Concrete is a mix obtained when cement, sand,
aggregates, and water along with admixtures are mixed. Here important checks
are discussed from production of concrete to its placement. Okey Card / Inspection
Request and Pour Card are also discussed.
Please refer details of concrete at the
following link:
https://www.techpostsk.com/2021/09/different-types-of-concrete.html
Topics Covered
General
Types of Concrete - Nominal Mix Concrete
Types of Concrete -Design Mix Concrete
Data Required for Design Mix Concrete
Brief description for types of concrete
Summary of Different types of Concrete
Project Concrete Requirements Management
Following important points are being discussed
for the subject blog
Surface preparation of cushion concrete,
Joint Filler & adjacent face joint tie bar
treatment,
Joints & Sealants Checking,
Rubber
Water Stops,
Copper Water Stops,
Joint Filler Material in various thickness as
per design requirement,
Bituminous Coating,
Reinforcement placement is done over the base
concrete,
Material Used for Reinforcement,
Splicing / Lapping of Reinforcement,
Placing of Steel Bar,
Placement Record of Steel,
Material Used for Formwork,
Material Used for Formwork,
Surface of Formwork,
Supporting of Formwork,
Removal of Form work,
Concrete Placement Equipment,
Curing Arrangement,
Inspection Request Format or Okey card Format
1. Surface Preparation of Cushion Concrete.
(removal / chipping of defective and loose
concrete & cleaning before laying the design mix concrete over base or
cushion concrete.)
The base concrete is done on the raw surface, such as below the design foundation level on the prepared ground surface.
2. Joint Filler & adjacent face joint tie bar
On large structures such as dams and barrages, concrete is
never done in the entire length. Instead, the length of
foundation area is divided in blocks of designed length. Base
concrete or leveling concrete or cushion concrete in designed
thickness is done for each block and over this base concrete
, structural concrete RCC is done in planned height, supported
by side shutters. The shutters are supported with the help of
tie bars embedded in concrete. (Tie bars should not be
attached to the
reinforcement bars).
After the removal of shutters, the tie rods remain exposed. The
concrete around these bars is removed to a certain depth as
per specifications and the tie bar is cut and the hole is filled
with concrete as per specifications. If not done as described,
the water / moisture will corrode the bar and the process of
corrosion move further and may damage the concrete and
reinforcement.
As such all the tie bar on the face are treated and the entire
side surface is covered to maintain a joint between the blocks
. The surface may be painted and provided with a spacer
sheet of designed thickness. This is done to maintain the
separation between the blocks.
3. Joints & Sealants Checking:
The general check shall be done for following
measures / points or otherwise as per design specifications.
Material Used: The dimensions detailed for
water stops ere indicative and the specified dimensions should be followed.
(a). Rubber
Water Stops. Please refer the water stop image.
Size: 300mm wide and 8 mm thick
Lapping = 150 mm by thermal adhesion or thermal
welding
Surface Cleaning
Location: Line & Elevation
(b). Copper
Water Stops
Size: 340 mm wide and 1.2 mm thick
Lapping = 20 mm by brazing and double-sided
welding
Surface Cleaning
Filling of Foamed Materials
Location: Line & Elevation
4. Joint Filler Material in various thickness as per design
requirement
The material used for expansion joint fillers
include low viscosity epoxy resins, silicone gels, and cork and woods....
Epoxy and silicone sealants also offer excellent moisture, dirt protection.
Polyethylene Seam Fill Board is also a good
alternative for underwater structures. Thermocol sheets use in under water
structures must be avoided as it may be harmful for aquatic animals.
Bitumen coat of specified grade is applied as
per following sequence:
Surface Cleaning
Surface Dry
Two layers of coating
Note: Before placing joint filler material the
adjacent concrete surface must be clean, smooth, and free from form ties.
6. Reinforcement placement over the base concrete.
The reinforcement must be placed over the
chairs. Check for sufficiency of these chairs.
In larger works each block may have concrete on
all four sides. These blocks are separated by joints and shear keys.
Check for reinforcement provision around shear
keys and joint face. Reinforcement of raft (bottom) checking as per approved
drawings
Anti-crack reinforcement checking if provided.
Other Reinforcement checks:
Concrete cover (Top, Bottom & side)
Lapping of bars
Tying of bars
Spacing of reinforcement bars
Staggering of lap joints
Cleaning of bar
Steel bar coupling placement as per design
Coupler tightening
Welded Bars (weld Lap length &
quality)
Cleaning
of surface of loose material with necessary cover to reinforcement.
Concrete
surface preparation after green cutting.
Concrete
surface preparation after green cutting.
