QUALITY ASSURANCE IN Civil WORKS BY S.N.PANDEY, CIVIL WORKS MANAGER, BIHAR EDUCATION PROJECT COUNCIL, PATNA - PowerPoint PPT Presentation

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QUALITY ASSURANCE IN Civil WORKS BY S.N.PANDEY, CIVIL WORKS MANAGER, BIHAR EDUCATION PROJECT COUNCIL, PATNA

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Title: QUALITY ASSURANCE IN Civil WORKS BY S.N.PANDEY, CIVIL WORKS MANAGER, BIHAR EDUCATION PROJECT COUNCIL, PATNA


1
QUALITY ASSURANCE IN
Civil WORKS BY S.N.PANDEY, CIVIL WORKS
MANAGER, BIHAR EDUCATION PROJECT COUNCIL, PATNA
  •  

2
QUALITY CONSTRUCTION
  • Quality construction increases the lifespan,
    stability and serviceability of the structure.
    It also combines all the resources into
    economical output and reduces unnecessary repairs
    and maintenance. To cap all it disseminates the
    reputation of the agency.
  • Quality of Civil Work depends on the use of
    correct structural design, specifications and
    proper material and workmanship.
  • Rational design is an effective tool for cost
    effective and quality construction. As such the
    design should be based on the latest relevant
    Indian Standards

3
SPECIFICATION AND PROPER MATERIALS
  • The quality building material, like Cement,
    Brick, Aggregate (Course fine) should be
    procured at competative rate. The community
    should be trained about quality of each building
    material and how to procure them. The aim is to
    procure best possible quality material at
    competative rate.

4
CEMENT CONCRETE
  • Followings are constituents of concrete -
  • Aggregate
  • Sand
  • Cement
  • Plasticizers for workability.

5
CEMENT
  • Followings are the grades of cement being
    manufactured-
  • 33,43 53 MPa.
  • ISI / ISO marked cement of ACC, Ultra
    tech/Ambuja Birla Gold/Lafarge, Concreto etc to
    be procured.

6
CEMENT
  • Price increases with increase in grades
  • For good construction 33 43 grades are ideal.
  • Initial setting time is 30 minutes final
    setting time is 600 minutes
  • With the passage of time cement loses strength
    due to hydration as follows-
  • Period - loss in strength of cement
  • Three months 20
  • Six 30
  • Twelve months 40
  • As such fresh cement is to be used

7
AGGREGATES
  • Coarse aggregate- 20mm down, well graded is
    required for all the R.C.C. works in buildings.
  • Sand- Sand of I.S. Zone II and F.M. not less than
    2.25
  • Grading of coarse and fine aggregates shall
    follow the curve of Road Note 4 which is
    attached. On the basis of large nos. of cube
    tests carried out combination of the aggregates
    is recommended for higher strength and quality
    concrete in concluding Para of this note. The
    method of test for aggregates for concrete is
    given in IS 5779.
  • The nominal maximum size of coarse aggregate
    should be as large as possible within the limits
    specified but in no case greater than one-fourth
    of the minimum thickness of the member, provided
    that the concrete can be placed without
    difficulty so as to surround all reinforcement
    thoroughly and fill the corners of the form.
  • For heavily reinforced concrete members as in the
    case of ribs of main beams, the nominal maximum
    size of the aggregate should usually be
    restricted to 5 mm less than the minimum clear
    distance between the main bars or 5 mm less than
    the minimum cover to the reinforcement whichever
    is smaller.

8
BRICKS
  • Bricks as per I.S. 1077 of class 125 preferably.
    The water absorption by the brick should be
    maximum up to 20.

9
WATER CEMENT RATIO BULKAGE IN SAND
  • I.S. 456 clauses 9.3 and 9.3.1 deals with
    quantity of water of maximum amount to be added
    to per 50 Kg. of cement.
  • Water present in sand should be determined. The
    simplest method of determining the bulking of
    sand in the field is to fill a graduated jar with
    the sand being used in the work upto a mark. Add
    sufficient water. Sand will settle down to lower
    mark. Difference in the levels of sand gives the
    rough idea of bulking which has to be compensated
    by increase in the amount of sand. The moisture
    content and bulking of medium size sand is given
    below.
  • Moisture content Bulkage
  • 0.4 2
  • 0.75 4
  • 1.45 8
  • 3.1 16
  • 4 20

10
WATER CENMENT RATIO BULKAGE IN SAND
  • Moisture content Bulkage
  • 5 22
  • 8 28
  • 10 26
  • 12 18
  • 15 14
  • 20
  • There is no bulkage in sand if fully saturated or
    completely dry.
  • It is needless to say that very effort be made to
    make silt, clay, dust in the aggregates almost
    nil. The maximum percentage of fines in aggregate
    is limited to 3 of coarse and uncrushed fine
    aggregate according to I.S. 383

11
WORK FORCE
  • The work force consists of skilled unskilled
    workers as under
  • SKILLED Masons, carpenter, plumber,
    electrician, blacksmith, bar benders, etc. if
    these are very well trained, this can make lot of
    dent in quality construction.
  • UNSKILLED Labour force, which assist the
    skilled workers, should also be trained in order
    to achieve quality. (examples)

