120
Table 19. Harmlessness corrosion results.
a.
Control
Dosage
Current
(20 C)
A/cm2
Admixture
mL/kg (fl oz/cwt)
80
Pozzutec 20
30 (45)
0.539
EY11
Pozzutec 20
60 (90)
0.405
( 5 C)
EY-11
50 (75)
0.724
EY-11
100 (150)
0.651
40
ACI
(5 C)
der and protruding from the top. The test area of
the rebar is limited to 30 cm2 (4.7 in2) by epoxy
0
120
paint. The specimens were cured for four days in
b.
saturated calcium hydroxide solution to within
12.7 mm (0.5 in.) of the top surface. They were
80
then kept at a potential of +260 mV vs. a saturated
calomel electrode. The current flowing through a
1000-ohm resistor placed in the circuit is mea-
sured at regular intervals by voltage drop across
40
the resistor. If the current density is below 1 A/
cm2, the admixture is considered not harmful.
Table 19 shows the results for Pozzutec 20 and
0
EY-11. Both admixtures provided results below 1
10
20
30
Age (days)
A/cm2, indicating that neither admixture caused
Figure 6. Strength gain of concrete made with
corrosion at the dosages used.
EY-11 cured at 5C (23F) compared to con-
One of the corrosion measuring methods used
trol concrete cured at two above-freezing tem-
in Phase I to measure the potential of Pozzutec 20
peratures. The line denoted as ACI (5C) is
to initiate corrosion damage to embedded steel
based on guidance provided by ACI (1988).
rebar, the Lollipop Corrosion Test, was again used
That line represents the minimum curing con-
to measure the potential of EY-11 to initiate corro-
dition used by the construction industry today.
sion. Two dosages of EY-11 were used (60 and
Figure 6a is for concrete containing a 365-kg/
100 mL/kg [90 fl oz/cwt]), the result being com-
m3 (611 lb/yd3) cement factor and a 100-mL/kg
pared in the same test with the same two dosages
(150 fl oz/cwt) EY-11 dosage. Figure 6b con-
of Pozzutec 20 and two references without ad-
tains a 420-kg/m3 (705 lb/yd3) cement factor
mixture. The specimen size was 75- 150-mm (3
and a 100-mL/kg (150 fl oz/cwt) EY-11 dosage.
6 in.) cylinders, each concrete mix being prepared,
and the concrete specimens cured and otherwise
treated, in the same manner as were the earlier
lollipop examinations of Phase I, except that 15%
to warm conditions. The 100-mL/kg (150 fl oz/
sodium chloride solution was used for ponding
cwt) dose with the 420-kg/m3 (705 lb/yd3) ce-
in place of the 3% solution of Phase I; weekly
ment factor exceeded the ACI reference strength
measurements were taken. Figure 7 shows that
at all ages (Fig. 6b).
EY-11 caused corrosion to be initiated at about
week 12 with the higher dosage (100 mL/kg, 150
Task 2: Corrosion potential
fl oz/cwt) and around week 43 with the lower
The potential of EY-11 to corrode steel rein-
dosage (60 mL/kg, 90 fl oz/cwt). Pozzutec 20, on
forcement was tested according to the so-called
the other hand, was found to initiate corrosion at
"Harmlessness Test" (modeled after a German
earlier times, at about week 6 with the higher
DIN standard according to discussions during
dosage and week 23 with the lower, each dosage
meetings of ASTM Committee G-1.14 199495).
causing initiation to occur earlier by about one-
The method employed in this project uses small
"lollipop" cylinder specimens measuring 50 100
half the time period. Two admixture-free refer-
mm (2 4 in.). The mortar used Type I cement, an
ence specimens were shown to have initiated cor-
ASTM C 109 sand in a 1:3 cement:sand ratio and a
rosion at weeks 39 and 43 for an average of 41
0.50 w/c. The embedded rebar is a No. 4 axially
weeks for the two references. The trial admixture
EY-11, therefore, was found in this 75- 150-mm
located 25.4 mm (1 in.) off the bottom of the cylin-
15
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