measurement of the air permeability of concrete in-situ status quo
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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
Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
Fundamentals and evolution of the method
4Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
5Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
6Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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)
7Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
Key Test Feature : Pe = Pi
i e
Concrete
100 mm50 mm
e
Controlled air flowinto the inner chamber
2-Chamber Vacuum cell
8Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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)
9Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
10Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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)
11Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
12Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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):
13Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
14Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
15Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
‘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
Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
Correlation with other durability measurements
17Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
18Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
19Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
Service Life assessment based on site measurement of kT and cover depth
21Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
22Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
23Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
Assessment of DCl based on kT measurements
c² Ti = ---------------------------- with DCl = Do . (to / tf)n erf-1 (1 - Cc / Cs) . DCl
24Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
25Torrent / Ebensperger ICCRRR 2012, SA September 5th, 2012
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
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