Sustainable Application of Wool-Banana Bio-Composite Waste Material in Geotechnical Engineering for Enhancement of Elastoplastic Strain and Resilience of Subgrade Expansive Clays
1
Department of Transportation Engineering and Management, Faculty of Civil Engineering, University of Engineering and Technology, Lahore 54890, Pakistan
2
Independent Researcher, Lahore 54792, Pakistan
*
Author to whom correspondence should be addressed.
Sustainability 2022, 14(20), 13215; https://doi.org/10.3390/su142013215
Submission received: 25 August 2022
/
Revised: 10 October 2022
/
Accepted: 11 October 2022
/
Published: 14 October 2022
(This article belongs to the Special Issue Geotechnical Engineering towards Sustainability)
Download keyboard_arrow_down
Figure 1
<p>Clay, wool and banana fiber materials.</p> "> Figure 2
<p>Clay material particle size distribution.</p> "> Figure 3
<p>The clay (C) and clay with wool (W), banana (B) and wool-banana (WB).</p> "> Figure 4
<p>UCS curves for optimal blends of clay, clay-wool (W), clay-banana (B) and clay-wool-banana (WB) blends.</p> "> Figure 5
<p>Failure patterns in clay and clay-fiber composite samples.</p> "> Figure 6
<p>Fibers in a portion of C + WB sample after failure.</p> "> Figure 7
<p>Cost of clay-fiber blends compared with M<sub>R</sub>, S<sub>p</sub> and CBR.</p> ">
Review Reports
Versions Notes
<p>Clay, wool and banana fiber materials.</p> "> Figure 2
<p>Clay material particle size distribution.</p> "> Figure 3
<p>The clay (C) and clay with wool (W), banana (B) and wool-banana (WB).</p> "> Figure 4
<p>UCS curves for optimal blends of clay, clay-wool (W), clay-banana (B) and clay-wool-banana (WB) blends.</p> "> Figure 5
<p>Failure patterns in clay and clay-fiber composite samples.</p> "> Figure 6
<p>Fibers in a portion of C + WB sample after failure.</p> "> Figure 7
<p>Cost of clay-fiber blends compared with M<sub>R</sub>, S<sub>p</sub> and CBR.</p> ">
Abstract
:Agro-biogenic stabilization of expansive subgrade soils is trending to achieve cost-effective and sustainable geotechnical design to resist distress and settlement during the application of heavy traffic loads. This research presents optimized remediation of expansive clay by addition of proportionate quantities of waste renewable wool-banana (WB) fiber composites for the enhancement of elastoplastic strain (ԐEP), peak strength (Sp), resilient modulus (MR) and California bearing ratio (CBR) of expansive clays. Remolded samples of stabilized and nontreated clay prepared at maximum dry density (γdmax) and optimum moisture content (OMC) were subjected to a series of swell potential, unconfined compressive strength (UCS), resilient modulus (MR) and CBR tests to evaluate swell potential, ԐEP, MR, and CBR parameters. The outcome of this study clearly demonstrates that the optimal WB fiber dosage (i.e., 0.6% wool and 1.2% banana fibers of dry weight of clay) lowers the free swell up to 58% and presents an enhancement of 3.5, 2.7, 3.0 and 4.5-times of ԐEPT, Sp, MR and CBR, respectively. Enhancement in ԐEP is vital for the mitigation of excessive cracking in expansive clays for sustainable subgrades. The ratio of strain relating to the peak strength (ԐPS) to the strain relating to the residual strength (ԐRS), i.e., ԐPS/ԐRS = 2.99 which is highest among all fiber-clay blend depicting the highly ductile clay-fiber mixture. Cost-strength analysis reveals the optimized enhancement of ԐEPT, Sp, MR and CBR in comparison with cost using clay plus 0.6% wool plus 1.2% banana fibers blend which depicts the potential application of this research to economize the stabilization of subgrade clay to achieve green and biogeotechnical engineering goals.
