measurement of the air permeability of concrete in-situ status quo

Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012

Measurement of the Air Permeability of Concrete “in situ”: status quo

Roberto Torrent / Luis Ebensperger

2Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012

Give a brief overview of the test method and itsevolution

How it correlates with other durability measurements

Application of the method to the specification, control“in-situ” and service life assessment of concretestructures

Objectives

2


Fundamentals and evolution of the method


Quality of Concrete in a Real Structure

Moulded specimens, made and cured under standard conditions, DO NOT represent the quality of the vital “covercrete”

Re-bars

Due to:• Segregation• Compaction• Curing• Bleeding• Finishing• Microcracking

“Covercrete” ofPoorer Quality

CO2 Cl- SO42-, Abrasion, Frost


Valve 1

Vacuum Pump

PressureRegulator(Pe=Pi)

PiPe

ii : Inner chambere : External chamber

2-ChamberVacuum cell

ComputerTouch-screen

Concrete

Soft rings

Valve 2

e

2-Chamber Vacuum cell

Air-Permeability Test Method: Fundamentals


Evolution of the pressure in the inner chamber

01020304050607080

0 5 10 15 20 25 30

Pres

sure

Pi (

mba

r)

60 720

t ~35Pi~200

Close V2

Regulator Activation

Close V2

∆P=0

t =0Pi~1000

Close V1

0 135tf

time (s) – square root scale

∆P~20 mbar

tmax

kT = 9.2 10 -16 m²

kT = 0.070 10-16 m²

(360)


Key Test Feature : Pe = Pi

i e

Concrete

100 mm50 mm

e

Controlled air flowinto the inner chamber

2-Chamber Vacuum cell


Calculation of kT

kT =A

ln

2 ε Pa

Vc2

2

µPa + ∆Pieff (tf)Pa - ∆Pieff (tf)√ tf - √ to

• kT: coefficient of air-permeability (m2)• Vc : volume of inner cell system (m3)• A : cross-sectional area of inner cell (m2)• µ : viscosity of air (= 2.0 10-5 N.s/m2)• ε : estimated porosity of the covercrete (= 0.15)• Pa : atmospheric pressure (N/m2)• ∆Pieff: effective pressure raise in the inner cell at the end of the test (N/m2)• tf : time (s) at the end of the test ( 2 to 12 min)• to : time (s) at the beginning of the test (= 60 s)


Prototype, Initial Tests and Classification (1993)

Very High10 – 100PK5High1.0 – 10PK4

Moderate0.1 – 1.0PK3Low0.01 – 0.1PK2

Very Low< 0.01PK1

PermeabilitykT(10-16 m²)

Class

Very High10 – 100PK5High1.0 – 10PK4

Moderate0.1 – 1.0PK3Low0.01 – 0.1PK2

Very Low< 0.01PK1

PermeabilitykT(10-16 m²)

Class


Torrent Permeability Tester (Proceq, 1995)

1st Commercial Instrument:

Plastic cell (lighter)

Automatic calculation of kT and L

Storage of data in memory

Download data to PC

Combined with Wenner electrical resistivity (optional accessory)


Permea-TRR (Materials Advanced Services 2008)2nd Commercial Instrument:Maximum duration of test reduced

from 12 to 6 minMeasures Pi and Pe

Fully automaticOperates above vapour pressureGraphical progress of test and early

kT estimateExtended range for highly porous

materials (kT>100 10-16 m²)Reprogrammable software

No Wenner


Standard Test Method with Recommended Limits

Included as Swiss Standard Test (SIA 262/1-E:2003)

ASTRA Recommendations propose limiting values as function of exposure conditions (2009):


Measurement Points (6 at random per Lot)

Surface LotH > 150 mm

H > 150 mm

D > 50 mm D > 50 mm

kT1

kT2

kT3

kT4 kT5

kT6


Condition 1:Not more than 1 test (out of the 6) with kT > kTs

Condition 2:If 2 tests > kTs, 6 new points are selected at random from the same Lot

Not more than 1 (out of the new 6 tests) with kT > kTs

Conformity Criterion

If none of the above Conditions is fulfilled, the Lot is considered as non-compliant with the specified kTs


‘Covercrete’Quality = K-1

K = Penetrability

Swiss Performance Approach to Durability

Execution:• Placing• Compaction• Finishing• Curing

kT checked on site

ConcreteProduction

Standard “K” Tests on cast Specimens

DESIGN PRACTICE CONTROLSpecification

of Kmax

on Delivered and SiteConcrete


Correlation with other durability measurements


Water Sorptivity vs. kT (own data)

0

5

10

15

20

25

0.001 0.01 0.1 1 10 100

kT (10-16 m²)

24-h

Sor

ptiv

ity (

g/m

²/s½

) LaboratoryTunnelBridge


ASTM C1202 Coulombs vs. kT (various authors)

100

1000

10000

100000

0.001 0.01 0.1 1 10 100

kT (10-16 m²)

Cou

lom

bsHigh (+ Very High)

Moderate

Low

Very Low


Water Penetration under Pressure (EN/DIN) vs. kT

0

25

50

75

100

125

150

0.001 0.01 0.1 1 10

kT (10-16 m²)

Max

. Pen

etra

tion

(mm

)Low Moderate HighVery Low


Service Life assessment based on site measurement of kT and cover depth


Measurement of the coefficient of air-permeability kT

Measurement of cover depth c Application of models for

carbonation-induced corrosion basedon site air-permeability (e.g. Parrott,site data)

Application of models for chloride-induced corrosion based on air-permeability kT through correlations ofDCl and kT (e.g. Life-365 or EHE-08)

Allows estimating service life from measurements conducted on the end-product (finished structure):

Service Life assessment based on kT and c


Site kT vs. Carbonation Rate (old structures)

0

1

2

3

4

5

6

0.001 0.01 0.1 1 10 100 1000

Coeff. of Air-Permeability kT (10-16 m²)

Car

bona

tion

Rat

e (m

m/y

½)

Underpass 30yBridge 60yBridge 30yBldg. 30 y

Very Low Low Moderate High Very High Ultra High


Assessment of DCl based on kT measurements

c² Ti = ---------------------------- with DCl = Do . (to / tf)n erf-1 (1 - Cc / Cs) . DCl


Relation of kT with South African Indices

0

0.5

1

1.5

0.01 0.1 1 10

kT (10-16 m²)

Cl- C

ondu

ctiv

ity (m

S/cm

)

9.5

10

10.5

11

0.01 0.1 1 10

kT (10-16 m²)

OPI

Data from EMPA (Switzerland)

Opens prospects of combined approach:

kT + South African Service Life Design


Recent Worldwide Applications

ShCC IndustrialFloor (Argentina)

Segments Port of Miami Tunnel (USA)

Museum WesternArt (Japan)

Wotruba Church (Austria)

Estimating Service Life with c and kT

(Holland)

New Panama Canal

measurement of the air permeability of concrete in-situ status quo

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