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Waterproofing New Technology & Appraoch

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Waterproofing   New Technology & Appraoch Waterproofing New Technology & Appraoch Document Transcript

  • Waterproofing : New Technology & Approach Dr. M. S. Modak, Head- R&D and Arijit Basu , Corporate Market Field Manager (Waterproofing & Sealants) Sika India Pvt. Ltd Synopsis: A building for any use is constructed generally by using ---- concrete, brick, mortar, window, and door. The purpose of the building is to protect inhabitants from rainwater, heat from Sun, and storm. In performing so the building is also exposed to the environment existing around it. Although a building will resist water infiltration but water leakage may take place through concrete, wall, joints, pipe entries, gap between door and window frames. Out of these, leakage through concrete takes place mainly due to high porosity. The other defects are due to bad workmanship. To solve all these problems, Chemicals and accessories are available at present. Proper use of these materials will enhance the durability of a building. But selection of such materials will play a major role to impart the beneficial properties. Chemicals and accessories: During the manufacture of Concrete either Water Reducing or High Range Water Reducing Admixtures can be used like Plastiment or Sikament of Sika India. The dosage of Plastiment is normally 0.2 to 0.6% by weight of Cement and that of Sikament is 0.5 to 1.5%. The following figures will explain the benefits. Effect of Plastiment on Slump Effect of Sikament on Slump Cement = 350 kg/m 3, W/C= 0.45 Cement = 350 kg/m 3, W/C = 0.43 150 250 120 210 Slump, mm 200 Slump, mm 100 92 150 73 50 100 95 40 50 30 0 0 0 0.2 0.4 0.6 0 0.5 1 Dosage, % by w t Dosage, % by w t. The effect of Chemical on slump is observed from the above figures. To get this slump without Chemical high w/c ratio of more than 0.55 should have been used. This excess water will generate high porosity due to bleeding and evaporation, which may lead to leakage problem. So the use of Chemical is beneficial from waterproofing point and this impart permanent solution. The above products satisfy the requirement of Indian Standard IS 9103 – 1999. Leakage through brickwork is another problem. In this case leakage takes place through the mortars. To stop this Chemical like of Sika India can be used. This has the bifunctional property of waterproofing and reduction of rebound loss. The rebound loss is that when green plaster falls down during application. The rebound loss reduction will make the plastering job faster. Sika Plastocrete Plus should be used @ 0.2% by weight of cement. The other material, which can be used, is Sika Noleek CP of Sika India. This will bring in waterproofing and should be used @ 1.0% by weight of cement. These products reduces water permeability by more than 50% as per the requirement of Indian Standard IS 2645. Both the material should be used during making the plaster.
  • =2= Use of Polymers in the form of dispersion in water with plaster brings in multiple benefits. To use it in plasters, first it should be diluted with clean water in the ratio of 1:1 to 1:8, where 1 is Polymer and the other part is water. The sand cement mixture is then mixed with this diluted Polymer without using raw water. The benefits that is imparted are: Good bond with the brick & concrete surface Excellent waterproofing Less shrinkage Example of such Polymer is Sika Cemflex of Sika India. The following figures will show the benefits. Effect of Sika Cemflex on Water Absorption 0 1:08 1:04 1:02 14 12 12 12.5 11 11.5 Absorption, % 10 8 8.5 6 6.5 4.8 5 4.5 4.85 5 4.6 4 4 4.2 2.5 3 2 0 0 0 5 10 25 Immersion time, hour Effect of Cemflex on Bond Strength 4 Bond, kg/cm2 3.6 3.4 3 2.9 2.5 2 1 0 0 1:04 1:06 1:08 Cemflex : Water From the above figures it is clear, properties are better with more Sika Cemflex, which is expected. The gaps between doors and window frames can be insulated against water by the use of a suitable sealant. This is available in sausage, cartridge or paste. It is applied on the gap and finished properly. The aesthetic look increases to a great extent by its use. Examples of such sealants are Sikaflex Construction and Sikacryl of Sika India. Sikaflex Construction is based on PU and Sikacryl – acrylic. These sealants stretches with the movement of the gaps due to heat and cold and keeps the gap sealed. Consumption of such sealant is around 5 running meter with 600ml material for 8x15 mm groove.For sealing pipe, electric cable entry points and the gap around AC machines in the wall, PU foam can be used. This is available in metal containers in ready to use form and is liquid in nature. As soon as it is injected in the gaps it expands to form foam. The foam is allowed to hardened and then trimmed off to finish. Example of such product is Sika Boom of Sika India. This also acts as
  • =3= thermal and electrical insulations. 1 cm thick Sika Boom has the insulation power equivalent to 40 cm concrete and 20 cm brick. For sealing joints on roof, wall, expansion joints a new concept can be used which is to apply a synthetic polymer based, UV resistant, tough sheet of 1 to 2 mm thick having width of 10 – 20 cm. The sheet is bonded on the surface by an adhesive. One such very successful system is Sikadur Combiflex of Sika India. It is very easy to apply and is effective for long time. This can be used also to seal pipe entries into the building. The following figures will illustrate the matter. Sikadur Combiflex Rec Another chances of leakage are through the joints in the basement. To stop such leakage conventionally water bars are used. The main drawback of water bars is to keep its profile straight during construction. If it is not straight it cannot act as a barriers for water flow through the joint. The new concept in this area is to use a sealant at the joint, which will expand in contact with green concrete as well as water. This helps to keep the joint sealed for flow of water. A product in this class is Sika Swell S2 of Sika India. It is PU resin based special sealant, which will expand in presence of water. This is supplied in Cartridge. The following figures will illustrate its performance. Sika Swell S2 Sika Swell S2 is available in two triangular sections 15 and 20mm. 15 mm is used for structures less than 30 cm thickness and 20mm is used for 30 – 50 cm thickness. Sika Swell S2 expands 100% by volume in 7 days in contact with water.
