Cold Regions Science and Technology 60 (2010) 63–65

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Cold Regions Science and Technology

j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c o l d r e g i o n s

Freezing–thawing behavior of fine-grained soils reinforced with polypropylene fibers

A. Sahin Zaimoglu
Technical Vocational School of Higher Education, Atatürk University, Erzurum, Turkey

a r t i c l e i n f o a b s t r a c t

Article history: A number of studies have been conducted recently to investigate the influence of randomly oriented fibers on
Received 9 February 2009 some engineering properties of cohesive and cohesionless soils. However, very few studies have been carried
Accepted 10 July 2009 out on freezing–thawing behavior of soils reinforced with discrete fiber inclusions. This experimental study
was performed to investigate the effect of randomly distributed polypropylene fibers on strength and
Keywords: durability behavior of a fine-grained soil subjected to freezing–thawing cycles. For strength behavior, a series
Freezing–thawing
of unconfined compression tests were conducted. Mass losses were also calculated after freezing–thawing
Unconfined compression strength
Fiber reinforcement
cycles as criteria for durability behavior. The content of polypropylene fiber was varied between 0.25% and 2%
Elastic modulus by dry weight of soil in the tests. The test results for the reinforced specimens were compared with that for
the unreinforced sample. It was observed that the mass loss in reinforced soils was almost 50% lower than
that in the unreinforced soil. It was also found that the unconfined compressive strength of specimens
subjected to freezing–thawing cycles generally increased with an increasing fiber content. On the other hand,
the results indicated that the initial stiffness of the stress–strain curves was not affected significantly by the
fiber reinforcement in the unconfined compression tests.
© 2009 Elsevier B.V. All rights reserved.

1. Introduction 1984; Taspolat et al., 2006). A number of studies have been conducted
recently to investigate the influence of randomly oriented fibers on
In seasonally frozen areas, soils are exposed to at least one some engineering properties of the cohesive and the cohesionless
freezing–thawing cycle every year. This has a significant effect on soils (Yetimoglu et al., 2005; Latha and Murthy, 2007; Consoli et al.,
many engineering applications such as road, railroad, pipeline, and 2003; Al-Refeai and Al-Suhaibani, 1998; Trindade et al., 2006;
building constructions. Chauhan et al., 2008; Ghazavi and Lavasan, 2008; Park, 2008; Babu
Most of the engineering properties of soils are severely affected by et al., 2008; Nataraj and Manis, 1997; Consoli et al., 2005; Alrefeai,
freezing–thawing period. Some engineering properties of soils (e.g., 1991). However, very limited information has been reported on the
strength, permeability, and compressibility) could be changed freezing–thawing behavior of the fiber-reinforced soils in the
significantly due to freezing–thawing cycles (Tsytovich, 1973; Konrad, literature (Yarbasi et al., 2007).
1989; Hohmann-Porebska, 2002; Qi et al., 2006, 2008). Guney et al. The main objective of this study was to investigate the effect of
(2006) have reported that in any stabilization application, the polypropylene (PP) fiber reinforcement content on the strength and the
stabilized material should also withstand additional stresses caused durability behavior of a fine-grained soil subjected to freezing–thawing
by seasonal temperature differences, particularly freeze–thawing cycles. A series of unconfined compression tests was carried out on both
cycles. The effect of freezing–thawing on fine-grained soils can be the unreinforced and the fiber-reinforced soil specimens. Also, mass
more pronounced than that of the coarse-grained soils. Fine-grained losses were calculated after freezing–thawing cycles to highlight the
soils influenced by freezing and thawing show changes in volume, durability behavior. The test results were compared and discussed.
strength and compressibility, densification, water content, bearing
capacity and microstructure. In the freezing period, ices in various
sizes and shapes tend to segregate in soils resulting in the formation of 2. Experimental study
characteristic structures in micro and macro scales (Hohmann-
Porebska, 2002). The frozen layer begins to thaw from the top and Soil used in this study was obtained from a fine-grained soil
the bottom at the same time during the thawing period. deposit of Konaklı–Erzurum in the Eastern Anatolia Region of Turkey.
Different additive materials (e.g., fly ash, cement, and lime) are In this region, there is a long winter, and snow remains on the ground
used to improve some engineering properties (e.g., swelling, perme- from November until the end of April. From the data obtained at a
ability, and strength) of soils under freezing–thawing cycles (EM 1110, station in Erzurum between 1988 and 2005, long term mean
temperature is 5.1 °C, daily temperature range is 15.0 °C, the highest
temperature measured so far is 35.6 °C and the lowest temperature
E-mail address: zaimoglu@atauni.edu.tr. is − 37.2 °C (Toy et al., 2007). This soil deposit resembles an area

0165-232X/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.coldregions.2009.07.001
64 A.S. Zaimoglu / Cold Regions Science and Technology 60 (2010) 63–65

Table 1
Some properties of soil.