1. Introduction
Flexible pavements transfer heavy traffic loads to the subgrade and large settlements are expected in subgrades comprising expansive clays [1,2,3,4,5]. Peak strength (Sp), elasto-plastic strain (ԐEP) and resilient modulus (MR) are the significant geotechnical parameters required for design of durable subgrade layer. Weak expansive clays are encountered frequently in pavement subgrades, hence, the replacement of huge quantities of expansive clays with granular non-cohesive materials presents a challenge for the economy of the road infrastructures.
Consumer’s demand for the life cycle is increasing day-by-day for green construction materials and eco-environment, where plant and animal fibers are being used extensively with cement and polymers for the stabilization of weak clayey soils [6]. Post-peak strength of soil can be appreciably increased by the use of discrete randomly distributed fibers [7]. The extensive use of waste fibers has diverted the huge volumes of waste materials from landfill to construction projects for real benefits in the construction industry [8]. Past studies show that industrial waste materials are extensively used in stabilization of expansive soils for enhancement of compressive strength and reduction in swell potential [9,10,11,12,13]. Cement, lime, and fibers have been used in small to large projects for the last few decades as feasible stabilizers for the remediation of soft clays [14,15,16]. Cement and lime release CO2 in the environment causing an increase in carbon footprint which necessitates the use of green stabilizers, such as agricultural and animal fibers, to address the environmental concerns [17,18,19]. The use of fibers in soil stabilization are considered as eco-friendly alternatives to the lime and cement which are the main factors for emissions of greenhouse gases [20].
In recent practice, waste natural fibers are replacing the non-renewable synthetic fibers due to their recyclability and low cost [21]. The inclusion of waste virgin fibers in random fashion to ameliorate the expansive clay is the attractive aspect of soil stabilization to achieve ductility and high post-peak strength. A brittle failure pattern is changed to ductile failure by the inclusion of waste carpet fibers in unconfined compressive strength (UCS) test [22]. Composite fibers are being used in soil improvement due to the optimum use of characteristics of each fiber. The incorporation of fiber in clay improves ductility and compressive strength of the soil-fiber mixture which is observed as maximum level up to optimum moisture content (OMC) [23,24].
Clay-fibers mixtures affinity and their respective properties, e.g., strength and swell behavior were investigated and deliberated in recent study [25]. The inclusion of 0.6% PP fibers in clay caused an increase in apparent friction angle (ϕ) from 7.3° to 12.3° whereas apparent cohesion decreased from 105 kPa to 78 kPa [26]. Polypropylene (PP) fibers also increased the compressive strength and ductility of clay [27]. However, the PP fibers delayed the failure of the clay by increasing the elasto-plastic strain. The cracks in clay, due to their brittle behavior at low moisture content, can lower the performance of subgrade due to early initiation of cracks [28]. The brittleness and cracking potential of lime-treated plastic clay is also decreased by the addition of wheat-straw fibers by restraining the shear band where the strain-hardening is observed in fiber-reinforced clay due to mobilization of tensile strength of fibers [29]. The inclusion of fibers also changes the failure pattern in clay, i.e., brittle failure is changed to ductile failure due to increase in total strain. The brittleness of unsaturated clay depends upon residual strength and peak strength.
The rapid infrastructure and socioeconomic development necessitate the use of existing weak soils as road subgrades. The strain softening of the clays is very dangerous as it results in severe settlement. Strain-hardening can be achieved in clays by the addition of fibers. Usually, the fibers are randomly and uniformly distributed in soil. The distribution of fibers (fibers-soil friction and interlocking) restricts the movement of soil particles in all directions, hence, limiting the deformation in soil [30].
Waste natural agricultural fibers are being used as construction materials for the enhancement of unconfined compressive strength (UCS) and California bearing ratio (CBR) index and reduction in carbon footprints to achieve environmentally friendly pavement projects [31,32,33].
