Effects of Ground Granulated Blast Furnace Slag in Portland Cement ...

days until that determination could be made. Length change was measured using a vertical
length comparator. To find the length change at a given age the average percentage length
change for the three specimens was found. Equation 2 from ASTM C157 was used to find
the percentage length change for each prism.
∆L x = (CRD – initial CRD)/G *100 (Eqn. 2)
∆L x = length change of specimen at any age, %
CRD = difference between the comparator reading of the specimen and the
reference bar at any age
G = gage length (10 in.)
Two length comparators were used in measuring the specimens. A second comparator
became necessary because some of the specimens were stored offcampus at the WisDOT
central office laboratories. Instead of transporting the dial comparator to the secondary
location, a digital comparator was purchased to measure the specimens located at the
secondary facility. A discrepancy was found to exist between the standard bar of the dial
comparator and the standard bar of the digital comparator. To reconcile this difference, Eqn
2 was adjusted. The value of .0101 was added to CRD when using the new digital
comparator. This value was used because the reference bar supplied with the digital
comparator was .0101 longer than the reference bar of the older comparator.
Scaling blocks were prepared in accordance with ASTM C672. Approximately seven days
before initiating the brine pond testing, foam dikes were applied to the specimens to retain
the deicer solution. Compressed air was used to clear the surface of the blocks of any loose
debris. Next, two one-quarter inch passes of a foam insulation material were applied to the
specimen surface. 1 The foam insulation expanded after application so the width of the foam
was approximately one inch wide around the perimeter of the block surface and three-quarter
inches high. After the insulation set, eight minutes according to the manufacturer, a quarter
inch bead of caulk was applied to the inner and outer surfaces of the dike where the
insulation met the concrete. 2 The caulk was applied to provide an extra barrier to water
leakage.
Scaling tests were performed according to ASTM C672 with two modifications. First, C672
specifies that the specimens be subject to a temperature of -18°C for 16 to 18 hours and 23°C
for 6 to 8 hours. This was modified to -20°C for 20 hours and 30°C for 4 hours. The room
in which the specimens were placed contained 120 blocks and was only capable of achieving
temperatures of -20°C, so the modification was made to ensure that the blocks were
completely frozen. A thermocouple was placed inside one block, and the observed values
confirmed that the blocks were frozen below 0°C consistently. The higher temperature of
30°C was specified so that the blocks would adequately thaw in the four hour time period.
All specimens were subjected to 100 freeze/thaw cycles. The brine pond was a 4% solution
of sodium chloride.
1 Great Stuff window and door insulating foam sealant, manufactured by Dow Chemical.
2 DAP Alex Plus Acrylic Latex Caulk plus Silicone, a window and door indoor/outdoor caulk.
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