or=black height=1> Yahoo! is not affiliated with the authors of this page or responsible for its content.
Properties of Tire Rubber Ash Mortar Al-Akhras and Smadi
1
Properties of Tire Rubber Ash Mortar
Nabil M. Al-Akhras
(Corresponding author)
Assistant Professor
Civil Engineering Department
Jordan University of Science and Technology
P.O.Box 3030
Irbid 22110
Jordan
alakhras@just.edu.jo
Mohammed M. Smadi
Associate Professor
Civil Engineering Department
Jordan University of Science and Technology
P.O.Box 3030
Irbid 22110
Jordan
Paper Number: 03-2660
Word count = 5850
TRB 2003 Annual Meeting CD-ROM Paper revised from original submittal. Al-Akhras and Smadi
2
ABSTRACT
The present study explores the effect of tire rubber ash (TRA) filler on different
properties of Portland cement mortar. The properties investigated include air content,
setting time, compressive and flexural strengths, freeze-thaw damage, and chloride ion
penetration. The TRA was obtained by incinerating bulk quantities of tire rubber chips in
an oven at a controlled temperature of 850
°
C for 72 hours. The TRA filler was utilized
as partial replacement of sand in mortar specimens in four levels: 2.5, 5, 7.5, and 10% by
weight. The water to cement ratio used in the mortar mixes was 0.65. The test results
showed that TRA could be used as partial replacement of sand in mortar mixes to
produce workable mortar. The air content of fresh mortar decreased with increasing the
TRA content. The initial and final setting times of fresh paste increased with increasing
the TRA content.
The mortar containing different TRA replacement levels showed
higher compressive strengths at various curing periods up to 90 days compared with
control mortar. Also, the flexural strength of the TRA mortar was higher than that of
control mortar. The mortar containing 5% and 10% TRA showed higher resistance to
freeze-thaw damage and chloride ion penetration than that of control mortar.
Keywords
:
tire rubber ash, mortar, compressive strength, setting time, freeze-thaw
damage, chloride ion penetration.
TRB 2003 Annual Meeting CD-ROM Paper revised from original submittal. Al-Akhras and Smadi
3
INTRODUCTION
Solid waste management is a major environmental issue in many countries around
the world. Previous studies have indicated that waste tires constitute a significant portion
of non-hazardous solid waste materials (1,2). Many waste tires are currently stockpiled
in many countries around the globe. These stockpiles are dangerous because they pose a
potential environmental concern, fire hazards, and provide breeding grounds for
mosquitoes (3).
The practice of disposing waste tires in landfills is becoming
unacceptable because of the rapid depletion of available landfill sites. Additionally, tires
may break through landfill covers, floating upward through a sea of trash (4).
Innovative solutions to deal with waste tire disposal are being developed. Among the
most promising solutions are: reuse of ground tire rubber in a variety of rubber products,
thermal incineration of waste tires for the production of heat and electricity, and use of
tire rubber in asphalt pavement and Portland cement concrete mixes (5,6). Unfortunately,
the generation of waste tires far exceeds its current applications.
Previous studies on the utilization of waste tires in asphalt pavement mixes were very
encouraging. They reported that rubberized asphalt had better skid resistance, reduced
fatigue cracking, and achieved longer asphalt pavement life than conventional asphalt
pavement (7,8,9). However, the initial cost of rubberized asphalt is higher than that of
conventional asphalt and the long-term durability of rubberized asphalt is questionable
(10).
The use of waste tires in Portland cement concrete mixtures has not been
researched as much as their use in asphalt pavements. Most of the studies have dealt with
waste tires as individual particles replacing coarse aggregates.
Recent results have
indicated that rubberized concrete mixtures possess lower density, increased toughness
and ductility, higher impact resistance, lower compressive and splitting tensile strengths,
lower durability to freeze-thaw damage, and more efficient heat and sound insulation
(11,12,13). However, no research studies have been reported in the literature concerning
the use of tire rubber ash (TRA) in concrete mixes. This study investigates the influence
of TRA waste filler on different properties of Portland cement mortar.
EXPERIMENTAL PROGRAM
Materials
Cement: Type I ordinary Portland cement was used in the study. The physical properties
and chemical analysis of the cement are presented in Tables 1 and 2, respectively.
