Engineeringcivil.com-Project Report Six Months Summer Training

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Project Report – Six Months Summer Training

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Here is the project report of a civil engineering student who has spent 6 months on a training site.Dueto security reasons,the project details, estimation, some portion of design and quantity calculations havebeen omitted.But to help the civil engineering students we had shown all the necessary works..

Sequence of Structure Work

1) Site Clearance

2) Demarcation of Site

3) Positioning of Central coordinate ie (0,0,0) as per grid plan

4) Surveying and layout

5) Excavation

6) Laying of PCC

7) Bar Binding and placement of foundation steel

8 ) Shuttering and Scaffolding

9) Concreting

10) Electrical and Plumbing

11) Deshuttering

12) Brickwork

13) Doors and windows frames along with lintels

14) Wiring for electrical purposes

15) Plastering

16) Flooring and t iling work

17) Painting

18)

Final Completion and handing over the project Construction Process And Materials Used

Site Clearance- The very f irst step is site clearance which involves removal of grass and vegetation alongwith any other objections which might be there in the site location.

Demarcation of Site- The whole area on which construction is to be done is marked so as to identif y theconstruction zone. In our project, a plot of 450*350 sq f t was chosen and the respective marking was done.

Positioning of Central coordinate and layout- The centre point was marked with the help of a threadand plumb bob as per the grid drawing. With respect to this center point, all the other points of columnswere to be decided so its exact posit ion is very crit ical.

Excavation

Excavation was carried out both manually as well as mechanically. Normally 1-2 earth excavators (JCB’s)were used f or excavating the soil. Adequate precautions are taken to see that the excavation operationsdo not damage the adjoining structures. Excavation is carried out providing adequate side slopes anddressing of excavation bottom. The soil present beneath the surf ace was too clayey so it was dumped andwas not used f or back f illing. The f illing is done in layer not exceeding 20 cm layer and than its compacted.Depth of excavation was 5’4” f rom Ground Level.

PCC – Plain Cement Concrete

Af ter the process of excavation, laying of plain cement concrete that is PCC is done. A layer of 4 incheswas made in such a manner that it was not mixed with the soil. It provides a solid bas f or the raf tf oundation and a mix of 1:5:10 that is, 1 part of cement to 5 parts of f ine aggregates and 10 parts ofcoarse aggregates by volume were used in it. Plain concrete is vibrated to achieve f ull compaction.Concrete placed below ground should be protected f rom f alling earth during and af ter placing. Concreteplaced in ground containing deleterious substances should be kept f ree f rom contact with such a groundand with water draining there f rom during placing and f or a period of seven days. When joint in a layer ofconcrete are unavoidable, and end is sloped at an angle of 30 and junctions of dif f erent layers break jointin laying upper layer of concrete. The lower surf ace is made rough and clean watered bef ore upper layer islaid.

Laying of Foundation

At our site, Raf t f oundations are used to spread the load f rom a structure over a large area, normally theentire area of the structure. Normally raf t f oundation is used when large load is to be distributed and it isnot possible to provide individual f ootings due to space constraints that is they would overlap on eachother. Raf t f oundations have the advantage of reducing dif f erential settlements as the concrete slabresists dif f erential movements between loading posit ions. They are of ten needed on sof t or loose soilswith low bearing capacity as they can spread the loads over a larger area.

In laying of raf t f oundation, special care is taken in the reinf orcement and construction of plinth beams andcolumns. It is the main portion on which ult imately whole of the structure load is to come. So a slightesterror can cause huge problems and theref ore all this is checked and passed by the engineer in charge ofthe site.

Apart f rom raf t f oundation, individual f ootings were used in the mess area which was extended beyond theC and D blocks.