12
QUALITY CONTROL MEASURES
  • Visual inspection.
  • Quantitative Quality measures.
  • Testing of building material like
  • Sand
  • Bricks
  • Concrete Mix
  • Cement Water ratio
  • Cement mortar

13
QUALITY CONTROL OF CEMENT CONCRETE
  • 1. Concrete Mix Design
  • Concrete must be satisfactory in two stages,
    namely in the plastic stage and the hardened
    stage. If the condition of the plastic concrete
    is not satisfactory it can not be properly
    compacted and its structural value is reduced.
    Thus, if there are 5 of air voids due to
    incomplete compaction, the strength will be
    reduced by 30 and 10 of air voids will cause a
    loss of strength of about 60. The satisfactory
    compaction can be obtained only if the concrete
    is satisfactorily and sufficiently workable. The
    property of workability, therefore become of
    vital importance from structural point of view.
  • 2. Workability of Concrete
  • A Concrete is said to be workable, if it can be
    easily mixed, placed, compacted and finishes at
    the surface.
  • A workable concrete should not show any
    segregation or bleeding.
  • Segregation occurs when coarse aggregate try to
    separate out from the paste and get accumulated
    at one side. This results in large voids, less
    strength and less durability.

14
QUALITY CONTROL OF CEMENT CONCRETE
  • 3. Tests for workability
  • Slump Test I.S. 1199 para 5 deals with this
    test. The slump test apparatus is very simple and
    cheap and the test can be conducted during the
    progress of work in the filed. I.S. 456 para 7.1
    prescribes the values of workability.

15
QUALITY CONTROL OF CEMENT CONCRETE
  • 4. Durability
  • The durability of concrete depends on adequate
    cement content and low water cement ratio. Cement
    and water is needed to bind together the
    aggregates firmly. Thus, the suitable combination
    of the aggregates is key to quality concrete. The
    proper grading of the aggregates make the
    concrete dense. This also governs the quantity of
    water required for workability

16
FACTOR GOVERNING QUALITY OF CONCRETE
  • Cement Aggregate ratio
  • Grading of the aggregates
  • Volume/ weight batching
  • Mixing
  • Compaction
  • Curing
  • Water / Cement Ratio
  • Quality of Sand
  • Quality of Water

17
FACTOR GOVERNING QUALITY OF CONCRETE
  • Machine Mixing Sequence
  • First pour 25 of the total quantity of water in
    the drum.
  • Dry coarse and fine aggregates are to be
    discharged into drum
  • Full quantity of cement is to be deposited in the
    drum
  • Finally balance quantity of water to be poured.
    25 to 30 revolutions are needed for mixing with
    drum rotating _at_ 15-20 revolutions per minute

18
(I.S. 456 Clauses 6.1.2, 8.2.4.1 9.1.2)Minimum
Cement Content, Maximum Water-Cement Ratio and
Minimum Grade of Concrete for Different Exposures
with Normal Weight Aggregates of 20 mm Nominal
Maximum Size
  • Reinforced Concrete

Minimum Cement Content Kg/m3 Maximum Free Water- Cement Ratio Minimum Grade of Concrete
300 0.55 M 20
19
(I.S. 456 Clauses 9.3 9.3.1) PROPORTIONS FOR
NOMINAL MIX CONCRETE
Grade of Concrete Total Quantity of dry Aggregates by Mass per 50 kg of Cement, to be Taken as the Sum of the Individual Masses of Fine and Coarse Aggregates, Kg, Max Proportion of Fine Aggregates to Coarse Aggregates (by Mass) Quantity of Water per 50 kg of Cement, Max
M20 250 kg i.e. coarse aggregate - 166.66 Kg Fine aggregate- 83.33 kg Generally 12 but subject to an upper limit of 11½ and a lower limit of 12½ 30
20
Volume batching per bag of cement i.e. 35 liters
  • 50 kg cement 250 aggregate (maximum)
  • volume 0.0347 m3 Volume - 0.1389 m3
  • i.e. cement aggregate ratio ¼ by volume.
  • M20 (1 1.5 3)
  • i.e. Cement Aggregate ratio 14.5
  • By volume (per bag cement) 11.53 3552.5 105
    (all in litres)
  • Hence batching is to be done by mass of the
    aggregate.

21
REINFORCEMENT
  • The standard trade/ I.S. marks is to be taken
    into account. In case standard bars are not
    available the weight of piece bar is to be
    determined by weighing in the shop which should
    be compared with the following table to know
    whether the bar is standard one.
  • Diameter of the rod Weight in Kg/metre
  • 6mm 0.222
  • 8mm 0.395
  • 10mm 0.617
  • 12mm 0.888
  • 16mm 1.578

22
TIMING OF CONCRETING IN SUMMER SEASON
  • In freshly laid slabs, sometimes cracks occur
    before concrete has set due to plastic shrinkage.
    This happens if concrete surface loses water
    faster than bleeding action brings it to top.
    Quick drying of concrete results in shrinkage and
    as concrete is plastic stage can not resist any
    tension, short cracks develop in the material.
    These cracks maybe 5 to 10 cm. in depth and the
    is width could be as much as 3 mm.
  • Rate of evaporation from the surface of the
    concrete depends on temperature of concrete, gain
    of heat from suns radiation, relative humidity
    of ambient air and velocity of wind playing over
    concrete surface. As such in winter days, there
    is no problem of timing of concreting. In summer
    concreting should be done during early hours of
    day when aggregates and mixing water is
    comparatively cool and sun rays are slanting.
    After concreting, top surface of concrete should
    be covered with plastic sheets/gunny bags, straw
    or any other available materials. This will
    minimise surface shrinkage cracking in the
    concrete.

