Portland Cement Concrete

47
1 CE 2512 Materials for Civil Engineering CE 2512 Materials for Civil Engineering Properties of Concrete Properties of Concrete Crushed Stone Crushed Stone or Gravel or Gravel Sand Sand Water Water Portland Portland Cement Cement Concrete Basics - Materials

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Construction engineering, Construction materials, Civil Engineering,Building materials,

Transcript of Portland Cement Concrete

Page 1: Portland Cement Concrete

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CE 2512 Materials for Civil EngineeringCE 2512 Materials for Civil Engineering

Properties of ConcreteProperties of Concrete

Crushed Stone Crushed Stone or Gravelor Gravel

SandSand WaterWater PortlandPortlandCementCement

Concrete Basics - Materials

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Concrete Basics - Materials

Supplementary Cementing Materials

• Fly ash• Slag• Silica Fume• Natural Pozzolans

Chemical Admixtures

• Air entrainment• Water reducers• Set modifying• Corrosion inhibitors• Shrinkage reducers• Wide range of others

Concrete Basics - Materials

• Steel• Polypropylene• Nylon• Glass• Carbon

Fibers

Not covered in CE 2512

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Concrete Basics - Materials

Hydration

Abrams’ LawFor given materials the strength of the concrete (so long as we have a plastic mix) depends solely on the relative quantity of water compared with the cement, regardless of mix or size and grading of aggregate.

Duff A. Abrams, 1918

Concrete Basics - Materials

strength = f (W/C)

where: W = mass of water, C = mass of cement

strength = f (W/CM)

where: W = mass of water, C = mass of cementing materials

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W/CM = 0.61 by massW/CM = 0.33 by mass

Volume of Water

Volume of Cement= 1 Volume of Water

Volume of Cement= 2

Concrete Basics - Materials

Original water-filled spaces: “Capillary Porosity”

Low W/CM:• Low capillary porosity• Small pores poorly connected• Low permeability• High strength

High W/CM:• High capillary porosity• Large pores - well connected• High permeability• Low strength

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Concrete Basics - Materials

Reducing the water content and W/CM of concrete leads to:

• Increased strength and stiffness• Reduced creep• Reduced shrinkage• Lower permeability• Increased resistance to weathering• Better bond between concrete and reinforcement

Less Water Better Concrete

Provided the concrete can be consolidated properly!

Concrete Basics – Essentials of Quality Concrete

The performance of concrete depends on:

• Suitable materials

• Mixture proportions

• Mixing and transporting

• Placing and consolidation

• Finishing & jointing

• Curing

• Workmanship

• Environment

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Properties of Fresh Concrete – Freshly Mixed Concrete

Requirements of fresh concrete:

• Easily mixed and transported• Uniform throughout a given batch (and between

batches)• Flow properties such that it is capable of completely

filling the forms• Ability to be compacted fully without an excessive

amount of energy being applied• Must not segregate during transportation, placing

and consolidation• Capable of being finished properly (either against

the forms of means of trowelling or other surface treatment)

Mindess et al, 2003

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Properties of Fresh Concrete - Workability

that property of freshly mixed concrete or mortar that determines the ease with which it can be mixed, placed, consolidated, and finished to a homogenous condition.

Workability

the relative mobility or ability of freshly mixed concrete or mortar to flow; the usual measurement is slump for concrete …

Consistency

ACI 116R-00 Cement and Concrete Terminology

Properties of Fresh Concrete - Workability

Factors affecting slump:• Water content• Cement type• SCM’s (especially fly ash or silica fume)• Chemical admixtures (water reducers,

plasticizers and air entrainers)• Temperature• Haul time• Mixing time

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Properties of Fresh Concrete – Setting & Hardening

Time

Rig

idity

Limits of handling

Beginning ofmechanical strength

InitialSet

FinalSet

Transition(Setting) Rigid

Final setInitial setAddition of water

Dormant Period Setting Hardening

Young et al, 1998

Properties of Fresh Concrete – Setting & Hardening

C-S-H bridging the gap between cement grainsRigid structure develops

Photomicrograph courtesy of Lafarge

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Properties of Fresh Concrete – Setting & Hardening

