SEMINARSEMINARON ON

BY naser ur

rahman 3gn09cv024

Topics coveredTopics covered

Introduction Concrete specificationLaying techniquesRepair worksConclusion

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.

Performance requirements for UWCWorkability & self compactionCohesion against washout, segregation & laitance

formation Low bleedingLow heat of hydrationControlled set timeCompressive strengthAdequate bond

Problems facedSegregation of fine aggregates from coarse aggregatesWater pollutionIncreased w/c ratiowashout

Types of Materials Types of Materials used used ::

Cement Coarse Aggregates Fine Aggregates Admixtures

CEMENT :CEMENT : Types of cements used in UNDERWATER

CONCRETING :

Ordinary Portland Cement (OPC)

Sulphate Resisting -Portland Cement ( SRPC )

Low Heat - Portland Cement ( LHPC )

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.

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%

Use of Different Use of Different AdmixturesAdmixtures

Anti-washout admixturesHydrocem Mellose Rheomac uw-450

Viscosity modified admixturesNaphthalene FormaldehydeSulfonated Melamine Formaldehyde

Concrete Particles with adding MELLOSE

Concrete Particles without MELLOSE

Concrete laying Concrete laying techniquestechniquesPlacing in Bags

Tremie method

Bucket placing

Prepacked concrete

Tremie methodTremie method

Use of Tremie Method

Divers Using Tremie Concreting

Bucket placingBucket placing

Prepacked concretePrepacked concrete

Repair worksRepair works

Defining the AreaCleaning the Affected AreaEquipment HaulageUse AWAPersonnel requirementsInspection methodsEnvironment considerations

An Inspection Machine

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 Concrete Technology - M L Gambhir Concrete Technology - A R Santhakumar