civil work in ppc

1
Larsen Toubro Limited ECC Division- DLRO

• WELCOME
• TO
• QUALITY IN CIVIL CONSTRUCTION PROJECT
• PRESENTATION
• By
• N.Nirapandian

2
WHAT IS QUALITY?

• The totality of features and Characteristics of a
  product or service that on its ability to
  satisfy stated or implied need.

3
TOPICS

• FORM WORK
• CEMENT
• REINFORCEMENT
• AGGREGATE
• - COARSE AGGREGATE
• - FINE AGGREGATE
• WATER
• ADMIXTURE
• FLY ASH
• BRICK
• CONCRET
• POST CONCRETE CHECK

4
FORMWORK

• MATERIAL
• FORMWORK SCHEME
• DIMENSIONS
• LINE
• LEVEL
• VERTICALITY/PLUMB
• RIGHT ANGLE
• CLEANLINESS

5
FORMWORK

• DISTANCE BETWEEN ADJACENT MEMBERS
• COLUMN AND BEAM JUNCTIONS
• LEAK TIGHT JOINTS
• CLEANLINESS OF FORM SURFACE
• APPLICATION OF FORM RELEASE AGENT

6
FORMWORK
DO

• Follow the schemes given in Formwork manual
  strictly and avoid misuse of components.
• Apply form work releasing agent to the form work
  surface,to prevent absorption of water from
  concrete and adhesion of concrete and damage when
  shuttering is removed. The form work releasing
  agent should be applied before reinforcement is
  fixed in position.
• Provide tight joints use foam sheets to
  prevent leakage of grouts.
• Remove shuttering slowly and avoid sudden
  application of load.
• Allow specified time before removing
  shuttering.Follow the de shuttering time
  specified in contract / Indian standards.

7
COLUMN FORMWORK SYSTEM
WALER
TIE ROD
PROP
8
WALL FORMWORK SYSTEM
9

• CEMENT

10
CEMENT PHYSICAL PROPERTIES( Testing as per IS
4031)

• Normal Consistency
• Fineness
• Specific Gravity
• Soundness
• Initial and Final setting time
• Compressive strength at various ages-
• 3,7 28-days

11
CEMENT CHEMICAL PROPERTIES ( Testing as per IS
4032 )

• Chemical composition
• Heat of Hydration (if applicable)

12
CEMENT CHEMICAL COMPOSITION

• SI. NO. OXIDES
  PERCENT CONTENT
• 1 Lime (CaO)
  60-70
• 2 Silica (SiO2)
  17-25
• 3 Alumina ( Al2O3)
  3-8
• 4 Iron oxide ( Fe2O3)
  0.5-6
• 5 Magnesia ( MgO )
  0.1-4
• 6 Alkalies ( K2O,Na2O )
  0.4-1.3
• 7 Sulphuric Anhydride (SO3)
  1.3-3

13
TYPES OF CEMENT

• 1.Ordinary Portland Cement
• - 33 Grade
  -confirm to IS 269
• - 43 Grade
  -confirm to IS 8112
• - 53 Grade
  -confirm to IS 12269
• 2. Portland Pozzolana Cement
  -confirm to IS 1489
• 3. Portland Slag cement
  -confirm to IS 455
• 4. Rapid Hardening Cement
  -confirm to IS 8041
• 5. Sulphate Resisting Cement
  -confirm to IS 12330
• 6. Low Heat Cement
  -confirm to IS 12600
• 7. Coloured Cement White Cement -confirm to
  IS 8042
• 8. High Alumina Cement
  -confirm to IS 6452

14
CEMENT SAMPLING TUBE
15
STACKING STORAGE OF CEMENT

• Storage of cement bags shall be done by
  completely covered dry and moisture proof godawn.
• It should not be stacked directly on ground.
• Stacking should be done on wooden blanks at
  height of 150 to 200 mm from floor level.
• Godawn should not have any permanent opening.
• Stacking should be done week wise(Batch/lot).
• No of cement bag should not be more than 12 in a
  single stack.
• Gap of 300 mm at least should be maintained
  between stack of different weeks/lots/Batch.
• Gap of 450 mm should be maintained between stacks
  and side wall of godawn.
• Gap of 600 mm between two consecutive row of
  stacks should be maintained.
• Sufficient lighting arrangement should be
  provided in cement godawn for handling the
  cement bag.

