This document discusses underwater concrete, including its production, placement methods, and quality control. It notes that underwater concrete must have proper mix design and flowability to consolidate under its own weight without vibration. The main placement methods described are tremie, pump, toggle bags, and bagwork. Quality control includes monitoring placement rate and volume. Common issues with underwater concrete include cement washout, laitance, and segregation, which mix design and proper placement seek to prevent.

1. UNDERWATER CONCRETE
SANTHINI K.P
S8, CE 28
GUIDED BY
MANASWI C.M

2.  Concrete is the premier construction material across the
world and the most widely used in all types of civil
engineering works.
 During the construction of bridges , dams or any other
structure where the foundation part of the structure is lie
underwater, we have to opt for underwater construction
 When concrete is placed under water, it induces concrete
to deteriorate uniformity
 Therefore should be follow proper mix design, concrete
production and placement and quality control.

3. PRODUCTION OF UNDER WATER
CONCRETE
 Proper mix design
 Proportioning underwater concrete are same
as conventional concrete
 According to its performance there are two
classes of concrete mixture
standard mixture
high-performance mixture
 Concrete placed underwater is susceptible to
cement washout
laitance
Segregation

4. CONT…….
Mix design influence certain workability
characteristics such as
Flowability
Self-consolidation
Cohesion
Mix design also influence by rheology
o It describes flow and deformation of materials
o The behaviour of fresh concrete can be described
by two parameters-yield stress and plastic
viscosity

5. Cont….
o water content is the important factor affecting
the rheology of concrete
o water content in a mixture can be classified
into two categories
o water absorbed in the aggregate
o free water

6. PLACEMENT METHODS
 Tremie method.
 Pump method
 Toggle bags
 Bags work.

7. TREMIE METHOD
 A Tremie is a watertight pipe
 Generally 250mm in dia.
 Funnel shaped hopper at its upper end and a
loose plug at the bottom.
 It is supported on a working platform above
water level.

8. LAYING OF CONCRETE BY USING TREMIE
Fig. 2.2 Tremie method

9. PUMP METHOD:
 Pumping concrete directly into its final position,
involving both horizontal and vertical delivery of
concrete.
 Pumping concrete has the advantage of operational
efficiency with potential savings of time and labour.
 For massive underwater concrete construction of
navigation structures, the pump method should be
prohibited.

10. PUMP METHOD OF LAYING CONCRETE

11. CONT….
TOGGLE BAGS
• Toggle bags are ideal for small amounts of concrete
placement.
• The bag is filled in the dry with wet concrete
• Used for repair work.
• The concrete is squeezed out by a diver.
BAGWORK
• Bags are made of open weave material.
• Diver-handled bags are usually of 10 to 20 litres capacity
but 1cub.m bags can be placed using a crane.

12. Concrete production
 The standard requirements of underwater concrete is
same as conventional concrete
 Production and delivery system be capable of
producing concrete at the required placement rate
 It is essential that the materials can be supplied to the
batch plant at the required rate
 The logistical planning should include
 Provision for alternative supplies
 Provision of all the accessory items

13. CONSTRUCTION TECHNIQUES
Caissons
 Watertight retaining structure .
 Permanent in nature.
 Used to work on foundation of bridge pier, construction
of concrete dam or for the repair of ships.
 Constructed in such a manner so that the water can be
pumped out.
 Keeps working environment dry.

14. CONT…..
Box caisson
 Pre fabricated concrete box, it is set down on the prepared
bases
 Once in place it is filled with concrete as part of placement
work
 Must be ballasted or anchored to prevent this phenomenon
the floating of hollow concrete structures
Open caisson
 similar to a box caisson but does not have bottom face
 Used in soft clays not having large obstructions
beneath
 During sinking it may filled with water

15. CONT…….
Compressed-air caisson
 It has the advantage of providing dry working
conditions
 Compressed air is used to keep the water and
mud out
 Used to work on river bed
Monolithic caisson
 It is more suitable for off shore construction
 larger than the other types of caisson, but similar
to open caissons