23
FORMWORKS
  • The shape, and surface finish of concrete depends
    upon the Form Work.
  • Suitable chamber in the form works shall be
    provided in horizontal members of the structures,
    specially in long span to counteract the effects
    of deflection. As a rough guide, it may be 1 to
    250 for beams and 1 in 50 for cantilevers.
  • The inside surfaces of formwork shall be coasted
    with soap solutions, raw linseed oil or any other
    material, approved by the Engineer in-charge so
    as to prevent adhesion of concrete to formwork.
    Release agents shall be applied strictly in
    accordance with the instructions and shall not be
    allowed to come into contact with any
    reinforcement. Immediately before concreting, all
    formwork shall be thoroughly cleaned.
  • Propping and centering- Props used for centering
    shall be of steel or timber post, ballies or any
    other material, approved by the
    Engineer-in-charge.

24
FORMWORKS
  • The shape, and surface finish of concrete depends
    upon the Form Work.
  • It should be strong to support wet concrete and
    have smooth surface to prevent loss of slurry
    from the concrete.
  • Thin, deteriorated or non-vertical ballies will
    not be permitted at site.
  • Timber ballies shall always be vertical and never
    be in inclined position.
  • Any scaffolding shall only be on hard ground and
    not soft soil.

25
STRIPPING TIME OF FORM (Ref
IS-456, Para 11.3.1)
Sl. No. Type of Formwork Minimum period before striking forms
1. Vertical formwork to columns, walls, beams 16-24 h
2. Slabs spanning up to 4.5 m Slabs spanning over 4.5 m 7 days 14 days
3. Beams and Arches spanning up to 6.0 m/ over 6.0 m 14 days/21 days
26
CONCLUSION MIX DESIGN
  • Following mix design of 124 (Cement Sand
    Aggregate) gives strength required for M20
  • Cement Aggregate ratio - 16 (i.e. 124)
  • Sand - 24
  • Nominal size 10mm - 16
  • Nominal size 20mm - 60
  • This combination gives a minimum of 100 excess
    strength over nominal mix of 124. i.e. M15

27
WATER ABSORPTION OF BRICKS
  • Field Test The Test specimen shall consist of
    five whole dry bricks and shall be selected at
    random from the stack. The apparatus shall
    consist of a balance sensitive of within 0.2 to
    0.3 percent of the weight of the specimen.
  • The test specimen shall be weighed and shall then
    be completely immersed in clean water at room
    temperature and allowed to remain in this State
    for a period of 24 hours. The specimen shall then
    be taken out wiped with a damp cloth and then
    weighed immediately.

28
Percentage of water absorption
  • Weight of bricks after 24 hours immersion
  • ________________________________ x
    100
  • Weight of dry bricks

29
WATER ABSORPTION OF BRICKS
  • Laboratory Test The Test specimen shall
    consist of five whole selected at random from the
    lot of bricks obtained. The apparatus shall
    consist of a balance sensitive to within 0.1
    percent of the weight of the specimen.
  • The test specimen shall be dried to constant
    weight in ventilated oven at 1100 to 1150 . The
    specimen, shall then be cooled approximately to
    room temperature and weighed.

30
  • The dry specimens shall be completely immersed
    without preliminary partial immersion, in clean
    water at 15.50 to 300 C for 24 hours. Each
    specimen shall then be removed, the surface water
    wiped off with a damp cloth 2nd the specimen
    weighed. Weighing any one specimen shall be
    completed within three minutes after removing the
    specimen from the water.

31
DETERMINATION OF COMPRESSIVE STRENGTH
OF BRICKS
  • Five bricks shall be immersed in water at 250
    to 290 C for 24 hours. They shall then be removed
    and allowed to drains at room temperature for
    about five minutes and wiped free from surplus
    moisture. Their frogs shall be filled with mortar
    composed of one part portland cement and one and
    a half parts clean coarse sand graded to 3 mm and
    down. The bricks shall then be stored under damp
    sack for 24 hours. After the expiry of this
    period, they shall be immersed in water for seven
    days.

32
  • At the end of seven days, the samples of
    bricks shall be taken out, wiped dry and placed
    with the flat surfaces horizontal and the mortar
    filled face up wards between two-three plywood
    sheets each approximately 3 mm thick and
    carefully centered between the plates of the
    compression to testing machine. The load shall
    be applied axially at the uniform rate until
    failure occurs.
  • Arithmetic mean of the Maximum load at failure
  • Compressive Strength Area of bricks

33
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