16
CODES GOVERNING REINFORCEMENT BARS

• IS 1786 - 1985
• BS 4449 - 1997
• ASTM A 615 1984
• EN 10080
• RUSSIAN (GOST)

17
REINFORCEMENT

• MATERIAL
• CHEMICAL PROPERTIES (TC)
• TENSILE STRENGTH
• ELONGATION
• BEND REBEND
• MEAN PROJECTED AREA
• SECTIONAL WEIGHT
• WELDABILITY

18
CHEMICAL COMPOSITION OF REBARS AS PER IS 1786 -
1985
19
MECHANICAL PROPERTIES OF REBARS AS PER IS 1786 -
1985
20
ALLOWABLE TOLERANCE ON NOMINAL MASS OF BARS AS
PER IS 1786 - 1985

• By using bars of negative tolerance effective
  savings in cost can be achieved. (The design
  construction is based on specific theoretical bar
  diameter, but the bars are supplied by weight)
• If the bars are with plus weight, it means
  reduced geometrical properties of ribs, which in
  turn reduces the bond between concrete steel.
  And also leads to increase in the project cost.

21
TYPES OF REBARS

• Cold Twisted Deformed (CTD) rebars.
• Torsteel Rebars.
• Thermo-Processed (TMT) rebars.
• Corrosion Resistant (CRS) rebars.
• Micro alloyed Steel rebars.
• Coated rebars either galvanized or epoxy coated.

22
ADVANTAGES OF TMT BARS

• TMT bars contain lower carbon content thus
  exhibit better ductility weld ability (can be
  butt welded or lap welded)
• TMT bars have better yield strength, tensile
  strength, and elongation than CTD bars of same
  grade.
• TMT bars display easy bend ability and thus
  requires less energy for bending rebending
  along with superior reverse bending properties.
• They possess in built ability to resist loss of
  strength when exposed to higher temperatures.
• They display better corrosion resistance than CTD
  bars due to absence of cold twisting stresses.
• TMT bars are also available in higher strength
  levels than those listed in the Indian Standard.
  Use of Fe 500 grade TMT bars can result in saving
  of more than 15 in steel consumption when
  compared to CTD bars.

23
REINFORCEMENT

• BAR BENDING SCHEDULE
• CUTTING/BENDING TO REQUIRED DIMENSIONS
• SPACING AS PER REQUIREMENT
• LAPS
• TYING
• COVER/CHAIRS

24
CUTTING BENDING

• Jigs used for manual bending for correct
  dimensions before going for mass production.
• Cutting schedule.
• Use of latest revision of drawings bar bending
  schedules.
• Check bent shape for dimensional accuracy
  (against a template), bent radius for signs of
  fracture.
• Always bend the bars by Cold. Bars larger than
  25mm in size may be bent hot at cherry red heat
  (not exceeding 8500C) except those bars which
  depend for their strength on cold working. Hot
  bars shall not be cooled by quenching. ( Clause
  6.1.1 of IS 2502 1963)
• Bundling labeling bars of identical size, shape
  type.

25
METHODS OF JOINING REBARS

• WELDING
• SPLICING BY SWAGED COUPLER METHOD
• SPLICING BY USING THREADED COUPLERS

26
(No Transcript)
27
REINFORCEMENT COVER COVER BLOCK

• Cover to reinforced concrete member is the
  minimum thickness of concrete provided over the
  reinforcement steel measured from the exposed
  concrete surface to the closest reinforced steel.
  The role of concrete in the cover region can be
  compared to the role human skin plays in
  protecting the flesh other parts of the body.
• Concrete in the cover region protects steel
  reinforcement in two ways
• By providing dense, strong, impermeable barrier
  against ingress of moisture, oxygen, chlorides,
  sulphates, carbon dioxide, other aggressive
  gases chemicals.
• By providing passive coating on steel surface.
  Due to alkaline nature of concrete, this coating
  prevents corrosion of steel.

28
REINFORCEMENT COVER AS PER IS 456 - 2000
PERMISSIBLE TOLERANCE FOR COVER
Unless specified, actual concrete cover should
not deviate from the required nominal cover by
10mm there is no negative tolerance.
29
PROTECTION OF REBARS

• If the work is suspended for a longer period,
  then the dowel bars left in the first phase have
  to be protected. The protection can be done by
  the following methods
• By applying a firm coat of neat cement slurry to
  the exposed reinforcement bars leaving no point
  untouched.
• Apply suitable anti corrosive chemical to guard
  against corrosion.
• Encase the dowel bars in concrete either fully or
  partly.

