test used a saturated calomel electrode (SCE), 60

99 at the end of the test. The 100 mL/kg (150 fl

mV should by added to the ASTM values to make

oz/cwt), on the other hand, failed after 204 cycles

them useful to our readings (to convert to mV

of freezing and thawing. The lower dosage (90 fl

SCE). Based on this guidance, potential indicative

oz) of Pozzutec is the maximum dosage recom-

of corrosion for a saturated calomel electrode is

mended by Master Builders.

290 mV. The admixture-free specimens and the

specimens containing both dosages of Pozzutec

Task 4: Equivalent insulation

20 partially submerged in 3% sodium chloride

The minimum temperature at which concrete

solution showed beginning signs of corrosion (Fig.

with Pozzutec 20 can be cured to produce com-

3). The interest, however, is that the Pozzutec 20

pressive strengths equal to that of control con-

crete cured at 10C (50F) was determined. Table

did not increase the level of corrosion when com-

pared to the reference. All specimens in deion-

8 shows the strength of the various concrete mix-

ized water show no indication of corrosion. Thus,

tures studied. As can be seen, the minimum tem-

the Pozzutec 20 did not adversely affect the mor-

perature for the 40-mL/kg (60 fl oz/cwt) dosage

of Pozzutec 20 (mixture 2,1) was 2C (35.6F),

tar from the corrosion point of view.

Previous testing by others (Nmai et al. 1994)

where its strength equaled or bettered that of the

corroborates the above results by showing that

control at all ages. The 60 (90) and 100 (150) mL/

mortar containing 60 mL/kg (90 fl oz/cwt) of

kg (fl oz/cwt) had minimum temperatures of 1

and 0C, respectively. For the mixture made with

Pozzutec 20 and tested by the aforementioned

method of FHWA over the 50-week examination

high early strength cement, the zero dose and 60

period showed no sign of rebar corrosion. The

mL/kg (90 fl oz/cwt) dose had minimum tem-

peratures of 2 and 4C (28.4 and 24.8F), re-

FHWA test, also known as the modified Southern

Climate Accelerated Corrosion Test, subjects the

spectively.

top surface of concrete slabs, embedded with two

layers of rebar, to intermittent ponding with 15%

sodium chloride solution. The presence of corro-

sion is determined by the voltage drop between

Table 8. Equivalent insulation test results for con-

the layers of rebar.

crete made with Pozzutec 20.

Compressive strength--MPa (psi)

Task 3: Durability

Mixture ID

7 days

14 days

28 days

Table 7 shows the results from subjecting con-

2,0,10 (control)

23.5 (3405)

28.5 (4131)

33.1 (4800)

crete beams to up to 300 cycles of freezing and

thawing according to ASTM C 666, Procedure A.

2,1,4

23.7 (3442)

29.6 (4291)

33.0 (4791)