Cement

Portland cement is composed of calcium silicates and aluminate and aluminof errite It is obtained byblending predetermined proportions limestone clay and other minerals in small quantit ies which is pulverizedand heated at high temperature – around 1500 deg centigrade to produce ‘clinker ’. The clinker is thenground with small quantit ies of gypsum to produce a f ine powder called Ordinary Portland Cement (OPC).When mixed with water, sand and stone, it combines slowly with the water to f orm a hard mass calledconcrete. Cement is a hygroscopic material meaning that it absorbs moisture In presence of moisture itundergoes chemical reaction termed as hydration. Theref ore cement remains in good condition as long asit does not come in contact with moisture. If cement is more than three months old then it should be testedf or its strength bef ore being taken into use.

The Bureau of Indian Standards (BIS) has classif ied OPC in three dif f erent grades The classif ication ismainly based on the compressive strength of cement-sand mortar cubes of f ace area 50 cm2 composed of1 part of cement to 3 parts of standard sand by weight with a water-cement ratio arrived at by a specif iedprocedure. The grades are

(i) 33 grade

(ii) 43 grade

(iii) 53 grade

The grade number indicates the minimum compressive strength of cement sand mortar in N/mm2 at 28days, as tested by above mentioned procedure.

Portland Pozzolana Cement (PPC) is obtained by either intergrinding a pozzolanic material with clinker andgypsum, or by blending ground pozzolana with Portland cement. Nowadays good quality f ly ash is availablef rom Thermal Power Plants, which are processed and used in manuf acturing of PPC.

Advantages of using Portland pozzolana cement over OPC

Pozzolana combines with lime and alkali in cement when water is added and f orms compounds whichcontribute to strength, impermeability and sulphate resistance. It also contributes to workability, reducedbleeding and controls destructive expansion f rom alkali-aggregate reaction. It reduces heat of hydrationthereby controlling temperature dif f erentials, which causes thermal strain and resultant cracking n massconcrete structures like dams. The colour of PPC comes f rom the colour of the pozzolanic material used.PPC containing f ly ash as a pozzolana will invariably be slightly dif f erent colour than the OPC.One thingshould be kept in mind that is the quality of cement depends upon the raw materials used and the quality

control measures adopted during its manuf acture, and not on the shade of the cement. The cement getsits colour f rom the nature and colour of raw materials used, which will be dif f erent f rom f actory to f actory,and may even dif f er in the dif f erent batches of cement produced in a f actory. Further, the colour of thef inished concrete is af f ected also by the colour of the aggregates, and to a lesser extent by the colour ofthe cement. Pref erence f or any cement on the basis of colour alone is technically misplaced.

Settling Of Cement

When water is mixed with cement, the paste so f ormed remains pliable and plastic f or a short t ime. Duringthis period it is possible to disturb the paste and remit it without any deleterious ef f ects. As the reactionbetween water and cement continues, the paste loses its plasticity. This early period in the hardening ofcement is ref erred to as ‘setting’ of cement.

Init ial and f inal sett ing t ime of cement

Init ial set is when the cement paste loses its plasticity and stif f ens considerably. Final set is the point whenthe paste hardens and can sustain some minor load. Both are arbitrary points and these are determined byVicat needle penetration resistance

Slow or f ast setting normally depends on the nature of cement. It could also be due to extraneous f actorsnot related to the cement. The ambient conditions play an important role. In hot weather, the setting isf aster, in cold weather, setting is delayed Some types of salts, chemicals, clay, etc if inadvertently get mixedwith the sand, aggregate and water could accelerate or delay the setting of concrete.

Storage of Cement

It needs extra care or else can lead to loss not only in terms of f inancial loss but also in terms of loss inthe quality. Following are the don’t that should be f ollowed -

(i) Do not store bags in a building or a godown in which the walls, roof and f loor are not completelyweatherproof .

(ii) Do not store bags in a new warehouse until the interior has thoroughly dried out.

(iii) Do not be content with badly f itt ing windows and doors, make sure they f it properly and ensure thatthey are kept shut.

