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Cyprus International UniversityCollage of Engineering

Civil Engineering Department

CLE532 Concrete TechnologyTitle : UNDERWATER CONCRETE

Submitted to : Dr. Salaheddin Sabri

By : Muftah Aljoat

ID : 20153680 Dec/2015

TABLE OF CONTENTS

1. Introduction2. Types of materials used in underwater concrete 2.1 Cement 2.2 coarse aggregates 2.3 Fine aggregates 2.4 Admixtures for UWC3. Placement methods 3.1 Tremie method 3.2 Pump method 3.3 Bagwork method4. Construction Techniques 4.1 Caissons 4.2 Cofferdam5. Production of underwater concrete6. Quality control & Cost7. Damages and Maintanance8. Conclusion9. References

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.

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 )

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%

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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.

3. PLACEMENT METHODS:

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.

3.1 TREMIE METHOD

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

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.

LAYING OF CONCRETE BY USING TREMIE

(Figure 2) Tremie method

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TREMIE METHOD (VIDEO 1)

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TREMIE METHOD (VIDEO 2)

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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.

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.

(Figure 3) PUMP METHOD OF LAYING CONCRETE

CONT….

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

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.

(Figure 5) working area of caissons

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

(Figure 6) Suction Caissons

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.

4.2 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

For dam construction, two cofferdams are

usually built, one upstream and one

downstream

(Figure 7) working area of cofferdams

(Figure 8) working area of cofferdams

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

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

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

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.

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.

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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.

7. DAMAGES AND MAINTENANCE

Damage and Problems

1. Rebar corrosion2. Spalling concrete3. Scour 4. Scaling and Cracks

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

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. 

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.

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.

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.

ANY QUESTIONS??