strength and durability characteristics of bio-improved ... · strength and durability...
TRANSCRIPT
Strength and Durability Characteristics of Bio-Improved Sand of Al-Sharqia Desert, Oman
*Mohsin U. Qureshi1), Ilhan Chang2) and Khaloud Al-Sadarani3)
1), 3) Faculty of Engineering, Sohar University, PO Box. 44, PC. 311, Sohar, Sultanate of
Oman 2) Department of Civil Engineering, Korean Advanced Institute for Science and Technology, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Republic of Korea
2) [email protected] 3) [email protected]
ABSTRACT
Bio-improvement of geomaterial to develop sustainable geotechnical systems is an important step towards the reduction of global warming. The cutting edge technology of bio-improvement is not only environment friendly but also has widespread application. This paper presents the strength and slake durability characteristics of bio-improved sand sampled form Al-Sharqia Desert in Oman. The specimens were prepared by mixing sand at various proportions by weight of xanthan gum biopolymer. To make a comparison with conventional methods of ground improvement, cement treated sand specimens were also prepared. A series of strength tests were conducted on dry specimens as well as at saturated state. To demonstrate the effects of wetting and drying on bio-improved and cement treated sand, standard slake durability tests were conducted on the specimens. According to the results of strength tests, bio-improvement has increased the strength of sand, similar to strengthening effect of mixing cement in sand. The slake durability test results indicated that the resistance of bio-improved sand to disintegration upon interaction with water is stronger than that of cement treated sand. The percentage of xanthan gum to treat sand is proposed to be 2-3 % for optimal performance in terms of strength and durability. The present study concludes that the bio-improvement is an eco-friendly technique to improve the mechanical properties of desert sand. However, the strengthening effect due to the bio-improvement of sand can be weakened upon interaction with water in unconfined state. Therefore it is expected that the bio-
1)
Assistant Professor 2)
Senior Researcher, Ph.D. 3)
Technician
improvement technique may perform well in confined geotechnical systems. KEYWORDS : Desert sand; bio-improvement; strength; durability 1. Introduction
Anthropogenic global warming is not only responsible for the rise in sea levels and abnormal climate problems but is also due to geo-environmental hazards from the unsustainable geotechnical systems supporting the civil infrastructure. Both new construction sites and rehabilitation works on weak soils require ground improvement. Over the past century, various ground improvement methods have been developed, and today many of them are widely employed to build geotechnical systems. It is appropriate to classify a wide variety of soil treatment methods as mechanical or chemical. Mechanical methods improve the soil by densification/dewatering, however in the chemical methods cementation is induced mainly by ordinary Portland cement or chemical additives. The basic principles of these techniques have not changed since the early of the twentieth century. The practices, however, have been changing with the time mainly because of the development of new materials, new machinery, and new technologies. A largely unrecognized fact is the impact of traditional geotechnical construction processes that can be on biological processes. Such as, during, soil compaction the reduction in void ratio introduces a fundamental shift in biological processes (from aerobic to anaerobic metabolism), which creates conditions harmful to biodiversity, consequently affecting the vegetative growth (DeJong et al. 2006).
Some of the products used in soil improvement are not considered as environment friendly due to high emission of greenhouse gases during their production and toxic nature after application. The addition of these materials, while beneficial from an engineering performance perspective, might not necessarily be advantageous for the environment. Ordinary cement production emits carbon dioxide, a significant greenhouse gas, during chemical calcination and fuel burning. It has been reported that 5% of the global carbon dioxide emissions are induced by the cement industries (Worrell et al. 2001). Both the disuse and recycling of cement-concrete waste are potentially hazardous to the environment due to the potential for pollutant leakage into the soil and groundwater. Meanwhile, several alternatives such as geo-polymers, alkali activated cement, geo-cement, and inorganic polymer concrete have been developed in an attempt to reduce or replace cement use.
However, the carbon dioxide reduction efficiency of these methods is insufficient due to their dependency on ordinary cement and heavy industry by-products (e.g. blast furnace slag, fly ash, etc.). Alternative, natural biologically – based treatment methods could meet the same engineering requirements without environmental concerns. Therefore, demand for the development of environmentally friendly construction materials that are relatively harmless and easily reused without environmental impacts is increasing significantly in the 21st century (Cabalar and Canakci 2011). Thus, the biopolymers can not only applicable in the development of geotechnical systems also a
renewable source as a component of greenhouse gas reduction strategies (Vink et al. 2003). The great promise of the use of biological treatments has been already demonstrated in other fields such as in petroleum industry to directing the oil flow in the required direction, in concrete technology to remediate cracks (Ramachandran et al. 2001), development of shields for zonal remediation and stabilization of contaminated soils (Khachatoorian et al. 2003). Biopolymers are sustainable, because they are made from anthropogenic agricultural nonfood crops.
