Dynamic Behavior of Sand/Rubber Mixtures. Part I: Effect ...
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Behaviour of Sand-Rubber Mixtures
Siemens Research Competition 2014
Abstract
Scrap tire disposal rates have increased and has posed a threat to the environment.
There have been research efforts to find ways in which scrap tires can be used in
civil engineering, by reusing the rubber (Lee, Changho, Hosung Shin, and Jong‐Sub
Lee, 2014) . Civil engineers have discovered different applications of the rubber and
one of the ongoing efforts is that of Sand-Rubber Mixtures. Sand is brittle, but was
found to be more ductile with rubber mixed. The research I conducted dealt with the
behaviour of the sand-rubber mixtures and was specifically geared towards studying
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its dynamic properties, one of which was its density, to be able to use the
information to implement it in constructions sites. Some tests that were taken
included the calculation of water content, determination of specific gravity, and
developed a procedure to create adequate and uniformed test samples. Through this
extensive research it was found that the density gave a negative correlation to the
volume ratio percentage of rubber mixed in a sample. Data on other dynamic
properties of the Sand-Rubber Mixtures are still yet to be recorded.
Introduction
The increase of scrap tire is critically affecting us globally. It is through civil
engineering that we find most of the rubber use applications that include recreational
park facilities, roadways, and railways. It is using rubber such as the ones found in
car tires, a resource that is disposed of improperly, and reusing them in different
ways. The research in Sand-Rubber mixtures is fairly new and there have been
studies to see how Sand-Rubber Mixtures could be able to be applied at construction
sites. Sand is known for being a very brittle material to work with, but recent
research such as (Neaz Sheikh, M., Mashiri, M., Vinod, J., & Tsang, H., 2013)
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suggest that mixing it with rubber could provide some beneficial outcomes. The
rubber is seen to reinforce the stability of the sand meanwhile it still keeps its
lightweight ability. It could certainly be advantageous in a construction site, not only
by being able to support an infrastructure but also through its eco-friendly material.
The research gives a more in depth look at the aspects of the mixture researchers
have to take into consideration that of which includes the density and how forces
may affect it. It has data that shows several test done on the amount of force that it
was able to handle and how it compared to other mixtures. The research was done in
a controlled environment and looked at the differences between pure sand deposits
and sand-rubber mixtures. It also tries to explain specific uses and is trying to be
approved as a method of building foundations on construction sites. Research was
able to provide some insightful information into the properties that sand-rubber
mixtures, but failed to test out every factor that may go into the construction of
foundations. It showed that sand-rubber mixture were quite strong compared to
simply pure sand and gave further details as to how much pressure it could handle
under specified circumstances. The research did not look at how the difference in
just how much rubber content could be mixed with sand before it could give way to
other problems. The research gave new data that is now being used to look at sand-
mixtures and the rest of the factors that contribute to its establishment as material in
construction sites. The data presented gave leeway to in depth research as to how
liable the Sand-Rubber Mixture could be when creating new foundation and lead to
other research.
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Materials and Methods
I began my research with a general idea of the civil engineering field and specifically
studied the structure of foundations and their properties. The research was started by
finding a specific method in which we would be able to find the density of samples
accurately in the most uniformed manner. Below is a list of materials used for
specific experiments that proved more influential for my research.
● Sand - It is pure sand collected in small grains all of one type.
● Rubber - It is tire shredded rubber that is mixed into the sand.
● Funnel - Used to drop the sand and rubber into the sample base and gave the
procedure a uniformed manner of placing the materials.
● LoadTrac-II, Cyclic-RM, FlowTrac-II - This mechanism was used to
calculate the density of the sample in the chamber.
● FlowTrac Cell/Base – This was the base of the sample and is the what is
inserted in the testing chamber.
● Porous Stone (2) - These stones are placed between the samples to mimic the
pressure of bedrock.
● Rubber Membrane – The rubber was used to create the sample and gave the
sample a malleable material to give way to pressure and other factors when
testing it.
● O Rings (2) – These were put at the base and top of the sample to keep the
sample enclosed and water from entering the sample.
● Top Cap – Used to enclose the sample to keep the test constant.
