(3 6 in.) cylindrical mortar specimens, each fit-
Table 4. Phase I test variables.
ted with an axially located No. 4 reinforcing bar
Variable
Quantity
positioned 31.8 mm (1.25 in.) off the bottom of the
cylinder. The rebar protrudes out from the top of
308, 365, 420 kg/m3
Cement factors
each specimen. In the test, six specimens were
(517, 611, and 705 lb/yd3)
cast from two mortar mixtures: one mixture with
Pozzutec 20
0, 40, 60, 100 mL/kg
no admixture, and one with Pozzutec 20 dosed at
(0, 60, 90, and 150 fl oz/cwt†)
60 mL/kg (90 fl oz/cwt). Three of the six speci-
Test ages
7, 14, 28, and 56 days
mens from each of the two mixtures were sub-
merged to a depth of 75 mm (3 in.) in a 3% so-
20, 5, 5, 10, and 20C
Curing temperatures
dium chloride solution, and the other three
(70, 40, 23, 14, 4F)
specimens were partially submerged in deion-
w/c ratios
0.44, 0.48, and 0.52 for the 308,
ized water. Another mixture was also prepared
365, and 420 cement factor
with a Pozzutec 20 dose of 100 mL/kg (150 fl oz/
mixtures, respectively
cwt), from which only three specimens were cast
Cement types
I and III (Type III w/mix [*2,2]
and placed in the sodium chloride solution. All
and [*2,0])
specimens were made with standard ASTM C 109
mortar with a 0.485 w/c. They were cured at
Plasticizer
For the 308 factor mixture only
100% relative humidity according to normal ACI
† cwt denotes 100 lb of cement.
accepted practice. The deionized water provided
* Denotes Type III cement.
a nonaggressive environment and the sodium
chloride solution an aggressive one. The speci-
mens were monitored for corrosion by regularly
Table 5. Phase I mixture identification.
recording the reinforcing bar`s half-cell potential
using ASTM C 876, and periodically running im-
kg/m3
Admixture
mL/kg
pedance spectroscopy to approximate the corro-
(lb/yd3)
Cement factor
dosage
(fl oz/cwt)
sion rate. Testing, which was expected to run for
1
308 (517)
0
0 (0)
up to two years, began during April 1994 and was
2
365 (611)
1
40 (60)
completed after 1 1/2 years in October 1995, when
3
420 (705)
2
60 (90)
all specimens in chloride solution began corrod-
--
--
3
100 (150)
ing. Specimens in sodium chloride solution were
found to have corroded only under an epoxy coat-
until tested or until 28 days. After 28 days, all
ing upon final inspection.
untested cylinders were placed in the 20C (70F)
room for 28 days of additional curing. This addi-
Task 3: Durability
tional curing showed whether any permanent
The resistance of concrete beams to deteriora-
strength loss was caused by the freezing tempera-
tion from repeated cycles of freezing and thawing
tures.
was tested according to ASTM C 666, Procedure
A. Pozzutec 20 was tested at two dosages: 60 and
Task 2: Corrosion potential
100 mL/kg (90 and 150 fl oz/cwt). The concrete
The potential of Pozzutec 20 to corrode rein-
for the beams was made with a cement factor of
365 kg/m3 (611 lb/yd3), a w/c of 0.434 for the
forcing steel was tested according to two differ-
ent procedures: initially via the well-known pro-
concrete made with Pozzutec 20 (for the admix-
cedure reported in FHWA/RD-86/193 of the
ture provides water reduction) and 0.45 for plain
Federal Highway Administration (this method
concrete, and an entrained air content of 6%. Three
was the predecessor of ASTM G 109, a modifica-
beams were made from each mix, each beam mea-
suring 75 102 406 mm (3 4 16 in.). They
tion of and more reliable one than that of the
FHWA) and the MB-labeled "Lollipop Microcell
were moist-cured for 14 days, then wrapped in
Corrosion Test." The latter test, based on several
plastic and stored in a freezer until tested. All
references (Sagues 1987, Dawson and Langford
beams were cycled through 300 freezing and thaw-
1988, Aguilar et al. 1990, and Tourney and Berke
ing cycles or until failure, whichever occurred
1993) uses a lower w/c ratio than the ASTM
first. Changes in relative dynamic modulus de-
method, thereby providing a better quality con-
rived from resonant frequency readings were used
crete. The lollipop procedure uses 75- 150-mm
to monitor the deterioration. Criteria of ASTM C
4
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