Wool fibers are used globally for the enhancement of comfort in domestic use. Wool has been demanded for the domestic use in fabric for thousands of years and produces the largest part of the waste, presenting a challenge to landfill infrastructure and the environment [8,34]. Animal wool fibers are strong enough to cause the enhancement of compressive strength of weak clay soils [35].
Banana fibers are abundant low-cost waste fibers, which are available in large quantities for use in clay stabilization. The banana fibers are an important reinforcing material in composites [36]. The demand for low-cost soil stabilization is the need of society. Banana fibers comprise high cellulose material and low micro-fibril angle which play an important role in clay stabilization. The increase in UCS of clay by the addition of fibers is dependent on the initial dry density and initial moisture content, hence, mixing the moisture in field is an important parameter for clay stabilization [37].
Past research on fiber reinforced clays showed that animal and agricultural fibers are rarely used in conjunction. Instead, the chemical stabilization of clay by lime and cement is common. The waste animal and agricultural fibers are abundant; hence, they exert immense pressure on landfill infrastructure. The present environmental scenario necessitates the use of waste animals and agricultural fibers as an alternative to the chemical stabilization for the enhancement of the geotechnical parameters of clays. Studies on the use of agro-biogenic fibers, i.e., wool (biogenic)-banana (agriculture) fibers composite for the enhancement of elastoplastic strain (ԐEPT), peak strength (Sp), residual strength (Sr) and resilient modulus (MR) of clays, are rare in literature.
Following are the objectives of the study:
- i.
- Evaluation of the optimal doses of agro-biogenic fibers, i.e., wool, banana and wool-banana composite for amelioration of expansive clay.
- ii.
- Optimum quantification of free swell, ԐEPT, Sp, MR, and CBR parameters for individual fibers (wool and banana) and composite fibers (wool plus banana).
- iii.
- Evaluation of impact of increase in moisture content on the strength and resilience of optimum blend.
- iv.
- Statistical analysis of datasets for the evaluation of data health.
2. Materials and Methods
Three types of materials were selected for this research, namely high swelling clay (C), wool (W) and banana (B) fibers. Physical samples of three materials used are shown in Figure 1.
The clay is initially dried in sunlight as the oven drying of clay causes the loss of organic matter which can result in lowering of plasticity index (PI). The typical characteristics of expansive clay used with respective testing standards are tabulated in Table 1 below.
Figure 2 shows the typical gradation curve of clay obtained by hydrometer test analysis (ASTM D7928).
Wool fibers are eco-friendly as these fibers are biodegradable over the years in soil with good natural phenomena of release of natural ingredients to the soil making the soil suitable for growing the grass where the grass additionally lowers the erosion of clay particles in wet seasons. The wool fibers are considered as breathable fibers as these fibers absorb the moisture and then release the moisture vapors into the air. Hence, wool fibers do not permanently retain the higher moisture. This breathing property of wool fibers is most feasible for wetting and drying. The properties of wool fibers used are summarized in Table 2.
The banana fibers are hydrophilic (water absorbing) in nature which can be changed to hydrophobic (water resistant) by treatment for use as reinforcing material [38,39]. Banana fibers were drawn from pseudo-stem and dried in air at average temperature of 18 °C for 3 days. Treatment was then provided to remove lignin and hemicellulose from the surface of banana fibers [40]. Initially, during treatment the banana fibers were washed by 2% detergent-water and air dried. Then, fibers were soaked in 5% NaOH aqueous solution for one hour, washed with distilled water and dried up to 43 °C. The banana fibers index properties are tabulated below in Table 3.