Biopolymers are polymers produced by living organisms, and most biopolymer applications are in the field of medical engineering, such as drug delivery systems, wound healing, and surgical implantations (Van de Velde and Kiekens et al. 2002). More recently, research in biology and earth science has enabled important advances in understanding the crucial involvement of microorganisms in the evolution of the earth, their ubiquitous presence in near surface soils and rocks, and their participation in mediating and facilitating most geochemical reactions (Mitchell and Santamarina 2005). According to Ivanov and Chu (2008), biocementation can replace the high energy demanding mechanical compaction or the expensive or environmentally harmful chemical grouting. To achieve the aim of environment friendly development, in the fields of soil science, geotechnical engineering, and geo-environmental engineering, biopolymers have been employed as soil stabilizers to enhance the mechanical response of ground against the external loading and the environment.
Table 1 Generalized review of soil improvement by using biopolymers
Sr. No.
Reference Soil Type Biopolymer The effects of bio improvement
1 Sutterer et al. 1996 Soil Agar Efficiency in undisturbed sampling
2 Khachatoorian et al. 2003
Silty sand Xanthan gum Reduction in hydraulic conductivity
3 Bouazza et al. 2009 Silty sand
Xanthan gum, guar gum and sodium alginate
Reduction in permeability
4 Nugent et al. 2009 Increase in undrained shear strength and liquid limit
5 Cabalar and Canakci 2011
Sand Xanthan gum Improvement in shear strength
6 Chang and Cho 2012
Soil Beta-glucan Improvement in uniaxial
compressive and tensile strength
7 Chang et al. 2013
Soil Beta-glucan Xanthan gum
Reduction in Water erosion and increased potential of vegetation growth
8 Khatami and O’Kelly Sand Agar and Increase in unconfined
2013 modified starch
compressive strength, cohesion and stiffness
9 Qureshi et al. 2015 Sand Xanthan gum Slake durability
10 Chang et al. 2015 Xanthan gum Soil strengthening
11 Ayeldeen et al. 2016 Sand, silt
Xanthan gum, modified starch, guar gum
Increase in shear resistance and reduction in permeability
12 Chang et al. 2016 Sand Gellan gum
Increase in shear strength at various moisture contents and decrease in permeability
Xanthan gum is a polysaccharide that is made by the Xanthomonas campestris bacterium, and is generally used as a viscosity thickener due to its hydrocolloid rheology (Barrére et al. 1986). Xanthan gum has been introduced to geotechnical engineering to reduce the hydraulic conductivity of silty sand via pore filling (Khachatoorian et al. 2003; Bouazza et al. 2009) as well as to increase the undrained shear strength of soil by increasing the liquid limit (Nugent et al. 2009). Another recent study has studied possibilities for using xanthan gum as a soil strengthener, and showed that xanthan gum preferentially forms firm xanthan gum-clayey soil matrices via hydrogen bonding (Chang et al 2015). More recently, Khatami and O’Kelly (2013) reported the mechanical behavior of sand treated with agar and six modified. Their results showed the increase in unconfined compressive strength, cohesion and stiffness of the treated sand. Qureshi et al. (2015) investigated the effects of wetting and drying on the xanthan gum treated sand and concluded that the xanthan gum treated sand is durability against slaking. A remarkable increase in shear resistance and reduction in permeability of sand and silt is reported by Ayeldeen et al. (2016). They employed xanthan gum, modified starch and guar gum to improve sand and silt. The application of agar for temporary stabilization of soil has been described by Sutterer et al. (1996) to development procedures for undisturbed sampling. Chang et al. (2016) reported an increase in shear strength parameters and reduction in permeability of sand treated with gellan gum. Further, they interpreted that the gellan gum treated sand is sensitive to moisture however, durable enough for the application to support shallow foundations.
