Before You Start; Procedure - Elcometer 331 Operating Instructions Manual

elcometee
;
MEASURING HALF-cELL PoTENTIAL
8 MEASURING HALF-CELL POTENTIAL
Your
CovermeterP
is
capable
of
measuring half-cell potential
-
an
electrochemical technique
commonly used to assess the severity of corrosion in reinforced concrete structures
\Mren
set
to
half-cell mode, your
Covermeter
acts as
a
voltmeter which
measures
the
potential
difference
between the steel reinforcement
in
the concrete structure and a reference electrode (the
half-cell)
olaced
on
the surface
of
the concrete
Half-cell readings can
be
stored
in
memory in batches
in
the same way as readings of cover
8.1 Before
you start
.
Are
you
using the
correct half-cell probe?
See "Half-cell probes" on page
28
8.2
Procedure
1
Use
the Covermeter to locate a reinforcing
bar.
2
Expose the
bar, e
g
by
drilling through the cover using a
large drill
3
Drill
a small diameter hole
into
the bar suitable for attachment
of
the positive (red) cable
using
a
screw or lead plug
4
Mark out a grid on the
concrete Measurements will be taken at the intersection points of the
grid
Typical grid spacing is
1 m
x
1 m,
howeverthis
may be reduced if localised corrosion
is
suspected lf the measured half-cell potential between two adjacent poqitions differs by more
than
100
mV
it
rs
recommended that the grid spacing
is
reduced
5
lf
necessary,
use tap water
to
wet
the
whole of the test area,
or just the
measurement
oositions
6
Connect
the
red cable
and
extension reel between
the
exposed reinforcing
bar
and
the
red
terminal on the Covermeter (Figure
14)
Connect the black cable between the
probe and the
black terminal
on
the Covermeter
7
Switch on the Covermeter
8
Ensure the inslrument
is set
to Half-cell mode
\
MENU /
|NSTRUMENT
MoDE /
HALFCELL
IHSTRUHEHT
IIIDE
lr
9
Remove the end
cap
from the probe and store the cap
safely
10
Press the electrode against the concrete surface
11
View the reading of half-cell potential
on
the display
12
llyouaresatisfiedwiththereading,recordthehalf-cell
potential andthenmoveontothenext
measurement
location
21
p
Half-cell mode is not included on the Elcometer 331 Model
B