30
Reinforcement
DO

• Conduct applicable tests for the reinforcement
  bars for every lot / as stipulated in the
  specification
• Store reinforcing bars under cover, until
  required to use, kept clear of mud, dirt and oil
  and preferably stacked by sizes on racks.
• Use only bars that are free from mud, dirt, oil,
  grease, paint, loose rust, mill scale and pitting
  due to corrosion, Slightly oxidized bars are not
  good for adhesion with concrete

DONT

• Dont use bars with mud and dirt sticking to
  them. Mud and dirt can be easily washed off with
  water.
• Dont use bars with oil, grease and paint
  sticking to them. These should first be dissolved
  in suitable solvents.
• Dont use bars with loose rust and mill scale.
  These can be removed with a wire brush.

31
BAR BENDING AND FIXING
DO

• Cut and bend bars according to detail schedules,
  paying special attention to bends and hooks.
• Join wires securely at crossings with soft iron
  wire of 18 or 20 S.W.G. or with galvanized wire
  clips specially made for this purpose or by spot
  welding.
• Carry out bending of bars cold in the normal
  course. In certain circumstances, such as bars of
  large diameter, heating to cherry red ( 1550 F
  ) may be permitted and after bending, the bars
  allowed to cool naturally , quenching by dipping
  in oil should not be allowed.
• To maintain adequate cover to the steel
  reinforcement, use concrete spacer blocks or
  concrete rings of thickness equal to the cover
  required preferably wired to bars to prevent
  their displacement.

32
BAR BENDING AND STEEL FIXING

• Read drawing and bending schedules
• Identifies the types and grades of reinforcement
  requirement.
• Measure and set out the work
• Calculates from codes and standards the cut
  length, the weights of bar the weights involved
  in the job.
• Computes the quantity of materials used in day to
  day work
• Estimate the time requirement of a particular
  job.
• Programmes and maintains progress of material and
  labour
• Plans necessary work force for the job
• Plans cutting schedule to minimise scrap
• Cuts and bends reinforcement exactly as per the
  requirement of the schedule.
• Ensure that bent bars of the same type are
  bundled together and tagged for identification.

33
BAR BENDING AND STEEL FIXING

• Ties and fastens bundled bars to ensure they
  remain in position whether horizontal and
  vertical
• Stacks and stores tidily and safely to ensure
  correct utilization based on size and type
• Keep accurate and uniform spacing of
  bars,staggers laps and maintain correct cover
• Recognizes main bars and distributors
• Correlates the sequence of reinforcement placing
  with fixing of inserts,sleeves, electrical
  conduits anchors.
• Prefabricates mesh and cages including additional
  bars for lifting safely
• Identifies and uses correct ties on structures.
• Protects the steel from corrosion and weathering
  action
• Prepare reinforcement patterns for special
  structures
• Work safely at heights using ladders,scaffolds
  and safety bolts.

34
AGGREGATE
35
AGGREGATE

• Coarse Aggregate
• Aggregate most of which retained on 4.75 mm IS
  sieve
• Fine Aggregate
• Aggregate most of which passed through 4.75mm IS
  sieve.
• Aggregates must confirm to IS 383 requirement.

36
AGGREGATE TESTING

• PETROGRAPHIC examination as per IS 2386 -
• ( part- VIII ).
• COARSE AGGREGATE
• Sl.No. Tests Test standard
  Requirement as
• 
  per IS 383
• 1 Deleterious Material IS 2386
  (part-II) Ref. Table-1 of IS 383
• 2 Sieve analysis IS
  2386 (part-I) -----
• 3 Specific gravity IS
  2386 (part-III) 2.6 2.8
• 4 Elongation
• Flakiness Index IS
  2386 (part-I) -----
• 5 Soundness test IS
  2386 (part-V) 12 tested with Na2SO4
• 
  18
  tesed with MgSO4
• 
  
  
  (Max. )
• 6 Water absorption IS
  2386 (part-III) --------

37
AGGREGATE TESTING

• Sl.No. Tests Test standard
  Requirement
• 7 Crushing Value IS 2386
  (part-IV) Max. 30 for Road
• 
  
  Runway 45 for other
• 
  
  concrete
• 8 Impact Value IS
  2386 (part-IV) Max. 30 for Road
• 
  
  Runway 45 for
• 
  
  other concrete
• 
  
  9 Abrasion
  Value IS 2386 (part-IV)
  Max. 30 for Road
• 
  
  Runway 45 for other
• 
  
  concrete
• 10 Alkali reactivity IS 2386
  (part-VII) --------
• 11 Chloride sulphate
• content ASTM
  (1411) ---------

