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Avoid 5 construction methods |
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Some construction methods introduced decades ago as per materials and equipment available at those times are still prevalent in India. There is a vast improvement in the quality of materials and availability of equipment now and these old and bad methods are no more relevant to today’s times. Yet people continue to follow these in many parts of the country. The force behind using these methods are those masons who are skilled in these practices and enforce them upon the house builder. Whenever a house builder tries to depart from the old and bad methods of construction, a mason’s standard reply is, “ If you want to differ, I won’t be responsible for the consequences.” The house builder is caught in a dilemma. This standard plea of the masons influences the house builder who resigns to the mason’s will. To have good quality and safety in construction of your house, don’t allow the mason’s dictum to prevail. Follow your engineer’s advice. Not only the quality and safety but also economy and durability in construction shall be achieved. Here are a few bad methods of construction. Avoid these and see the results: 1. RB ROOFING IN HOUSING It is a major practice followed in India. Reinforced Brick (RB) roofing in houses is more common than the strong, impervious and economical RCC. There prevails a belief that RCC roofing develops cracks while RB roofing does not. RB roofing has bricks laid on edge and covered with a 40 mm thick layer of concrete. Steel reinforcement is laid in the gaps left between the bricks laid on edge. A bottom cover of 12 mm is provided to the reinforcement. Total thickness of slab works out as 167 mm. Spacing of reinforcement gets decided by the brick-laying-arrangement in this type of roofing. On the other hand, RCC roofing laid under similar conditions is just 113 mm thick. Its’ reinforcement spacing is decided by the designer. In the long run, RCC roofing in fact proves cheaper. As and when RB roofing is laid, bricks being highly porous, soak water from concrete resulting in cracks in top layer of concrete. Steel bars placed in between bricks come in contact with them and rusting of bars occurs after a few years. Then there is no remedy except to dismantle the slab and re-lay it afresh. This is an impossible task as the whole of the house is to be undone. The only factor that goes in favour of RB roofing is the low thermal conductivity of bricks. This may help in lesser expansion of slab and better insulation to heat. However this factor weighs little against the drawbacks this type of roofing suffers from. If proper end treatment is given to RCC slabs by providing a 6 to 8 mm gap at its end, filled with asbestos filler and a 10 mm bearing plaster is provided at the base, no cracks will appear in the RCC roofing. The practice of using RB roofing should therefore be stopped altogether and only RCC roofing should be used. 2. HAND MIXING OF CONCRETE Indian specifications sometimes allow ‘Hand mixing’ of concrete. Whatsoever precautions you may take, hand mixing of concrete will not produce desirable blending of concrete ingredients. Consumption of cement will also be more. Water-cement-ratio will also not remain under control. Therefore, avoid hand mixing of concrete. If unavoidable, allow it for lean concrete only. Non-uniform mixing of ingredients in hand mixed concrete means lack of workability, strength and density of concrete. 3. USING UNCONTROLLED CONCRETE Some specifications and Common Schedule of Rates widely followed in execution of works allow use of un-designed concrete in construction of houses and buildings. Naturally, specified minimum cement content factors for this concrete are very high as compared to the cement required for designed concrete. There is double loss on use of un-designed concrete. More cement is used resulting in higher expenditure. Secondly, you are not sure about the strength of concrete. Mere addition of extra cement doesn’t assure strength and durability. Proper mix design is necessary. Use of RMC (Ready Mixed Concrete) is now increasing in India. It is concrete produced under fully controlled conditions. If you have an RMC plant near your plot, feel blessed and use RMC. You will avoid a lot of trouble and tension. Recently, some RMC plants have come up in Panchkula. So people of the tri-city can avail of its availability. 4. USING EXTRA REINFORCEMENT Inserting extra reinforcement in beams and slabs does not help in strengthening the structure. Masons and bar binders try to insert the steel cut pieces here and there in the slab under the impression that this will make the slab stronger. They are badly mistaken. Steel bars require certain free spacing between them to allow easy flow of concrete and bajri through them. Inserting of cut pieces stops this flow and makes the concrete less dense. Result is that the slab may rather be weaker. Get your slab designed from a structural engineer. He may bring lot of saving to you. Sometimes, a mason is so disturbed over the design of slab that he refuses to accept such less quantity of steel. Don’t allow his fears to prevail upon you and get the steel laid as per design given by the engineer. Know that over reinforced slabs and beams make a building unhealthy. 5. NON-USAGE OF ADMIXTURES There is a revolution in the development of admixtures and compounds. Development of Super plasticisers, water proofing admixtures and sealants have opened endless possibilities of easier laying of concrete, saving old buildings, making new buildings damp-proof, impervious and efflorescence free. However people are reluctant in use of these admixtures. These admixtures and compounds can enhance the quality of construction itself. Make use of this synthesis of chemistry and construction. Ask a house owner, hotel manager, maintenance engineer or care taker, the major problems being faced by him are leakage, seepage, cracks or efflorescence. Right use of admixtures and compounds can help in eliminating these problems. However the use of these admixtures has not become common in India. There are no reasons for not taking full benefit of these wonderful materials. It is a bad practice with us to adopt new materials at a very slow pace and with suspicion thus depriving ourselves of their benefits at the right moment.
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Tip of the Moment
53 grade cement is strongest among all these though its cost difference is marginal.
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