(iv) Do not stack bags against the wall. Similarly, don’t pile them on the f loor unless it is a dry concretef loor. If not, bags should be stacked on wooden planks or sleepers.

(v) Do not f orget to pile the bags close together

(vi) Do not pile more than 15 bags high and arrange the bags in a header-and-stretcher f ashion.

(vii) Do not disturb the stored cement until it is to be taken out f or use.

(viii) Do not take out bags f rom one tier only. Step back two or three tiers.

(ix) Do not keep dead storage. The principle of f irst- in f irst-out should be f ollowed in removing bags.

(x) Do not stack bags on the ground f or temporary storage at work site. Pile them on a raised, dry platf ormand cover with tarpaulin or polythene sheet.

Coarse Aggregate

Coarse aggregate f or the works should be river gravel or crushed stone .It should be hard, strong, dense,durable, clean, and f ree f rom clay or loamy admixtures or quarry ref use or vegetable matter. The pieces ofaggregates should be cubical, or rounded shaped and should have granular or crystalline or smooth (butnot glossy) non-powdery surf aces.Aggregates should be properly screened and if necessary washed cleanbef ore use.

Coarse aggregates containing f lat, elongated or f laky pieces or mica should be rejected. The grading ofcoarse aggregates should be as per specif ications of IS-383.

Af ter 24-hrs immersion in water, a previously dried sample of the coarse aggregate should not gain inweight more than 5%.

Aggregates should be stored in such a way as to prevent segregation of sizes and avoid contaminationwith f ines.

Depending upon the coarse aggregate color, there quality can be determined as:

Black => very good quality

Blue => good

Whitish =>bad quality

Fine Aggregate

Aggregate which is passed through 4.75 IS Sieve is termed as f ine aggregate. Fine aggregate is added toconcrete to assist workability and to bring unif ormity in mixture. Usually, the natural river sand is used asf ine aggregate. Important thing to be considered is that f ine aggregates should be f ree f rom coagulatedlumps.

Grading of natural sand or crushed stone i.e. f ine aggregates shall be such that not more than 5 percentshall exceed 5 mm in size, not more than 10% shall IS sieve No. 150 not less than 45% or more than 85%shall pass IS sieve No. 1.18 mm and not less than 25% or more than 60% shall pass IS sieve No. 600micron.

BRICKWORK

Brickwork is masonry done with bricks and mortar and is generally used to build partit ion walls. In our site,all the external walls were of concrete and most of the internal walls were made of bricks. English bond wasused and a ration of 1:4 (1 cement: 4 coarse sand) and 1:6 were used depending upon whether the wall is4.5 inches or 9 inches. The reinf orcement shall be 2 nos. M.S. round bars or as indicated. The diameter ofbars was 8mm. The f irst layer of reinf orcement was used at second course and then at every f ourthcourse of brick work. The bars were properly anchored at their ends where the portions and or where these

walls join with other walls. The in laid steel reinf orcement was completely embedded in mortar.

Bricks can be of two types. These are:

1) Tradit ional Bricks-The dimension if tradit ional bricks vary f rom 21 cm to 25cm in length,10 to 13 cm inwidth and 7.5 cm in height in dif f erent parts of country .The commonly adopted normal size of tradit ionalbrick is 23 * 11.5*7.5 cm with a view to achieve unif ormity in size of bricks all over country.

2) Modular Bricks- Indian standard institution has established a standard size of bricks such a brick isknown as a modular brick. The normal size of brick is taken as 20*10*10 cm whereas its actual dimensionsare 19*9*9 cm masonry with modular bricks workout to be cheaper there is saving in the consumption ofbricks, mortar and labour as compared with masonry with tradit ional bricks.