The specific percentages of wool and banana fibers were selected as per guidelines of past studies available in literature [6,35,38,39]. Three types of clay-fiber mixtures were prepared, i.e., clay plus wool fibers, clay plus banana fibers and clay plus wool-banana composite. Wool fibers in the proportions of 0.2%, 0.4%, 0.6% and 0.8% and banana fibers in the proportions of 0.4%, 0.8%, 1.2% and 1.6% were mixed in clay on individual basis (i.e., wool and banana) and on composite-fibers basis (wool plus banana). The fibers were separated by wire brush before and after mixing with clay for uniform distribution of fibers. All the mixtures in this study were prepared with random mixing of fibers to ensure the absence of any potential weak plane. The random mixing of fibers has significant advantage in the economy of roads construction due to simple and fast in situ mixing process [41,42]. Twenty-four mixtures were prepared with variable fiber content. Modified compaction tests were performed as per ASTM D 1557 [43]. Modified compaction tests were opted for use of higher density in subgrade design for heavy traffic. All the remolded samples were prepared at maximum dry density (γdmax) and optimum moisture content (OMC) determined from modified proctor compaction tests. The testing program details are presented in Table 4.
Free swell tests as per ASTM D4546, were performed for clay and all the blends. Unconfined compressive strength (UCS) tests were performed as per ASTM D 2166 [44] for the evaluation of peak shear strength as per schedule mentioned in Table 4. UCS samples were prepared in length to diameter (L/D) ratio of 2. Samples were cured for 24 h as design input parameter for stabilized subgrade soils. UCS tests were conducted at the strain rate of 1 mm/min in vertical axial direction. Remolded samples for unconfined compression tests are shown in Figure 3.
Resilient modulus (MR) tests were performed according to the test procedure outlined in AASHTO T-307 [45]. The aspect (L/D) ratio of 2 was used during samples preparation. California bearing ratio (CBR) tests were performed as per ASTM D1883 [46], respectively. Standard dead load (10 lbs) was applied in the saturation and shearing phase of the CBR test.
3. Results and Discussion
Grain size tests showed proportions of sand, silt and clay as 3%, 28% and 69%, respectively. The plasticity index (PI) of clay samples were evaluated as 41%. According to ASTM D2487, the parent clay was classified as “high plastic clay i.e., CH”. Specific gravity (Gs) of the clay soil was evaluated as 2.69 as per ASTM D854 and natural moisture content (NMC) as 26.3% as per ASTM D 2216.
Presented in Table 5 is the effect of individual fibers, i.e., wool fibers and banana fiber along with the effect of wool plus banana fiber composite on the geotechnical properties of high plastic swelling clay to be used in road subgrade. It was observed that with specific proportions of wool fibers, i.e., 0.2%. 0.4%, 0.6% and 0.8% of dry weight of clay, a decrease of 6.5%, 13%, 16% and 25.8% of free swell was observed, respectively. The comparison of effect of individual fibers and composite fibers on swell potential in Table 5 shows that optimal content of mixtures, i.e., (C + 0.6% W), (C + 1.2% B), (C + 0.2% W + 1.2% B), (C + 0.4% W + 1.2% B), (C + 0.6% W + 1.2% B) and (C + 0.8% W + 1.2% B) show a decreasing trend of swell potential whereas it was observed that mixing of the optimum content of WB composite with clay, i.e., clay plus 0.6% wool plus 1.2% banana fibers, showed a 58% reduction in free swell potential.
The peak strength (Sp) of clay and clay-fiber mixtures can be evaluated as the maximum stress determined from the stress-strain curve of UCS test. Presented in Figure 4 are the stress-strain curves of the clay, clay plus individual fibers and clay plus composite fibers. It was observed that specific proportions of wool fibers, i.e., 0.2%. 0.4%, 0.6% and 0.8% of dry weight of clay, an increase of 1.06, 1.27, 1.38 and 1.19-times of peak strength (Sp) of untreated clay was observed, respectively. Banana fibers in the proportion of 0.4%. 0.8%, 1.2% and 1.6% of the dry weight of clay, caused a 1.04, 1.15, 1.21 and 1.1-times increase in UCS of expansive clay, respectively. It was observed that the mixing of the optimum content of WB composite with clay, i.e., clay plus 0.6% wool plus 1.2% banana fibers, showed a 2.67-times enhancement in Sp. The clay-fiber blends showed high strength as compared to the nontreated clay. Hence, the ratio of clay-fiber strength (SCF) to the nontreated clay strength (SC), i.e., SCF/SC increases with increase in fiber content. The data shows that composite fibers, i.e., wool plus banana are more effective as compared to individual fibers, i.e., wool and banana for the enhancement of peak strength (Sp).
