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1. National Education Society ®
JNN College of Engineering
Sawalanga Road, Navule, Shivamogga -277204
(Accredited by NBA, NAAC 'B' & Certified by UGC 2f & 12B)
Department of Civil Engineering
Under the guidance of;
Dr. Sughosh P (PhD)
Associate Proff
Presented by;
Adarsh p
4jn16cv004
Seminar on

2.  Introduction.
 Requirements of U.W.C.
 Constituents of U.W.C.
 Methods of placing concrete.
 Causes of Deterioration of concrete.
 Conclusion.

3.  Concreting that is done in the water is known as under water
concreting.
 The variations in properties are not much different, the problem
associated with washout of concrete poses requirement of
addition of admixtures to reduce the washout properties of
UWC.
 Placing concrete under water and also in very deep foundations,
such as caissons requires different methods than ordinarily
employed for placing in air.
 The repair of concrete underwater is usually difficult, requiring
specialized products and systems, and the services of highly
qualified and experienced professionals.

4. • Pumping of water is not permitted while concrete is being
placed, nor until 24 hours thereafter.
• Concrete should not be placed in water having temperature
below 1.7 deg.C., because it will harden very slowly.
• The temperature of the concrete when deposited should be
between 15 and 28 deg.C.
• The proportion of the fine and coarse aggregate should be
adjusted to produce the desired workability.

5.  Admixtures.
 Viscosity Modifying Admixture (VMA).
 The key function of a VMA is to modify the rheological
properties of the cement paste.
 The Rheology of fresh concrete can be mainly described by its
yield point and plastic viscosity.
 The balance between the yield point and the plastic viscosity
is key to obtaining the appropriate concrete properties.

6. Pumping of concrete with
V.M.A.
Pumping of concrete without
V.M.A.

7.  Tremie.
 Bucket.
 Grouted aggregate.
 Concrete pump.

8.  The tremie consists of a water pipe, often 250 mm in diameter,
long enough to reach from a working platform above water
level to the lowest point of deposit.
 A receiving hopper is provided at the top of the pipe and a
lower end is some time equipped with a valve.
 Every precaution should be taken both in handling and placing
the concrete to a minimum the tendency to segregate.
 During the placing operation the previously placed concrete
should be disturbed as little as possible and top surface of the
concrete should be kept as near level as practicable.
 Once the concreting is been started the tremie should not be
moved laterally through the deposited concrete as this will
disturb it.

10.  The bucket for placing concrete under water is an open –top
rectangular or cylindrical bucket with a drop bottom or roller –
gate opening in the bottom.
 the bucket should be completely filled and the top covered
with a canvas flap.
 Care must be taken to prevent discharging the bucket before it
has reached the surface on which the concrete is to be
deposited, there by avoiding dropping it through water.
 Sounding at frequent interval is desirable to assist in placing
so that the top surface of the concrete is kept level.

11.  In this method the placing of coarse aggregate in the forms,
 The piping are takenout as grouting proceeds. The grout forces the
water out of the forms and fills the interstices in aggregate.
Concrete pump
In this method concrete by pumping into position without the use
of separate tremie has been done.
 The pipe is plugged at the bottom end and lowered in water where
concreting is to be done, such as caissons or piers after removing
muck from it.
 Pumping of concrete was then started.

12.  Underwater concrete deterioration in tidal and splash zones is
a serious economic problem.
CAUSES OF DETERIORATION OF UWC
 Marine organisms.
 Deficient construction practices and errors.
 Chemical attack.
 Corrosion.
 Mechanical damage.
 Freezing-and-thawing damage.
 salt scaling.

13. Deteriorated pile in tidal and Advanced deterioration the pile has
exposed zone been cleaned.

14.  By using grouting.
 By using tremie.
 By using concrete pump.
 By using epoxy grouting.
 By epoxy injecting.
 By hand placing.

17. • Tremie and concrete by pumping are better methods of
concreting for U.W.C.
• It was found that on this work that the rate of hardening was
faster than had been expected .the surface of undisturbed
concrete hardened within 45 minutes instead of several hours
as might have been expected.
• Use of VMA in u.w.c. will not make concrete to segregate and
reduces anti washout properties.
• The purpose of the addition of a VMA is to replace or limit the
addition of fines, thus making a fresh concrete more cohesive.

18.  EFNARC www.efnarc.org ENC 179VMA r12, 25/09/06.
 Concrete information portland cement association, no 33 wesr grand
avenue, Chicago. Structure buero.st12-1 to st12-2.
 UNDERWATER CONSTRUCTION CORPORATION 110 Plains Rd ,
Essex, CT 06426,
 800-USA-DIVE. www.uccdive.com
 Guide to Underwater Repair of Concrete Reported by ACI Committee 546.
 Case study: www.hvfacprojectindia.com
 M.sonebi and Khayat “effect of mixture composition on relative strength of
highly flowable underwater concrete”ACI materials journal/may-June
2001.

19. THANK YOU