Investigating the Feasibility of Using Tire Derived Aggregate (TDA) for

Investigating the Feasibility of Using Tire Derived Aggregate (TDA) for
Basement Construction Applications in Manitoba
Shokry Rashwan1a, Greg Rennie1b, Neil Chandler1c
1
Red River College, 2055 Notre Dame Avenue, Winnipeg, MB, Canada R3H 0J9
a
b
[email protected], [email protected],
c
[email protected],
Keywords: Tire Derived Aggregate (TDA), basement construction, TDA material
properties, lateral pressure of TDA, hydraulic conductivity of TDA.
Abstract
A number of experiments were conducted at Red River College (RRC) to investigate the technical
feasibility and advantages of using tire derived aggregate (TDA) produced from shredding off-theroad (OTR) waste tires in a proposed new application. The proposed new application targets
replacing natural materials used under basement concrete slabs and as wall backfill for residential
homes with TDA. The experimental work was conducted over a year and a half and focused on
addressing the material properties and short-term characteristics of OTR TDA. These included:
compressibility, gradation distribution, unit weight, hydraulic conductivity and lateral pressure. Test
results show that the gradation distribution of OTR TDA is comparable to results achieved by
previous researchers for similar products. The unit weight of TDA is approximately one-third of
that known for natural soils while the hydraulic conductivity results for OTR TDA indicate that this
material will certainly allow free drainage of rain water, an advantageous property for backfill
adjacent to basement walls. Results of the lateral pressure test show that the maximum horizontal
pressure induced by TDA on small scale basement walls is much lower than that known for natural
materials. These results indicate that a significant economic advantage may be achieved if TDA is
used as wall backfill and fill underneath basement slabs in lieu of natural materials.
This paper provides a review of the tests conducted and presents a plan for the next experimental
program to assess the long-term technical and economic viability of using OTR TDA in this new
application.
Introduction
Use of recycled tires has been growing over the past two decades due to a number of factors
including: increase in environmental awareness, overcrowded and lack of new landfills, and
advancements achieved in processing technologies and equipment. Different uses of this material
include: substitute fill for road base material and embankments, fuel for cement production plants
and kilns, as well as in manufactured tiles and landscape products. Materials used for these
applications come from different sources such as light passenger vehicles or off-the-road tires, the
latter mainly from large equipment. The two recycled tire sources are processed in different ways
using different equipment dependent on the application itself. Many researchers, [1] to [8], have
studied the properties of the material used in the different applications as well as the economic
viability of its use compared with using original material (e.g. earth for road fill). This heightened
interest and the associated research efforts in turn have led material standards organizations to
develop specifications and guidelines for most of these applications [9,10].
As the supply of this material for use in those well-established applications, some of which are
identified above, is growing, it appears that market demands are driving the tire recycling industry
to develop new applications and hence the ultimate goal of this project. This research project
focuses on understanding and further determining the characteristics of tire derived aggregate
(TDA) produced from off-the-road ties (OTR) that may enable its effective use in a new
application. This new proposed application is defined as “a replacement of natural aggregates used
as backfill for walls and under slab base for residential home basements in Manitoba.” Fig. 1,
below, is a schematic illustration of the proposed use.
concrete masonry
filled w light grout
made w rubber
crumbs & cement
tire derived
aggregate backfill
Part b
under slab TDA
Figure 1. Graphic illustration for the proposed use of OTR TDA in basements
Although a few researchers have investigated similar applications, e.g. for retaining walls and septic
fields [11, 12], there are no conclusive studies in the literature regarding this specific application.
The research work for the new application is a collaborative effort between the researchers at Red
River College, the tire recycling industry in Manitoba, and Manitoba Hydro. The research work is
planned to investigate a number of expected benefits (or hypotheses) for the proposed new use of
OTR-TDA including: reducing heat losses, improving drainage and reducing lateral pressure on
basement walls. The results from this research could ultimately translate to savings in energy cost as
well as home construction, operation and maintenance costs.
Project Work Methodology
In order to address these hypotheses; the project was divided into three phases. Phase I focused on
addressing the issue of compressibility of this material and whether it is adequate for the intended
application. Phase II continued focusing on determining both material properties essential for
design purposes and short term characteristics. Ultimately, Phase III will study long-term behavior
through a full-scale demonstration of a home basement. This paper focusses on the work done
during phase II.
Work on this phase of the project (Phase II) entailed two parts, the first part deals with material tests
and the second deals with a laboratory test of a panel representing basement wall. The work on the
first part began in late November 2014 with the primary objective of these tests is to establish
numerical values for the main properties of this material which are needed for design purposes for
the intended new application. These properties included: gradation distribution, unit weights,
specific gravity and permeability and drainage coefficients. The objective of the second part was to
understand the limits of lateral pressure exerted by this material on basement walls due to applied
vertical loading.
The following provides a summary of the tests, procedures, and tools used and the results for both
parts of the work conducted during Phase II.
First: TDA gradation tests
Test samples of the OTR TDA were randomly collected after two passes through a typical industrial
shredder. Material was delivered in two totes weighing almost one tonne each. Fig. 2 shows one of
the totes and a close-up to the TDA delivered.
