The Barnstead Thermolyne SSDetect
is the only system on the market today that “directly measures”
the saturated surface dry condition of the fine aggregate. This
is done by way of an infrared light source “tuned” to
water. This infrared signal “looks” at the surface of
the aggregate for traces of water. By measuring the amount of infrared
reflectance, the Saturated Surface dry condition can be accurately
measured time after time. Using a light source of a specific wavelength
to detect specific trace elements is a proven science that has been
used for many years.The user begins with two
samples of the desired material dried to a constant mass. One sample
is placed in the special volumetric flask (provided), filled with
water to the calibrated line and weighed. Mount the flask to the
mixing platform of the Automated Vacuum Mixer (AVM). Press the start
button and the AVM will automatically mix and vacuum the sample
until it has reached the Apparent Specific Gravity condition. Remove,
refill the flask and weigh.The second sample
is placed in the special bowl provided with the SSD device. This
sample and bowl is weighed and then mounted to the mixing platform
of the SSD device. Information derived from the AVM test will be
used and entered into the SSD device. This is known as the film
thickness coefficient. The user then places the lid on the test
bowl and closes the door of the SSD device. Press start and the
unit will begin mixing the sample in the bowl and injecting small
amounts of water into the material, allowing it to absorb water
until it reaches the Saturated Surface Dry condition.The
infrared signal is looking at the material during the mixing/water
injection process for trace amounts of water to begin to build on
the aggregate surface. Once a stable SSD condition has been reached,
the unit will automatically stop and alert the user. The test bowl
is then removed and weighed. The net weight of the material is the
weight at SSD. You have now obtained all of the values necessary
to determine the bulk specific gravity and absorption of the fine
aggregate.