Figure 4 shows the three parts of the stress-strain curve as elastic, elasto-plastic and plastic. The elasto-plastic portion of the curve is very critical in the failure phenomena for the assessment of failure time. The strain involving the elasto-plastic portion of the stress-strain curve is the elasto-plastic transition strain (ԐEPT) after which the strain increases in plastic manner resulting in the complete failure of clay. However, the ԐPS/ԐRS decreases as the fiber content increases more than optimal dose for all type of clay-fiber blends due to increase in total strain up to the residual strength level. It was also observed that total strain was also increased with the increase in fiber content.
The inclusion of fibers in clay relatively transforms its brittle behavior into ductile. This may be is due to enhanced strain in the elasto-plastic portion of clay-fiber mixtures stress-strain curve. The following steps elaborate the behavior of the clay-fiber mixtures:
- Elastic phase:
The compression of clay starts and the stress is transferred from grain to grain. Additionally, the elasticity of fibers starts mobilizing and shows combined effect with elasticity of clay.
- Elasto-plastic phase:
The elasto-plastic strain of clay-fiber mixture increases due to full mobilization of elasticity of fibers. At this stage, the brittle failure of the clay is changed to ductile due to the delayed failure caused by enhanced strain (due to fibers).
- Plastic strain:
The plastic strain at the failure stage is enhanced due to relative movement between clay particles and the fiber surface.
Hence, the strain increases in elastic, elasto-plastic and plastic phases of the stress-strain curve of clay-fiber mixtures due to inclusion of fibers resulting in the change in brittle behavior to ductile behavior.
It was also observed that the failure pattern in UCS test samples was gradually transformed from brittle to the ductile phase as the inclusion of fibers caused lateral bulging in samples making the samples barrel shaped. Figure 5a,d show the failure patterns of clay, clay plus wool, clay plus banana and clay plus wool-banana (WB) composite. The brittle behavior of clay (Figure 5a) changed to ductile Figure 5b–d.
Figure 6 shows typical wool and banana fibers orientation in clay sample after failure in UCS test.
Post peak straining behavior was analyzed for clay and clay-fiber mixtures. It was observed that the ratio of strain related to peak strength (ԐPS) to the strain related to residual strength (ԐRS), i.e., ԐPS/ԐRS increases with increase in fiber content. Hence, the brittle failure observed in clay samples (Figure 5a) is changed to ductile failure (Figure 5b–d). However, the ԐPS/ԐRS decreases as the fiber content increases more than optimal dose for all type of clay-fiber blends. It was observed that clay and optimal blends of clay-fiber mixtures, i.e., C, (C + 0.6% W), (C + 1.2% B), (C + 0.2% W + 1.2% B), (C + 0.4% W + 1.2% B), (C + 0.6% W + 1.2% B) and (C + 0.8% W + 1.2% B) showed ԐPS/ԐRS as 1.41, 2.02, 1.87, 2.03, 2.09, 2.99 and 2.73, respectively. It is inferred that the blend of clay plus 0.6% wool + 1.2% banana was observed as the most influential among all studied blends as it showed ԐPS/ԐRS = 2.99 which is highest among all fiber-clay blends, depicting the high ductility mixture.
