Concrete Waterproofing Basic Guide
Concrete by itself is not waterproof in nature, it is porous. Water
seepage through concrete may cause damage to the construction leading to
money losses, besides other inconveniences. Thus, waterproofing the
concrete is a must.
This is a construction material composed of cement, water, aggregates, reinforcing materials, chemical and mineral admixtures. The aggregates include sand and gravel, while the reinforcing material is mostly the metal bars. Glass and plastic fibers can also be used as reinforcements. Chemical admixtures add special characteristics to the plain concrete. Mineral admixtures are added to the concrete to improve its strength. These can also be used as a replacement to Portland cement present in the concrete. Let us find more about the water proofing systems and related concepts.
The two important systems in these are Integral Waterproofing System and the other that uses membranes. Hydrophilic system and hydrophobic system are the subtypes of the Integral Waterproofing System. Among different hydrophilic waterproofing systems, crystalline technology is the most popular one. In this method, the water present in concrete is converted into insoluble crystals. Some hydrophilic waterproofing products make use of a property called hydraulic swelling. Here, the waterproofing material swells as it absorbs water, eventually filling pore spaces present in the concrete. In the hydrophobic system, externally applied products viz. coatings, membranes, etc, are used as a protection against water.
Waterproofing membranes are either liquid or sheet membranes. The liquid membranes are sprayed on the concrete, forming a rubber-like coating about 60 mm thick on the concrete surface. Quick application and low pricing are its major advantages. The sheet membranes are prepared from asphalt. These membranes are laminated to polythene films and the sheets thus formed are then pasted onto the concrete. The sheets are consistent in thickness. Excellent waterproofing can be provided to foundation walls, parking lots, tunnels, etc, using these sheet membranes. As the sheets need to be manually pasted, it raises the labor cost which proves to be its main disadvantage.
Unlike the hydrophobic membranes, 'hydrophobic concrete' is totally a different and innovative concept. Instead of applying any external agent to the concrete for waterproofing, here the concrete itself is manufactured waterproof. The concrete is made hydrophobic by adding admixtures to it at the time of production. These admixtures stop capillary action occurring in the concrete, thereby making it waterproof. This kind of concrete has been successfully used in Asia, Europe and Australia. It has also proved to be a boon for construction teams, since it allows construction to carry on even in the rains.
Let's see how this technology can be used as an option to Integral Waterproofing System. First of all, the concrete which has to be waterproofed is saturated with water and then a low density solution is applied, followed by the crystalline waterproofing material, which is a high density solution. After this, the chemical diffusion process starts. The high density crystalline waterproofing solution seeps inside the concrete and travels towards the low density solution until an equilibrium is attained. Since water is applied to the concrete, cement hydration occurs. This hydrated cement now reacts with the crystalline material to form crystals inside the concrete. The diffusion process may take this crystalline waterproofing 12 inches inside the wall. This waterproofing is highly efficient, because crystals that are formed within the concrete remain protected from any kind of external damage. Resistance to 130 degree heat in a constant state is another advantage of this kind of waterproofing. It also resists chemical reactions like carbonation - which reduces alkalinity and damages the concrete. It stops chloride ion diffusion in the wall, protecting the steel present in the concrete from oxidation and also expansion.
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ABOUT THE AUTHOR
Graeme Stephens has been running the largest owned carpet cleaning company
in new Zealand for 24 years. IICRC qualified "master restoration technician"