38
AGGREGATE TESTING

• Fine Aggregate
• Si.No. Tests Test
  standard Requirement
• 1 Deleterious Material IS 2386
  (part-II) Ref. Table-1 of IS 383
• 2 Sieve analysis IS
  2386 (part-I) Ref. Table-1 of IS 383
• 3 Specific gravity IS
  2386 (part-III) 2.6 2.8
• 4 Soundness test IS
  2386 (part-V) 10 tested with Na2SO4
• 
  15
  tested with MgSO4
• 
  
  
  (Max. )
• 5 Water absorption IS 2386
  (part-III) --------
• 6 Chloride sulphate
• content
  ASTM (1411) ---------

39
PROPERTIES OF AGGREGATE

• S. No. PROPERTIES INFLUENCE ON
  CONCRETE
• 
  PROPERTIES
• Sp. Gravity/Porosity
  Strength / Absorption
• Chemical stability
  Durability
• Surface Texture Bond
  grip
• Shape
  Water demand ( strength )
• Gradation or particle Water
  demand (strength),
• size distribution
  Cohesion, bleeding and segregation
• Maximum size
  Strength and water demand
• Deleterious Materials Water
  demand (strength), bond cohesion
• 
  and durability

40
Aggregate
DO

• Test aggregates as stipulated in the
  specification
• Stacking of aggregates of different sizes
  separately in the stack yard.
• Stack on leveled surface and higher elevations
  than the surroundings.

DONT

• Mixing of different sizes of aggregate in stack
  yard.
• Mixing of aggregates with dirt, mud other
  unwanted materials.

41
AGGREGATE SAMPLING SCOOP
42
WATER

• Water used in Construction shall be tested as
  per IS 3025
• and confirm to IS 456
• SI. NO. PROPERTIES TEST
  MIN. MAX.
• 
  PROCEDURE LIMIT LIMIT
• PH-Value IS 3025
  6 ---
• Organic solid
  --do -- 200mg/lit.
• Inorganic solid
  --do-- --- 3000mg/lit.
• Sulphates ( as SO3)
  --do-- --- 4000mg/lit.
• Chloride ( as Cl )
  --do-- --- 2000mg/lit.for
• 
  
  PCC 500mg/lit.
• 
  
  for RCC.
• Suspended matter
  --do-- --- 200mg/lit.
• To neutralise 100 ml sample of water using
  phenolphthalein as an indicator, it should not
  require more than 5 ml. Of 0.02 normal NaOH.
• To neutralise 100 ml sample of water, using mixed
  indicator, it should not require more than 25 ml.
  Of 0.02 normal H2SO4.

43
ADMIXTURE

• It is a material, other than the cement,water
  and aggregate in concrete to modify the
  properties of ordinary concrete so as to make it
  more suitable for any situation.

44
TYPE OF ADMIXTURE

• 1. Mineral admixture
• 2. Chemical admixture
• Mineral admixture
• Fly ash
• Silica fumes
• Rice husk ash
• Metakaoline
• Ground Granulated Blast Furnace

45
Chemical admixture

• Plasticizers
• Superplasticizers
• Retards and Retarding Plasticizers
• Accelerators and Accelerating Plasticizers
• Air- entraining Admixtures
• Damp proof and Waterproofing admixtures
• Workability Admixtures
• Gas forming Admixtures
• Grouting admixtures
• Bonding Admixtures etc

46
FLY ASH

• PHYSICAL PROPERTIES
• Bulk density gm/cm3 1.21
• Specific gravity
  2.22
• Resistivity at 500 VDC and 25 0 C
• Surface resistivity
  3.79x109
• Volume resistivity
  1.1x108
• Lime reactivity
  5.8
• Blains surface area, m2/N 35.15

47
FLY ASH

• Chemical Properties
• S No. CHEMICAL PERCENT
  BY WEIGHT
• COMPOSITIONS AS PER IS
  38122000PART- I
• SiO2
  35 ( min.)
• Al2O3
  -----
• Fe2O3
  -----
• SiO2Al2O3Fe2O3 70
  (min.)
• MgO
  5.0 (min.)
• SO3
  2.75 (max.)
• Loss of Ignition
  5.0 (max.)
• CaO
  -----

48
COMPARISION OF PHYSICAL PROPERTIES OF OPC AND FLY
ASH CONCRETE

• S.No. PROPERTIES OF OPC MIX
  OPCFLY
• CONCRETE
  ASH MIX
• Workability, slump (mm)
  60 70
• Compressive Strength, N/mm 2
  