Strength of brick masonry

The permissible compressive stress in brick masonry depends upon the f ollowing f actors:

1. Type and strength of brick.

2. Mix of motor.

3. Size and shape of masonry construction.

The strength of brick masonry depends upon the strength of bricks used in the masonry construction. Thestrength of bricks depends upon the nature of soil used f or making and the method adopted f or moldingand burning of bricks .since the nature of soil varies f rom region to region ,the average strength of bricksvaries f rom as low as 30kg/sq cm to 150 kg /sq cm the basic compressive stress are dif f erent crushingstrength.

There are many checks that can be applied to see the quality of bricks used on the site.Normally the bricksare tested f or Compressive strength, water absorption, dimensional tolerances and ef f lorescence.However at small construction sites the quality of bricks can be assessed based on f ollowing, which isprevalent in many sites.

• Visual check – Bricks should be well burnt and of unif orm size and color.

• Striking of two bricks together should produce a metallic ringing sound.

• It should have surf ace so hard that can’t be scratched by the f ingernails.

• A good brick should not break if dropped in standing posit ion f rom one metre above ground level.

• A good brick shouldn’t absorb moisture of more than 15-20% by weight, when soaked in water Forexample; a good brick of 2 kg shouldn’t weigh more than 2.3 to 2.4 kg if immersed in water f or 24 hours.

Precautions to be taken in brick masonry work

• Bricks should be soaked in water f or adequate period so that the water penetrates

to its f ull thickness. Normally 6 to 8 hours of wetting is suf f icient.

• A systematic bond must be maintained throughout the brickwork. Vertical joints

shouldn’t be continuous but staggered.

• The joint thickness shouldn’t exceed 1 cm. It should be thoroughly f illed with the

cement mortar 1:4 to 1:6 (Cement: Sand by volume)

• All bricks should be placed on their bed with f rogs on top (depression on top of the

brick f or providing bond with mortar).

• Thread, plumb bob and spirit level should be used f or alignment, verticality and

horizontality of construction.

• Joints should be raked and properly f inished with trowel or f loat, to provide good bond.

• A maximum of one metre wall height should be constructed in a day.

• Brickwork should be properly cured f or at least 10 days

REINFORCEMENT

Steel reinf orcements are used, generally, in the f orm of bars of circular cross section in concrete structure.They are like a skeleton in human body. Plain concrete without steel or any other reinf orcement is strong incompression but weak in tension. Steel is one of the best f orms of reinf orcements, to take care of thosestresses and to strengthen concrete to bear all kinds of loads

Mild steel bars conf orming to IS: 432 (Part I) and Cold-worked steel high strength def ormed barsconf orming to IS: 1786 (grade Fe 415 and grade Fe 500, where 415 and 500 indicate yield stresses 415N/mm2 and 500 N/mm2 respectively) are commonly used. Grade Fe 415 is being used most commonlynowadays. This has limited the use of plain mild steel bars because of higher yield stress and bondstrength resulting in saving of steel quantity. Some companies have brought thermo mechanically treated(TMT) and corrosion resistant steel (CRS) bars with added f eatures.

Bars range in diameter f rom 6 to 50 mm. Cold-worked steel high strength def ormed bars start f rom 8 mmdiameter. For general house constructions, bars of diameter 6 to 20 mm are used

Transverse reinf orcements are very important. They not only take care of structural requirements but alsohelp main reinf orcements to remain in desired posit ion. They play a very signif icant role while abruptchanges or reversal of stresses like earthquake etc.

They should be closely spaced as per the drawing and properly t ied to the main/longitudinal reinf orcement

Terms used in Reinforcement

Bar-bending-schedule

Bar-bending-schedule is the schedule of reinf orcement bars prepared in advance bef ore cutting andbending of rebars. This schedule contains all details of size, shape and dimension of rebars to be cut.

Lap length

Lap length is the length overlap of bars t ied to extend the reinf orcement length.. Lap length about 50 timesthe diameter of the bar is considered saf e. Laps of neighboring bar lengths should be staggered andshould not be provided at one level/line. At one cross section, a maximum of 50% bars should be lapped. Incase, required lap length is not available at junction because of space and other constraints, bars can bejoined with couplers or welded (with correct choice of method of welding).