Fig. 1 Location of sampling site at Al-Bidiya, Wahiba sand Dunes, Al-Sharqia,
Oman (Pease et al. 1999)
2. Materials
2.1 Al-Sharqia Desert Sand Sand is sampled from Al-Bidiya in northern part of Wahiba sand dunes (Fig. 1), in Al-
Sharqia Region which is about 200km to the south of Capital Muscat. The Wahiba Sand formed in Quaternary period (Glennie 1998) is composed of two physiographic units that can be roughly divided into northern and southern regions. The Northern Wahiba is predominantly a large megaridge system, whereas the Southern Wahiba mostly comprises linear dunes, sand sheets, and sabkha fields (Pease and Tchakerian 2003). Carbonate sands are present throughout the Wahiba sand area with some quartz-rich sands in the Southern region. The Al-Sharqia sand (AS) used in this study is
sampled from the Northern region. The grain size distribution (BS 1990a) of the sand is shown in Fig. 2(a). The sand can be classified as poorly-graded fine sand (SP) according to the Unified Soil Classification System (USCS). The sand has a specific gravity (BS 1990b) of 2.62 and a fine content of 1.1%. The standard Proctor compaction test (BS. 1990c) gave a maximum dry density of 1.64g/cc at an optimum water content of 19.5%. The micrograph of AS indicates sub-rounded particles and lacking in fines as shown in Fig. 2(b).
0.01 0.1 1
0
20
40
60
80
100
Perc
ent P
assin
g b
y w
eig
ht (%
)
Particle size (mm)
Gs=2.62
Fc=1.1%
emax
=2.52
emin
=0.484
Cc=0.8
Cu=1.8
(a) Gradation Analysis (b) Photomicrograph
Fig. 2 Physical properties of Al-Sharqia Sand (AS)
2.2 Xanthan Gum Xanthan gum (C35H49O29) which has high viscous rheology was discovered in the
1950s, is a natural anionic polysaccharide composed of D-glucuronic acid, D-mannose, pyruvylated mannose, 6-O-acetyl D-mannose, and a 1,4-linked glucan (Garcia-Ochoa et al., 2000; Hassler and Doherty, 1990), which is the most rigid biological repeating molecule (Yevlampieva et al., 1999). The most well-known characteristic of Xanthan gum is pseudo plasticity (viscosity degradation with an increase of shear rate) (Milas and Rinaudo, 1986) and high shear stability (Chen and Sheppard, 1980) even at low concentrations. Moreover, it has several properties including, pH stability, storage stability, and ionic salt compatibility (Hassler and Doherty 1990). Because of these properties, xanthan gum itself has found a wide range of applications in the cosmetic, oil, paper, paint, pharmaceutical, food and textile industries as a gelling, thickening, suspending agent, as a flocculent or for viscosity control. 3. Experimental Program
3.1 Equipments
A standard Proctor compaction test was performed in accordance with BS 1377-4.3
(BS 1990c). The test was essential for determining the maximum dry density for each soil type and its corresponding optimal moisture content. The consistency limits of the xanthan gum treated specimens were obtained in accordance with the BS 1377-2.4.5 (BS 1990d) and BS 1377-2.5.3 (BS 1990e). Unconfined compressive strength tests were obtained—according to BS 1377-7.7 (BS 1990f) by using a strain rate of approximately 1%/min for xanthan gum treated sand (ASG). To study the mechanical behavior of dry and saturated ASG specimens in confined state, unconsolidated undrained triaxial tests were performed in accordance with BS 1377-7.8 (BS 1990g). A state-of-the-art triaxial test equipment manufacture by Utest, Turkey, was employed as shown in Fig. 3(a). The salient features of the equipment were, 50kN loadcell, LVDT of 50mm stroke length, maximum confining pressure 2MPa, axial strain controlled loading and eight channel data logging system. The effects of wetting and drying on the durability of ASG is elucidated by performing standard slake durability test (Franklin and Chandara 1972). The slake durability test device used in this study is shown in Fig. 3(b).
(a) A-state of-the-art triaxial test equipment (b) Slake durability test device
Fig. 3 Equipment
3.2 Specimen Preparation The Al-Sharqia sand (AS) was oven dried at 105 °C for 24 h. The xanthan gum used
in this study was delivered as powder and mixed with water to produce gels to supplement as colloids for thickening water-based systems, which can act as binder. Distilled-deaired water was used to dissolve the biopolymer powder with different concentrations to avoid the effect of any additional factors such as the chemical components that may exist in portable water (Chen et al. 2013). The solution concentration was calculated as the ratio between the weight of the used powder and the overall weight of the sand. The powder was gently added into the water to avoid clumping, and then the solution was mixed until a homogeneous solution was obtained.
