Construction Equipment Planning

8/13/2019 Construction Equipment Planning

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PLANNING OF CONSTRUCTION EQUIPMENTPLANNING OF CONSTRUCTION EQUIPMENTPLANNING OF CONSTRUCTION EQUIPMENTPLANNING OF CONSTRUCTION EQUIPMENT

Extent of mechanization

Nature & Magnitude of work Indi enous e ui ment

Cost comparison for Machine & Labour

Large quantity of material handling &speed of constructionPossibility of using manual labour shouldbe explored


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DISADVANTAGES CONSTRUCTION EQUIPMENTDISADVANTAGES CONSTRUCTION EQUIPMENTDISADVANTAGES CONSTRUCTION EQUIPMENTDISADVANTAGES CONSTRUCTION EQUIPMENT

Success of a mechanized Construction

Coordination of all equipmentsEx : Failure of pump employed for dewatering afoundation pit may cause the excavator and hauling

un s o ecome eRegular Maintenance is neededIf maintenance is poor, it may increase cycle time of theconcerned activities and increase downtime..

Adequate Service & Maintenance req.

Safety at Work is important.


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CRITERIA FOR SELECTION OF EQUIPMENTCRITERIA FOR SELECTION OF EQUIPMENTCRITERIA FOR SELECTION OF EQUIPMENTCRITERIA FOR SELECTION OF EQUIPMENT

Use of available equipment

- New Equip may not be fully utilized

-

- Economics, Depreciation etc

Suitability of Job Conditions- Demand of job. Soil & Valley Condition,

climate, working condition etc


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Uniformity in types- Min No of Types

- Common types of engines for different machines

Size of EquipmentUse of Standard Equipment

- Commonly manufactured

- Easily available- Moderately priced

- Spare parts should be easily available


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Unit Cost of Production- Freight

- Packing

- Insurance

- Erection

Country of Origin- Soft currency

Availability of Spare parts


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Versatility

Selection of ManufacturerSuitability of local labour

Adaptability for future use


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COMMON CONCRETING EQUIPMENTCOMMON CONCRETING EQUIPMENTCOMMON CONCRETING EQUIPMENTCOMMON CONCRETING EQUIPMENT

CONCRETEPUMP


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Pumping, as a means of transporting and placing

concrete, has been used in developed countriesover last 4 to 5 decades. Often it has been found

uconcrete from mixing plant to the form, becauseby eliminating the use of dumpers, barrowshoists, etc., it can provide a considerablereduction in labour.


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But its other main advantage is, it can place

concrete in congested sites with little access.Pumping is a means by which concrete can be

y v y,and, with hydraulically driven pumps mounted ontrucks or trailers, quick site to site movement, forplacing of concrete is possible.


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From the usage point of view, there are two variety of pumps, the first one is the static type

usually mechanically driven models , and useslarger size bore, (125 mm to 250 mm) pipelines.

n n l hif in f m n r i n ndismantling of relatively heavier pipe lines arerequired. The second type is usually

hydraulically driven, uses comparatively smallerbore (75 mm to 100 mm) pipelines. They areusually mounted ontruck or trailer and this is

relatively recent development in technology.


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This type of pump consists of a hopperthrough which concrete is fed, below whichthere is a rotary valve such that it can open, toallow inflow of concrete into the pump

Mechanically driven pumps

cy n er ur ng suct on stro e. The piston in the pump cylinder movesbackward during suction stroke and concrete is

sucked in. During the pumping stroke when the piston

moves forward the inlet valve closes and blocksthe entry of concrete from hopper.


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The outlet valve closes during suction strokeand opens during pumping stroke allowing concrete to flow into the delivery pipe. Thusthe concrete moves along the pipeline with a

pu sat ng ow. The hopper is usually equipped with remixing blades to agitate the concrete. Water iscontinuously flushed in the back of the cylinder,i.e. the non-concrete side, to remove any concreteslurry that may have entered. This is done to

reduce the friction between piston and cylinder.


