4.3.2 workability of fresh concrete definition workability importance of workability...

4.3.2 4.3.2 Workability of Workability of Fresh CFresh Concreteoncrete

Definition WorkabilityDefinition Workability Importance of WorkabilityImportance of WorkabilityMobilityMobilityViscidityViscidityWater retentionWater retention

• Fresh ConcreteFresh Concrete– Fresh Concrete is the concrete before hardenFresh Concrete is the concrete before harden

ed, e.g., concrete composite.ed, e.g., concrete composite.• WorkabilityWorkability

– The properties of Fresh Concrete The properties of Fresh Concrete havehave sufficient workabsufficient workabiillityity to be mixed, to be mixed, transported, transported, and placed properlyand placed properly..

DefinitionDefinitionDefinitionDefinition

Workability of Workability of Fresh ConcreteFresh Concrete

Concrete in ConstructionConcrete in Construction

Fig.4.3.1 Concrete in ConstructionFig.4.3.1 Concrete in Construction

• Concrete which cannot be placed properly Concrete which cannot be placed properly will not produce qualiwill not produce qualified fied structures structures regardless ofregardless of the qua1ity of the mixturethe qua1ity of the mixture..

• Concrete which may be considered Concrete which may be considered suitsuitable able for one structure may not for another.for one structure may not for another.

WorkabilityWorkability

ImportanceImportanceImportanceImportance

MobilityMobilityViscidityViscidity

WorkabilityWorkabilityWorkabilityWorkability

Water retentionWater retention

WorkabilityWorkability

MobilityMobility• The The capacity for a concrete mixture to respond capacity for a concrete mixture to respond

to to vibrationvibration readily readily and fill all parts and corners and fill all parts and corners of a form is defined as mobility.of a form is defined as mobility.

• Overcome interior friction, paste viscidity and fiOvercome interior friction, paste viscidity and fiction between aggregates in composite.ction between aggregates in composite.

WorkabilityWorkabilityViscidity (Viscidity (Plasticity)Plasticity)• ViscidityViscidity is th is thee property of property of a concrete mixture a concrete mixture

which allows it to bewhich allows it to be molded without molded without segregationsegregation..

• SegregationSegregation– Composition of Composition of concrete mixture concrete mixture segregates segregates

by differences of their density and grain size.by differences of their density and grain size.

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WorkabilityWorkabilityWater retentionWater retention• The The capacity capacity toto prevent water prevent water bleedingbleeding from from

concrete composite.concrete composite.

– BleedingBleeding• Water flows from composite and raises to the

surface of concrete.

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Bleeding Path orBleeding Path or

Water PackageWater Package

Floating PasteFloating Paste

SettlementSettlement

Deteriorate durabilityDeteriorate durability

Cause crazingCause crazing

in Concretein Concrete

Wreck the bond toWreck the bond to

new Concretenew Concrete