Anchorage Length

This is the additional length of steel of one structure required to be inserted in other at the junction. Forexample, main bars of beam in column at beam column junction, column bars in f ooting etc. The lengthrequirement is similar to the lap length mentioned in previous question or as per the design instructions

Cover block

Cover blocks are placed to prevent the steel rods f rom touching the shuttering plates and there byproviding a minimum cover and f ix the reinf orcements as per the design drawings. Sometimes it is commonlyseen that the cover gets misplaced during the concreting activity. To prevent this, tying of cover with steelbars using thin steel wires called binding wires (projected f rom cover surf ace and placed during making orcasting of cover blocks) is recommended. Covers should be made of cement sand mortar (1:3). Ideally,cover should have strength similar to the surrounding concrete, with the least perimeter so that chances ofwater to penetrate through periphery will be minimized. Provision of minimum covers as per the Indianstandards f or durability of the whole structure should be ensured.

Shape of the cover blocks could be cubical or cylindrical. However, cover indicates thickness of the coverblock. Normally, cubical cover blocks are used. As a thumb rule, minimum cover of 2” in f ootings, 1.5” incolumns and 1” f or other structures may be ensured.

Structural element Cover to reinforcement (mm)

Footings 40

Columns 40

Slabs 15

Beams 25

Retaining wall 25 f or earth f ace

20 f or other f ace

Things to Note

Reinf orcement should be f ree f rom loose rust, oil paints, mud etc. it should be cut, bent and f ixed properly.The reinf orcement shall be placed and maintained in posit ion by providing proper cover blocks, spacers,supporting bars, laps etc. Reinf orcements shall be placed and tied such that concrete placement is possiblewithout segregation, and compaction possible by an immersion vibrator.

For any steel reinf orcement bar, weight per running meter is equal to d*d/162 Kg, where d is diameter of thebar in mm. For example, 10 mm diameter bar will weigh 10×10/162 = 0.617 Kg/m

Three types of bars were used in reinf orcement of a slab. These include straight bars, crank bar and anextra bar. The main steel is placed in which the straight steel is binded f irst, then the crank steel is placed

and extra steel is placed in the end. The extra steel comes over the support while crank is encountered atdistance of ¼(1-distance between the supports) f rom the surroundings supports.

For providing nominal cover to the steel in beam, cover blocks were used which were made of concrete andwere casted with a thin steel wire in the center which projects outward. These keep the reinf orcement at adistance f rom bottom of shuttering. For maintaining the gap between the main steel and the distributionsteel, steel chairs are placed between them

SHUTTERING AND SCAFFOLDING

DEFINITION

The term ‘SHUTTERING’ or ‘FORMWORK’ includes all f orms, moulds, sheeting, shuttering planks, walrus,poles, posts, standards, leizers, V-Heads, struts, and structure, t ies, prights, walling steel rods, bolts,wedges, and all other temporary supports to the concrete during the process of sheeting.

FORM WORK

Forms or moulds or shutters are the receptacles in whichconcrete is placed, so that it will have the desired shapeor outline when hardened. Once the concrete developsadequate strength, the f orms are removed. Forms aregenerally made of the materials like timber, plywood, steel,etc.

Generally camber is provided in the f ormwork f orhorizontal members to counteract the ef f ect of def lectioncaused due to the weight of reinf orcement and concreteplaced over that. A proper lubrication of shuttering platesis also done bef ore the placement of reinf orcement. Theoil f ilm sandwiched between concrete and f ormworksurf ace not only helps in easy removal of shuttering butalso prevents loss of moisture f rom the concrete throughabsorption and evaporation.

