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Advancing Concrete for Bridges andAdvancing Concrete for Bridges and Infrastructure:Petrography (TR71) and other testing methods
7 July 2011
7 July 20111 Petrography (TR71) and other testing methods - Jeremy Ingham
AgendaAgenda
• What is petrography?p g p y
• What’s involved – the techniques of petrography?q p g p y
• What can and can’t be achieved by petrography?What can and can t be achieved by petrography?
• Key publicationsKey publications
7 July 20112 Petrography (TR71) and other testing methods - Jeremy Ingham
What is Petrography?What is Petrography?
• from the Greek petra meaning rock and• from the Greek petra meaning rock and graphus meaning writing or record
l i l t h i d ti b k 150• geological technique dating back 150 years• 40 year history of industrial concrete
petrography
7 July 20113 Petrography (TR71) and other testing methods - Jeremy Ingham
The Role of Petrography in Assessment ofConcrete Bridges
• New construction – may be required in case of cube strength non-compliance or if concrete quality is in doubtq y
• Existing structures – can be useful as part of condition survey inspections e.g. to Design Manual for Roads and Bridges to Design Manual for Roads and Bridges BD 63/07 ‘Inspection of Highway Structures’ and BA 35/90 ‘Inspection
d R i f C t Hi h and Repair of Concrete Highway Structures’
• Used in Principal Inspections (every 6 p p ( yyears) and Special Inspections (as required)
7 July 20114 Petrography (TR71) and other testing methods - Jeremy Ingham
Standards and Competencies for Concrete Petrography
• Concrete petrography is unlike most laboratory tests as it requires particularly highly qualified operators and expensive microscopical equipmentp q p
• The Applied Petrography Group of the Geological Society maintains a list of competent petrographic test houses –www appliedpetrographygroup comwww.appliedpetrographygroup.com
• Currently no BS or EN Standard• ASTM C856 ‘Standard Practice for the Petrographic Examination g p
of Hardened Concrete’ – long standing and widely accepted• APG SR2 – The Applied Petrography Group has a code of practice
for the petrographic examination of concretefor the petrographic examination of concrete
7 July 20115 Petrography (TR71) and other testing methods - Jeremy Ingham
AgendaAgenda
• What is petrography?p g p y
• What’s involved – the techniques of petrography?q p g p y
• What can and can’t be achieved by petrography?What can and can t be achieved by petrography?
• Key publicationsKey publications
7 July 20116 Petrography (TR71) and other testing methods - Jeremy Ingham
What’s Involved – the techniques of qPetrography?• Inspection design considerations• Inspection design considerations• Sampling• Specimen preparation• Visual examination & low power microscopyy• Polarised light (high power) microscopy• Fluorescent light microscopy• Fluorescent light microscopy• Scanning electron microscopy
7 July 20117 Petrography (TR71) and other testing methods - Jeremy Ingham
Inspection Design ConsiderationsInspection Design Considerations
• Involve the petrographer in the inspection design, to ensure correct sample number/type scheduled to achieve the investigation objective
• Plan a ceiling budget based on likely number of samples for visual g g y pexamination (typically £50-80 per sample) and microscopical examination (typically £200-300 per sample), and then add a contingency sum
• Allow sufficient turnaround time for petrography in the inspection programme (typically 3 weeks)programme (typically 3 weeks)
• Review the petrography test programme and budget with the petrographer once the samples have been obtained petrographer once the samples have been obtained
7 July 20118 Petrography (TR71) and other testing methods - Jeremy Ingham
SamplingSampling
• Petrography requires intact concrete samples – ideally 70-100mm diameter core samples, depth at least 150mm or to centre of element
• Cores should be double wrapped and labelled at siteM st al a s consider the str ct ral • Must always consider the structural impact of core sampling and avoid cutting reinforcement
7 July 20119 Petrography (TR71) and other testing methods - Jeremy Ingham
Specimen PreparationSpecimen Preparation
• Thin sections • Finely ground slices• Highly polished specimens
7 July 201110 Petrography (TR71) and other testing methods - Jeremy Ingham
Visual Examination & Low Power MicroscopyVisual Examination & Low Power Microscopy
• Examination of sample ‘as-received’• Unaided eye• Low power binocular microscope (up to x100)
7 July 201111 Petrography (TR71) and other testing methods - Jeremy Ingham
Polarised Light (High Power) MicroscopyPolarised Light (High Power) Microscopy
• Polarised light examination of thin sections (up to x600)
7 July 201112 Petrography (TR71) and other testing methods - Jeremy Ingham
Fluorescent Light MicroscopyFluorescent Light Microscopy
• Concrete impregnated with resin containing fluorescent dye• Microscopical examination in UV light• Highlights porosity & cracks
7 July 201113 Petrography (TR71) and other testing methods - Jeremy Ingham
Scanning Electron MicroscopyScanning Electron Microscopy
• Electron images of highly polished specimens
• Micro-chemical analysis using X-ray microanalysis system
7 July 201114 Petrography (TR71) and other testing methods - Jeremy Ingham
AgendaAgenda
• What is petrography?p g p y
• What’s involved – the techniques of petrography?q p g p y
• What can and can’t be achieved by petrography?What can and can t be achieved by petrography?