The setting time of concrete is influenced by:

• Type and quantity of cement

• Supplementary cementing materials

• Chemical admixtures (retarders & accelerators)

• W/CM

• Temperature

Properties of Fresh Concrete – Testing

• Slump

• Temperature

• Air content

• Unit weight & yield

• Making samples for strength tests

• Uniformity

Tests on fresh concrete

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Properties of Hardened Concrete – Strength Development

Compressive Strength ofCompressive Strength ofHardened ConcreteHardened Concrete

The compressive strength is the most commonly-used measure of concrete quality and is used in:

• design calculations

• specification

• quality control

the maximum resistance of a (cylindrical) specimen to axial loading

Strength = Max loadArea

0

10

20

30

40

Age (days)

Stre

ngth

(MPa

)

1 3 14 28

Strength Development of Concrete

Concrete will continue to gain strength as long as:

• some unhydrated cement remains

• concrete remains moist (relative humidity > 80%)

• Temperature is above freezing

• The 28-day strength is usually used to characterize a particular concrete mix

35MPa (5000 psi)

Properties of Hardened Concrete – Strength Development

7

6000

4000

2000

0

Strength (psi)

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0

10

20

30

40

Age (days)

Stre

ngth

(MPa

)

23C40C15C5C

1 3 14 28

Strength Development of Concrete – Effect of Temperature

Properties of Hardened Concrete – Strength Development

7

6000

4000

2000

0

Strength (psi)

Increased Temperature

Increased Rateof Hydration

Increased Strengthat Early Age

But decreasedLong-term strength

0

10

20

30

40

Age (days)

Stre

ngth

(MPa

)

Continuous 7 days 3 days 1 day

1 3 14 28

Strength Development of Concrete – Effect of Curing

Properties of Hardened Concrete – Strength Development

7

6000

4000

2000

0

Strength (psi)

MoistCuringPeriod

10028

897

713

491

28-day strength (% of concrete

cured for 28 days)

Moist curing period

100 x 200 mm (4 x 8 in.) concrete cylinders

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0

20

40

60

80

100

0

4000

8000

12000

3d 7d 28d 3m 1y 3y 10y20y5y

W/CM = 0.40W/CM = 0.53W/CM = 0.71

Stre

ngth

(MP

a)

Strength (psi)

Age at TestKosmatka et al. 2002

Strength Development of Concrete – Outdoor Exposure

Properties of Hardened Concrete – Strength Development

• 150-mm (6-in.) Cubes

• Type I Cement

• Outdoor exposure in Skokie, Illinois

Exposed concrete will continue to gain strength when the exposure conditions (temperature, moisture availability) are suitable for cement hydration

Strength Development of Concrete – Indoor Exposure

Properties of Hardened Concrete – Strength Development

0

20

40

60

80

850 daysnatural drying

114 daysnatural drying

150-mm (6-in.) Thick Concrete Wall

Rel

ativ

e H

umid

ity o

f Con

cret

e (%

)

Ambient Air= 35% RH

10028 daysnatural drying

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Properties of Hardened Concrete – Strength Development

Compressive strength of concrete with a given composition is dependent on:

• Age of the concrete at the time of test• Extent of moist-curing• Curing temperature

Standard-cured, 28-day compressive strength of concreteindicates that the strength test was carried out on a specimen which was:

• 28 days old at the time of test• Cured in a fog room (100% RH) or in limewater• Cured at a temperature of 23oC (70oF)

Properties of Hardened Concrete – Strength Development

0

20

40

60

80

0

2000

4000

6000

8000

10000

0.25 0.35 0.45 0.55 0.65 0.75 0.85

Com

pres

sive

Stre

ngth

(MP

a) Com

pressive Strength (psi)

W/CM

• 28-day strength

• Moist-cured cylinders

• Non-air-entrained concrete

• Portland cement only

• Over 100 mixtures (1985 to 1999)

