Field Testing of Reinforced Concrete Structures

(with references to International Standards)

F.Papworth

BuildingsBuildings

MinesMinesIndustrialIndustrial

HistoricalHistorical

Expected Outcomes – Site Surveys Understand what sort of job

you can do yourself with minimal risk

Understand what sort of information can be obtained

Understand when you should get help

Have a little background in the common tests You may be able to use with

minimal training Testing companies may use on

site

Lets take a closer Lets take a closer look at this …look at this …

Corrosion TestingPotentials ResistivityPolarisation ResistanceEmbedded Half CellCarbonation DepthChloride Penetration

Visual InspectionMagnifierGaugeDeformationMonitorStrainCamera

Buried DefectsImpact EchoPulse EchoThermographyRadarNuclear

Cover QualitySorptivityAir PermeabilityWater Permeability

CoatingsPeel TesterPull offThickness

EmbedmentCable TensionBolt Pull OutCover

SurfaceFlatness/LevelnessAbrasion ResistanceDusting

Insitu StrengthSchmidt ReboundPunditBreak offPull outMaturity

Corrosion Reaction

CathodicReaction

4(OH)-

Electrolyte

CurrentAnodicReaction

SecondaryReaction

H2O

2Fe(OH)2

O2

2Fe++ 4e-

WaterChloride Oxygen

Fe2O3H2O(Rust)

4e- Electron Transfer

H2O O2

Strength Assessment – Early Age Why Early Age Assessment

Check before lifting/stripping Check before applying prestress Check to stop curing

Water retaining code = 75% f’cBridges Code = 60% 60% f’c

Schmidt Hammer Method Repetitive so establish conversion curve

Accurate to 10-15%If 8MPa required lift safe to lift at 10MPa

Surface strength only

Maturity Measurement Method Doubles as temperature measurement

Cylinder strengths underestimate insitu strength

7 or 14 day specs overstate requirements

Strength AssessmentCheck Old Structures

Check capacity for increased load Floor slabs when changing usage Buildings where heavy equipment to be located Bridges for increased capacity

Check continued capacity of historic structures Where no design information available

Check for progressive weakening Leaching of water retaining structures

Schmidt Rebound No conversion curves available Surface hardening due to carbonation ±25% with carbonation allowance, ±50% no carbonation allowance

Strength AssessmentRebound HammerUltrasonicsMaturityPull off tests