• 7-days
  20
  23.6
• 28-days
  30.1
  35.1
• 56-days
  34.6
  42.2
• Water Permeability at
  
• 28 days m/s x 10-12
  8.7
  6.6
• Modulus of elasticity at
  
• 28 days, mpa x 104
  2.2
  2.71

49
BRICK ( Common burnt clay brick as per IS 1077 )

• CLASSIFICATION
• Class Designation Avg. Compressive
  strength not
• 
  less than (N/MM2)
• 35
  35
• 30
  30
• 25
  25
• 20
  20
• 17.5
  17.5
• 15
  15
• 12.5
  12.5
• 10
  10
• 7.5
  7.5
• 5
  5
• 3.5
  3.5

50
QUALITY OF BRICKS

• Free from cracks,flaw and noudles of free lime.
• Smooth rectangular faces with sharp corner.
• Uniform in colour and ringing sound.
• PHYSICAL REQUIREMENTS
• (Brick of size (230x110x70) mm
• Dimensional test
• Test should be conducted on 20 no. sampled bricks
• Dimensions of 20 no. bricks together should be as
  below-
• Length (4600 /- 80) mm
• Width (2200 /- 40) mm
• Height (1400 /- 40) mm

51
QUALITY OF BRICKS

• Frog size(Brick mark) should be (60x40x)mm
  with depth 10-20 mm and radius 20mm as shown in
  IS 1077- clause 6.1.1, fig. 1A.
• Water absorption-
• (When tested as per IS 3495- part-2)
• Absorption shall not be more than 20 by weight
  up to class
• 12.5 and 15 for higher classes.
• Compressive strength-
• (When tested as per IS 3495-part I)
• Average Compressive strength of 5 no. sampled
  bricks shoild not be less than the minimum
  compressive strength specified for the
  corresponding class of bricks.

52
CONCRETE

• CONSTITUENTS
• CEMENT SUPPLEMENTARY CEMENTITITIOUS
  MATERIAL (10 15)
• AGGREGATES (60 80)
• WATER (15 20)
• ADMIXTURE

53
WATER CEMENT RATIO
In a cement slurry, the ratio of water to cement
expressed as percent, the number of parts of
water used to mix with 100 parts of cement.  If
all the water absorbed by the aggregate particles
is neglected just water on the surface is
considered along with the water added to the mix,
then the W/C is called Free water cement
ratio.  If water absorbed by the aggregate
particles is also considered in addition to the
water on the surface of the particles as well as
water added to the mix, then the W/C is called
total water cement ratio.  In the concrete
mixes, besides cement, if any cementitious
materials like fly ash, silica fume, ground
granulated blast furnace slag, etc is used, and
then the ratio will be known as Water
cementitious ratio.
54
SIGNIFICANCE OF WATER CEMENT RATIO
When the concrete is fully compacted, its
strength is taken to be inversely proportional to
water cement ratio.  Water cement ratio
determines the porosity of the hardened cement
paste at any stage of hydration hence
influences the durability permeability of
hardened concrete. When concrete is made using
very high water cement ratio, large capillary
pores in cement paste allows high permeability of
water along with other chemicals like chlorides
sulphates, which cause deterioration of concrete.
To have durable concrete structures, it is
desirable to specify low water cement ratios.
55
IMPORTANCE OF WATER CONTENT IN THE MIX

• CEMENT W/C
• 400 KG /CUM 0.55
• 300 KG/CUM 0.55

56
CHECK FOR CONCRETE

• SLUMP/WORKABILITY
• COHESIVENESS/SEGREGATION
• AIR CONTENT
• COMPACTION
• FINISHING
• CURING
• COMPRESSIVE STRENGTH
• YIELD (SOURCE CONSISTENCY)
• TEMPERATURE CONTROL (Beyond 40 Deg.C)

57
CONCRETE SAMPLING SCOOP
58
PRODUCTION AND PLACEMENT

• MIXING
• PLACE WITHIN INITIAL SETTING TIME
• VIBRATION
• CURING
• SUPERVISION
• CONSTRUCTION JOINT PREPARATION

59
PLACING CONCRETE
DO

• Place concrete in position before initial set
  occurs i.e., within 30 minutes of mixing.
• Fill all nooks and corners in formwork, surround
  all reinforcement with concrete using tamping
  rods or vibrators.
• Place concrete in horizontal layers ( 6 to 12
  deep for R.C. work and 15 to 18 for mass
  concrete work) each of which should be compacted
  properly, before subsequent layers are placed.
• Place each layer before the previous layer has
  hardened, except, of course, where concreting of
  the previous layer was stopped at the end of the
  days work. In fact concrete placing should be
  continued without interruptions until the
  placement is completed to avoid intermittent cold
  joints.