The steel f orm work was designed and constructed to theshapes, lines and dimensions shown on the drawings. Allf orms were suf f iciently water t ight to prevent leakage ofmortar. Forms were so constructed as to be removable insections. One side of the column f orms were lef t openand the open side f illed in board by board successively as the concrete is placed and compacted exceptwhen vibrators are used. A key was made at the end of each casting in concrete columns of appropriatesize to give proper bondings to columns and walls as per relevant IS.

CLEANING AND TREATMENT OF FORMS

All rubbish, particularly chippings, shavings and saw dust, wasremoved f rom the interior of the f orms (steel) bef ore the concrete isplaced. The f orm work in contact with the concrete was cleaned andthoroughly wetted or treated with an approved composition toprevent adhesion between f orm work and concrete. Care was takenthat such approved composition is kept out of contact with thereinf orcement.

DESIGN

The f orm-work should be designed and constructed such that the

concrete can be properly placed and thoroughly compacted to obtainthe required shape, posit ion, and levels subject

ERECTION OF FORMWORK

The f ollowing applies to all f ormwork:

a) Care should be taken that all f ormwork is set to plumb and true to line and level.

b) When reinf orcement passes through the f ormwork care should be taken to ensure close

f itt ing joints against the steel bars so as to avoid loss of f ines during the compaction of

concrete.

c) If f ormwork is held together by bolts or wires, these should be so f ixed that no iron is

exposed on surf ace against which concrete is to be laid.

d) Provision is made in the shuttering f or beams, columns and walls f or a port hole of

convenient size so that all extraneous materials that may be collected could be

removed just prior to concreting.

e) Formwork is so arranged as to permit removal of f orms without jarring the concrete.

Wedges, clamps, and bolts should be used where practicable instead of nails.

f ) Surf aces of f orms in contact with concrete are oiled with a mould oil of approved

quality. The use of oil, which darkens the surf ace of the concrete, is not allowed. Oiling

is done bef ore reinf orcement is placed and care taken that no oil comes in contact with

the reinf orcement while it is placed in posit ion. The f ormwork is kept thoroughly wet

during concreting and the whole time that it is lef t in place.

Immediately before concreting is commenced, the formwork is carefully examined to ensure thefollowing:

a) Removal of all dirt, shavings, sawdust and other ref use by brushing and washing.

b) The tightness of joint between panels of sheathing and between these and any hardened core.

c) The correct location of t ie bars bracing and spacers, and especially connections of

bracing.

d) That all wedges are secured and f irm in posit ion.

e) That provision is made f or traf f ic on f ormwork not to bear directly on reinf orcement

steel.

VERTICALITY OF THE STUCTURE

All the outer columns of the f rame were checked f or plumb by plumb-bob as the work proceeds to upperf loors. Internal columns were checked by taking measurements f rom outer row of columns f or their exactposit ion. Jack were used to lif t the supporting rods called props

STRIPPING TIME OR REMOVAL OF FORMWORK

Forms were not struck until the concrete has attained a strength at least twice the stress to which theconcrete may be subjected at the time of removal of f orm work. The strength ref erred is that of concreteusing the same cement and aggregates with the same proportions and cured under conditions oftemperature and moisture similar to those existing on the work. Where so required, f orm work was lef tlonger in normal circumstances

Form work was removed in such a manner as would not cause any shock or vibration that would damagethe concrete. Bef ore removal of props, concrete surf ace was exposed to ascertain that the concrete hassuf f iciently hardened. Where the shape of element is such that f orm work has re-entrant angles, the f ormwork was removed as soon as possible af ter the concrete has set, to avoid shrinkage cracking occurringdue to the restraint imposed. As a guideline, with temperature above 20 degree f ollowing time limits shouldbe f ollowed:

Structural Component Age

Footings 1 day

Sides of beams, columns, lintels, wall 2 days

Underside of beams spanning less than 6m 14 days

Underside of beams spanning over 6m 21 days

Underside of slabs spanning less than 4m 7 days

Underside of slabs spanning more than 4m 14 days

Flat slab bottom 21 days