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Usually, they are powered by electric motor ordiesel engine, and operates at a maximum rateof 40 strokes/minute. Stroke length is of theorder of 300 mm and diameter of the cylinder

may e mm o mm.Output is of the order of 18m 3/h for singlecylinder model and that for twin cylinder model

is about of 34 m3/h. Pumping distance can beof the order of 450m or a vertical lift of 40 mfor cylinder dia of 180 mm for a single cylindermodel.


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These are simple in principle, but with their mechanicalsystem they are heavy and require mounting at the base.

The pipe diameter for delivery line is large and erectionand dismantling of such pipe line is cumbersome.

These pumps operate from one position for long time.But they can handle a large volume of concrete overconsiderable distance, thus, suited where large volume of

concrete is needed for a long time.By providing feeder pipeline at discharge end, greaterflexibility in placing can be obtained


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This is the most popular type of equipmentused these days. Hydraulic system using wateror oil as hydraulic fluid, being lighter can bemounted on a truck to make them mobile, thuscan be used for smaller jobs. The stroke

Hydraulic pumps

length is usually more and thus less numberof strokes allow the concrete flow to be morecontinuous. Control of pumping speed ispossible by varying the delivery pipe diameterof the pump. Hydraulic mechanism of pistonallows for a steady pressure on the concrete formost of the


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length of stroke, thus sudden pressure onconcrete is avoided. The hydraulic pumps areeasy to operate from maintenance point of such pump is much larger than that of amechanical pump, therefore velocity of

concrete to be lifted to higher elevations, theratio of maximum horizontal pumping of view also. The pipe dia of the delivery is muchsmaller , thus easy to handle, and outputdistance to vertical lift is much lower, usually of the order of 3 to 4 compared to 10 to 11 incase of mechanical pumps


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Oil driven piston pumps

Oil driven hydraulic systems are most common. A double acting hydraulic ram connected to thepiston, drives the piston in each cylinder. Oil tothe ram is supplied by a pump, driven by adiesel engine or motor. The twin cylinder

operate in sequence, such that hen one isadmitting the concrete the other one isdischarging. Flushing by water is also done inorder to reduce friction between piston and thecylinder.


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The length of the pumping stroke is 600-2000mm and the range of cylinder bore is to mm. Output may be in the range of 15-114m3/h. Maximum pumping heights can be 70 to80 m with maximum horizontal distance of

pumping about 400 m. Fig. 1.2 shows diagramof such a pump


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Water driven hydraulic pumps

In this type of hydraulic pump a centrifugal water pump applies pressure to the piston. When twin cylinders are used, the pressure isapplied alternately to each piston. The pistonshave no rods, but are connected to each other

by steel rope so that, as one piston is pushedforward on the delivery stroke the other ispulled back on the suction stroke. Stroke lengthis usually 2 to 3 m. The output can be of theorder of 125 m3/h with a delivery height of 7.5ms


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Peristaltic pumps

A pump based on peristaltic or squeeze principle is usually designed for small-boreoperation

The concrete from the hopper, fitted withrotating blades to assist flow of concrete into

pumping cylinder and for mild remixing, passesthrough a flexible tube, to the pumping chamber. The pumping chamber is circular. Two

diametrically opposite rollers are fixed to theinner side of the pumping chamber. The flexibletube which carries concrete lies between theroller and the inner side of chamber.


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The rollers are rotated about their spindles by hydraulic power. This causes a squeezing actionon concrete and thus a local compression, whichin turn forces the concrete forward towards theoutlet. Since there is no valve and with pipe

diameter same as the squeeze tube, concrete doesnot undergo any further changes in diameter. Toassist this action a high vacuum is maintained in

the pumping chamber, thus concrete enters thedelivery line under pressure. With this kind of roller action thus a continuous flow of concretetakes place.


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These pumps are also light, self-contained andpipe bore being small on be made mobile. Pipebore is usually in the range of 75 to 100 mm,

with the squeeze tube also of same dimension.Output upto 69 m3/h, with a maximum

horizontal pumping distance of 183 m and vertical lift of 46 m have been reported.