DONT

• Dont place concrete during rains unless proper
  cover can be provided.
• Dont drop concrete from a height greater than 5
  feet to avoid segregation.
• Dont use concrete in which initial set of
  cement has already started.

60
IRONITE FINISH( Patent stone with Metallic
Hardner)

• i) This will consist of a topping
  (incorporating iron particles) to bond with
  concrete base while the concrete is green.
• ii) The metallic hardner finish shall be of
  12 mm depth over 28 mm thick concrete base.
• iii) Total thickness shall be 40 mm thick.
• The hardening compound shall be uniformely graded
  iron particles free from non-ferrous metal
  impurities, oil, grease,sand or other injurious
  materials
• 1 part of metallic hardener shall be mixed dry
  with 4 parts of cement, by weight.
• To this mixture 6 mm nominal size stone chips
  shall be added in proportion of 1 part cement
  (mixed with hardener ) to 2 parts of stone chips
  by volume and uniformly mixed.
• Minimum qty. of water shall be added to make it
  workable.
• The surface shall be roughened by wire brush as
  soon as possible.
• This Topping layer shall be pressed firmly and
  worked vigorously and quickly to secure full bond
  with the concrete base.
• The surface shall be finished smoothened with
  steel trowel.
• The finished floor shall be cured for 7- days by
  keeping it wet/ponding.

61
PLASTERING WORKS

• SAND
• Sand should consist of natural sand,crushed stone
  sand crushed gravel sand.
• Sand should confirm to IS 383 and grading should
  confirm to IS 1542.
• Total of all deleterious substances should not
  exceed 5 by weight.
• Fineness modulus of sand should be 2.0 to 2.2
• MIXING
• Non observant surface should be used for mixing
  the cement sand mortar.

62
PLASTERING WORKS

• Cement sand should be mixed in dry state first
  and then add water and mixed.
• The mortar should be consumed within half an hour
  of mixing.
• Measuring box should be used to ensure proper
  proportion of mix.
• If machine mixed, mixing time (Rotation )should
  be 1.5 to 2 minutes
• APPLICATION OF PLASTER
• For external plaster, the work shall be from the
  top floor and downwards.
• For internal plaster,ie wall, the work shall be
  top and carried downwards.
• Plastering shall be carried out to the full
  length of the wall or to natural breaking points
  like door/windows etc.

63
PLASTERING WORKS

• Ceiling plaster shall be completed before
  commencing wall plastering.
• No single coat, shall exceed 12 mm in thickness.
• Curing shall be 2 days for each coat and for
  finished surface at least 7 days.

64
CURING
What is Curing? Curing is the process of
preventing loss of moisture from the concrete
while maintaining a satisfactory temperature
regime. Why curing is required? Concrete in its
early life needs to be carefully looked after
like parents looking after their newborn baby. If
the concrete is not nurtured properly by carrying
out the required curing protected against wind
extreme ambient conditions, then the structure
will loose its strength, durability, the
concrete will behave like a child born weak.
65
METHODS OF CURING

• Water cure by flooding, ponding, mist spray.
• Water retaining method By using absorptive
  coverings such as sand, canvas, burlap or straw
  that are kept continuously wet.
• By mechanical barriers.
• By using chemical membranes.

66
MINIMUM CURING PERIOD AS PER IS 456 - 2000

• For OPC or Super sulphonated cements
  Minimum Seven days
• For concrete having blended cements like Portland
  pozzolana cement, Portland slag cement or mineral
  admixtures
• - Minimum 10 days. This may be extended to 14
  days.
• 3. For concrete exposed to dry hot weather
  conditions
• - Minimum 10 days.