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Properties of Hardened Concrete – Strength Development

Factors affecting 28-day standard-cured compressive strength:

• W/CM

• Type of portland cement

• Type and amount of SCM

• Air content (~ 5.5% reduction for each 1% air)

• Aggregate strength (in high-strength concrete)

General use concrete: 20 to 40 MPa (3000 to 6000 psi)

Special applications: 70 to 140 MPa (10,000 to 20,000 psi) can be achieved

• Strength usually specified at 28 days and w/cm selected to provide the required strength

• However, strength may be specified at any other age such as at 7 days for loading or 1 day for form removal

• In such cases, relationships between strength and w/cm have to be developed for these ages

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• When different cementing materials are used the relationships between w/cm, age and strength change

• For example, if 25% fly ash is introduced into a mix – the w/cm will have to be reduced by a small amount to main the same 28-day strength and by a larger amount to maintain the same 3-day strength

• w/cm can be reduced by reducing water content (use of fly ash, water-reducing admixture) or increasing cementitious material content, or both (see example below)

90 days

28 days

3 days25% Fly ash

100% Portlandcement

303028-day strength (MPa)

0.500.60W/CM

160180Water (kg/m3)

800Fly Ash (kg/m3)

240300Portland cement (kg/m3)

Mix BMix A

Tensile Strength of ConcreteTensile Strength of Concrete

Tensile strength of concrete is very difficult to measure directly. It is usually determined indirectly using either:

• Flexural test

• Cylinder splitting

(Indirect tensile test)

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2P

2P

3L

3L

3L

2bdPLR =

R = flexural strength (MPa)P = maximum load applied (N)L = span length (mm)b = width of specimen (mm)d = depth of specimen (mm)

Flexural StrengthFlexural Strength(Modulus of Rupture)(Modulus of Rupture)

nct fkf ⋅=

A number of empirical formulae for predicting the tensile strength (ft) from the compressive strength (fc) have been developed; many of these are of the type:

The direction of crack propagation in uniaxial tension is perpendicular to the stress direction.

The initiation & growth of each new crack reduces the load carrying area.

c

tf

f = 0.07 to 0.11Typically

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LdPT

π2

=

T = tensile strength (MPa)P = load at failure (N)L = length of specimen (mm)d = diameter of specimen (mm)

For design purposes, the secant modulus at 40% of the strength of the concrete is usually used

σ = 0.40 fc’

E - secant modulus

1

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LVD

T

LVD

T

P

PBottom ring firmly fixed(no rotation permitted)

Top ring pivoted(rotation permitted)

The deflection measured by the LVDT is twice the deformation of the sample

150

mm

LVD

T

LVD

T

P

PBottom ring firmly fixed(no rotation permitted)

Top ring pivoted(rotation permitted)

The deflection measured by the LVDT is twice the deformation of the sample

150

mm

CE2512 Concrete Lab 2 - Testing

The load (in Newtons) and the displacement of the LVDT (in mm) will be collected by datalogger and emailed to you in a spreadsheet. You will have to convert load to stress (MPa) and displacement to strain (mm/mm) in order to calculate the modulus

Properties of Hardened Concrete – Strength Development

Other mechanical properties

Flexural strength(Modulus of Rupture)

= 0.7 to 0.8 x √(compressive strength, MPa)

= 7.5 to 10 x √(compressive strength, psi)

Direct tensile strength= 0.4 to 0.7 x √(compressive strength, MPa)

= 5 to 7.5 x √(compressive strength, psi)

Splitting tensile strength = 8% to 14% of compressive strength

Modulus of elasticity= 5000 x √(compressive strength, MPa)

= 57000 x √(compressive strength, psi)

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Poisson’s ratio, μ, may vary from 0.15 to 0.25 depending on strength, aggregate, moisture content, and concrete age

Properties of Hardened Concrete – Volume Stability & Crack Control

Hardened concrete changes volume due to changes in:

