 "Adding a touch of modernity to waterproofing for leak-proof results")
The construction industry has witness a sea change over the years with the adoption of new techniques and increased use of new materials of construction. These modifications have been triggered by changes in demand from customers and rise in urbanisation in the country. Following the alterations in construction methodologies, waterproof solution providers have also adopted modern techniques for enhanced results.
In the first part of this two-part series, we examined conventional waterproofing systems and offered tips to use them for optimum effect. Here, we will examine various modern waterproofing systems & their advantages, and also precautions to be taken for better waterproofing results.
Modern techniques in waterproofing
Modern waterproofing technique aims to understand the functional behaviour of the structure, understand the properties of the available materials arrive at a system, which is best suited for the structure and incorporate the system at the design stage only.
A single product or technique is not usually enough, involvement of various bodies and techniques in coordination is essential for making structures waterproof. For success of any system the building structure should have sufficient and efficient control joints if the slabs dimensions are more than twenty meter in any direction.
Control joints are structural engineering design features. These joints are supposed to be designed and their configuration marked on the drawings and their detailing needs to be given with respect to waterproofing system proposed in large buildings. Different types of control joints are construction joints or day joint, crack inducer joint, contraction joint and expansion joint. Coefficient of thermal expansion of concrete is between 6 to 10 X 10-6 mm/mm/oC. If proper control joints are not provided in large slabs, no waterproofing system works. Modern technique relies basically on two main waterproofing systems, which are fool proof and simple. They are crystalline waterproofing system, and flexible membrane water proofing system.
Crystalline waterproofing system
This system involves blocking the water bearing capillaries with insoluble crystals. This method is used for waterproofing water-retaining structures like overhead/underground water tanks, sunk slabs of bathrooms and toilets, swimming pools, basements, terrace gardens etc. The main product in this system is a grey or brown looking powder.
The method of treatment involves saturating with water the surface to be treated. Then mixing two and half volume of the powder with one volume of water to form neat consistency hot slurry. This slurry is brush applied on the saturated surface. The active ingredients in the slurry pass through the water bearing capillaries and react with calcium oxide in the concrete to form insoluble crystals, which effectively block the capillaries.
Further the chemical ingredients of the product remain in concrete to reactivate the process of crystallisation as and when a new capillary is developed. This system of water proofing the water retaining structures is practiced in all the developed countries. Typical specification for this type of system is as follows:
Flexible membrane waterproofing system
The main product used in this system comprises of two components one liquid and the other is a powder packed roughly in the proportion of 1:4 by weight. The liquid component is an acrylic emulsion and the powder component is a polymer-modified cement with film forming chemicals and fillers, and some manufacturers add reinforcing fibres to make the product extra effective.
When these two ingredients namely the pre-weighed powder and the liquid are mixed together an uniform slurry results. This slurry is brush applied on the roof surface, which upon drying forms a flexible film. Since there is cement in this product its compatibility with concrete is excellent. The film further allows the breathing of the concrete without any hindrance hence there is no problems of its de-lamination from the concrete surface.
This film being flexible takes care of the deflections in the slab and the movements caused because of primary or secondary settlements, movements due to wind loads and temperature stresses developed in the concrete. This system can be used on surfaces, which had bituminous treatment earlier. In European countries, this type of product is used as coating on pre-stressed concrete bridge girders to protect them from aggressive chemical atmosphere.
A typical waterproofing specification using flexible membrane system will be as follows:
Reasons for waterproofing system failure
Application of a waterproofing product in non-specified areas, such as, using a crystalline waterproofing system in waterproofing the terrace or using a flexible membrane system in the water tank results in failures even though the products themselves may be genuine.
Stretching the coverage of the products beyond the specified limits by the manufacturer results in inefficiency of the product and hence a failure.
Precautions to be taken
For optimum effect of waterproofing system, following measures should be taken:
Keep it leak-proof
Generally, architects in India, do not specify in depth waterproofing details and leave this aspect generally to ignorant client to choose whatever system he likes, and many structural designers give least importance to the control joints. As a result of this many systems have failed in several prestigious buildings and the blame went to waterproofing contractors or the product manufacturer.
There is a need for the architects and the structural designers to understand the various systems available and specify them clearly and in sufficient detail, taking into consideration the in-service conditions of the structure.
The client should also insist on the architect to provide waterproofing design details in advance so that no ambiguity remains till the end. This would give enough time in selecting the specified material.
____________________________________________________________________________________________________
M A Waheed is the Director of Perma Construction Aids Pvt Ltd, www.permaindia.net
For details, contact at info@permaindia.com
In the first part of this two-part series, we examined conventional waterproofing systems and offered tips to use them for optimum effect. Here, we will examine various modern waterproofing systems & their advantages, and also precautions to be taken for better waterproofing results.
Modern techniques in waterproofing
Modern waterproofing technique aims to understand the functional behaviour of the structure, understand the properties of the available materials arrive at a system, which is best suited for the structure and incorporate the system at the design stage only.
A single product or technique is not usually enough, involvement of various bodies and techniques in coordination is essential for making structures waterproof. For success of any system the building structure should have sufficient and efficient control joints if the slabs dimensions are more than twenty meter in any direction.
Control joints are structural engineering design features. These joints are supposed to be designed and their configuration marked on the drawings and their detailing needs to be given with respect to waterproofing system proposed in large buildings. Different types of control joints are construction joints or day joint, crack inducer joint, contraction joint and expansion joint. Coefficient of thermal expansion of concrete is between 6 to 10 X 10-6 mm/mm/oC. If proper control joints are not provided in large slabs, no waterproofing system works. Modern technique relies basically on two main waterproofing systems, which are fool proof and simple. They are crystalline waterproofing system, and flexible membrane water proofing system.