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● Cans – These were used in the water content experiment to determine its
percentage.
Procedure for Making Samples (See Figure 1)
The main focus on the research conducted was finding a procedure to make a
sample, simply because you wanted it to be as uniformed as possible. To begin,
attach the Rubber Membrane at the base of the cell and enclose it with the iron
encasing for sample module. Pull the rubber membrane tightly against the wall of the
module and vacuum the air out, getting closer to the inner wall, to enclose the
sample. Place a porous stone at the bottom and an O-Ring around; ensure it is
attached tightly around the indentation in the sample base. Measure a set amount of
pure sand using a weight consistently throughout the procedure. Pour sand into
funnel in a circular motion, keeping an even amount of sand pouring in. Use funnel
to mimic sand falling naturally and uniformly. Create layers, stop half-way when
pouring to level it out (with the same amount of hits each time) and then pour in the
rest, after two layers create small vibrations on the outside of the cell to level out the
sand and flatten down evenly across the sample. Keep it as consistent as possible to
ensure the results are uniformed. Once you have reached the top of the sample
flatten it out yet again evenly, with the same amount of hits each time. and put the
porous stone on top. Take the top cap and cover the sample, also cover top cap with
rubber membrane and seal it with an O-Ring (Make sure the sample is sealed tight).
Release the vacuum and remove the iron encasing showing the sample in the rubber
membrane. Study sample and look at layering before further testing, check to see if
layers are uniformed. Each time you create a sample look for improvements on
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making future samples. The sample is then ready for further testing on the LoadTrac-
II for force and load tests. After you have tested the pure sand you then make
samples that include sand and rubber mixtures at different levels, 5% rubber, 20%
rubber, 50% rubber, . . . etc, and repeat the process.
Figure 1: A test sample was made of pure sand and has
eight layers about one and a half inches apart.
Finding Water Content
Start by measuring the weight of three cans, it doesn't’ matter what size, and
record your data. Pour some wet sand into the can and measure the weight of the can
with the sand. The amount of sand does not matter, at this time record your data. Do
this to all three cans and record your data for each. Afterwards proceed to putting
them into a dry oven. At this point you wait a certain period of time to give the
sample ample time to dry off, make it as dry as possible for better results. It is then
that you take the samples out of the dry oven and measure their weight in respect to
their previous weight. Record your data. The weight of each sample should be far
less heavier than before, it is then that you record the difference between the weight
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of your wet sand and can sample and the mass of the dry sand and can sample,
record your data. When finding the difference of the dry soil do not forget to deduct
the weight of the can from the total weight of both measurements, then record your
data. This, in turn, will give you the mass of the moisture trapped in the sand
samples, record your data. Once you have found these measurements you divide the
mass of moisture and dry sand to get the water content. Average out all of the water
content measurements from the other cans. Convert the water content into a
percentage giving you roughly the same percentage overall from all the other three
samples. (See Figure 2)
Figure 2: This data table shows the approximate average water content
percentage.
Calculating Specific Gravity (See Figure 3)
We then proceeded to calculate the specific gravity of the pure sand used. You
would need a volumetric flask making sure it is dry. Fill the flask with distilled water
up to 500 ml. Measure the mass of the flask and the water, insert the thermometer
into the flask with water and determine the temperature of the water. Put
approximately 100 grams of air dry sand into an evaporating dish. Transfer the sand
into the volumetric flask. Add distilled water to the flask containing the sand to
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make it about two-thirds full. Remove the air from the san-water mixture, by
applying the vacuum until all the air is out. Add de-aired, distilled water to the flask
until the meniscus touches the 500ml mark. Dry the outside of the flask ad inside of
the neck of the meniscus. Determine the combined mass of the flask and the sand-
water mixture. Pour the sand and water into the evaporating dish into an oven to dry
to a constant weight. Find the mass of the dry sand in the evaporating dish.
Figure 3: The flask has the sand inside while the air
is being vacuumed out of the flask.
