underwater concrete

1. Cyprus International University
Collage of Engineering
Civil Engineering Department
CLE532 Concrete Technology
Title : UNDERWATER CONCRETE
Submitted to : Dr. Salaheddin Sabri
By : Muftah Aljoat
ID : 20153680 Dec/2015
1

2. TABLE OF CONTENTS
1. Introduction
2. Types of materials used in underwater concrete
2.1 Cement
2.2 coarse aggregates
2.3 Fine aggregates
2.4 Admixtures for UWC
3. Placement methods
3.1 Tremie method
3.2 Pump method
3.3 Bagwork method
4. Construction Techniques
4.1 Caissons
4.2 Cofferdam
5. Production of underwater concrete
6. Quality control & Cost
7. Damages and Maintanance
8. Conclusion
9. References
2

3. 1. INTRODUCTION
 Concrete is the construction material across the world
and the most 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
most likely to lie underwater, we have to opt for UWC.
 construction in water poses many difficulties especially
in the places where there the depth is large .
 Therefore should be follow proper mix design, concrete
production and placement and quality control.
3

4. 2. TYPES OF MATERIALS USED IN (UWC):
2.1 Cement :
Types of cements used in Underwater concrete :
1. Ordinary Portland Cement (OPC)
2. Sulphate Resisting -Portland Cement( SRPC )
3. Low Heat - Portland Cement ( LHPC )
4

5. CONT…
2.2 Coarse Aggregates
The coarse aggregate for intruded in concrete shall
conform to the following gradation:
 Maximum Size - 1.5-2 inch (100% shall pass a 75 mm sieve
)
 Minimum Size - material passing a 19 mm sieve shall not
exceed 5% by mass of the coarse aggregate.
2.3 Fine Aggregates
The sand for the intruded grout shall be well graded,
preferably of round grains and shall conform to the
following gradation:
 Passing 1.18 mm sieve 95 - 100%
 Passing 600 mm sieve 60 - 85% 5

6. 2.4 ADMIXTURES FOR UWC:
o Anything that improves workability should be considered.
o Slump approximately 7in .
o MSA should be 45% of total aggregate .
o Use air-entraining admixture .
o Requires the use of an antiwashout , Some of these admixtures
are formulated from either Cellulose ether or Whelan gum, and
they work simply by increasing the cohesion and viscosity of
the concrete.
6

7. 3. PLACEMENT METHODS:
7
It is a process in which the prepared concrete is
poured below the water surface by using suitable
methods.
PLACEMENT
METHODS:
Tremie method. Pump method. Bagwork.

8. 3.1 TREMIE METHOD
8
 A Tremie is a water tight pipe
 Generally 250mm in diameter.
 Funnel shaped hopper at its
upper end and a loose plug at
the bottom.
 It is supported on a working
platform above water level.
(Figure 1) Tremie Method

9. CONT…
 Tremie Concrete is done by using a formwork/pipe
which will have one end of the formwork/pipe above
water and other bottom end immersed under the water
and with the help of gravity.
 Before concreting air and water must be excluded
keeping the pipe full of concrete all the time.
 For this the funnel and the pipe should have equal
capacity.
 Firstly plug is inserted in the pipe with pressure of fresh
concrete so that the air is displaced. 9

10. LAYING OF CONCRETE BY USING TREMIE
(Figure 2) Tremie method 10

11. TREMIE METHOD (VIDEO 1)
11

12. TREMIE METHOD (VIDEO 2)
12

13. SPECIFICATIONS OF CONCRETE TO BE USED IN
TREMIE METHOD:
 Coarse Aggregate: Gravel of 3/4” (20mm) max. size. Use 50-55
% of the total aggregate by weight.
 Sand, 45-50% of the total aggregate by weight.
 Cement: Type II ASTM (moderate heat of hydration), 600 lbs./yd3
 Water/Cement Ratio: 0.42 (0.45 Maximum).
 Water-Reducing Admixture (preferably it is also
plasticizer): Do not use super plasticizers.
 Air-Entrainment Admixtures: To give 6% total air.
 Retarding Admixture: To increase setting time to 4-24 hours, as
required.
 Slump: 6 1/2" ± 1"
 This mix will develop compressive strength in the range of 5,600 –
7,000 psi at 28 days. 13

14. 3.2 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.
14

15. (Figure 3) PUMP METHOD OF LAYING CONCRETE
15

16. CONT….
16
3.3 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.
(Used only in special cases like repair works, etc.)
(Figure 4) Bagwork used to form a dam

