Under water concreting
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Transcript of Under water concreting
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BANGALORE INSTITUTE OF TECHNOLOGY
DEPARTMENT OF CIVIL ENGINEERING
UNDER THE GUIDEANCEOF
B S KARTHIKAsst.professor
PRESENTED BY
AGNESH B S1BI11CV008
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Topics coveredTopics covered
Introduction Concrete specificationLaying techniquesRepair worksConclusion
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Introduction Introduction
There are often situations such as basements , sewerage ,ducts , harbours , bridges and marine works ,in which concrete is to be placed underwater.
Special precaution need to be taken whenever the concrete is to be placed underwater.
The concrete should be plastic and cohesive but should have good flowability.
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Performance requirements for UWCWorkability & self compactionCohesion against washout & segregationLow heat of hydrationControlled set timeCompressive strengthAdequate bond
Problems facedSegregation of fine aggregates from coarse aggregatesWater pollutionIncreased w/c ratiowashout
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Types of Materials Types of Materials used used ::
Cement Coarse Aggregates Fine Aggregates Admixtures
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CEMENT :CEMENT : Types of cements used in UNDERWATER
CONCRETING :
Ordinary Portland Cement (OPC)
Sulphate Resisting -Portland Cement ( SRPC )
Low Heat - Portland Cement ( LHPC )
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AGGREGATES AGGREGATES :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.
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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 um sieve 60 - 85% Passing 300 um sieve 20 - 45% Passing 150 um sieve 15 - 30% Passing 75 um sieve 0 - 10%
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Use of Different Use of Different AdmixturesAdmixtures
Anti-washout admixturesHydrocem Mellose
Viscosity modified admixturesNaphthalene FormaldehydeSulfonated Melamine Formaldehyde
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Concrete Particles with adding MELLOSE
Concrete Particles without MELLOSE
* Black Dots Indicates Water
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Concrete laying Concrete laying techniquestechniques
Tremie method
Bucket Placing
Pump method
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TREMIE METHOD
A Tremie is a watertight pipeGenerally 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.
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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 weightWater/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.
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Laying of concrete by using Tremie 14
Basic principle behind Method
of underwater concreting -
Tremie method
Method of underwater concreting— Tremie method (inside view)
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Divers Using Tremie Concreting
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Bucket placingBucket placing
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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.
17
PUMP METHOD OF
LAYING CONCRETE
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Repair worksRepair works
Defining the AreaCleaning the Affected AreaEquipment HaulagePersonnel requirementsInspection methodsEnvironment considerations
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At present, the Tremie placement method is the standard way of placing high-quality concrete underwater. The other placement method are not able to reliably place high-quality underwater concrete for major structures, although they may find application in special cases.
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ReferencesReferences::
www.ce.berbley.edu/~parmont/165/tremie
www.vulcanhammer.net www.ce.gatech.edu/~kk92/classpress/
uwater/index.htm www.scanecm.com.au/products/
additives/hydrocem/index.htm www.ce.ecn.purdue.edu/cem/cliproj/
civil/mellose.htm www.masterbuilder.com/uc.htm
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