extent of shrinkage cracks due to an increase in the flexural strength of the matrix.
Additionally, using polymers in cement concrete/ mortar increases the adhesion of the concrete mortar to the surface. This integral addition of polymer in mortar is handy and beneficial for any high-rise structure if applied in the form of plaster, particularly the fact that it becomes difficult for any engineer, either from the client’s side or from the contractor’s side, to supervise the work effectively on the floors beyond 3rd or 4th floor.
Various researchers, including the authors, have experimentally checked the permeability of polymer-modified mortars. The studies have revealed that at approximately 4 percent dosage of polymer to cement, a substantial reduction in permeability is observed.
Though on a long-term basis, incorporating polymer in concrete/mortar is very useful to the structures from a waterproofing point of view or even otherwise, there is also an essential role of economics, which comes into play.
Since polymer consumption in the earlier case of waterproofing, the film is to be considered only on the surface spread basis. Comparatively, the cost per unit will be substantially less in a small thickness.
However, when the polymer is to be dispersed throughout the mass of concrete/mortar, then depending on thickness, the consumption of polymer substantially increases, adding to the cost.
But the fact should not be overlooked that the addition of polymer throughout the mass of concrete/mortar adds to the durability of the structure due to a substantial increase in impermeability, adhesion, and flexural strength (i.e., decrease in shrinkage cracks) and adds resistance to aggressive in-service attacks by environmental pollutants or even carbonation. Once again, the prevailing wisdom will decide the course of selection of the option.
4. Looking at the cost and benefit ratio, another method is gaining ground and acceptance with the consultants and clients. This method applies the polymer cementitious comatrix film to the existing RCC slab or the mother surface.
This application is made so that no pinholes or holidays are left on the surface. This layer is tested for impermeability by ponding test and then is sandwiched by completing subsequent brickbat Coba or the IPS as the case may be.
In this option, even if the IPS develops cracks due to shrinkage etc. (which can be minimized by adding anti-shrinkage compounds and good curing) and the water percolates through the section, it will be stopped at the polymeric cementitious film which is applied on the bare slab. In this case, though the water is effectively controlled, the cost would not unduly increase, as the polymer demand will be only for the film formation.
Moreover, the film is not likely to get damaged due to wear and tear as the same is sandwiched between two vital phases. RCC slab and subsequent BB coba and IPS.
In our opinion and experience, this method is more acceptable due to its cost and effectiveness in fulfilling the requirement of healthy and durable structures.
All four options illustrated above can be applied to waterproof toilets, baths, swimming pools, flowerbeds, overhead and underground tanks, etc.
Related parts of the article.
- Waterproofing for healthy structures.
- Waterproofing of the structures
- Mechanism of the waterproofing
About author
Dr. S. K. Manjrekar (Ph.D. Bombay University – 1977), Dr. S. K. Manjrekar is Chairman and Managing Director of a well-known construction chemicals company in India – M/s. Sunanda Speciality Coatings Pvt. Ltd., for the last 40 years. Operations in UAE, Oman, Nepal, Tanzania, and the USA.
He is actively working on several technical and administrative committees of the American Concrete Institute (ACI) in the USA.
He teaches ACI concrete field testing courses to engineers in India as a ‘Train the Trainer’ initiative.
He has published more than 200 papers in various national and international journals.
He has given over 100 keynote lectures on concrete, corrosion prevention, waterproofing, nanomaterials, etc.
Lectured extensively internationally in Countries – United Kingdom – London, Leeds University, United States of America – Pittsburgh, Malaysia, Oman, Dubai, Sharjah, Kuwait, Romania, Hong Kong – Hong Kong University, and many more as an invited keynote speaker.
He is the guest editor of International journals in the UK, USA, and Mexico.