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There are four types of valves which are normally used in concrete pumps,

(1)Flat gate or slide valves, usually operate on sliding

principle, and serve both as inlet and outlet valve. They are used in both single cylinder and twincylinder pumps.

Pump valve system

(2)Spade valves, have curves profile to aid the flow of concrete are separate for inlet and outlet operation.

Thus there are four valves in a twin cylinder pump.

(3)Flapper valves, which perform both inlet and outletfunction in a twin cylinder pump. The valve can rotateabout a vertical axis allowing concrete to pass on both

sides of the blade, one side allows concrete to flow


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from cylinder to pipe line and the other side fromhopper to cylinder. Easy maintenance and quick clearance of blockages are the advantages of this

system, however concrete need to be taken through atortuous path.

(4) Rotary valves are used mostly on mechanical pumps.


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Major consideration in the selection of pipelines are,they need be capable of with standing the abrasiondue to concrete flow and also capable of withstanding

the rough handling at site. At the same time they needto be light for ease of handling.Steel has been the commonest material and recent

Pipelines for the pump

development in metal technology has reduced the weight/length of steel pipe for require abrasionresistance and strength.

Aluminum pipes have also been used but strength of concrete delivered through aluminum pipes isadversely affected by the reaction between cement

paste and aluminum, Ca (OH) and reactive alkalistake part in such a reaction generating hydrogen, thus


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causing expansion of plastic concrete, with theconsequence that, strength and durability of concreteis lowered considerably.

Limited use of plastic pipes have also have also beenreported, but plastic pipes need reinforcement andstrengthening at the end, for coupling.

Flexible hoses are used on booms and at delivery endof the pipelines, where pressure is relatively low. Lowfrictional resistance and high resistance to wear are

the qualities which are required for hoses.Helical reinforcement can be used to avoid kinks.Other pipe accessories include, pipe couplings, rotary

distributors, shut-off valve, discharge pocket, washoutgun, adjustable pipe support, trap basket etc.


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The following points need consideration whileplanning the pumping operations.

Type of pump required.

Concrete mix designPump locationsConcrete supply

Operation and cleaning

Layout of pipeline and boomPump location and space for cleaning Cleaning operation is normally done by compressed

air or water. This process is continued till overallflashing is over. Cleaning with water is generallysafer.


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COMMON CONCRETING EQUIPMENTCOMMON CONCRETING EQUIPMENTCOMMON CONCRETING EQUIPMENTCOMMON CONCRETING EQUIPMENT

RMC VEHICLES


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There are mainly two types of vehicle namely;truck mixer and agitator trucks, although tipper

trucks and dum er can also be used for

transporting ready mixed concrete.


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It consists of a mixing drum mounted on a truck chasis, which is capable of being revolved by power

take-off from the prime mover. The drum can mixconcrete or merely keep mixed concrete agitated. The vehicle is equipped with a water tank for carrying

Truck Mixer

the mixing water and an arrangement for adding the water to dry ingradients, in the drum. The truck mixers usually have a capacity ranging from 1 m3 to6m3. For maximum economy of operation they may have delivery radius of 10 to 16 kms, depending uponthe capacity of the truck. A swinging discharge chuteis usually provided so that concrete can be depositedover a wide area.


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The agitator consists of a conically shapeddrum of 1m3 2m3 capacity, the cone being

considerably more elongated than normal typeof mixer drum. The concrete is mixed before itis placed in the agitator and the agitator merely

Agitator Truck

keeps it mixed and prevents it from stiffeningprematurely. The spiral blades are much lesselaborate than those in a proper mixer. Theyare arranged to move the mix towards the openend of the drum to help discharge but iscountered during transit by tilting the drumupward.


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The agitator is usually driven by the prime moverat 1 to 3 r.p.m. and the agitation can be

continued when the truck is stationary byplacing the gear lever at neutral. The discharge

.

