2. Introduction
A casting yard is a confined place where all the concrete structures like
segments, parapets, I- girders/beams, boundary wall panels, cable troughs
etc. Re-casted/manufactured, shifted to their stack yard, cured for the
specific period/days and then shifted to the working site/viaduct after
they gain their required strength.
4. Requirements of a Casting Yard
• Site for any Casting Yard should be easily accessible from all site locations.
• Land should be available from 25 Acres to 40 Acres for establishing a
casting yard.
• Approach Road leading to Casting Yard should be easily identified.
• Good Environmental conditions.
• It should not more than 3 to 4 kms from working site.
• Proper Drinking Water facilities for Engineers, Supervisors & Labours.
• Canteen facilities for the staff & Labours.
• Medical treatment Centre in case of emergency.
6. Long Line Method
•
All segments of a span are manufactured on a fixed bed with the
formwork moving along the bed for successive casting operation.
• Shows profile of real structure at one time.
• Pier segment is cast first between the fixed bulkhead and the removable
formwork, then the segments.
7. Short Line Method
• It is a match casting process.
• Stationary forms are used next to the previously cast segment in order to
get a homogeneous perfect fitting match-cast joint.
9. Match-casting for a vertical curve
• Match cast segment first translated from its original position and then give
a small rotation in the vertical plane w.r.t. the horizontal axis.
10. Match-casting for a horizontal curve
• Match-cast segment is first moved to its position by pure translation and
then the segment is rotated in plan w.r.t. the vertical axis.
11. Geometry Control
• Establishment stations to the north and south side of the segment before
the casting is must.
• Tolerances are in the order of a fraction of a millimeter.
Geometry control Program
•
•
•
•
•
Calculate the theoretical casting coordinates of segment n.
Measure the actual casting coordinates
Calculate error in casting
Calculate correction to be made in casting n+1 match-casting with n
Adjust match-casting of n to compensate for error while
casting n+1
12. Batching & mixing of concrete
Raw material
Cement (OPC grade 53)
Fly Ash (Maximum 30% of cement)
Water (between 0.1 & 0.4)
Admixture (SP-430, SP-432)
Fine aggregate
Coarse aggregates of 10mm & 20mm size
13. Batching procedure
• Batching plant may be of manually operated type or may be operated with
the help of computer aided software.
• The quantities are filled in the computer and start key is pressed, the
sensors provided near the gates get into action and according to the load
scale value, that much quantity of sand, 10mm aggregates, & 20mm
aggregates are filled in a bucket.
• When the required quantity of the aggregates is filled the gates get closed
automatically and the bucket is pulled up.
14. For fine & coarse aggregate
For cement & fly ash
15. • As the bucket reaches the top, its contents are put into a mixing
pan, where it gets mixed with the cement, water & admixtures from their
separate hoppers.
Mixing tank
16. Quality Control
Survey Procedures
• Initial Set Up Survey - required for formwork setting and getting the match
cast segment in “rough” position
• Final Set Up Survey - required for final adjustments of the match cast
segment and small adjustments to the formwork once the forms have
been closed up to final position
• As Cast Survey - required to obtain “as cast” data on the segment used to
determine the positioning of the segment in the “match cast” position
• Inputting Data – required for geometry control for the
for the next segment to be cast
17. Test of concrete
For Ordinary Concrete
• Slump test
• Setting time test
Initial setting time
Final setting time
• Compressive strength test
For self compacting Concrete
• Flow test
• V-funnel test
• L box test
20. Precast vs Cast in Place Concrete
Precast
High Quality Control
Cast in place
Less Quality Control
Casting cannot be delayed due to weather It may be delayed.
conditions
Controlled pour conditions, strict quality
control measures and factory strength
testing ensure pre-cast concrete strength
and durability specifications.
Uncontrolled factors can decrease the
strength and durability of freshly poured
concrete.
Flexibility to make changes to structure
right up until the minute the concrete is
poured in the form
Last minute changes are difficult to make
and cost money