67
CURING
DO
Keep all surfaces of newly laid concrete damp for
7 days. Damping can be done in several ways by
hosing or sprinkling of water by wet sacking or
matting by ponding of horizontal surfaces with
raised edges in weak mortar and filling I 2
depth of water or by laying 2 3 thick
layers of sand kept soaked in water.
DONT
Dont neglect curing. It is better to over cure
than to under-cure. Under-curing results in loss
of strength which is irreparable and water is
cheap.
68
CONSTRUCTION JOINTS
Construction joints are surfaces where two
successive placements of concrete meet. They are
typically placed at the end of the days work.
But may also be required when the concrete
placement is stopped for longer than the initial
setting time of concrete. The location of
construction joints should be planned. It may be
desirable to achieve bond continue
reinforcement through a construction joint. For
monolithic concrete, a good construction joint
might be a bonded interface that provides a water
tight surface allows for flexural shear
continuity through the interface.
69
METHODS OF PREPARATION OF CONSTRUCTION JOINTS

• By using hand chisel hammer
• By using pneumatic bush hammer
• By using water jetting
• By applying surface retarder over the concrete
  surface. Cement paste and laitance were brushed
  away when the concrete was initial set.

70
USE OF SURFACE RETARDER

• Purpose Preparation of Construction Joint (CJ )
• Application
• After compaction and surface finishing of green
  concrete, water (if any) should be removed from
  surface.
• Surface retarder should sprayed or painted with
  brush on the surface of green concrete.
• Just before starting of final setting time of
  concrete, pressurised water jet at an angle of 60
  degree from vertical should be applied on the
  surface.
• Since surface retarder increase the setting time
  of concrete on the surface, cement from the top
  surface of concrete shall be cleaned off and the
  sound aggregate get exposed, which is required
  for good CJ surface.

71
USE OF SURFACE RETARDER

• Advantages
• It completely avoids chipping of concrete for CJ
  preparation
• Only air cleaning is required prior to the
  concreting
• This process is faster than the chipping process.

72
CONSTRUCTION JOINTS IN BEAMS SLABS

• Desirable location for construction joints placed
  perpendicular to the main reinforcement are at
  points of minimum shear or points of contra
  flexure. Construction joints are usually located
  at mid span or in the middle third of the span,
  but locations should be verified by the Engineer
  before placement.
• Horizontal construction joints in beams and
  girders are usually not recommended.Common
  practice is to place beams girders
  monolithically with the slab.
• For the beams where the members are of
  considerable depth, it is advisable to place the
  concrete in the beam section up to the slab
  soffit, then placing the slab in separate
  operation. This is to avoid cracking of the
  interface because of vertical shrinkage in deep
  member if beam slab concrete are placed
  monolithically.

73
CONSTRUCTION JOINTS IN BEAMS SLABS

• The main concern in joint placement is to provide
  adequate shear shear transfer flexural
  continuity through the joint. Flexural continuity
  is achieved by continuing the reinforcement
  through the joint with sufficient length past the
  joint to ensure adequate splice length for the
  reinforcement. Shear transfer is provided by
  shear friction between old new concrete or
  dowel action in the reinforcement through the
  joint.

74
CONSTRUCTION JOINTS IN SLABS
1
2
75
Ò
3
Ö
4
76
Ö
5
X
( X 1/3rd to 1/4th span )
77
CONSTRUCTION JOINTS IN COLUMNS
SMOOTH AND FULL OF LAITANCE
Ò
Ò
ROUGH AND FREE OF LAITANCE
Ò
Ö
78
CONSTRUCTION JOINTS IN FOOTINGS
Ò
Ò
KICKER
KICKER
Ö
Ö
79
EXPANSION JOINTS

• Expansion joints are used to limit member forces
  caused by thermally induced volume changes.
  Expansion joint permits separate segments of a
  structure to expand or contract without adversely
  affecting structural integrity or serviceability.
• Expansion joint isolates building segments
  provides relief from cracking because of
  contraction of the structure. Joint width should
  be sufficient to prevent portions of the
  structure on either side of the joint from coming
  in contact.
• Joints may vary in width from 25mm to 15mm. Wider
  joint are used to accommodate additional
  differential structural movement that may be
  caused by settlement or seismic loading. Vertical
  expansion joints should pass through the entire
  structure above the level of the foundation.