V hi l T d f k Ad R k


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Vehicle Type and range of work for which the vehicle is

best suited

Advantages Remarks

Truck Mixer Used to mix and transportconcrete to job site over short and very long hauls

Central Mixing plant is notneeded, only a batching plant is

plant necessary as concrete can be completely mixed in thetruck. Controlled discharge is

possible thus there is no loss of homogeneity of concrete ondischarge

Control of concretequality is not as goodas central mixing.Slump test of concreteconsistency are needed

on discharge.Careful preparations areneeded for receivingthe concrete at site.

ruc g a or

Non agitatingtrucks

se o ranspor concre e

for all uses in pavements,structures and buildings and

buildings. Haul distancemust allow discharge of concrete within 1 hoursof mixingUsed to transport concreteon short hauls

ruc ag a ors usua y opera e

from central mixing plants,where quality concrete is

produced under controlledcondition . Discharge from theagitator is well controlled.Capital cost of such a vehicle islower than truck mixer or truckagtators

m ng o e vers o

suit job organization.Concrete crew andequipment must beready on site to handleconcrete in large

batches.Concrete slump should

be limited possibilityof segregation. Heightis needed for high liftof truck body upon

discharge.


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T ti g d Pl i g f


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Transporting and Placing of

Concrete The uniform wet concrete produced from a mixer isrequired to be transported to the forms for placing.

This handling tends to produce more or less segregationand loss of slump, if the distance is long. The practicalconsideration of economy frequently operates to placethe mixer far from the forms.

Methods of transporting and placing, which permit theuse of drier mixes, reduce the water cement ratio andhence are better. Drier mixes also reduce the change of segregation.

The method selected may be adopted for the slumpspecified.

G l th d f t ti g &


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General methods of transporting &

placing concrete Discharge directly in to forms through short

chute or for a very small lead manually incontainers

By wheel barrows and power buggies umpers an ruc s ag a ng an non

agitating) Monorail system Elevating towers and hoists Skips operated by cranes or overhead cable

ways Belt conveyers and Boom conveyers


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General methods of transporting &placing concrete contd

Tremie

Truck mixers Concrete pumps and pneumatic placers

Any combinations of above.

h l


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1. Direct Discharge, Manual Transport in

Containers and Short Chutes

Manual means is least sophisticated.

Segregation resulting from throwing ofconcrete in to form, depends on the skill of

.height of 2m is to be avoided.

Chutes are usually regarded

undesirable,because they tend to producesegregation and loss of slump


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1. Direct Discharge, Manual Transport in

Containers and Short Chutes contd..

Short chutes with proper lower end treatmentdo not offend seriously in this regard

As they are simple to use and economical They are usually metallic, half round in section,

s ene a p aces n or er o avo ser ousdeformation and collapse under weight ofconcrete

The chutes must be steep enough to permitconcrete to flow without assistance

Chutes require cleaning by washing immediatelyafter each use


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2a.Wheel Barrow-manual Wheel barrows preferably pneumatically tyred

are used for small jobs and for small haullengths

Capacity of such a wheel barrow is about 80 kgof concrete They can be wheeled up and down on

scaffolding boards and can be easily handled byone man and accommodated in a usual materialhoist.

The time required to position and fill successivebarrow load usually controls the number ofbatches produced per hour .

Hand carts and prams are also of similarcapacity.


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2b.Power barrows The haul length and capacity of power barrows

are more than that of manual barrow more quantity of concrete is handled by a single

person, whose job is to control and direct the

The haul length may be about 300m andcapacity may be upto about 800 kg of concrete

Due to triangular arrangements of wheels theyhave better maneuverability and they can accentover a gradient of 20 percent easily


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2b.Power barrows contd Power barrows, while transporting concrete over

very rough terrain, may cause segregation of theconcrete due to jolting.

Usually power barrows are loaded from a,

which the barrow would be brought in for loading.

This type of transportation of concrete in

barrows prams, etc., is useful in construction ofslabs or similar flat structures . Thus for buildingconstruction casting of wall column and floor,etc. may be done together to obtain moreefficiency


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3.Dumpers and Trucks Used in road, dam or airport constructions,

where concrete is to be transported over arelatively long haul distance .