Crystalline waterproofing system
This system involves blocking the water bearing capillaries with insoluble crystals. This method is used for waterproofing water-retaining structures like overhead/underground water tanks, sunk slabs of bathrooms and toilets, swimming pools, basements, terrace gardens etc. The main product in this system is a grey or brown looking powder.
The method of treatment involves saturating with water the surface to be treated. Then mixing two and half volume of the powder with one volume of water to form neat consistency hot slurry. This slurry is brush applied on the saturated surface. The active ingredients in the slurry pass through the water bearing capillaries and react with calcium oxide in the concrete to form insoluble crystals, which effectively block the capillaries.
Further the chemical ingredients of the product remain in concrete to reactivate the process of crystallisation as and when a new capillary is developed. This system of water proofing the water retaining structures is practiced in all the developed countries. Typical specification for this type of system is as follows:
- Clean the surface to remove all loose particles, grease shuttering oil and such deleterious materials to get a sound concrete surface.
- Cracks if any should be cut into ‘V’ shaped grooves one inch wide and one inch in depth. Cut honey combed areas back to sound concrete.
- Repair these areas first by priming with crystalline waterproofing slurry and then by filling them with crystalline modified mortar produced by mixing crystalline waterproofing powder OPC and zone II sand in the proportion of 1:1:4 and water enough to produce a stiff consistence paste. Allow the repair mortar to dry.
- Thoroughly sprinkle water on the area to be treated till the surface becomes saturated. Some recommend overnight ponding for effective results
- Prepare crystalline waterproofing slurry by mixing the powder and water in the proportion of two and half volume of powder to one volume of water to form a hot slurry. Brush apply this slurry on the water saturated surface in two coats.
- When the second coat is still wet plaster the surface with 1:4 cement sand mortar admixed with an integral waterproofing compound and cure normally.
Flexible membrane waterproofing system
The main product used in this system comprises of two components one liquid and the other is a powder packed roughly in the proportion of 1:4 by weight. The liquid component is an acrylic emulsion and the powder component is a polymer-modified cement with film forming chemicals and fillers, and some manufacturers add reinforcing fibres to make the product extra effective.
When these two ingredients namely the pre-weighed powder and the liquid are mixed together an uniform slurry results. This slurry is brush applied on the roof surface, which upon drying forms a flexible film. Since there is cement in this product its compatibility with concrete is excellent. The film further allows the breathing of the concrete without any hindrance hence there is no problems of its de-lamination from the concrete surface.
This film being flexible takes care of the deflections in the slab and the movements caused because of primary or secondary settlements, movements due to wind loads and temperature stresses developed in the concrete. This system can be used on surfaces, which had bituminous treatment earlier. In European countries, this type of product is used as coating on pre-stressed concrete bridge girders to protect them from aggressive chemical atmosphere.
A typical waterproofing specification using flexible membrane system will be as follows:
- Clean the surface to remove all loose particles, grease shuttering oil and such deleterious materials to get a sound concrete surface.
- Cracks if any should be cut into ‘V’ shaped grooves one inch wide and one inch in depth. Cut honey combed areas back to sound concrete.
- Repair these areas with a stiff paste of fibre reinforced polymer repair mortar generally sold in the name of crack fill.
- Mix the powder and the liquid components of the product to form an uniform slurry and brush apply this slurry on the surface to be waterproofed.
- When the waterproofing coating is still tacky apply 1:4 cement sand screed and cure normally.
Reasons for waterproofing system failure
M A Waheed, Director, Perma Construction Aids
Especially in large buildings waterproofing systems fail if the control joints are not in position or not properly executed. This failure occurs after one complete year when the structure has passed through one complete summer and the winter cycle. One cannot repair this type of failures. It needs a different type of approach involving provision of crack inducer joints and then tackling the waterproofing in movement restricted bays.Application of a waterproofing product in non-specified areas, such as, using a crystalline waterproofing system in waterproofing the terrace or using a flexible membrane system in the water tank results in failures even though the products themselves may be genuine.
Stretching the coverage of the products beyond the specified limits by the manufacturer results in inefficiency of the product and hence a failure.
Precautions to be taken
For optimum effect of waterproofing system, following measures should be taken:
- Selection of an effective waterproofing system for a structure taking all the performance criteria of the structure into account and also taking into the consideration the performance of the materials in the system is of prime importance for any success of the waterproofing job.
- Waterproofing jobs awarded to waterproofing contractors purely on economical price considerations often fail.
- It is always advisable to involve the architect or the structural engineer in selection of a system, and requisite performance guarantees should be taken from the contractors.
- It is better to avoid bargaining for the job value out of contractor’s margins. This could result in stretching the product beyond the coverage specified by the manufacturer or substitution of cheaper material in the system to cover the cost.
- Always supervise the job and the incoming materials for the intact tamperproof seals and quantities.
- Use the services of an engineer or architect in selection of materials
Keep it leak-proof
Generally, architects in India, do not specify in depth waterproofing details and leave this aspect generally to ignorant client to choose whatever system he likes, and many structural designers give least importance to the control joints. As a result of this many systems have failed in several prestigious buildings and the blame went to waterproofing contractors or the product manufacturer.
There is a need for the architects and the structural designers to understand the various systems available and specify them clearly and in sufficient detail, taking into consideration the in-service conditions of the structure.
The client should also insist on the architect to provide waterproofing design details in advance so that no ambiguity remains till the end. This would give enough time in selecting the specified material.
____________________________________________________________________________________________________
M A Waheed is the Director of Perma Construction Aids Pvt Ltd, www.permaindia.net
For details, contact at info@permaindia.com