• Temperature

• Moisture

• Stress

Length/volume changes ~ 0.01% to 0.1 % (or 100 to 1000 microstrain)

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Properties of Hardened Concrete – Volume Stability & Crack Control

CreepStrain

Elastic strain

Elasticrecovery

Creeprecovery

Irreversiblecreep

0

20

400

600

800

1000

0 20 40 60 80 100 120

Mic

rost

rain

Time after loading (days)

After Mindess et al, 2003 Load applied

Load removed

Creep

Properties of Hardened Concrete – Volume Stability & Crack Control

Initial state

Cracking Due to Volume Change

Reduction in temperature and moisture

Unrestrained drying andthermal shrinkage

If unrestrained concrete shrinks due to loss of moisture or cooling

If restrained tensile stresses develop in the concreteTensile stresses

If tensile stresses exceed tensile strength – concrete cracks

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Properties of Hardened Concrete – Volume Stability & Crack Control

Cracking Due to Volume Change

External restraint

Surface cools (or dries) more rapidly than bulk

Internal restraint

Properties of Hardened Concrete – Volume Stability & Crack Control

Cracking Due to Volume Change

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Properties of Hardened Concrete – Volume Stability & Crack Control

Measures to reduce thermal cracking

• Minimize temperature rise above ambient• Lower cement content• Use low-heat Type IV cement• Use pozzolans or slag• Lower concrete placing temperature• Use embedded cooling pipes

• Minimize thermal gradient in concrete

Properties of Hardened Concrete – Volume Stability & Crack Control

Measures to reduce drying shrinkage

• Reduce the water content of the mixture

• Minimize paste content

• Increase the aggregate content• Use as large as practical

maximum aggregate size• Optimize grading

• Increase moist curing period

• Shrinkage-reducing admixtures

• Shrinkage-compensating cement

• Steel fibres

0

400

800

1200

150 200 250

250 300 350 400 450Water Content (lb/yd3)

Water Content (kg/m3)

Dry

ing

Shr

inka

ge (m

illio

nths

)

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Properties of Hardened Concrete – Volume Stability & Crack Control

Crack Control

Reinforcing steel

Isolation joints

Contraction joints

Construction joints

to reduce crack widths

to control the location of cracks

Properties of Hardened Concrete – Volume Stability & Crack Control

Isolation joint • Isolate adjoining parts of a structure• Permit differential movements

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Properties of Hardened Concrete – Volume Stability & Crack Control

Contraction joints(Control joints)

• Provide for movement within a slab or wall• Cracks induced at predetermined locations

Properties of Hardened Concrete – Volume Stability & Crack Control

Contraction joints(Control joints)

• Provide for movement within a slab or wall• Cracks induced at predetermined locations

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Properties of Hardened Concrete – Volume Stability & Crack Control

Contraction joints(Control joints)

• Provide for movement within a slab or wall• Cracks induced at predetermined locations

Slab

Wall

Seal outside with joint sealerif leakage is anticipated

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Properties of Hardened Concrete – Volume Stability & Crack Control

Construction joint

• Stopping place during the construction process (e.g. end of the day’s work)

• A true construction joint should bond new concrete to existing concrete and permit no movement. Deformed tie bars are often used to restrict movement

• However – construction joints are often designed and built to operate as contraction or isolation joints

Spacing of Contraction Joints in Meters

7.56.0250

6.755.5225

6.05.0200

5.254.25175

4.53.75150

3.753.0125

3.02.4100

Maximum-size aggregate ≥ 19 mm

Maximum-size aggregate < 19 mm

Slab thickness, mm

MetricMetric

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1084

2520102318920168181471512613105

Maximum-size aggregate ≥ ¾ inch

Maximum-size aggregate < ¾ inch

Slab thickness, in.