Xanthan gum concentrations of 1, 2, 3 and 5% by weight were used in this study. Finally, the sand was mixed with the solution until homogeneity had been achieved in the mixture. It was difficult to obtain certain densities for all specimens with several concentrations. Therefore, all the specimens (Fig. 4) were prepared at the maximum dry density according to their compaction characterizations. All specimens were cured at 45°C within an oven until tested after 1 week. The summary of prepared specimens is presented in Table 2. To compare the level of improvement achieved by the treatment of sand with xanthan gum, cement treated sand specimens were also prepared by adding 10% cement to the sand at water-cement ratio of 0.5 and cured at the same conditions. All the specimens prepared for strength tests were 5cm in diameter and 10cm in height.
Fig. 4 Typical specimens for Unconfined compression and triaxial compression
tests
Table 2 Summary of the specimens for compression tests
Sr. No. Specimen ID Xanthan gum
(%) Cement (%)
Dry density (g/cc)
1 AS 0 1.64
2 ASG1 1 1.67
3 ASG2 2 1.64
4 ASG3 3 1.635
5 ASG5 5 1.63
6 ASC10 - 10 1.58
4. Results and Analysis
4.1 Compaction The density and void ratio are very important parameters which control the stre
ngth of geomaterial. Standard proctor tests were performed on Al-Sharqia sand (AS) and xanthan gum treated Al-Sharqia sand (ASG) specimens. The plot of dry d
ensity and moisture content is shown in Fig. 5(a). The maximum dry density began to increase with the increase in gum content up to 1%. A further increase in the concentration of gum decreased maximum dry density. It can be seen in Fig. 5(b) that the maximum dry density of specimen ASG1 is 1.67g/cc in comparison to the untreated sand which has 1.64g/cc. The increase in maximum dry density of sand to a gum percent of 1% can be attributed to the reduction in friction between sand particles. Too high percentage of gum, i.e. more than 1 percent may have separated the sand particles. Simultaneously, the OMC was the lowest for the sand-gum mix ASG1. Ayeldeen et al. (2016) observed the similar behavior and concluded that the increase in maximum dry density is due to the increase in viscosity of water-gum solution. However, after a certain limit, increase in the viscosity results in the separation of sand particles with no further enhancement in maximum dry density.
0 5 10 15 20 25 301.3
1.4
1.5
1.6
1.7
AS
ASG1
ASG2
ASG3
ASG5
Dry
De
nsity, (
g/c
c)
Moisture Content, w (%)
Standard Proctor
ZAV of AS
0 1 2 3 4 5 61.60
1.62
1.64
1.66
1.68
12
15
18
21
24
Optim
um
Mois
ture
Con
tent, O
MC
, (%
)
d(max)
Max. D
ry D
ensity,
d(m
ax),
(g/c
c)
Xanthan Gum content (%)
OMC
(a) Plot of dry density and moisture content
(b) Max. dry density and moisture content plotted against xanthan gum cont
ent
Fig. 5 Compaction characteristics of xanthan gum treated Al-Sharqia sand
4.2 Consistency
The addition of xanthan gum forms a gel around the sand particles which may introduce the plasticity in cohesion-less sand. To investigate this fact, Atterberg limits (liquid limit and plastic limit) were elucidated by performing standard tests (BS 1990d) on sand treated with xanthan gum at different concentrations. The consistency limits of untreated sand could not be obtained due to its non-cohesive nature. The plot of moisture content and xanthan gum content in sand is shown in Fig. 5. Liquid limit of 1, 2, 3 and 5% xanthan gum-treated sand was determined to be 18.9, 23.6, 28 and 35.3 %, respectively. The liquid limit was observed to be increasing with the increase in xanthan gum content indicating the effect of hydrophilic property of xanthan gum on the plasticity behavior of Al-Sharqia. As the concentration of xanthan gum biopolymer in the soil mass would increase, the water retention capacity of soil would also become
larger. Thus the non-plastic nature of cohesionless Al-Sharqia sand is changed to cohesive by treatment with xanthan gum. Simultaneously, an increase in plastic limit is observed with the increased percentage of xanthan gum. The difference in liquid and plastic limit, i.e. plasticity index also increases with the increased percentage of xanthan gum to treat sand (Fig. 5).