Fine aggregate: The graded fine aggregate was natural silica sand. The bulk specific
gravity and fineness modulus of the sand were 2.63 and 2.2, respectively.
Tire rubber ash: Tire rubber ash was obtained by incinerating bulk quantities of tire
rubber chips in an oven at a controlled temperature of 850
°
C for 72 hours. The TRA
was collected from the oven and fine ground to pass a No. 100 sieve (150
µ
m). The
physical properties and chemical composition of TRA are presented in Tables 1 and 2,
respectively. The TRA has a specific surface area of 410-m
2
/kg using Blaine method.
The SiO
2
and CaO content of the TRA are 26.5% and 12.9%, respectively. The scanning
electron micrograph examination of TRA particles (Figure 1) shows that most particles of
TRA are porous and irregular in shape (some particles are sticky). The structure of TRA
is honeycomb.
TRB 2003 Annual Meeting CD-ROM Paper revised from original submittal. Al-Akhras and Smadi
4
Specimens Preparation
The mortar was mixed in a laboratory mixer for a total time of 3 minutes. The mortar
mixture proportions were 1:3:0.65 by weight for cement, sand, and water, respectively.
The TRA filler was added to mortar mixes as partial replacement of the sand in four
levels: 2.5, 5, 7.5, and 10% by weight. Table 3 shows the mortar mixture proportions
used in the study. The compressive strength specimens were cubes measuring 50 by 50
by 50-mm. The flexural strength specimens were beams measuring 40 by 40 by 160-mm.
Freeze-thaw test specimens were prismatic measuring 75 by 75 by 400-mm. Resistance
to chloride ion penetration specimens were cylinders measuring 100 by 200-mm. Three
test specimens were prepared and tested to obtain average values for each test condition.
Each specimen was cast in two layers and compacted on a vibrating table. After casting,
all specimens were covered with wet burlap and left in the casting room at 23
°
C for 24
hours. The specimens were then demolded and cured in lime-saturated water at 23
°
C
until the time of testing.
Testing Procedure
The air content of fresh mortar was measured using the pressure method according to the
ASTM C231-97. The setting time of fresh paste was conducted using the Vicat apparatus
according to the ASTM C191-01. The compressive and flexural strengths of hardened
mortar were conducted according to ASTM C109-02 and C348-02, respectively. The
compressive and flexural strengths specimens were tested using a universal testing
machine. The rates of loading of compressive and flexural specimens were 45 and 3
kN/min, respectively. The rate of loading was maintained constant throughout the testing
program.
Accelerated cycles of freeze-thaw damage were performed following
Procedure B (rapid freezing in air and thawing in water) according to ASTM C666-97.
The freeze-thaw damage was assessed through the measurement of the fundamental
transverse frequency of simply supported prisms according to ASTM C215-97. The
relative dynamic modulus of elasticity was calculated based on the fundamental
frequency measured. Resistance to chloride ion penetration was measured at the ages of
28 and 90 days using 50-mm disks on top portion of 10 by 20 cm cylinders according to
ASTM C1202-97.
RESULTS AND DISCUSSION
Figure 2 shows the effect of TRA replacement on the air content of fresh mortar.
The air content decreased with increasing the TRA replacement level from 2.6% for
control mortar to 1.5% for mortar containing 10% TRA. The percent decreases in the air
content of mortar mixes were 15, 27, 35, and 42% at TRA content of 2.5, 5, 7.5, and
10%, respectively. The decrease in the air content with increasing TRA replacement may
be attributed to the effect of TRA filler packing where TRA replaces some of the air
present in the mortar mixes. Thus, TRA reduces the porosity and increases the packing
density of mortar.
Figure 3 shows the effect of TRA replacement on the initial and final setting times for
fresh paste containing 0, 2.5, 5, 7.5, and 10% TRA replacement levels. Both the initial
and final setting times increased with increasing the TRA content. The initial setting
time increased from 145-minute for control paste mix to 220-minute for the paste
containing 10% TRA. The final setting time increased from 270-minute for the control
TRB 2003 Annual Meeting CD-ROM Paper revised from original submittal. Al-Akhras and Smadi
5
paste mix to 390-minute for the paste containing 10% TRA. The percent increases in the
initial setting time of paste were 10, 24, 45, and 51% at TRA content of 2.5, 5, 7.5, and
10%, respectively. The percent increases in the final setting time of paste were 7,