InchInch--PoundPound

2 feet spacing for each inch of slab thickness

2½ feet spacing for each inch of slab thickness(round up to nearest

whole foot)

Spacing of Contraction Joints in Feet

Properties of Hardened Concrete – Permeability & Watertightness

Watertightness the ability of concrete to hold back or retain water without visible leakage

Permeability amount of water migration through concrete when the water is under pressure or the ability of concrete to resist penetration by water or other substances (liquids, gas, ions, etc

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Outflow

= Q

Hydrostaticpressure, h l

X-sectionarea = A

hl

AQk ⋅=Coefficient of permeability,

Properties of Hardened Concrete – Permeability & Watertightness

Factors Affecting Permeability of Concrete

Principal Factors

Water/cementitious material

Water Content

Curing

Age

Use of SCM’s• Silica fume• Fly ash• Slag• Natural pozzolans

Secondary Factors

Cement factor

Chemical admixtures

Aggregate type

Air content

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Permeability does not go to zero – but very small value

Fig 7.28 in M&Z, 2006Fig 7.28 in M&Z, 2006

0.1

1

10

100

1000

0.2 0.3 0.4 0.5 0.6 0.7W/CM

Perm

eabi

lity,

x 1

0-14 m

/s

More appropriate to plot on semi-log scale

W/CM

Fig 7.28 in M&Z, 2006Fig 7.28 in M&Z, 2006

W/CM

Reduce W/CM0.70 → 0.40

Almost double strength

Reduce W/CM0.70 → 0.40

Red

uce

perm

eabi

lity

by 1

00 ti

mes

Compare with Strength

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Properties of Hardened Concrete – Permeability & Watertightness

Effect of SCM’s

• Fly ash

• Slag

• Silica fume

• Natural pozzolans (e.g. metakaolin)

Permeability reductions of 10 Xor more are possible if concrete is properly proportioned and adequately cured

Properties of Hardened Concrete – Durability

• Cyclic freezing and thawing• Deicer salt scaling• Corrosion of reinforcing steel• Alkali-silica reaction• Sulfate attack• Abrasion• Others

Causes of deterioration:

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Properties of Hardened Concrete – Durability

• Cyclic freezing and thawing• Deicer salt scaling• Corrosion of reinforcing steel• Alkali-silica reaction• Sulfate attack• Abrasion• Others

Causes of deterioration:

Low Permeability Durability

Involve movement of water(or transport of species in water)

Properties of Hardened Concrete – Durability

Freezing and Thawing of Concrete

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Properties of Hardened Concrete – Durability

Freezing and Thawing of Concrete

Properties of Hardened Concrete – Durability

Freezing and Thawing of Concrete

Concrete blocks on PCA outdoor test plot after 40 years exposure

(355 kg/m3 cement)

Non-air-entrained concrete Air-entrained concrete

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Properties of Hardened Concrete – Durability

Freezing and Thawing of Concrete

0

1000

2000

3000

4000

5000

6000

0.3 0.4 0.5 0.6 0.7 0.8 0.9

W/CM

Num

ber o

f Fre

eze-

Thaw

Cyc

les

to 2

5% L

oss

in M

ass Air-entrained

concrete

Non-air-entrainedconcrete

Fog cured 14 daysDried 76 days at 50% RH

Properties of Hardened Concrete – Durability

Freezing and Thawing of Concrete – Deicer Salt Scaling

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Properties of Hardened Concrete – Durability

Freezing and Thawing of Concrete – ‘D-Cracking’

• The aggregate is frost-resistant

• Sufficient strength is attained prior to first freezing (> 3.5 MPa or 500 psi)

• Sufficient strength is attained prior to cyclic freezing & thawing (> 28 MPa or 4000 psi)

• Adequate Air Void System

Properties of Hardened Concrete – Durability

Freezing and Thawing of Concrete

General criteria for resistance to freezing and thawing

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Properties of Hardened Concrete – Durability

Corrosion of Reinforcing Steel

Protective (passive) layer

Concrete pore solution: pH > 13

Chloride IonsCarbonation

Breakdown of passive layer

Properties of Hardened Concrete – Durability

Protective (passive) layer

Concrete pore solution: pH > 13

Cl ClChloride ions from:

• Deicing salt• Seawater• Groundwater

Corrosion of Reinforcing Steel – Action of Chlorides

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Properties of Hardened Concrete – Durability

# 1 cause of concrete deterioration

Corrosion of Reinforcing Steel – Action of Chlorides

Corrosion of Reinforcing Steel – High-Performance Concrete

Low-permeabilityconcrete

NaOHsolution

NaClsolution

60VA

NaOHsolution

NaClsolution

60VA

ASTM C 1202 – “Rapid Chloride Permeability Test”

Apply 60 V across a 100-mm diameter x 50-mm thick concrete sample

Measure total electrical charge passed (in Coulombs) over a 6-hour period

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Data from Ozyildirim, 1998

0

1000

2000

3000

4000

5000

6000

0 120 240 360Age (Days)

RC

PT (C

oulo

mbs

)

Negligible< 100

Very low100 – 1000

Low1000 – 2000

Moderate2000 – 4000

High> 4000

Chloride Ion Penetrability

Coulombs Passed

Control (no SCM)

20% Fly Ash7% Silica Fume

Fly Ash, slag & most pozzolansLittle effect at early age (e.g. 28 days)Reduction becomes more significant with ageSubstantial reduction at later age

Silica fume, metakaolin (highly reactive pozzolans)

Significant reduction at early age (e.g. 28 days)Smaller decreases with age

SCM Effect on Chloride Permeability

W/CM = 0.38-0.40

SCM & Chloride Permeability

What does the “Rapid Chloride Permeability Test” really measure?

• The RCPT measures electrical conductivity – which is a measures of the ease with which electrical charge can pass through a material.

• Electrical conductivity is the reciprocal of electrical resistivity – concrete with a low electrical conductivity has a high electrical resistivity

• Electrical charge passes through the pore structure of the concrete (the solid phases have a high electrical resistance) – as do chloride ions and water.

• High w/cm concrete with an open and well-connected pore structure will be permeable to water and chloride ions, and have a high electrical conductivity and low electrical resistance

• Low w/cm concrete that contains SCM’s will have a more refined pore structure (small and poorly connected pores) and will have low permeability to water and a high resistance to chloride ion penetration. It will also have a low electrical conductivity and high electrical resistivity

• Thus – electrical conductivity or resistivity – provides an indirect but reasonable indication of the permeability of concrete and its resistance to the ingress of deleterious species such as chlorides

• Care must be taken to ensure that concrete is saturated when its electrical properties are measured as dry concrete (with empty pores) has a very high electrical resistant no matter how open and well connected its pores are.

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Corrosion of Reinforcing Steel – Carbonation

pH reduced (colourless)Ca(OH)2 + CO2 →CaCO3 + H2OSteel corrodes

Original high pH maintained (purple)Steel in pristine condition

Properties of Hardened Concrete – Durability

Corrosion of Reinforcing Steel – Carbonation

Problems occur when:

• High W/CM

• Poor curing

• Inadequate cover

• High levels of SCM

• Outdoor-sheltered exposure

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Properties of Hardened Concrete – Durability

Alkali-Silica Reaction (ASR)

• Effects all types of exposed concrete structures

• Has occurred in most, if not all, states of U.S.A. and provinces of Canada

(CSA A864-00)

Occurrences of ASR in CanadaOccurrences of ASR in Canada

Fredericton?

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Properties of Hardened Concrete – Durability

Alkali-Silica Reaction (ASR)

Cement paste

Reactive chertAlkali-silica gel

Crack

Crack

Microscopic thin section through ASR-affected concrete

Properties of Hardened Concrete – Durability

Alkali-Silica Reaction (ASR)

Preventive Measures for ASR

Use of non-reactive aggregate

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Use a NonUse a Non--Reactive Aggregate?Reactive Aggregate?