0 1 2 3 4 5
5
10
15
20
25
30
35
40
Mo
istu
re c
on
ten
t (%
)
Xanthan gum content (%)
Liquid limit
Plastic limit
Plasticity Index
Fig. 5 Change in consistency limits of xanthan gum treated Al-Sharqia sand at
different gum contents
4.3 Unconfined Compression
The unconfined compression tests were performed on the dry specimens of xanthan gum treated Al-Sharqia sand. The plot of axial stress and axial strain is shown in Fig. 6(a). The unconfined compression response of untreated cement treated specimen is also plotted in Fig. 6(a). The unconfined compression strengths (UCS) for all the tested specimens are plotted against xanthan gum content in Fig. 6(b). The unconfined compressive strength of untreated sand is 15kPa, and when treated with 1, 2, 3, and 5% of xanthan gum, the elucidated UCS was 1076, 1700, 753 and 1024 respectively. So there is a remarkable improvement in UCS for all the mix percentages of xanthan gum in comparison to untreated sand. Cement treated sand on the other hand also showed higher UCS of 1767kPa. Further it can be observed in Fig. 6(a), that the residual response of xanthan gum treated specimens is higher than the cement treated specimens. Further the specimen having mix proportion of 2 percent of xanthan gum was strongest in unconfined compression and is comparable to the strength developed by 10% of cement treatment. In the case of residual response, the specimens treated with small percentage xanthan gum took precedence over specimens treated with higher percent of cement. The results reported by Chang et al. (2016) about the unconfined compression tests on dry specimens of gellan gum treated sand observed a similar behavior. Thus, the inter-particle strengthening resulted from the formation of thick and high-tensile dehydrated gel of xanthan gum among the sand particles which keep supporting the sand after failure.
0 1 2 3 4 50
500
1000
1500
2000 AS
ASG1
ASG2
ASG3
ASG5
ASC10
Axia
l S
tress,
a (
kP
a)
Axial Strain, (%)
Axial strain rate: 1%/min
0 1 2 3 4 5
0
500
1000
1500
2000
ASC10 Residual
Un
con
fine
d C
om
pre
ssio
n S
tren
gth
qu (
kP
a)
Xanthan Gum content (%)
ASC10 Peak
(a) Stress strain plot (b) UCS plotted against xanthan gum c
ontent
Fig. 6 Unconfined compression test results of xanthan gum treated Al-Sharqia sand
4.4 Triaxial tests Unconsolidated undrained response of the untreated and xanthan gum treated
Al-Sharqia sand was delineated by performing a series of triaxial tests on dried sand (AS) and sand (ASG) that had been treated with 1, 2, 3 and 5% of xanthan gum by weight. The tests were performed at three different radial stresses r) i.e. 50, 100 and 150kPa. All the tested specimens were having moisture content less than 1%, here noteworthy are that the xanthan gum gel was already dehydrated before testing. A typical deviatoric stress–strain response for the triaxial tests on untreated Al-Sharqia sand (r=1.64g/cc) is shown in Fig. 7(a). Thereafter, peak shear strength parameters, i.e. angle of internal friction and cohesion were determined by the Mohr Coulomb failure criterion.
The delineated cohesion for the mix percentage of 0, 1, 2, 3 and 5% xanthan gum specimens was 0, 36, 334, 343 and 223kPa is shown in Fig. 7(b). A remarkable increase in cohesion can be seen in Fig. 7(b) with the increase in xanthan gum content of treated sand; however this increase appears to diminish when the percentage of xanthan gum exceeds 3%. The angle of internal friction of untreated sand was 38o and that of xanthan gum treated sand ranges between 58o and 67o as shown in Fig. 7(b). The highest value of peak internal friction angle is observed in sand treated with a xanthan gum content of 1%. Generally it can be observed that both cohesion and angle of internal friction increases with the increase in xanthan gum content. However, at around 2-5% of the xanthan gum, the rate of increase shear strength parameters decreases. Therefore, the optimal concentration for the treatment of sand is around 2% if the improvement in shear strength of sand is in question.