Discussions
Many variables were taken into consideration when trying to come up with a reliable
method to make a sample that was as uniformed as possible. Every factor was
looked into some of which included:1) How much sand was poured into each layer
in the sample, 2) the height at which it was dropped from, How many times the
sample was pounded down, how to control the excess sand from falling out of the
sample, etc.. As the research continued we discovered other small methods in which
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it could provide more uniformed results. We measured the amount of sand by weight
(in kg) to keep it constant, we added, We measured increments of approximately 1.5
in. in distance every time we moved the funnel upwards. We counted about thirty
strikes on the sand when leveling it out, and added a cylindrical cone around the
sample to keep the excess sand from falling out. One of the main concepts to keep in
mind while conducting the research was studying the density differences between
pure sand and sand-rubber mixtures. This is where you must look at the water
content of the sand sample and eventually of the sand and rubber sample. Through
background information it is known that rubber is a lighter material than sand so the
density is expected to decrease, from this a problem arose, sand and rubber are not
the same density so when mixed they will not as uniformed. It was important to
understand in the research that the percent of rubber put in a sample was calculated
through its volume ratio.
Results
When conducting the water content experiment it presented numbers that were
approximate to the actual water content percentage of pure sand. The water content
received from the test was approximately 8.52%. (See Figure 4) There was a small
difference that could have been resulted due to the moisture in the air, if it isn’t
weighed quickly enough the air will moisten the sand. This data was then compared
to the actual water content percentage given to me my mentor. The number was
approximately the same and was found to be conclusive data to be used in the
research.
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Figure 4: This specific table shows the approximation of the water
content in the pure sand.
The specific gravity of most common minerals found in soils are within a range of
2.6 to 2.9. The specific gravity of sandy soil may be estimated at about 2.65. So, the
soil that was measured at about 2.606 and would fall into an average specific gravity
value. The specific gravity gave us the approximate specific gravity for the pure sand
and would use this data to be able to calculate more of its properties (one of which is
calculated through the LoadTrac-II).
Figure 5: This table shows the approximation of the pure sand’s specific
gravity through several calculations.
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Figure 6: This data sheet gives data that came directly from the
LoadTrac-II data log sheets.
The LoadTrac-II was able to give detailed results (See Figure 6) regarding the
samples density. Through all the experiments and test we were able to conclude that
the density of the Sand-Rubber mixtures would decrease as the rubber percentage
increased.
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Conclusion
The data was put into an excel data sheet and recorded it on a graph
where the trend is seen to decrease and was calculated by putting the average
density over the percentage of rubber. The research specified on the dynamic
properties that need to be taken into account to look at other factors of the Sand-
Rubber Mixtures. The research gave an insight to how civil engineering would be
able to apply a method to make foundations and make them available in construction
sites. Future work is still needed on the other dynamic properties Sand-Rubber
Mixtures could have in different conditions. It is through this research that we
advance our understanding of the Sand-Rubber mixtures density characteristics, but
are many other aspects that must be further studied.
Citations
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Lee, Changho, Hosung Shin, and Jong‐Sub Lee. "Behavior of sand–rubber particle
mixtures: experimental observations and numerical simulations."
International Journal for Numerical and Analytical Methods in
Geomechanics (2014).
Lee, J., Salgado, R., Bernal, A., & Lovell, C. (1999). Shredded tires and rubber-sand
as lightweight backfill. Journal of Geotechnical and Geoenvironmental
Engineering, 125(2), 132-141.
Neaz Sheikh, M., Mashiri, M., Vinod, J., and Tsang, H. (2013). ”Shear and
Compressibility Behavior of Sand–Tire Crumb Mixtures.” J. Mater. Civ.
Eng., 25(10), 1366–1374.
Pierce, CE, and MC Blackwell. "Potential of scrap tire rubber as lightweight
aggregate in flowable fill." Waste Management 23.3 (2003): 197-208.
Senetakis, Kostas, Anastasios Anastasiadis, and Kyriazis Pitilakis. "Dynamic
properties of dry sand/rubber (SRM) and gravel/rubber (GRM) mixtures in a
wide range of shearing strain amplitudes." Soil Dynamics and Earthquake
Engineering 33.1 (2012): 38-53.
Youwai, S., & Bergado, D. T. (2003). Strength and deformation characteristics of
shredded rubber tire sand mixtures. Canadian Geotechnical Journal, 40(2),
254-264.