Mactaquac Dam, NB

Aggregate passed criteria for “non-reactivity” that existed at the time of construction

Millions of $$$’s currently being spent trying to deal with ASR problems

Properties of Hardened Concrete – Durability

Alkali-Silica Reaction (ASR)

Preventive Measures for ASR

Use of non-reactive aggregate

Limit alkali content of concrete

1.8 – 3.0 kg/m3 Na2Oe

3.0 – 5.0 lb/yd3 Na2OeTypical values use in specifications

0

0.1

0.2

0.3

0.4

0.5

1.0 2.0 3.0 4.0 5.0 6.0

Alkali Content of Concrete (kg/m3 Na2Oe)

Expa

nsio

n at

2 Y

ears

(%)

CSA Limit

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Concrete alkali content < 3 kg/mConcrete alkali content < 3 kg/m33 NaNa22OeOe

Concrete alkali content < 2 kg/mConcrete alkali content < 2 kg/m33 NaNa22OeOe Concrete alkali content < 2 kg/mConcrete alkali content < 2 kg/m33 NaNa22OeOe

Examples of ASR in concrete structures with a low alkali content

Properties of Hardened Concrete – Durability

Alkali-Silica Reaction (ASR)

Preventive Measures for ASR

Use of non-reactive aggregate

Limit alkali content of concrete

Use of SCM’s

Concrete without fly ash Concrete with 25% fly ash

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ASR-Affected Hydraulic Structures, Ontario

A number of dams and associated structures affected by ASR with greywacke/argillite aggregate from Huronian Supergroup

Ontario

Lake Superior

LakeHuron

Lady Evelyn Dam

Diagnosed as ASR in 1965

Demolished and replaced in 1973

ASR-Affected Hydraulic Structures, Ontario

A number of dams and associated structures affected by ASR with greywacke/argillite aggregate from Huronian Supergroup

Ontario

Lake Superior

LakeHuron

Site of Lower Notch Dam

Dam completed in 1969 with known reactive aggregate from the same geological formation

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0.00

0.02

0.04

0.06

0 1 2 3

Age (Years)

Exp

ansi

on (%

) High-Alkali Cement

High-Alkali Cement+ Fly Ash

Low-Alkali Cement

Lower Notch Dam, Ontario

After testing the aggregate it was decided that the dam would be built using high-alkali cement (1.08% Na2Oe) and a Class F fly ash

– 20% in structural concrete and 30% in mass concrete

Properties of Hardened Concrete – Durability

Alkali-Silica Reaction (ASR)

Preventive Measures for ASR

Use of non-reactive aggregate

Limit alkali content of concrete

Use of SCM’s

Use of chemical admixtures

Concrete without lithium Concrete with LiOH

Long-term effectiveness not yet established

Indications that lithium is not effective with all reactive aggregate types

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Properties of Hardened Concrete – Durability

Sulfate Attack

The resistance of concrete to sulfate attack can be improved by:

• Use of low-C3A cement with:moderate sulfate resistance (Type II)high sulfate resistance (Type V)

Type I - 14.1% C3A Type V - 1.2% C3A

Courtesy of BRE

Properties of Hardened Concrete – Durability

Sulfate Attack

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The resistance of concrete to sulfate attack can be improved by:

• Use of low-C3A cement with:moderate sulfate resistance (Type II)high sulfate resistance (Type V)

• Use of low W/CM (to reduce permeability)

Type V Cement: W/C = 0.65 Type V Cement: W/C = 0.38

Properties of Hardened Concrete – Durability

Sulfate Attack

The resistance of concrete to sulfate attack can be improved by:

• Use of portland cement with low-C3A content:moderate sulfate resistance (Type II)high sulfate resistance (Type V)

• Use of low W/CM (to reduce permeability)

• Use of some supplementary cementing materials

Type I - 14.1% C3A Courtesy of BREType I + Fly Ash

Properties of Hardened Concrete – Durability

Sulfate Attack

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Properties of Hardened Concrete – Durability

Other Forms of Deterioration

• Thaumasite form of sulfate attack (TSA)

• Delayed ettringite formation (DEF)

• Salt crystallization

• Alkali-carbonate reaction (ACR)

• Chemical attack

TheThe EndEnd