80
MATERIALS USED FOR EXPANSION JOINTS

• Flexible boards
• Sealants hot poured, bituminous in origin
• Sealants cold applied, Poly sulphide sealant.
• Pre formed elastomeric
• PVC water stop
• Steel, copper

81
SURFACE DEFECTS IN CONCRETE CAUSES AND REMEDIAL
MEASURES

• Any defects in the finished concrete surface
  observed after removal of form work
•  
• Design and construction-related causes
•          Difficult placement due to design of a
  member
•          Improper design, construction and
  maintenance of forms
•          Improper selection of concrete mixture
  proportions
•          Failure to adjust concrete mixture
  proportions to suit
•          Placement condition
•          Improper placement practices
•          Improper vibration and consolidation
  practices
•          Improper steel detailing

82

• Equipment-related causes
• Improper equipment
• Improper equipment maintenance
• Equipment failure (crane, pump, concrete plant)
• Interruption of utility service
• Material-related causes
• Improper selection of release agent
• Cement characteristics
• Variation in mixture components
• Inappropriate use of admixtures
• Inappropriate use of release agents
•  
• Environmental causes
• Extreme weather conditions

83
Types of surface defects

• Surface defects which can result from ineffective
  consolidation procedures are discussed below.
• 1 Honeycomb
• Honeycomb is a condition of irregular voids due
  to failure of the mortar to effectively fill the
  spaces between coarse aggregate particles. Where
  bridging of the aggregate particles or stiffness
  of the mixture is a cause of honeycomb, vibration
  may assist in overcoming the bridging by
  increasing the flowability of the concrete.
• Causes congested reinforcement,
• insufficient paste content,
• improper sand-aggregate ratio,
• improper placing techniques,
• quick setting on hot concrete, and difficult
  construction conditions. Changes in mixture
  proportions to improve workability may assist in
  reducing or preventing honeycombing.

84
2- -Bugholes (Air surface voids) Bugholes on
vertical faces are normally caused by air
bubbles, but occasionally by water entrapped
between the concrete mass and the form,
especially in sticky or stiff concrete mixtures
of low workability which may have an excessive
sand and/or entrapped air content. Also, the use
of vibrators of too large an amplitude or the
lack of complete insertion of the vibrator head
may result in increased air-void formation.
85
3--Form-streaking Form-streaking is caused by
mortar leaking through form joints and may be
aggravated by over vibration from vibrators that
are too powerful, or by using forms that vibrate
excessively during consolidation. Placing
excessively wet or high-slump concrete mixtures
will result in more mortar washing out through
tie holes and loose fitting forms. Special care
is sometimes required when super plasticizers are
used, as they tend to increase leakage at form
joints and in pump lines.
4 --Aggregate transparency Aggregate
transparency is a condition characterized by a
mottled coloring on the surface which results
from deficiencies in the mortar. It may result
when concrete mixtures have low sand content, dry
or porous aggregates, or high slump with some
lightweight and normal weight aggregates. Also,
high density or glossy form surfaces may cause
aggregate transparency.
86
5--Subsidence cracking Subsidence cracking
results from the development of tension when the
concrete settles after or near initial set. The
cracks are caused because the upper concrete
bridges between the forms while the lower
concrete settles. These cracks may occur when
there is an insufficient interval between
placement of concrete in columns and placement of
concrete for slabs or beams. They may also occur
adjacent to block outs or over reinforcing bars
with shallow cover.   To prevent subsidence
cracking, the concrete can be revibrated.
Revibration is most effective when done at the
latest time at which the vibrator head will
penetrate the concrete under its own weight.
Subsidence cracking over reinforcing bars can be
controlled by increasing concrete cover during
the design phase and by using well-consolidated,
low-slump concrete.
87
6--Color variation Color variation may occur
within a placement if the concrete is not uniform
or is incompletely mixed. Vibrators inserted too
close to the form destroy the release agent or
mar the form surface. External vibration used
haphazardly may also cause color variation.
Furthermore, color variations may result from
nonuniform absorption and/or nonuniform
application of the release agent.
7 --Sand streaking Sand streaking is a streak of
exposed fine aggregate in the surface of the
formed concrete caused by heavy bleeding along
the form. It frequently results from the use of
harsh, wet mixtures, particularly those deficient
in 0.30 to 0.15 mm and smaller sizes. Sand
streaking is controlled by the use of tight forms
and proper mixture proportioning, using
well-graded fines to minimize bleeding.
88
8- -Layer lines Layer lines are dark horizontal
lines on formed surfaces which indicate the
boundary between concrete placements. Layer lines
are caused by stiffening or insufficient
consolidation of the lower level due to lack of
penetration of the vibrator into the lower
level.   9- -Form offsets Form offsets are
usually caused by inadequate stiffness or
anchorage of the forms and can be aggravated by
too high a rate of placement and/or using too
powerful a vibrator. 10--Cold joints Cold
joints frequently occur in concrete for many
reasons. Cold joints can often be avoided by
contingency planning, back-up equipment, working
to keep the concrete surface alive, and working
to vibrate into lower lifts.
89
THANKYOU