Waterproofing & Its Critical Role in Construction Industry

Waterproofing & Its Critical Role In Construction Industry Dr. Surendra P. Bhatnagar, Chairman & Managing Director–Tech-Dry (India) Pvt. Ltd.,Bangalore The reform process received a boost in the year 1991, when government initiated the economic reforms programme to bring about fast and substantial economic growth. Since 1991, India is going through an exciting phase of the reform process and has opened up its economy. India has already globalised its economy by relaxing several economic policies. As expected the construction industry is on the forefront of our economic development but unfortunately the technocrats involved in this industry are yet to understand the importance of waterproofing and they have to be prepared for a change and adopt modern technologies. In the recent past, everybody is talking about green concrete and arresting of global heating. Even during the Indo-American Nuclear deal global heating and environment were important factors. We entered this field in 1992 and set our company‘s mission as Our Company‘s Mission Saving our Environment Saving Energy Safety and durability of the buildings We operate through chain of network within the concept of our company ―Smaller companies win through co-operative, without loosing their independence, the market position of today‘s large multinationals.‖ Thomas J. Peters, Management Consultants We have spent several years in convincing the industry and the experts in this field that waterproofing is critical not only for durability and safety of the structure, but also equally important for sustainable, environment and friendly, energy saving technique. We faced lot of resistance because it is nature of human being to resist change, which is important fact of life. According to Harold Wilson― He who rejects change is the architect of decay. The only human institution which rejects progress is the cemetery.‖ We are happy to note that the experts in this field are slowly shifting towards green concrete concept and are accepting newer technologies. At the time when we entered this field brickbat coba and coatings like bitumen were in great demand, unfortunately even today there are several experts who do want to stick to the materials like brickbat coba. Inspite of all these odds, we continue with our efforts to introduce products, which are the need of 21stcentury. Factors affecting deterioration of reinforced concrete structures as well as the mechanism of deterioration are well-understood today. The deterioration in concrete is usually manifested in the form of carbonation, corrosion of reinforcing steel, cracking, spalling, excessive deflection etc. The effect of the environment on mineral building materials is a natural process, which has not attracted significant scientific interest until recently. The initial work in Germany around 1900 investigated the weathering of natural stones. The problem, which has now attracted is the entry of water containing dissolved toxic substances to the inner parts of the concrete by capillary action. This statement may be extended to the entry of deteriorating agents as a gas or in solution. Later a problem associated with modern concrete construction emerged-that of steel corrosion in steel-reinforced structures causing spalling. We have been creating this awareness through our several articles and Newsletters because unless this phenomenon of degeneration of reinforcement is not slowed or stopped, buildings will not be durable and can lead to problems of safety. Infact depending on the chemistry of the environment the malignancy can set-in as early as 3 months of the substrates exposure to the strong environment. Steel Reinforcement Corrosion The corrosion of steel reinforcement is by far the single most common cause of structural damage. This situation is rather remarkable, given that steel reinforcement in concrete is well protected against corrosion due to the highly alkaline environment generate from the hydration of cement. The widespread deterioration of structures emphasizes the vulnerability of concrete protection, as reinforced or prestressed concrete interacts with severe service environments. The key environmental factors that reduce the passivation of steel, as discussed earlier, are carbonation and chloride. Other factors which may influence either the initiation or rate of reinforcement corrosion include cracks in concrete, temperature, moisture, oxygen and inadequate concrete quality or cover. Concrete as an Environment The environment provided by good quality concrete to steel reinforcement is one of high alkalinity due to the presence of the hydroxides of sodium, potassium and calcium produced during the hydration reactions. The bulk of surrounding concrete acts as a physical barrier to many of the steel‘s aggressors. In such an environment steel is passive and any small breaks in its protective oxide film are soon repaired. If, however, the alkalinity of its surroundings are reduced, such as by neutralisation with atmospheric carbon dioxide, or depassivating anions such as chloride are able to reach the steel then severe corrosion of the reinforcement can occur. This in turn can result in to staining of the concrete by rust and spalling of the cover due to the increase in volume associated with the conversion of iron-to-iron oxide. In fact, the expense incurred in North America as a result of corrosion-induced repair numbers in the billions of dollars, without even considering the environmental toll of repeated construction and repair. Corrosion inhibitors are one of the most cost effective solutions to this problem, but little independent information is available on their effectiveness in actual use. It is estimated that even in India approx. 50% of the expenditure in the construction industry are spent on repair maintenance and remediation of existing structures. In future, these expenditures will probably increase even more. A large portion of these expenditures are due to lacking durability of concrete structures. This implies a need to make a design for durability, where the service life is expressed explicitly. There is also a need to plan for and thus reduce the costs for further maintenance and repair by making an appropriate durability design of the structure. Process of Corrosion Corrosion is a process, which at times is described as Electro-chemical process. It results in the deterioration of the steel section available for load carrying in a reinforced concrete section. It is dependent on the environment in which the steel exists the level of oxygen available for the corrosion process, presence or absence of water or moisture temperature, exposure level. 1. Fe+O+ 2CO2 + H2O = Fe (HCO3)2 2. 2Fe (HCO3)2 + O = 2Fe (OH) CO3+ 2CO2H2O 3. Fe (OH) CO3+ H2O =Fe (OH) 3 + CO2 Steel once corroded causes cracks on the surface of the concrete cover. Presence of corrosion activity is not detected till such cracks become visible. These cracks then help in conduction of oxygen, moisture which act as accelerators for corrosion. Corrosion also causes the effective steel cross section to increase (swsll) initially. Such increase is followed by separation of outer laminate of steel and its disintegration. However increase in cross section results in reduction of density. Scales occur which normally start to fall off or separate from the steel core with time. Excessive uncontrolled corrosion causes the entire steel section to disintegrate and crumble, total loss of section also results. Corrosion is an irreversible process. Remedial measures cannot help restore the section. It only helps in delaying the process. Green Concrete We often hear that India is going to become world power. It sounds musical to our ears but when you see the state of our Infrastructures, it is disappointing. In this paper, we will deal with one important aspect and that is the construction industry. All of us know that India is now poised for growth and is going to be one of the fastest growing industries and the real backbone of our economy. Crystallization What is crystallization product? With the modern penetrants, knowledge of emulsifiers, you can develop modified silicates which in conjunction with calcium ions would form crystals which would block the capillaries and pores and reduce the porosity to great extent. Protekta Base Protekta Base, viscous liquid consisting of silicates and special proprietary chemical penetrants, is used as a penetrating sealer/surface hardener on concrete to improve its resistance to the ingress of liquid water and contaminants. Protekta Base reacts with free Calcium and water to form a non-water soluble Calcium Silicate Hydrate gel complex in pore capillaries and cracks. This gel creates a sub-surface barrier. The crystalline product penetrates and reacts with the concrete forming a sub-surface barrier, waterproofing pores, capillaries and larger cracks against the ingress of water and contaminants. The depth of penetration depends on the time and durability of curing to ensure that all the products penetrates inside. We call it consolidation, porosity reduction and to some extent hydrophobic step, but any claims that it can function alone are not in line with the chemistry. Protekta Protex Protekta Protex is a unique chemical treatment. Protekta Protex is supplied as 2 component –powder and liquid, which are mixed and the slurry is coated on the concrete surface. From Protekta Protex special penetrants are released, which get impregnated into the concrete surface to provide crystalline product. Properties

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