The general subject of structural damp proofing and waterproofing as it confronts us today involves the methods and means of protecting structural materials against the disintegrating action of water. Masonry building materials are generally more or less porous and capillary in their structure, permitting the absorption and permeation of water. The presence of water in masonry is structurally injurious, due to its solvent action on any soluble content, but more particularly its disintegrating action by the expansive force that is manifested by the congealing of the water on freezing.
Water that is drawn into foundations from the surrounding soil gradually ascends into the structure, due to the capillary nature of the constructive materials, and finally permeates the entire wall, producing damp and clammy conditions that foster and spread disease. While the subject of structural waterproofing and damp proofing deals primarily with the prevention of gradual decay and disintegration of structural materials, it also performs the useful and necessary function of providing more hygienic conditions for the benefit of humanity in general.
These are few of the most commonly use system of waterproofing in the construction industry. They are :
1. Cementitious waterproofing
Cementitious waterproofing is often used in the internal wet areas such as toilets. Most of the time the type of cementitious waterproofing is semi-flexible, some even toward rigid type. It is still good to use because internal toilets are not exposed to sunlight and weathering and so it do not go through the contraction and expansion process continuously. The most used technique is Polymer coating with glass fiber mesh encapsulated in between. Due to the flexibility of the acrylic polymer and bonding of the glass fiber, cracking is limited and forms a successful water barrier.
2. Liquid waterproofing membrane
Liquid membrane is a thin coating which consists of usually a primer coat and two coats of top coats. It offers more flexibility than the cementitious types of waterproofing. The elongation properties of the coating can reach as high as 280%. But the durability of the waterproofing coating also depend on what type of polymer the manufacturer use for the making of the liquid waterproofing.
3. Bituminous coating
Bituminous waterproofing coating is made of bitumen based materials and it is not suitable for expose to sunlight. It becomes very brittle and fragile when long exposure to the sunlight unless it is modified with more flexible material such as polyurethane or acrylic based polymers. The flexibility of the finished products always depends on the solid content of the polymer added to the bitumen.
4. Bituminous membrane
Bituminous waterproofing membrane have torch on membrane and self adhesive membrane. Torch on membrane is the more preferred one use because of its shelf life and ease of use during application. APP Membrane is a widely used product and has been successful in variety of areas of application.
The self adhesive type must be use fast as the bonding properties of the membrane is reducing through time. Very often applicators find the self adhesion membrane already lose its bonding properties when they want to apply. Therefore, they have to use one additional primer to prevent the de-bonding problem in the near future.
Torch on membrane have exposed and covered types. Exposed membrane often has mineral granular aggregate to withstand the wear and tear of the weathering and the other types of membrane, contractor need to apply one protective screed to prevent the puncture of the membrane.
But one has to be very careful when applying the protective screed which is often cement mortar. The cement ratio has to be high and the mixing has to be thorough throughout the process. There are ready-mixed types of cement mortar in the market available for use for better quality and consistency. Site mix usually will compensate the quality of the finish work but the cost is always cheaper compared to premixed mortar.
5. Polyurethane liquid membrane
Polyurethane is also use for the flat roof area and exposed to weathering but it is expensive. It can offer higher flexibility. Polyurethane is very sensitive to moisture content present, therefore before application; one has to be very careful evaluating the moisture content of the concrete slab. Otherwise peeling or de-bonding easily observed after some time.
6. Injection Grouting
Injection grouting is a very important aspect in waterproofing of structures. Nozzles are placed into concrete construction joints and other weak areas which are susceptible to allow water ingress. There are different types of grouts for different purposes.
a.
Cement Slurry with Non-shrink Grout: This is the most basic and widely used grout which is economical and removes honeycombing and patches the weak areas in concrete.
b.
Polyurethane Grout: These are low viscosity, high density, rapid setting grouts which form a gel upon interaction with water, thereby eliminating seepage. These are used for areas having failed to sustain the water inflow and need immediate action.
C.
Epoxy Grout: These are low viscosity, high strength grouts used to impart strength to areas of application.
8. Drainage systems with geo-textile
For garden and landscape areas, the provision of drainage media is quite important to maintain longevity of the system. The drain boards/cells are used with geo-textile which filters the water and sustains the framework. There is a wide variety of drainage boards/cells or different technical requirements.
9. Loosely Laid Membranes
Nowadays there are engineered membranes which are being used for structural waterproofing. PVC and TPO are two widely used types.PVC waterproofing has been specified for many major projects. The membrane is welded using specialized equipment.
10. Crystalline Waterproofing
The crystalline system is a brush/spray applied waterproofing which penetrates into the cracks, micro-cracks and capillary tracts of the concrete through osmosis, Brownian movement and dry particle reactions. The crystalline active ingredients react with concrete minerals to form insoluble crystals, which fill out cracks, pores and voids up to a width of 400 microns. This crystalline growth takes place deep inside the concrete structure up to nearly 1 meter from the point of application. Water molecules (and a wide range of chemicals) now can no longer pass through the concrete. However, air can still pass, allowing the concrete to breathe. This avoids the build-up of vapour pressure. In the absence of further moisture, the crystalline components lie dormant. Should moisture recur at any time, the sealing process resumes automatically and advances deeper into the concrete.
These are a few types of waterproofing systems which are being widely used in the construction industry at present.
Areas of Application:
1. Foundation
2. Basement
3. Toilet and AHU
4. Construction and Expansion joint
5. Terrace and balcony
6. Swimming Pool
7. Water Retaining structures
8. Drain channels etc.