Lightweight Concrete for High Strength - Expanded Shale & Clay

were added in a specific sequence for each batch of concrete. The lightweight and normal
weight aggregates were added first with all the low range water reducer (LRWR), air entraining
agent (AEA), high range water reducer (HRWR), and approximately half the mix water. Next,
the Type III cement was added. Additional water was added as necessary to allow proper mixing
of the cement. Next the Class F fly ash was added with additional water as required. Last, the
silica fume was added. Any remaining water up to the specified mix design amount was added
and the result was observed. If the mix was still stiff, additional HRWR was added to bring the
mix to a workable state.
Upon batching of concrete, it was loaded into the transport vehicle and brought to the
quality control station. Tindall personnel performed a slump test according to ASTM C231, a
unit weight test according to ASTM C138, and recorded the temperature according to ASTM
C1064. Georgia Tech personnel performed an air content test using a roll-a-meter according to
ASTM C173. To the greatest extent possible, these tests were performed on each batch of
concrete.
After delivering concrete to the quality control station, the remaining concrete was
transported to the girder line where it was placed into the forms (Figure C.15). The Tindall
concrete workers placed the concrete in lifts vibrating each lift with a spud vibrator. One
Georgia Tech researcher was present on the girder line at all times during concrete placement to
insure the concrete workers did not damage any instrumentation or DEMEC inserts. After all
lifts of concrete were in place, the top of the girder was screeded and raked to give it the required
¼-inch variation for good bond between the deck and girder. The girders were then covered with
heavy plastic to protect them from rain and hold in heat during the curing process.
C.2.2 Concrete Curing
The girders were allowed to cure overnight. Temperature was monitored on each girder
using the embedded thermocouple and a printing thermometer. A typical temperature curing
curve for girder G1A is shown in Figure C.16 together with the temperature in the curing box for
test cylinders.
C-8