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Note for Prestressed Concrete Structures - PCS by Priyanka Priya

  • Prestressed Concrete Structures - PCS
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  • Civil Engineering
  • B.Tech
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38 :: Certificate in Construction Supervision (CIVIL) 2. Measures taken after completion of construction (Post construction technique) The termites which are seen in the building generally lives under the ground and breeds before the commencement of rainy season. Apart from this, it is also found to be present in the timber, rubber, etc. Some times before in the past, Aldrine, or DDT were being used for prevention purposes, but with the observance of bad effect of these two medicines on human being, the use of Aldrine and DDT have been stopped. Accordingly now a day following medicines are used: 1. Chloropyriphosh, which is available as Dermit/Dustbin in the market 1% solution of chlorophos is sprayed in the soil/water. This is very poisonous substance, hence hand should be properly washed withsoap each time after use. 2. Apart from dirmat or Dustbun, TC Hepafloor (5% solution) can also be used. 3. The solution of Chlorden (1% solution) can also be used. 6.4 TERMITE TREATMENT BEFORE CONSTRUCTION Before starting the concreting work in the foundation Dermit solution is sprayed by hand pump in the foundation soil. This job should not be carried out during rainy season or when water is present in the foundation trench. This process is carried out before pouring concrete mix in the foundation trench, in an orderly fashion in stops. Fig 6.1 (a) Foundation of load bearing wall Fig. 6.1 (b) Column and Footling Step 1 The Dermit solution of appropriate strength should be spread up to 30 cm from the foundation level to the wall, so that the termite is completely killed. It should be used at the rate of (@) 5.0 ltr. per sq. m of the area covered.

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Prevention of Building from Termite and Dampness :: 39 Fig. 6.1 (a) depicts that foundation on which the load of the load bearing wall will act. The Fig 6.1 (b) depicts the R.C.C. foundation. Step 2 If the soil from outside source is brought to fill the foundation space, the soil should be properly pulverized and mixed with 3 to 5 ltr. of Dermit solution and it should spread up to 30 cm from the determined area outwardly. Step 3 Starting from the foundation level and up to plinth level, holes @ 15 cm are made in the soil extending up to 5 to 7.5 cm. deep. After that @ 5 ltr. per square meter chemical solution of Dermit of appropriate strength is filled in the holes. Step 4 Treatment at the joint of wall and floor:- At the joint of wall and floor, Dermit solution of appropriate strength is applied @ 15 ltr. per. sq. m. Step 5 Treatment of soil which touches the building from outside:- After completion of the construction work of the building, holes 30 cm deep are made at every 15 cm along the length and the Dermit solution is filled @ 5 ltr. per m. length. Step 6 Treatment at other places:- Termite prevention treatment should also be carried out at places where the timber work in the building touches the soil or the conduit pipe is put in the floor and in the same way where construction joints occur. It is provided @ 3 ltr. per m. length.

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40 :: Certificate in Construction Supervision (CIVIL) In the same way the termite prevention treatment should be carried out in walls above the plinth level. Above the plinth, at 45o angle holes should be made at every 30 cm on both sides of the wall and the chemical should be pumped in the holes till the chemical starts coming out. After this the holes should be filled with cement mortar (1 : 2) 6.5 ANTI TERMITE TREATMENT OF BUILDING POST CONSTRUCTION At places whenever the timber work touches the wall, holes are made and the Dermit solution made in Kerosene oil is pumped into the 6.0 mm diameter holes. Hand pump should be used to push the chemical in the holes. 6.6 WORKS RELATED TO PREVENTION FROM DAMPNESS (DAMP PROOF COURSE) Damp proofing course is laid above the ground level adjoining plinth level of the building in the entire width of the wall. However it is kept below the floor level. The thickness of the DPC (Damp Proof Course) varies between 12 mm to 20 mm. At certain places it may be 40 mm thick also. It is also provided below the sill level of the doors. Method of laying Damp Proof Course When the brick work reaches plinth level a special type of mix known as Damp proofing compound is mixed with cement and sand (1 : 2) with adequate amount of water and is laid in the full width of the brick work below it. The thickness of this layer is usually kept at 2.5 cm unless and until specified otherwise. This layer prevents the dampness to rise above. Floor D.P.C. Lean Concrete Layer of sand Fig. 6.2: Application of DPC in Cohesionless soil

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Prevention of Building from Termite and Dampness :: 41 1. Layer of sand 2. Lean concrete 3. D.P.C. 4. Floor Fig. 6.3: Application of DPC in Cohesive soil D.P.C. is sometimes made of Cement concrete also. In this the ratio of cement: sand: stone chips is 1 : 2: 4 to which Damp Proofing Compound is also added. D.P.C. is kept wet (cured) for 7 days. After drying D.P.C. layer is coated with coal-tar. 6.7 WATER PROOFING AT THE JUNCTION OF PARAPET AND ROOF The method of water proofing at the junction of Parapet and proof is shown in Figs. 6.4(a), (b) and (c). Coping Coping Roof Slab D.P.C. Fig. 6.4(a)

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