0 1 2 3 4 5 6 7 80
300
600
r=50kPa
r=100kPa
r=150kPa
De
via
tor
Str
ess, (k
Pa
)
Axial strain, (%)
Axial strain rate: 1%/min
0 1 2 3 4 5 630
40
50
60
70
0
100
200
300
400
Peak Angle of
Internal Friction
Co
he
sio
n, c (
kP
a)
Pe
ak F
rictio
n a
ng
le,
p
o
Xanthan Gum content (%)
Cohesion
(a) A typical plot of deviator stress and axial strain of Al-Sharqia Sand
(b) Shear strength parameters plotted against xanthan gum content
Fig. 7 Triaxial test results of xanthan gum treated sand specimen in dry state
0 cycle ASG1 0 cycle ASG2 0 cycle ASG3 0 cycle ASG5 0 cycle ASC10
1 cycle ASG1 1 cycle ASG2 1 cycle ASG3 1 cycle ASG5 1 cycle ASC10
2 cycles ASG1 2 cycles ASG2 2 cycles ASG3 2 cycles ASG5 2 cycles ASC10
3 cycles ASG1 3 cycles ASG2 3 cycles ASG3 3 cycles ASG5 3 cycles ASC10
4 cycles ASG1 4 cycles ASG2 4 cycles ASG3 4 cycles ASG5 4 cycles ASC10
Fig. 8 Changes in xanthan gum treated (ASG) and cement treated (ASC) specimens due to slaking cycles
4.5 Slake Durability
The slake durability tests was initially designed to investigate the slaking behavior of clay bearing rocks (Franklin and Chandara 1972). One of main concern in the bio treatment of soil is the water effects on the strengthening behavior. So, the authors performed slake durability tests on xanthan gum treated and cement treated sand specimens. Ten pieces of each treated specimens weighing 40-50gm were oven died at 105oC. Those specimens were then shifter in to the wire mesh drum of slake durability device (Fig. 3(b)). The drum for rotated at 20rpm for 10 minutes half submerged in water. Thereafter, specimens were dried for 24 hours at 105oC in oven to complete one standard slaking cycle. Slake durability index after each slaking cycle is reported as the percentage of initial dried weight to the dried weight at the end of each slaking cycle. The qualitative changes in the specimen at the end of each slaking cycles is presented in Fig. 8. It can be seen that the specimen ASG1 is the least durable as compared to the sand treated with 2, 3 and 5 % xanthan gum. The cement treated specimen (ASC10) also showed a weak response against slaking as compared to sand treated with 3 and 5% xanthan gum (ASG3 and ASG5).
A decrease in slake durability index is observed after each slaking cycles for all the specimens as shown in Fig. 9(a). The slake durability indices obtained after 1, 2, 3 and 4 slaking cycles (SD1, SD2, SD3 and SD4) are plotted against the xanthan gum content in Fig. 9(b). The slake durability indices of ASC10 are also plotted in the same Fig. 9(b). It can be seen that that durability of treated sand against slaking increases with the increase in xanthan gum content up to 3%. A higher content of xanthan gum gel keeps the sand particles amalgamated during the wetting cycle, however the cement treated specimens loses unrecoverable cementation. During the drying cycle the xanthan gum gel dehydrated but remains available for the next wetting cycle.
0 1 2 3 40
20
40
60
80
100
Sla
ke d
ura
bili
ty ind
ex (
%)
Slaking cycles
ASG1
ASG2
ASG3
ASG5
ASC10
0 1 2 3 4 50
20
40
60
80
100
Sla
ke D
ura
bili
ty Ind
ice
s (
%)
Xanthan Gum Content (%)
SD1
SD2
SD3
SD4
ASC10
(a) Plot of slake durability and slaking
cycles (b) Slake durability indices plotted agains
t xanthan gum content
Fig. 9 Slake durability test results of xanthan gum (ASG) and cement treated (ASC) Al-Sharqia sand
5. Conclusions The objective of the current research was to investigate the possibility of improving
the engineering properties of dune sands by treatment with xanthan gum. Sand was sampled from Al-Sharqia desert of Oman. Al -Sharqia sand characterized as poorly graded fine sand was treated with xanthan gum at 1, 2, 3 and 5% as well as with cement at 10% by weight. A series of compaction, consistency limits, unconfined compression, triaxial and slake durability tests were performed on the treated and untreated sand specimens. Based on the results presented in this paper, the following conclusions can be drawn.
The xanthan gum has substantially increases the unconfined compressive strength of the treated sand. The unconfined compressive strength increases with xanthan gum content up to 2 % and then after that it decreases with the increase in xanthan gum content. The unconfined compressive strength of sand treated with a cement content of 10% was of the same order as of 1% treatment with xanthan gum.
The results of unconsolidated undrained triaxial tests showed that the sand treated with xanthan gum possess both angle of internal friction and cohesion. The dehydrated xanthan gum gel acted as a cementing agent between the sand particles. The angle of internal friction of bio-treated sand increases with the xanthan gum content up to 1 % and then decreases, however remain higher than that of untreated sand. The cohesion of bio-treated sand also increases with xanthan gum content up to 2% and then decreases, however remains higher than that of untreated sand. Thus, the treatment with xanthan gum has effectively improved the strength characteristics of Al-Sharqia sand. To achieve optimal results in terms of bio-strengthening of sand a mix percentage of 2-3% is optimal choice.
The standard proctor tests delineated that the maximum dry density of 1% xanthan gum treatment to sand was the highest. So in the field where compaction is to be practiced along with bio-improvement 1% xanthan gum content is the optimal choice.