  • =4= New age sealing technology with single component PU sealants: The usage of moisture curing , single component PU sealants are becoming fast popular over the conventional type of two component , reaction curing sealants like Poly sulphide due to several operational and performance related benefits. Sealant History : 120 100 Polysulpide 80 Silicone 60 Polyurethane STP-Tech 40 Acrylics 20 0 1940 1950 1960 1970 1980 1990 2000 S e a la n t M a r k e t to t a l W o r ld 2 0 0 0 (ttl / to n s ) 8 % 5 % 9 % 4 3 % 1 7 %
  • =5= For satisfactory performance a sealant in various joints must be: Waterproof It must be an impermeable material Durable Not adversely affected by aging weathering for a reasonable service life. Permanently elastic Sufficiently recover its original properties and shape after cyclical deformations. Deform to accommodate the movement occurring at the Of high cohesive Must not tear easily. strength Capable of adhering Must remain in intimate contact with the joint well to concrete etc. faces. Non toxic Be free of substances harmful to the user and environment especially in treatment plants and reservoirs where the water is for human consumption.
  • =6= Sealant System Polyurethane Silicone Polysulfide Acrylic Modified PU-Hybrid Properties Silicone Practical Elongation in an Expansion joint (based on 15 - 25 % 15 - 25 % 15 - 25 % 5 - 10 % 15 - 25 % 15 - 25 % German Study Building Sealant defects over a 20 year period) Recovery 60-80% >80% <80% <60% 30-70% >80% Capaity Transparent Yes Formulations No No Yes No No (some systems) -30o C -40o C -30o C -20o C -30o C -30o C Temperature up to up to up to up to up to up to Resistance +90o C +200o C 100o C 80o C +90o C +90o C Tear Strength + - + + 0 + + Paintability + - + + + Alkyd Cure Speed 1K + + 0 0 + + Skin Overtime + + + 0 + + Tack free time + +/- + 0 + + Adhesion + + 0 0 + + Grindability + - - - 0 0 Staining + - 0 + + + Primer Requirement + + 0 0 + + Gunability + + 0 + + + Storage Life + + - + 0 + Weatherability 0 + 0 0 0 + + Good - Poor 0 Depending on formulation and manufacturer Considering the above facts and figures , lets us now look into the comparison on advantages of 1 – component products over 2 – component products : Single component – no weighing and mixing at site, reduces chances of human error. Negligible wastage. Time saving, easy, user friendly and cleaner application. Uniformity of colour. No need for expensive mixer / guns. Can be applied with light weight guns. More friendly to environment / non toxic . World wide moisture curing, singe component polyurethane ( PU ) products are well accepted as the most suitable products for flexible sealing applications in various types of joints and cracks . The following details will substantiate this :
  • =7= Poly urethanes : Reaction products of Isocyanates with polyols and other H-Donors. The many possible permutations and combinations of commercially available raw materials result in a spectrum of polyurethane sealants which range from high quality high performance sealants to low quality low performance sealants of the one generic type. Thus, particular care must be exercised when selecting a PU sealant that is cost effective in the long term. Packaging: 1 and 2 Part systems 90% of the market 1 Part US market > 50% 2 Part Advantages: •Fast curing. •Cost / performance •Easy application. •Primer less adhesion on many non porous surfaces. •Wide variety of products for multiplicity of applications. • General purpose product. •Non staining. •Bonds well to itself in joint repairs. •Good abrasion and tear resistance (good for floor joints). Application: •Construction joints. •Perimeter joints (window and door frames). There is no single sealant type which works best in all situations. Final choice will depend on all aspects of specific project. •Joints in pre cast concrete panelling. •Concrete, quarry tile, floor and pavement joints. •Expansion joints. •General use in structural and civil engineering. •Water immersed joint. Sealing operation has become an important and integral part of waterproofing of a building construction and the pioneering technology with single component , flexible Poly urethane sealants are the most widely used one word over. Conclusion: This paper contains a few examples of different chemicals, which are very effective to get permanent solutions for various problems in constructing buildings and structures. There are many other chemicals, which can be used based on the requirement. Use of such chemicals increases the durability and aesthetic of a building.