Clay content (%) 42

Silt content (%) 34
Sand content (%) 24
Liquid limit, wL (%) 66
Plastic limit, wP (%) 35
Plasticity index, PI (%) 31
Specific gravity, Gs 2,72
Soil class (USCS) MH
Maximum dry unit weight⁎, γdmax (kN/m3) 15.4
Optimum water content a, wopt (%) 22
Electric conductivity (mmhos/cm) 3.3
pH 6.9
Dispersion 1–2
⁎Obtained from standard proctor tests. Fig. 1. Stress–strain curves after 12 freezing–thawing cycles.

where: C = original calculated oven-dry mass minus final corrected

exposed to freezing–thawing and is used much in engineering work in oven-dry mass (i.e., C = D − CODM), and D = original (i.e., before
Erzurum. The soil can be classified as “high plasticity silt (MH)” freezing–thawing cycles) calculated oven-dry mass.
according to the Unified Soil Classification System. Some index and Following the 12 freezing–thawing cycles, the mass losses were
engineering properties are given in Table 1. calculated and, the unconfined tests were performed for both the
The polypropylene fiber was supplied by a firm in Turkey. Some unreinforced and the reinforced soil specimens. The test specimens
properties of polypropylene fiber provided by the manufacturer are had a diameter of 38 mm and a height of 76 mm. The unconfined
given in Table 2. compressive strength tests were conducted under strain controlled
The soil was dried in an oven at approximately 105 ± °C for 24 h. conditions at a uniform loading rate of 0.8 mm/min in accordance
The required amount of soil was mixed with polypropylene fiber with ASTM D 2166. The tests were continued up to an axial strain of
under dry conditions. The content of the polypropylene fiber was around 20% to observe the post-failure behavior as well. Each test was
chosen as 0.25%, 0.5%, 0.75%, 1%, 1.25%, 1.5% and 2% by dry weight of repeated at least three times to assure their accuracy.
soil. Then, the required amount of water corresponding to the
optimum water content was added into the soil–fiber mixture. Since 3. Results and discussion
the fibers tended to flocculate, considerable care and time were spent
to get a homogeneous distribution of the fibers in the mixtures. Water The stress–strain curves obtained from unconfined compression
content (w) versus dry unit weight (γk) relationship for the tests on the unreinforced and the reinforced specimens subjected to
unreinforced and the reinforced soil was determined by performing 12 times freezing–thawing cycles are given in Fig. 1 and Table 3. It can
standard compaction test following to ASTM D 698. be seen that the peak stress was generally increased with the
The specimens were placed in a moist room having a temperature of increasing fiber content. As compared to the unreinforced sample,
21 °C and a relative humidity of 70% for a period of 7 days. At the end of the the unconfined compression strength of the reinforced sample at 2%
storage in the moist room, water-saturated felt pads were placed between polypropylene fiber content increased from 311 to 1335 kPa. It can also
the specimens and the carriers, and the assembly was placed in a freezing be seen that the fiber-reinforced soils exhibit more ductile behavior
cabinet having a constant temperature not warmer than −23 °C for 24 h. than the unreinforced soil. On the other hand, the initial stiffness of
Then, the assembly was removed and placed in a moist room with a soil appears not to be affected by the addition of fiber reinforcement.
temperature of 21 °C and a relative humidity of 100% for a period of 23 h. Similar results were also obtained for granular soils modified with
At the end of this period, the specimens were removed and firm strokes waste additives (Yarbasi et al., 2007).
were applied to the full height and width of the specimen with a wire To investigate the effect of the randomly distributed polypropylene
scratch brush as an experimental maneuver leading to the mass loss per fibers on the durability behavior of the soil, mass losses were
ASTM D 560. This process was called 1 cycle. Again the specimens were calculated after 12 freezing–thawing cycles. The variation of mass
placed in the freezing cabinet and the same procedure was continued losses with the fiber ratio was shown in Fig. 2 and Table 3. It can be
for 12 cycles. After 12 cycles, the test samples were dried in an oven at seen that the addition of fiber reinforcement into the soil decreased
110±5 °C for 12 h. Considering ASTM D 560-3, the corrected oven-dry the mass loss of soil after the freezing–thawing cycles. At the end of
mass of specimen (CODM) was calculated as follows: the 12 freezing–thawing cycles, the most noteworthy effect of fiber
was observed on the sample reinforced with 0.75% polypropylene
CODM = ð A = BÞ  100 ð1Þ fiber as compared with the unreinforced sample. While the mass loss
was around 40% for the unreinforced sample, the mass loss decreased
where: A = oven-dry mass after drying at 110 °C, and B = percentage up to 15% for the sample reinforced with 0.75% polypropylene fiber.
of water retained in specimen plus 100. Then, mass loss (ML) was
calculated as follows:
Table 3
The values of unconfined compression strength (UCS) and mass loss for different fiber
ML ðkÞ = ðC = DÞ  100 ð2Þ
ratios.

PP–fiber ratio (%) UCS (kPa) Mass loss(%)

Table 2
Some index and engineering properties of polypropylene fiber reinforcement. 0 311 39
0.25 313 20
Diameter, mm 0.05 0.5 966 22
Length, mm 12 0.75 905 15
Density, kN/m³ 9.1 1 673 20
Tensile strength , N/mm² 320–400 1.25 664 21
Elastic modulus, N/mm² 4000 1.5 1219 20
Specific surface, m2/N 20–30 2 1335 20
 A.S. Zaimoglu / Cold Regions Science and Technology 60 (2010) 63–65 65

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