Figure 2. OTR TDA delivered for tests
Due to the large sizes, and irregular shapes of the TDA, the test procedure followed the intent of
ASTM C136 as close as possible. Sample selected using splitting was around 80 kg, and was placed
in 5 gal pales as shown in Figure 3 below:
Figure 3. Sample splitting
A sieve analysis was conducted on particles passing a 3” (75 mm) screen using a Gilson shaker
(shown in Fig. 4). Although the TDA particles had very irregular shapes, the particles passed
through the screens in such a way that the screen size represents the particle width and not its
length. The percentage of flat and elongated particles larger than 75 mm was measured using a
proportional caliper according to the specifications in the ASTM D4791 -10. The resulting
gradation curve was as shown in Fig. 5, while the percentages of flat and elongated particles were
as listed in Table 1. The average particle width was approximately 2¼” (56 mm), while 90% of the
particle widths were greater than 1¼” (31 mm).
Figure 4. Gilson large screen shaker
Figure 5. Gradation distribution curve for OTR TDA
Table 1. Percentage of Elongated and Flat Particles
Flat Particles
Elongated Particles
Flat and Elongated
Particles
Neither Flat nor
Elongated Particles
33%
6%
22%
39%
Second: TDA Hydraulic Conductivity tests
Hydraulic conductivity is the property of the TDA that describes the ease with which water can
move through its voids. It mainly depends on the permeability of the material under different
loadings and the degree of saturation. Determining this property would help in understanding how
this material would behave when saturated with rain water for example. More specifically, the
hydraulic conductivity determines the ability of the rain water to flow through the TDA matrix
system under specified hydraulic conditions.
The test set up was as shown in Fig. 6 and test results are provided in Fig. 7. The measured
hydraulic conductivity varied from 4.9 to 6.3 cm/s corresponding to a material porosity ranging
from 43 to 53%, respectively. Table 2 shows comparison between the OTR TDA and other
materials with respect to the conductivity.
Figure 6. The set up for the hydraulic conductivity test
Figure 7. Hydraulic conductivity of OTR TDA as a function of applied stress.
Table 2. Hydraulic conductivity of various materials
Hydraulic Conductivity With No Applied Load (cm/s)
Tire Shreds
6.3050
Gravel
3.0000
Coarse sand
0.6000
Medium sand
0.0500
Fine sand
0.0200
Silt, loess
0.0020
Till
0.0002
In addition to determining the hydraulic conductivity, other parameters were also calculated using
the same test set-up. Those properties are listed in Table 3.
Table 3. Other TDA material properties
Dry (Bulk) Unit Weight of Tire Shreds = 4.891 kN/m3
Porosity = 5.299 x 10-1
Void Ratio = 1.127
Specific Gravity of Tire Shreds = 1.063
Third: lateral TDA pressure test
A small scale test was designed for the specific purpose of understanding & determining how much
lateral pressure would be exerted on basement walls when OTR TDA is used as backfill. The test
set up (Fig. 8 and 9) included four 1.8 m high wooden panels that formed the walls for a box 0.9 m
wide by 1.2 m long, approx. Four 20 cm diameter vibrating wire earth pressure cells were placed
near the base of the structure at the location of expected maximum pressure (Fig 8). A fifth
pressure cell was placed horizontally in the base of the structure to confirm the magnitude of the
vertical applied load.
Figure 8. Pressure cells placed inside the walls
dumping TDA into the test box
4
1
3
4" concrete slab laid on top of TDA
2
pressure cells reading poxes
5
Figure 9. The lateral pressure test set up
Based on the test results, the relation between vertical applied loads and lateral pressure was as
shown in Fig. 10. The value of Ko is the ratio of the change in horizontal stress to the change in
vertical stress. The results indicate a Ko value of 0.19, which can be compared with a Ko of
between 0.35 and 0.6 for natural granular material. The compressibility of the OTR TDA could
also be determined from the results of the hydraulic conductivity and lateral pressure tests. The
elastic Young’s modulus derived from these tests was approximately 185 kPa, with a Poisson’s
ratio of 0.16.
Figure 10. The relationship between vertical and horizontal stresses for TDA
Conclusions and Recommendations
The focus of work conducted throughout Phase II was on understanding and determining the
properties of OTR TDA that would enable its proposed use as a replacement for natural aggregates
for residential basement backfill applications. The following are conclusions based on analyzing
tests results.



Gradation distribution of OTR TDA shows that it is comparable to results achieved by
previous researchers for similar products. The results also indicate that this material has a
somewhat uniform particle distribution. that can be acceptable for consideration as backfill
material for basement walls without levels of compaction necessary for natural earth
The unit weight of TDA is approximately one-third of that known for natural soils. This
means that OTR TDA can be considered as a light-weight backfill material which definitely
advantageous for design of basement walls. The hydraulic conductivity results indicate that
this material is more conductive than granular backfill and will certainly allow free drainage
of rain water, which is an advantageous property for backfill adjacent to basement walls.
Results of the lateral pressure test, combined with the light weight of the material, indicate
that maximum horizontal pressure induced by the self-weight of TDA on basement walls
will be 10 to 15% of that for natural granular material. These results in turn indicate that
significant economic advantage may be achieved if TDA is used as backfill in lieu of natural
materials.
Acknowledgements
The authors would like to acknowledge the support provided by Red River College staff and the tire
recycling industry in Manitoba.
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