Maria Cruz Alonso

MISURARE E «MONITORARE» LA DURABILITA:

Predictive monitoring systems for rebar corrosion

assesment in aggressive environments

DURABILITY IN THE SERVICE LIFE OF THE STRUCTURES

• What are the aims for the service life of a structure? Identification of the exposure site aggressiveness (Std. classification) Recommendations from codes & standard for durability designIdentification of damage expectances Service life estimation length at project design

• When a structure should be monitored?Who takes the decisionAdditional monitoring measures during the service life

• How to select the most suitable monitoring system? Location of the structure and structure typologyMonitoring length and time scale Durability of structure vs. durability of the monitoring system

• What expectances of the owner from monitoring system?

Why rebar corrosion is a risk in service life of structures?

Alkaline Cover

Passive layer

En

vir

on

me

nt

CO2

Clˉ

En

vir

on

me

nt

CO2

Clˉ

Clˉ Clˉ

Pas

sive

laye

ral

tera

rio

Passive layer

Bro

ken

pas

sivi

typ

itti

ng

En

vir

on

me

nt

CO2

Clˉ

Dap

En

vir

on

me

nt

CO2

Clˉ

Dap Cl crit

Parameters to monitor service life of concrete structures

REBAR MONITORING

•Corrosion potential• Corrosion rate

CONCRETE MONITORING

• Electrical resistivity• pH changes• Cl content

CHANGES IN CONCRETE AND REBAR OCCUR DUE TO AGGRESSIVES ENTRANCE

Density Plot (Normal (Gauss))-Cl-

0.21 0.30 0.40 0.49 0.58 0.68 0.77 0.87 0.960.00

0.28

0.55

0.83

1.11

1.38

1.66

1.94

2.21

2.49

2.77Relative Frequency

Import Data ( Cl Total)

Density Plot (Normal (Gauss))-Cl-

0.21 0.30 0.40 0.49 0.58 0.68 0.77 0.87 0.960.00

0.28

0.55

0.83

1.11

1.38

1.66

1.94

2.21

2.49

2.77Relative Frequency

Import Data ( Cl Total)

Density Plot (Normal (Gauss))-Cl-

0.21 0.30 0.40 0.49 0.58 0.68 0.77 0.87 0.960.00

0.28

0.55

0.83

1.11

1.38

1.66

1.94

2.21

2.49

2.77Relative Frequency

Import Data ( Cl Total)

Density Plot (Normal (Gauss))-Cl-

0.21 0.30 0.40 0.49 0.58 0.68 0.77 0.87 0.960.00

0.28

0.55

0.83

1.11

1.38

1.66

1.94

2.21

2.49

2.77Relative Frequency

Import Data ( Cl Total)

Density Plot (Normal (Gauss))-Cl-

0.21 0.30 0.40 0.49 0.58 0.68 0.77 0.87 0.960.00

0.28

0.55

0.83

1.11

1.38

1.66

1.94

2.21

2.49

2.77Relative Frequency

Import Data ( Cl Total)

Density Plot (Normal (Gauss))-Cl-

0.21 0.30 0.40 0.49 0.58 0.68 0.77 0.87 0.960.00

0.28

0.55

0.83

1.11

1.38

1.66

1.94

2.21

2.49

2.77Relative Frequency

Import Data ( Cl Total)

Density Plot (Normal (Gauss))-Cl-

0.21 0.30 0.40 0.49 0.58 0.68 0.77 0.87 0.960.00

0.28

0.55

0.83

1.11

1.38

1.66

1.94

2.21

2.49

2.77Relative Frequency

Import Data ( Cl Total)

Density Plot (Normal (Gauss))-Cl-

0.21 0.30 0.40 0.49 0.58 0.68 0.77 0.87 0.960.00

0.28

0.55

0.83

1.11

1.38

1.66

1.94

2.21

2.49

2.77Relative Frequency

Import Data ( Cl Total)

• Monitoring with surface electrodes Periodic measurements• Monitoring with embedded electrodes Periodic vs. continuous (remote)

Sensor durability

stablecorrosiononset

Initiation period ends with

corrosion onset: ti = ttransp + tdep

Concrete monitoring of durability through embedded sensors

pH change

Electrical resistivity Segui Y. et al, mat &

struct (2017)

IETcc-CSIC

Blumentritt, 2008

Fiber optic

SMARTBOX(Giatec)

Segui Y. et al, mat & struct (2016)

Ag/ClAg

UPV

• Advantages : Possibility of periodic or continuous monitoring.

• Limitations: Need to know the life expectances of the sensor respect the

service life of the structure, pH and Cl sensors lack of market availability

Cl content

Active corr. Passive corr.

Wet sponje

voltmeter

Concrete cover

Referenceelectrode

-400 mV -200mV

On-site Ecorr

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

S1

S2

S3

S4

S5

S6

S7

S8

>-260<-250 >-400 <-400

Concrete monitoring from surface sensors / Periodic

On-site-

Rebar corrosion assessment with surface sensors/ Periodic

Direct connection of the rebar

- mapping

Ecorr- mapping

A

V

Re

= 2a Re

Electrodes

Concrete

Commercial equipment available

Rebar corrosion assessment from surface sensors / Periodic

Direct connection of the rebarEcorr/icor/

GCOR-8 (Geocisa) GALVAPULSE (German instruments)

x1/t1 =v1

Cross section or radio loss (PX = attack penetration) per unit of time (t) & unit of

total Surface (2rL)

Px = 0.0116 Icorr . t

Commercial equipment available

Icorr on embedded probes

Ecorr

Duffó et al.

Galvanic sensorINESSCOM (UPV)

INESSCOM (UPV)

ElectronicTongue

Multisensors

Remote data collection

CORROSOMETER 650c(Cosasco systems)

CONCRETE MULTI-DEPTH (Cosasco systems)

Rebar corrosion assessment from embedded sensors /Continuous

Commercial equipment availability

No market availability

Direct on the rebar

• What expectances of the owner from monitoring? Reassesment of service life prediction respect to design Identification of damage, location severityIdentification of optimal time for maintenance measures Take corrective measures in structure and in monitoringsystem

Need of multidisciplinary analyses of performance:• Rebar corrosion especialisation• Structural background performance• Electronic and data base management

DURABILITY IN THE SERVICE LIFE OF THE STRUCTURES

Maria Cruz Alonsomcalonso@ietcc.csic.es

https://www.ietcc.csic.es/