• Key publicationsKey publications
7 July 201115 Petrography (TR71) and other testing methods - Jeremy Ingham
What can and can’t be achieved by yPetrography?• Concrete Composition & Quality• Concrete Composition & Quality• Concrete Condition
7 July 201116 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Composition: AggregateConcrete Composition: Aggregate
• Aggregate type• Aggregate grading• Distribution (check for segregation)
U di i bl tit t• Undisirable constituents• ASR potential classification
7 July 201117 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Composition: Cement TypeConcrete Composition: Cement Type
• The main phases within Portland cements are readily observed through the microscope
• Confident determination of cement type - OPC/SRPC/White• Definitive identification of high alumina cement concrete • Definitive identification of high-alumina cement concrete
(HACC)
7 July 201118 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Composition: Mineral AdditionsConcrete Composition: Mineral Additions
• Presence of pfa or ggbsp gg• Quantity of pfa or ggbs• Difficult to detect Microsilica
and Metakaolin
7 July 201119 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Composition: Chemical AdmixturesConcrete Composition: Chemical Admixtures
• Can’t see plasticisers etc using microscopes• Effects of admixtures are sometimes seen through microscope (e.g.
entrained air voids)• Infrared spectroscopy can be used to determine admixtures typep py yp• Difficult to quantify admixtures even by infrared spectroscopy
7 July 201120 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Composition: Cement ContentConcrete Composition: Cement Content
• Mix proportions determined by point counting concrete slices• Point counting offers comparable/improved accuracy over
BS1881:Part 124 chemical analysis method
7 July 201121 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Composition: Water/Cement RatioConcrete Composition: Water/Cement Ratio
• Can be determined by fluorescence microscopy• Image analysis software has been developed• Argueably more accurate than physico-chemical method in
BS 1881: Part 124BS 1881: Part 124
7 July 201122 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Composition: Air VoidsConcrete Composition: Air Voids
• Visual examination for entrapped air voidspp• Manual bubble counting for detailed analysis (BS EN
480-11 or ASTM C457)• Automated option - ‘Rapidair’ machine
7 July 201123 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Composition: StrengthConcrete Composition: Strength
• Concrete composition data gained from petrography can be used to estimate strength using Feret’s formula
• Core strength tests more accurate than petrographic strength estimate
• Petrography often used to determine cause of low strength following cube strength failures in new build
7 July 201124 Petrography (TR71) and other testing methods - Jeremy Ingham
What can and can’t be achieved by yPetrography?• Concrete Composition & Quality• Concrete Composition & Quality• Concrete Condition
7 July 201125 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Condition: CarbonationConcrete Condition: Carbonation
• Phenolphthalein indicator solution can underestimate carbonation depth
• Petrography is the definitive • Petrography is the definitive method for carbonation depth determination
7 July 201126 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Condition: Chloride Ion IngressConcrete Condition: Chloride Ion Ingress
• Chloride content requires chemical analysis to BS q y1881: Pt 124
• Corrosion features (cracks, rust deposits) can be examined
7 July 201127 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Condition: CrackingConcrete Condition: Cracking
• Determining the cause of cracking by observation of crack morphology, understanding concrete composition and by eliminating possible causes
7 July 201128 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Condition: WeatheringConcrete Condition: Weathering
• Leaching actionsLeaching actions• Frost attack
S lt t lli ti• Salt crystallization
7 July 201129 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Condition: Sulfate AttackConcrete Condition: Sulfate Attack
• Sulfate from the groundwater causes formation of expansive ettringite with associated weakening
• Petrography definitive diagnostic tool for sulfate attack• Sulfate content requires chemical analysis to BS 1881: Pt124• Sulfate content requires chemical analysis to BS 1881: Pt124
7 July 201130 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Condition: Thaumasite Form of Sulfate Attack (TSA)
• Confident diagnosis of TSA• Determining the depth of damage
7 July 201131 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Condition: Delayed Ettringite FormationConcrete Condition: Delayed Ettringite Formation
• Delayed Ettringite Formation (DEF) – expansive reaction where concrete curing temperature exceeds 65°C
• Crack patterns often mistaken for ASR• Has characteristic microscopical featuresp
7 July 201132 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Condition: Alkali-Aggregate ReactionsConcrete Condition: Alkali Aggregate Reactions
• Definitive diagnosis of alkali-silica i (ASR) b di reaction (ASR) by direct
observation of reactions sites and gel deposits
• Alkali content measurement requires chemical analysis to BS 1881: Pt124
7 July 201133 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Condition: Multiple Deleterious Reactions• Evidence for several different deterioration mechanisms my be found
together making diagnosis difficult.• ASR/DEF combination relatively common, also TSA, leaching,
seawater attack and acid attack have all been found in co-existence with ASR
• Petrography is crucial to understanding relative significance of the various mechanisms
7 July 201134 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Condition: Fire Damage AssessmentConcrete Condition: Fire Damage Assessment
• Petrography provides the most accurate fire damage depth (300°C thermal contour)
7 July 201135 Petrography (TR71) and other testing methods - Jeremy Ingham
Concrete Condition: Assessment of RepairsConcrete Condition: Assessment of Repairs
• Assessing the quality of concrete repairsg q y p• Determining the causes of repair failure
7 July 201136 Petrography (TR71) and other testing methods - Jeremy Ingham
AgendaAgenda
• What is petrography?p g p y
• What’s involved – the techniques of petrography?q p g p y
• What can and can’t be achieved by petrography?What can and can t be achieved by petrography?
• Key publicationsKey publications
7 July 201137 Petrography (TR71) and other testing methods - Jeremy Ingham
Key PublicationsKey Publications
Concrete Society – www.concrete.org.uk
TR71 – Concrete Petrography: Ani t d t id f thintroductory guide for thenon-specialist
TR32 – Analysis ofHardened ConcreteHardened Concrete
7 July 201138 Petrography (TR71) and other testing methods - Jeremy Ingham
Key PublicationsKey Publications
St John, Poole & Sims -Concrete Petrography:A handbook of Investigative Techniques
Ingham –Geomaterials Under the Microscope
7 July 201139 Petrography (TR71) and other testing methods - Jeremy Ingham
Thank youThank you
Q ti ?Questions?
7 July 201140 Petrography (TR71) and other testing methods - Jeremy Ingham