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2 Marks
.Whrt is Vacuum concrcte?$ovlftg 2?14 Only about half of the water Bddcd in concrete go€s iDto chemical combination and the remaining water is us€d to makc concrete workable. After laying concretc, water which was making concreting workable is extracted by a special method
2.What arc the equiprt|ents.used in vscuum
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known as "vacuunr rnethod",
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The equipnent etsenrially consjsts of:I
vacuum pump
ii. water separator and
what is Qunite? [Dn,
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iii- filtering mat
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Gunite can be defined as mortar conveyed through :a hosg and
4. What
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pneumatically projected ar a high velocity on to a surface.
Are
ihe trvo types of proceis in Shotcrete?
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Wet mix process I
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Dry nrix process
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W z'ttz 5 whrt arc thcst{ges in dry mlx procels in shotcrete? + \n zay) i In this Proccss. lhc cotrcrctc is ltixed with water ss for ordirary conirete before
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conveying througl] rhe delivery pipeline to the nozzle, at which point it is jettcdby conrpressed air, onto thc rvork in thc same way as that
'lhc rver process has
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b0en generally desircd
if mix process,
in favour.of the dry mix
process,
owing to lhe groalrr succcss ofthe lattcr,
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Whnt is sho(cretcf
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Shotcrete is a rccenl dcvclopment on the sirnilar principle ofguniting for achicving
gr
ciilcr tllickless,witll srnall coarse aggregate.
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7. What rre lh€ preliminary investigatioos before demolitiorl ofa stiucture? The demolition contmctor should have ample experience of the type of work ro be offer€d;
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> Fully comprehensive insuance against all risks must be maintained at all rimes: ! An experienced supervisor should be continuously in charge of the work; > Thc contract price should include ail safelr precautions included in the relevant building regulations;
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achieve
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The compldtion date should be realjstic, avoiding and nEed to take risks to the date. !
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Write about prdtective clothing given before demolition.
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Buildings where chemicals have been stored or where asbeslos, lead pdint, dust or fumes may be present will require specialized protective clothing,
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9. Give a brief rotd on shoring and underpinning in demolition. I The demoliriOn cont&ctor has a iegal obligation lo show technical &rp"t"n"" when carrying out the work. When removing sections of rhe building which iould have leave other parts unsife, adequate temporary supports and shoring etc. must
10. What are the major factor!
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in selecting a demolition procedure?
Major's factors to be considered in selecling un uppropriut.
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include
> Safery ofpersonnel and public > Working methods Legisiation applicable
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.Give the categories of demolition tech n iq ues.
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Demolition techniques may be categorized as:-
Piecemeal demolition, using hand-lreld lools or machines. to reduce the height ol. the building or structrrre graduallyi Deliberate conlrolled collapse- denlolirion to be conrplctcd ar ground Ievei.
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12. Write short notes on demolitio[ by hand. Den)olilion of buildings o. by hand-held lools such as electric or "t*"rur" pneumatic breakers, sometimes as a preliminary to using other methods, should be carried out, where practicable, in the rcve$e order to the original constluctioD sequence.
Lifting appliqnces may be necessary to hold larger structural members iuring cuning and
13. In what
cases
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tbr lowering levered slructrtral mcmbers and other
,
demolition try machine can be done?
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Simnle roaf shlctures supported on wall plates should normoll! bc dernolished to lhc le!el ot wall plites by hand. but if this nray involve unsafe workin!, then demoiition i
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be apfropriate.
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totall) by madhine may
Write shoit notes on bxllioE machine.
Balling machines genemlly comprise a drag-line type crawler chassis fitted with a lanice crane iib. The demolilion ball, with a steel anri-spin device, is suspended liom the
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lifting rope and swung by the drag rope.
How are explosives used for demolition of
a
structure? $or
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shot-lirer nray be sufficient.
Whnt is a hydroulic pusher
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for smaller work.
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Ifexplosives are to be used for demolition, the planning and execution, include prerveakening, shoutd be under lhe control of a person competent in these techniques. For large demolition. the competent person is likely to be an experienced explosive engineer;
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Articulated, hydraulically,powercd pusher-amr,machines are normally mounted oD a lracked or wheeled chassis, and have a toorhed plare or. hook for applying for applying a
fiflr
level base and apply force
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horizontal force to a lvall. The machine should sland on a
b),a controlled rnov€ntent ofthc pusher arm.
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17.
What is pre-rverkening?
Buildings and structures normally have strloural elemenls designed to carry safely the loading likely to be imposed during their life. As a preliminary to a deliberate cottlolled collapse, afler loads such as fumishings, planr
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and machinery have been removed, thb demolition conhactor may be able to weaken some
stmctural elements and remove thosF new redundant. This preweakening is essentially a planned exercise and must be ireceded by an analysis of its possible effects on the structure until it collapses, to ensure that the structuml integrity of the building is not i
18.
What is deliberate collapse?
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jeopardized accidentally. Insufficient infrirmation and plaming rclating to lhe structure may result in dangerous and unsafe work.
The deliberate collapse of the whole or part of a buililing or sructure requires panicularly high slandards of planning, supervisions and execurior, and careful
of its effect on other parts of the structure or on
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consideration
adjacent buildings or
structures. A surou[ding clear area and exclusion zone are required to protect bolh pemonnel and property from the fall ofthe structure itselfand debris u,hich may be
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thown up by the impact.
19. How can you deyelop a demolition strate$/?
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need to lake into account the method
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The strategy
ofconstruction used for the
original building and its proximity to other buildings. suuctures and the general public. These factors, togeth;r with localion, the cost and availabiliry oftipping and disposal and
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the desirability and eionomr'cs ofreuse, musr be taken into account in rhe developmenl arl appropriate strategy for the demolition ofa structure.
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20. What xre nibblers? Nibblers use a rotating action to snap briftle malerials such as concrete or masonq,. In either case, material should be removed f'ro the top ol\valls or coluntns in courses not greater than 600mm in depth, steel reinforcement should be cul separatElv as necessarJ.
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