The response of bio-treated sand to the slaking also increases with the content of xanthan gum. The slake durability index of bio-treated sand increases up to 3% gum content and remains same thereafter. In comparison, the cement treatment showed a low durability against slaking. The results suggest that the bio-improvement of sand is a sustainable and eco-friendly practice in the desert environment which will not after the biodiversity and it will be very attractive to develop geotechnical systems.
Acknowledgments The research described in this paper was jointly supported by a Faculty Mentored Undergraduate Research Award Program (FURAP) funded by the Research council Oman and the Final Year project support funded by Sohar University, Oman. The authors are also indebted to their colleagues at sohar University for a continuous support during the experimentation. References
Ayeldeen, M., Negm, A., and El Sawwaf, M. (2016), "Evaluating the physical
characteristics of biopolymer/soil mixtures", Arabian Journal of Geosciences, 9, 371 Barrére, G.C., Barber, C.E. and Daniels, M.J. (1986), ―Molecular cloning of genes
involved in the production of the extracellular polysaccharide xanthan by Xanthomonas campestris pv. Campestris‖, Int. J. Biol. Macromol., 8, 372–374.
Bouazza, A., Gates, W.P. and Ranhith, P.G. (2009), ―Hydraulic conductivity of biopolymer-treated silty sand‖, Geotechnique, 59, 71–72.
BS. (1990a), ―BS designation 1377: Standard test method for determination of particle size distribution‖, British Standard, Methods of test for Soils for Civil Engineering Purposes-Part 2 Classification tests, 2.9.
BS. (1990b), ―BS designation 1377: Standard test method for determination of particle density‖, British Standard, Methods of test for Soils for Civil Engineering Purposes-Part 2 Classification tests, 2.8.
BS. (1990c), ―BS designation 1377: Standard test method for determination of dry density/moisture content relationship‖, British Standard, Methods of test for Soils for Civil Engineering Purposes-Part 4 Compaction related tests, 4.3.
BS. (1990d), ―BS designation 1377: Standard test method for determination of liquid limit‖, British Standard, Methods of test for Soils for Civil Engineering Purposes-Part 4 Compaction related tests, 2.4.5.
BS. (1990e), ―BS designation 1377: Standard test method for determination of plastic limit‖, British Standard, Methods of test for Soils for Civil Engineering Purposes-Part 4 Compaction related tests, 2.5.3.
BS. (1990f), ―BS designation 1377: Standard test method for determination of the unconfined compressive strength‖, British Standard, Methods of test for Soils for Civil Engineering Purposes-Part 7 Shear strength tests (total stress), 7.7.
BS. (1990g), ―BS designation 1377: Standard test method for determination of the undrained shear strength in triaxial compression with measurement of pore pressure (definitive method)‖, British Standard, Methods of test for Soils for Civil Engineering Purposes-Part 7 Shear strength tests (total stress), 7.8.
Cabalar, A. F. and Canakci, H. (2011), ―Direct shear tests on sand treated with xanthan gum‖, Proceedings of ICE-Ground Improvement, 164(2), 57-64
-1,3/1,6-glucan biopolymer‖, Construction and Building Materials, 30, 30–35.
Chang, I., Cho, G. and Santamarina, J. C. (2013), ―Soil erosion control and vegetation stabilization using biogenic biopolymers‖, Proceedings of the 5th International Young Geotechnical Engineers Conference-5iYGEC2013, 77-80.
Chang, I., Im, J., Prasidhi, A.K. and Cho, G.C. (2015), ―Effects of Xanthan gum biopolymer on soil strengthening‖, Constr. Build. Mater., 74, 65–72.
Chang, I.; Im, J.; and Cho, G.C. (2016), ―Geotechnical engineering behaviors of gellan gum biopolymer treated sand‖, DOI.10.1139/cgj-2015-1475
Chen, C.S.H. and Sheppard, E.W. (1980), ―Conformation and shear stability of xanthan gum in solution‖, Polymer Engineering Science, 20(7), 512–516.
Chen, R., Zhang, L. and Budhu, M. (2013), ―Biopolymer stabilization of mine tailings‖, Journal of Geotechnical and Geoenvironmental Engineering, 139,1802–1807
DeJong, J. T., Fritzges, M. B. and Nüsslein, K. (2006), ―Microbially Induced Cementation to Control Sand Response to Undrained Shear‖, Journal of Geotechnical and Geoenvironmental Engineering, 132(11), 1381-1392.