17. 4. CONSTRUCTION TECHNIQUES
4.1 Caissons :
 Used to work on foundation of bridge pier, construction
of concrete dam or for the repair of ships.
 Watertight retaining structure .
 Constructed in such a manner so that the water can be
pumped out.
 Keeps working environment dry.
17

18. 18
(Figure 5) working area of caissons

19. TYPES OF CAISSONS
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
19

20. 20

21. 21(Figure 6) Suction Caissons

22. ADVANTAGES OF CAISSON :
 Economic.
 Slightly less noise and reduced vibrations.
 Easily adaptable to site conditions.
 High axial and lateral loading capacity.
 Minimal handling equipment is required for
placement of reinforcing cage.
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23. 4.2 COFFERDAM
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 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
 For dam construction, two cofferdams are
usually built, one upstream and one
downstream
(Figure 7) working area of cofferdams

24. 24
(Figure 8) working area of cofferdams

25. ADVANTAGES OF COFFERDAM
 Allow excavation and construction of structures in
otherwise poor environment.
 provides safe environment to work
 contractors have design responsibilty
 steel sheet piles are easily installed and removed
 materials usually reused on other projects
25

26. 5. PRODUCTION OF UNDER WATER
CONCRETE
 Proper mix design
• Proportion underwater concrete are 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
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27. CONT…
 Performance requirements for UWC
• Workability & self compaction
• Cohesion against washout & segregation
• Low heat of hydration
• Controlled set time
• Compression strength
 Problems faced
 Segregation of fine aggregates from coarse aggregates
 Water pollution
 Increased (w/c) ratio
 washout 27

28. 6. QUALITY CONTROL & COST
 Five critical items should be observed
throughout concrete placement :
 Rate of concrete placement.
 Depth of concrete in different locations.
 Size of concrete produced opposite volume of in-
place concrete measured by sounding.
 Concrete delivery system.
28

29. CONT…….
 Specific recommendations for quality control,
include:
 The workers should have been properly trained.
 Contractor should conduct frequent testing of
concrete .
 The concrete placement rate should be carefully
monitored and controlled.
 checking of concrete delivery and placement
equipment. 29

30. COST
 Considered underwater concrete is
high cost compared to plain concrete, due to
the high cost of equipment and maintenance in
addition to the cost of the caring.
 In the United Kingdom also it estimated the cost of
repairing the bridges as a result
of corrosion in rebar at about 616 million pounds
and is only 10% of the total bridges in the
United Kingdom. 30

31. 7. DAMAGES AND MAINTENANCE
 Damage and Problems
1. Rebar corrosion
2. Spalling concrete
3. Scour
4. Scaling and Cracks
31

32. CONT….
1. Rebar corrosion
 Happen when chloride ions migrate to material like steel
bars,
 that is Type of corrosion that happen in most highway
bridges.
2. Spalling concrete
 The concrete that has broken up or flaked.
 This happened because of poor installation and
environmental factors .
 It can also result in structural damage
32

33. CONT…..
3. Scour
 Scour is the removal of sediments from
around bridge foundations or piers
 It caused by swiftly moving water, can scoop out scour holes
 It is one of the three main causes of bridge failure.
4. Scaling and Cracks
 It is very common for concrete to have cracks, scaling.
 Concrete expands and shrinks with changes in humidity and
temperature.
 Irregular cracks are ugly and difficult to maintain but generally
do not affect the safety of concrete.
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34. MAINTENANCE :
 Maintenance procedure consists of initial
inspection, deterioration prediction, inspection,
evaluation.
 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. 34

35. 8. CONCLUSION
 if 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.
 The essential difference between underwater concrete
and conventional concrete is in the workability
requirements.
 Underwater concrete must flow horizontally and
compact itself under its own weight, while conventional
concrete is compacted with mechanical vibration.
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36. 9. REFERENCES
 www.ce.berbley.edu/~parmont/165/tremie
 www.vulcanhammer.net
 www.ce.gatech.edu/~kk92/classpress/uwater/index.htm
 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 .
 Nagataki, S. (1992). "Use of antiwashout underwater concrete for
marine structures," Tokyo Institute of Technology, Tokyo, Japan.
 Saucier, K. L., and Neeley, B. D. (1987). "Antiwashout admixtures in
underwater concrete," Concrete International 9(7), 42-47.
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ANY QUESTIONS??

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