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This video demonstrates the Sand Equivalent Test.
Conducting this test provides a measure
of how much clay is contained in an aggregate sample.
The test is completed on aggregates
used for asphalt paving mixtures and also for aggregates
used for microsurfacing projects.
The Sand Equivalent Test is important
because aggregates that contain a large amount of fine dust
or clay can have an adverse effect on the performance
of an aggregate and asphalt mix.
The extra dust or clay prevents the asphalt
from properly binding to the aggregate
and that may cause the road to break down much faster.
North Dakota uses alternate method two
and performs two trials of the test,
and then averages the results of the two tests.
The Sand Equivalent Test is the only test
that requires you to always round up
the results to the next higher number.
First, collect the equipment to conduct the test.
You need a pan, trowel or spatula, water bottle,
damp cloth, and plastic splitting cloth.
You also need two three-ounce sample tins with covers.
You need a funnel, graduated plastic cylinder,
weighted foot assembly, timer, and a rubber stopper.
In addition, you need some calcium chloride solution
and irrigation tube and a mechanical sand equivalent
shaker.
Next, obtain an aggregate sample and then reduce it
to testing size.
The sample should be approximately 1,000 to 1,500
grams of unwashed minus number four material.
Place the sample in a pan.
If the sample is dry, you will need
to add water and thoroughly mix until it is damp enough
to hold a cast.
If the sample is already damp, you may not need to add water.
In either case, the sample must be moist enough
to hold a light cast when squeezed in your hand.
It is important to thoroughly mix the sample
so the moisture content is uniform.
After you have determined the sample is at the right moisture
content, cover with the damp cloth.
Make sure the cloth does not come
into contact with the sample.
Let the sample sit for a minimum of 15 minutes.
This allows the aggregate to absorb the moisture.
Next, pour the sample onto a non-absorbent splitting
cloth and mix.
Mix the sample by pulling from corner to corner.
Mixing the material this way is similar to the test method
for reducing an aggregate sample on a quartering cloth.
After thoroughly mixing the material,
the sample should be in the center of the cloth.
Take the three-ounce sample container
and place a hand on one side of the pile
and the sampling container on the other side of the pile.
Push the can through the sample to your hand
on the opposite side, then firmly
push the sample into the can with your hand
to cause it to overfill.
Strike off the material above the top of the can and cover.
Next, remix the sample, pulling the cloth from corner
to corner, bringing the sample over the top of itself.
Take the second tin and repeat the procedure, bringing
the sample container in your hand
together, pushing the material into the sample can.
Strike off the top of the can.
After preparing the sample, pour four, plus or minus a tenth
of an inch, of calcium chloride solution into a cylinder.
Add the material from one of the tins into the cylinder.
Take care not to lose any material.
Sharply strike the bottom of the cylinder
with the palm of your hand to remove any air bubbles that
may be trapped in the bottom of the cylinder.
Now, let the sample stand undisturbed for 10,
plus or minus one, minute.
Securely place the stopper on the cylinder
and shake loose the material from the bottom.
Place the cylinder into the mechanical shaker for 45,
plus or minus one, second.
After the 45 second shake period,
remove the cylinder from the shaker
and then remove the stopper, being
careful not to lose any material.
Then, add calcium chloride solution
up to the 15 inch line.
When doing this, wash any material
that may be sticking to the sides of the cylinder walls.
When flushing the sample, push the irrigation tube
down to the bottom of the sample in a twisting,
turning motion while filling.
This flushing and twisting will wash the fines
from the bottom of the sample and bring them into suspension.
Continue this procedure until you
are close to the 15 inch mark.
When nearing the 15 inch mark, be prepared
to pull out the irrigation tube at the same time
the cylinder fills to the 15 inch mark.
Let the sample sit undisturbed for 20 minutes, plus or minus
15 seconds, to allow sedimentation to occur.
At the end of the 20 minutes sitting period,
check the sample and determine the clay reading.
If the reading is in between two marks,
record to the next higher number.
Next, take the weighted foot assembly
and carefully lower it into the cylinder.
Take the sand reading.
Again, if the reading is in between two marks,
round up to the next higher number and then subtract 10.
10 is the distance between the bottom
of the weighted foot and the reading indicator.
Repeat the process on the second sample.
When completing the Sand Equivalent Test calculations,
round the results of each test to the next higher whole
number.
Then, average the two numbers, and again,
around the average up to the next higher whole number.