The haul distance may be even 5 to 10 kms aneuvera y o umpers are more an are

suitable also for rough and soft terrain. For controlled discharge hydraulic tipping may

be used to discharge concrete into bucket,platform or directly into mould

The capacity of a dumper may range from 0.5m 3to 0.75m 3, where as a truck can be of capacity

ranging from 3m 3 to 15m 3.


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3.Dumpers and Trucks contd Because of the jolting on the ground,

ordinary trucks and dumpers tend to causesegregation of concrete during transit To reduce se re ation durin loadin and

discharge, distribution of concrete over thewhole surface area of truck body isnecessary, rather than forming a heap.

The agitator truck of course totally aeliminates the possibility of segregation

4 Elevating Tower and Hoists


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4. Elevating Tower and Hoists

(Vertical transport) In concreting of high level bridge deck, multistory

buildings, etc., elevating towers are used for lifting

concrete buckets . On a very large dam, the tower height may be 50 m or so, with a bucket capacity of about 1.5m 3

,

operated winches are used for lifting the concrete Hoists operate on a similar principle. A cantilever

platform hoist operates along a steel lattice mast For, chimneys, narrow shafts and slip form constructions

rope guided hoists are used, instead of hoists in centraltower or tower masts

4 Elevating Tower and Hoists


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4. Elevating Tower and Hoistscontd

The rate of output per hour, maximum height of

elevation, the power source, available space atground level and secondary distribution systemto be used are the major considerations whileselecting the type of hoist required for aparticular construction site

One of the major disadvantages of hoists is that,

they are always associated with a secondarymeans of distribution of concrete at top andcosts of such a distribution system is the mainconsideration in selection of hoist


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5.Monorail System Monorail system needs a track and consists of a

power wagon mounted on the single rail track,which can move at a speed of 80-90 m/min

The wagon needs no driver an e ue powere eng ne or r ve, or can e

battery driven or driven directly by electricity This system can transport concrete through a

maximum gradient of 1 in 12 The segregation of concrete may take place

due to jolting of concrete in the wagon over eachrail joints

6 Cranes and Cableway (Two or three


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6. Cranes and Cableway (Two or three

dimensional transport) When a large area is to be covered for concrete

transport without a secondary distribution system, cranes

or cableways may be used Cable way is useful in river valley projects Cranes and cable-ways are often used for transporting

other objects in addition to transporting concrete Derrick crane, tower crane, crawler mounted, or wheel

mounted, or a hydraulic crane may be used. The main consideration in selecting the crane is height

and radius of operation, the ground condition, etc

6 Cranes and Cableway


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6. Cranes and Cablewaycontd

The hydraulic crane can be used in

situation where accessibility is very difficult A cable way has the advantage of being

,interference with the other activities in thesite is least

Stiffer concrete can be handled forconsiderable distances


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7.Belt conveyor Power required to drive a conveyor is usually

small By increasing the speed of running the

discharge can be as high as 115 m 3/hour on a

Conveyor lengths can be varied, and toughing of belt through suitable idlers may be provided

Conveying concrete through a limited elevationof 30 0 is possible

Belt conveyors are suitable for large thick raftsor large area slabs


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7.Belt conveyor contd A dumper mounted unit is used to transport

concrete from dumper to mould One of the major drawbacks of conveyors, when

it is long, is that, in case of a breakdown of,

remain in the belt itself Initial cost of setting up is also high Both dry as well as wet mixes can be handled

with conveyors for slump of 50 mm inclination may be 24 0 but

for a slump of 150 mm the inclination is 12 o only


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8.Concrete buckets or skips Buckets or Skips are most popular

containers used for transportingconcrete. ,

are two types of bucket or skip,1) Roll-over

2) Constant altitude type

8.Concrete buckets or skips


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contdHeight required during loading is more in

constant altitude skip compared to that of aroll-over skip, but clearance under the hook .

The capacity of skip may vary from 0.2 m 3 insmall jobs to 10 m 3 in mass concreting



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contd The roll-over skip may require manual

assistance for low slump concrete, it issuitable for discharge into narrow openingfrom works .