Material
Used for Reinforcement
Grade of steel
Free from loose mill scale, rust, grease,
paint, splashed concrete or other coatings
Splicing / Lapping of
Reinforcement
Overlap Length
Welding: Single weld / double weld length
Coupler Tightening
Stagger of lapping
Line
Required Elevation
Diameter
Length
Shape
Number
Spacing
Plumb for Vertical Bars
Cover – Side, Top & Bottom cover
Concrete Cover Block
Sufficient steel chairs, spacers, hangers, and
any other steel supports
Tying of steel bar with binding wire, diameter
of binding
wire
> 1.6 mm
Placement Record of Steel
Bar Mark
Diameter of bar
Number
Sizes
Length
Weight
7. Form Work Checks
Form work must be
checked for following points
Straight / smooth (Free from depression)
Cleaning
Oiling
Line and layout
Required markings for concrete levels
Plumb / Verticality / inclined angle of forms
Hole / Gap filling / taping
Tie bar / Anchor bolt (must not be welded or tied
with main reinforcement)
Steel
Plywood
Timber
Any other
Straight / smooth (Free from depression)
Cleaning
Oiling
Ties
Anchor Bolt
Props
Others
Hole / Gap Sealing of Formwork
Mastic tape
POP
Mortar
Any other
Removal of Form work
Lifts 1.5m and under – Not less than 24 hours
Lifts over 1.5m – Not less than 48 hours
Tunnel Linings - Not less than 16 hours
Mass Concrete – Not less than 24 hours
8. Concrete Placement Equipment
Tower Crane
Other Cranes
Concrete Dumping
Conveyor Belt - Function ability of conveyor
belt, drop height of concrete
Pumped Concrete
Concrete Placer
Onsite mixers and Batching Plants
Transportation of Concrete
Ready Mix Concrete
Concrete placement plan
Requirements
Transit Mixers – Number
Rear Dumpers- for small reach of concrete
placement
Pumped Concrete – It is high slump concrete
where aggregates remain in suspension in concrete mass during pumping
operation. Poor slump control may lead to segregation of aggregates which may
lead to chocking of supply pipe system.
Concrete Placer Pump – It can place the
concrete at desired coordinate in open area concrete placement concrete.
Thermal insulation to concrete - to manage temperature variations (to manage
temperature difference in manufactured concrete and placed concrete )
Vibrator Numbers required including emergency
requirement
No movement of concrete by vibrators by
vibrator
9. Inspection Checklists - Concrete
Placement
The following aspects of concrete placement
should be reviewed:
Placing area is clean and free of loose
concrete, mud, and other debris that could jeopardize the quality of the
structure.
Reinforcing steel and embeds are clean and free
of loose rust, grease or other matter that may adversely affect concrete bond.
Reinforcement and embedded parts are as per
drawing.
Joints and surfaces to receive concrete are
free of deleterious materials and well formed.
Forms are clean, free of foreign materials and
oiled.
Concrete is placed in a manner to prevent
segregation.
Placement of concrete is made in lift thickness
as specified and within time restrictions between lifts for high lift
placements.
Concrete is properly vibrated.
Placement is made to avoid excessive drying of
fresh concrete before next lift is placed.
Concrete is sampled and tested at specified
frequency for strength, slump, temperature, and unit weight.
Concrete is brought to final grade and finish.
The surface is protected by covers and cured
properly. Curing arrangements must be sufficing the requirement.
Green cut the concrete surface to remove mortar
to expose the aggregates and loose concrete if any and cleaning of rebars
Inspection of the surface to be done after form
removal and the surface shall be jointly inspected before any repairs.
Check for availability of concrete ingredients
at batching plant, staff for operation, transportation facilities and testing
facilities at plant.
Follow the Inspection Request check sheet
closely for final approval.
All the work shall conform to the technical
specifications.
Anything abnormal during the concrete process cycle
shall be reported to Construction Agency immediately.
Check arrangements for curing such as for clod
weather curing and hot weather curing
11. Embedding concrete temperature measurement device
Location & numbers
Frequency of temperature measurement decision.
Inlet & outlet of pipe design, layout,
location in case curing is facilitate by embedded hot water pipes.
Time and method for green cutting and
arrangement- after 8-10 hours completion of concrete with air-water jet
Arrangement for shading of concrete pour
Reinforcement and Embodiment summary sheet.
All above points must be kept in mind before
going for supervision checks. The checks
suggested are of generic nature. These checks must e modified in reference to
drawings, specification, and approved methodology. Constructing agency must
ensures that all the check points are taken care before asking the supervision agency
for inspection and getting Okey of the work.
Accordingly, Inspection requests or okey cards
format are prepared as per requirement and should be submitted for getting approval. A samples format is given below.
12. Inspection Request Format or Okey card
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(INSPECTION REQUEST (IR) FORM FOR
CONCRETE/SHOTCRETE) / Okey Card
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Construction Agency (CA): |
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IR No: |
Date: |
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Location: |
RD / E.L: |
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Grade of Concrete |
Slump: |
*Approximate Qty & Duration: |
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Pertaining to Civil Works |
Construction Unit |
QA/QC Unit |
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Status |
Status sig |
Status |
Status sig |
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1. Cleaning of Blocks / Area |
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2.Roughning & Cleaning of old
concrete |
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3. Reinforcement placement |
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4.Cleaning & Oiling of Shuttering |
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5.Fixing & alignment of shuttering
/ wire mesh |
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6.Availability of Dewatering
arrangements |
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7.Availability of Vibrators (2 Nos minimum
in case of needle vibrators) |
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8.Concrete Thickness Required |
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9.Fixing of block out & embedment,
etc. (HM) |
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10.Fixing of inserts & embedment’s
(EM) |
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11.Fixing of block out, embedment etc.
(Geology) |
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12.Others Misc. embedment |
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13.Concrete placement arrangement |
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Pertaining to Quality Control concrete |
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14.Status of mix design required |
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15.Status of B&P -Auto
recording/Manual recording |
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16.Availability of cement required for
the blocks |
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17.Availability of coarse & Fine
Aggregate required |
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18.Availability of Admixture required
at Batching Plant |
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19.Availability of curing arrangement
at Pouring point |
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Contractor construction agency |
Contractor: QA/QC unit |
Consultant checking |
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Signature: |
Signature: |
Signature: |
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Date: |
Date: |
Date: |
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Name: |
Name: |
Name: |
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Designation: |
Designation: |
Designation: |
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NOTE |
Quantity as per generated report at
Batching Plant |
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