16. COFFERDAM
 Temporary enclosure
 Built within or in piers across a body of water
 Allows the enclosed space to be pumped out, creating a
dry work environment .
 Cofferdams are usually welded steel structures
 With components consisting of sheet piles, and
cross braces
 For dam construction, two cofferdams are usually built,
one upstream and one downstream

17. Fig. 3.2 coffer dam

18. QUALITY CONTROL
 Five critical items should be observed throughout
concrete placement
 Rate of concrete placement
 Depth of concrete at various locations
 Volume of concrete produced versus volume of
in-place concrete measured by sounding
 Concrete delivery system
 Embedment depth of the tremie

19. CONT…….
 Specific recommendations for quality control include
 The workers should have been properly trained
 Contractor should conduct frequent testing of
concrete
 Continuous soundings should be taken
 The concrete placement rate and sequence
should be carefully monitored and controlled
 Compare vol.of concrete produced and fed into
the tremie
 Periodic checking of concrete delivery and
placement equipment

20. DAMAGES AND MAINTANANCE
 Damage and Problems
 Rebar corrosion
 Scaling and Cracks
 Spallingconcrete
 Scour

21. CONT….
Rebar corrosion
 Rebar is steel reinforcement bars passively
embedded within the concrete before it sets
 Occurs when chloride ions migrate to material
like steel bars
 Type of corrosion that occurs in most highway
bridges
Spalling concrete
 The concrete that has broken up, flaked, or
become pitted
 It is occurred due to poor installation and
environmental factors
 It can also result in structural damage

22. CONT…..
Scour
 Scour is the removal of sediments from
around bridge abutments or piers
 It caused by swiftly moving water, can scoop out scour
holes
 It is one of the three main causes of bridge failure
Scaling and Cracks
 It is very common for concrete to have cracks, scaling,
crazing and pitting
 Concrete expands and shrinks with changes in moisture
and temperature
 Irregular cracks are unsightly and difficult to maintain
but generally do not affect the integrity of concrete.

23. MAINTENANCE
 Maintenance procedure consists of initial
inspection, deterioration prediction, inspection,
evaluation, and remedial measures
 During construction the engineering as well as
social and economical aspects should be required.
 Adequate protection from corrosion can be
achieved by using anticorrosion or protective
products
 By placing concrete carefully spalling of concrete
can be avoid up to an extend

24. CONCLUSION
 For in-the-wet construction of navigation structures,
underwater concrete construction is a critical
component
 underwater concrete construction can be
accomplished with the same degree of reliability as
above water construction
 it is not carried out properly, with the proper
concrete mixture and placement, it can result in a
major overrun in construction cost and schedule.

25. CONT…..
 The essential difference between underwater
concrete and conventional concrete is in the
workability requirements
 Underwater concrete must flow laterally and
compact itself under its own buoyant weight, while
conventional concrete is compacted with
mechanical vibration

26. REFERENCES
i. Yao, S.X., Berner, D.E., Gerwick, B.C., “Assessment of Underwater
Concrete Technologies for In-the-Wet Construction of Navigation
Structures”, U.S. Army Corps of Engineers Publication, TR INP-SL-
1, 1999.
ii. Neeley, B. D, Netherlands Committee for Concrete Research,
“Underwater Concrete”, HERON, 1973 ACI 304R-00, "Guide for
Measuring, Mixing, Transporting, and Placing Concrete", Chapter 8
"Concrete Placed Under Water", American Concrete Institute, 2000
iii. Yao, S. X., and Gerwick, B. C., “Underwater Concrete Part II: Proper
Mixture Proportioning” and “Underwater Concrete Part III:
Construction Issues”, Concrete International, February and March
2004
iv. Nagataki, S. (1992). "Use of antiwashout underwater concrete for
marine structures," Tokyo Institute of Technology, Tokyo, Japan.
v. Saucier, K. L., and Neeley, B. D. (1987). "Antiwashout admixtures in
underwater concrete," Concrete International 9(7), 42-47.
vi. Strange, C. (1970). "Submarine placing of concrete by the tremie
method," Offshore Technology Conference 2(1311), 813-18.

27. THANK YOU