By :

SelvarajYogeswarenMohamad AfiqHezam AliLogaswaran

UNDER WATER CONCRETING

Under Water Concreting

Past Under Water Concreting UsageCurrent Under Water Concreting Usage

Under Water Concreting

•Current Under Water Concreting Usage…

•Method’s

•Problems

Under Water Concreting

…Method’s…

Anti-washout Admixtures (AWA)

Anti-washout Admixtures (AWA)

What are they ? Characteristics Uses Advantages Disadvantages Examples

What are they…?

Viscosity – modifying admixture Consist of long molecule chains Cellulose derivatives (most common)

› Welan hum› Hydropupropyl methyl cellulose

What are they…?

Non – cellulose derivatives› Polyethylene Oxide

Characteristics…

Improve cohesiveness› Resists bleeding› Reduce Segregation› Results in minimal loss of fines

Tremies…

Placement Method’s

› Bucket Placement› Tremie

Wet pipe Dry pipe

Tremies…

Tremies…

Mixtures for under water placement.

Mixture for under water concrete…

Anything that improves workability should be considered

Slump approximately 7in. MSA should be approx 1.5in – 2.0in FA should be 45% of total aggregate Use air-entraining admixture

Methods…

Concrete Bagwork Grounting preplaced aggregate Concrete mixed conventionally Placement by Jercuie

Problems

Segregation of FA from CA Water pollution from contact between

fresh concrete and surrounding water Increased water cement ratio Washout

Uses

Concrete in large, underwater placements› Offshore platforms› Docks› Harbors› Bridge Structures

Advantages

Workability is improved Set time, cure time, shrinkage & creep

are not affected Reduced chloride ion permeability

Disadvantages

Reduction in elastic modulus 80% - 100% of original

Reduction in strength› Compressive 75% - 100% of original› Fexural 84% - 100%

Example

Example

Hydrocem

RHEOMAC UN450

Mellose

Hydrocem - Properties

Power admixture Increases cohesiveness while

maintaining high workability Increases strength up to 39 times the

strength under water without admixture

Hydrocem – Test Results

Hydrocem Test

Results

Sample 2 : Concrete

With Hydrocem

Sample 1 : Concrete

With Silica Fume

All other variables constant

Strength of concrete outside of water after 28 days.

› Sample 1 : 35% stronger than sample 2

All other variables constant

Strength of concrete underwater after 28 days

› Sample 2 : 39 times stronger than sample 1

Mellose

Mellose

Mellose

Cellulose based admixture

Used by Koren Company on the Kwangan Great Bridge

Reomac UW - 450

Properties

More Information

Testing

Reomac UW - 450

Reomac UW – 450 Properties

Cellulose based admixture No affect on slump or setting time Useful for mortar or grouting where

mixtures have a high water cement ratio

Lessens strength when used out of water

Increases strength when used underwater

Reomac UW – 450 More Information

Air-entraining admixtures may be necessary to achieve desired air content

Pozzalans & WRAs are recommended to achieves maximum result.

Should be placed by pump ortremie.

Reomac UW – 450 Testing

Washout test – Determines relative amount of cement lost when concrete is exposed to a large amount of water.

Some Of The Example Of Under Water Concreting

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