Buckets are also used for under waterconcreting One of the disadvantages of using bucket

in underwater concreting is that,turbulance of the water caused duringlowering of the bucket may wash away the

mortar from already placed concrete

9.General Consideration in


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placing of Concrete Maintaining uniformity of the concrete segregation control Concrete behaves like a heavy emulsion For higher slump mixes there is a tendency for

heavier particles to settle below During lateral movement coarse aggregate and

mortar tends to separate Pouring concrete at the same place or when

dumped at an angle cause lateral movement For proper bond between two horizontal layer,

each layer shall be soft when a new layer isplaced upon it.

9.General Consideration in


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placing of Concrete At joints compaction must be ensured When concrete is placed over rock or hardened

concrete a layer of mortar shall be placed at allportion of the joint before concrete is poured.

s necessary o ensure a concre e reac esall corners of the form and is well compacted

The concrete shall be placed generally within 20minutes of mixing and should not be disturbedafter 1 hr of mixing the water with cement

It the temperature is more than 30 0 precautionsare required to be taken by using cooler water,

cooler aggregate

10. Under water placing and the


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p g

tremie Concrete cannot be compacted and may get

mixed with water Concrete must be self compacting and wet

enough to flow under its own weight, and must

The common methods of placing the concreteunderwater are:

1) use of pre packed or grouted concrete2) Tremie pipe or using bottom open bucket

described earlier3) Pumping4) Dumping by bags

10. Under water placing and the tremied


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contd The tremie consists of a rigid pipe either metallic or

plastic, with a hopper at the top for feeding the concretein to the pipe from a concrete source

The pipe must be jointless or formed by bolting togethera series of flanged section with water tight joints

lowering and raising it, whenever required At the beginning the tremie pipe is lowered fully and

loose pug of material such as plastic sponge, coir orpaper is inserted at the top concrete is then loaded ontop of such a plug

10. Under water placing and the


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p g

tremie contd The plug forms a separation between the water

and concrete And as the concrete is fed, this plug forces out

the water in the pipe s e p ug reac es e o om e p pe s

raised a little to drive out the plug and theconcrete is then placed at the bottom

The diameter of the tremie pipe is usually of theorder of 150 mm and above.

The tremie is very useful in diaphragm wallconstruction where concreting is done under

bentonite slurry in trenches.

Equipment Type & Range ofoperation

Advantages Remarks

Crane & Hoists Work above groundlevel

also handles itemsother than concrete

careful planning isrequired


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level other than concrete required

Buckets & skips Useful on cranes andcableways Convey concrete frommixer to form utilizesversatility of cranes

controllable discharge isnecessary

Barrows & Prams For short hauls Labour intensive slow process

Chutes Conveying concrete toa lower level

Low cost Proper slope anddischarge arrangementis necessary

Belt Conveyor Conveying concretehorizontally or throughlimited slope

Can handle largevolume of concrete atfast rate

Cleaning of belts isneeded

Pneumatic Placers can place concrete in

difficult location

Ideal for tunnel

concreting

Skilful operation is must

Drop chutes &Elephant trunking

Placing concrete invertical forms

Segregation freeconcreting

Cross-section shall belarge enough so that nointerference withreinforcement

Tremies For under waterconcreting

--- Careful operation isnecessary richer mix is

requiredScrew spreaders Used in pavements --- ---

Monorail For horizontalmovement of concrete

--- Capital intense

Cableways Used in river valleyprojects

Can carry other items

also

careful planning is

required

11.Economic aspects and selection


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Wheeled transports are essentially meant for relativelylong horizontal hauls

The rate of delivery, mixer type and their output,distance of haulage, site conditions and place of

delivery, and discharge characteristics are the factorson which selection of wheeled transport is dependentWhile comparing the cost involved in different

,

Capacity, speed of travel, charging and discharging time of the transport,

number of vehicles required ,

11 Economic aspects and selection contd


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11.Economic aspects and selection contd

4. labour cost,

5. hire rates,6. fuel cost,

7. maintenance cost8. and cost of access, etc

Documents

Construction Equipment Planning