Franklin, J. A. and Chandara, R. (1972), ―The slake durability test‖, International Journal of Rock Mechanics and Mining Science & Geomechanics Abstracts, 9(3), 325-328.
Garcia-Ochoa, F., Santos, V.E., Casas, J.A. and Gomez, E. (2000), ―Xanthan gum: production, recovery, and properties‖, Biotechnology Advances, 18(7), 549–579.
Glennie, K.W. (1998), The desert of SE Arabia: a product of climatic change. In: Alsharhan AS, Glennie KW, Whittle GL, Kendall CGStC (eds) Quaternary deserts and climatic change. Balkema, Rotterdam, 279-291.
Hassler, R.A., Doherty, D.H. (1990), ―Genetic engineering of polysaccharide structure: production of variants of xanthan gum in Xanthomonas campestris‖, Biotechnology Program, 6(3), 182–187
Ivanov, V. and Chu, J., (2008), ―Applications of microorganism to geotechnical engineering for bioclogging and biocementation of soil in situ‖, Rev Environ Sci Biotechnol, DOI 10.1007/s11157-007-9126-3.
Khachatoorian, R., Petrisor, I.G., Kwan, C.C. and Yen, T.F. (2003), ―Biopolymer plugging effect: Laboratory-pressurized pumping flow studies‖, J. Petroleum Sci. Eng., 38, 13–21.
Khatami, H. and O’Kelly, B. (2013), "Improving Mechanical Properties of Sand Using Biopolymers", J. Geotech. Geoenviron. Eng., 10.1061/(ASCE)GT.1943-5606.0000861, 1402-1406.
Milas, M. and Rinaudo, M. (1986), ―Properties of xanthan gum in aqueous solutions: role of the conformational transition‖, Carbohydrate Research, 158(1), 191–204.
Mitchell, J. K. and Santamarina, J. C. (2005), ―Biological Considerations in Geotechnical Engineering‖, Journal of Geotechnical and Geoenvironmental Engineering, 131(10), 1222-1233.
Nugent, R.A., Zhang, G. and Gambrell, R.P. (2009), ―Effect of exopolymers on the liquid limit of clays and its engineering implications‖, Transp. Res. Rec. J. Transp. Res. Board, 2101, 34–43.
Pease, P.P. and Tchakerian, V.P. (2003), ―Composition and sources of sand in the Wahiba Sand Sea, Sultanate of Oman‖, Can Geotech J., 40(5), 416-434.
Pease, P.P., Bierly, G.D., Tchakerian, V.P. and Tindale, N.W. (1999), ―Mineralogical characterization and transport pathways of dune sand using Landsat TM data, Wahiba Sand Sea, Sultanate of Oman‖, J Geomorphol., 29(3-4), 235-249.
Qureshi, M.U., Al-Qayoudhi, S., Al-Kendi, S., Al-Hamdani, A. and Al-Sadrani, K. (2015). ―The Effects of Slaking on the Durability of Bio-improved sand‖, International Journal of Scientific and Engineering Research, 6(11), 486-490.
Ramachandran, S. K., Ramakrishnan, V. and Bang, S. S. (2001), ―Remediation of concrete using micro-organisms‖, ACI Mater. J., 98(1), 3–9.
Smitha, S. and Sachan, A. (2016), "Use of agar biopolymer to improve the shear strength behavior of sabarmati sand", International Journal of Geotechnical Engineering, 10.1080/19386362.2016.1152674, 1-14, 10(4), 387-400
Sutterer, K.G., Frost, D.J., and Chameau, J.L.A. (1996), ―Polymer impregnation to assist undisturbed sampling of cohesionless soils‖, J. Geotech. Engrg, 122(3), 209-
215. Van de Velde, K. and Kiekens, P. (2002), ―Biopolymers: overview of several properties
and consequences on their applications‖, Polym Test, 21(4), 433–442 Vink, E.T.H., Rábago, K.R., Glassner, D.A. and Gruber, P.R. (2003) ―Applications of life
cycle assessment to NatureWorks™ polylactide (PLA) production‖, Polym Degrad Stab., 80(3), 403–419.
Worrell, E., Price, L., Martin, N., Hendriks, C. and Meida, L. O. (2001), ―Carbon dioxide emissions from the global cement industry‖, Annu Rev Energy Env, 26, 303–329.
Yevlampieva, N.P., Pavlov, G.M. and Rjumtsev, E.I. (1999), ―Flow birefringence of xanthan and other polysaccharide solutions‖, International Journal of Biological Macromolecules, 26(4), 295–301.