Presented in Table 5 is the effect of individual fibers, i.e., wool fibers and banana fibers along with the effect of wool plus banana fiber composite on the resilient modulus (MR) of high plastic swelling clay. MR tests were performed on the samples which showed optimal trend in peak strength (Sp) during unconfined compressive strength (UCS) test. It was observed that optimal blends, i.e., (C + 0.6% W), (C + 1.2% B), (C + 0.2% W + 1.2% B), (C + 0.4% W + 1.2% B), (C + 0.6% W + 1.2% B) and (C + 0.8% W + 1.2% B) showed 1.45, 1.26, 1.95, 2.29, 2.95 and 2.70-times MR of the nontreated clay. The study showed that clay plus 0.6% wool + 1.2% banana mixture presented the highest MR value among all clay-fiber blends.
A slight decrease in maximum dry density (γdmax) and a considerable increase in optimum moisture content (OMC), in modified compaction test, was observed because of the addition of wool and banana fibers in high plastic expansive clay. The decrease in γdmax was seen as 11%, 14.2% and 18.7% in case of optimized content of wool, banana, and wool plus banana composite blends, i.e., (C + 0.6% W), (C + 1.2% B) and (C + 0.6% W + 1.2% B), respectively. It was observed that optimal blends, i.e., (C + 0.6% W), (C + 1.2% B), (C + 0.2% W + 1.2% B), (C + 0.4% W + 1.2% B), (C + 0.6% W + 1.2% B) and (C + 0.8% W + 1.2% B) showed 2.2, 1.6, 4.0, 4.3, 4.5 and 3.3-times CBR as compared with nontreated clay. It was observed that clay plus 0.6% wool + 1.2% banana presented the highest CBR value among all clay-fiber studied mixtures. It is inferred that the clay plus composite fibers enhanced the CBR of clay substantially as compared to the individual fibers. Hence, the use of WB composite fibers is most feasible for use in subgrade clay.
An attempt was also made to increase the moisture content of optimized blend, i.e., clay + 0.6% wool + 1.2% banana fibers to assess the impact of wet conditions on the optimized reinforced clay. Moisture content (MC) was increased from 16.3% (OMC) to 26% (wet condition) which caused a decrease in peak strength from 128 kPa (at OMC) to 50 kPa (at 26% moisture). This aspect showed that the blend, i.e., clay + 0.6% wool + 1.2% banana fibers, works well in wet seasonal conditions also.
The datasets for the free swell, ԐEP, MR, and CBR parameters for individual fibers (wool and banana) and composite fibers (wool plus banana) were analyzed by analysis of variance (ANOVA). The results showed good data health and no outlier was identified validating the data for confident application to geotechnical challenges encountered in stabilization of weak and expansive clays. ANOVA was performed for the data of swell potential, ԐEP, MR, and CBR values which authenticated the reliability of results of this research for use in stabilization of subgrade clay with confidence as shown in Table 6.
The comparison of cost versus peak strength (Sp), resilient modulus (MR) and CBR for optimal composites of clay plus wool (W) and banana (B) fibers is very important for use in pavement subgrade design by remediation of high expansive clay.
In the field, the cost stabilization of clay with the use of fibers mainly depends upon (i) cost of fibers (ii) cost of blending equipment, (iii) cost of labor for mixing (iv) cost of spreading and (v) cost of compaction of stabilized clay. Hence, the cost analysis in this study only covered the cost of waste wool and banana fibers to achieve cost-effective optimum values of free swell, ԐEPT, Sp, MR, and CBR parameters for treatment of one ton of clay.
The average cost of waste wool fibers is $8/Kg and cost of waste banana fibers is $3/Kg. The banana fibers are available abundantly at a low cost, which infers that optimum quantities of banana fibers can be used for the amelioration of subgrade clay. The optimal blends of wool, banana and wool-banana composite fibers are 0.6%, 1.2% and 0.6% plus 1.2%, respectively. It is observed in Figure 7 that the optimal blends of wool plus banana, i.e., 0.6% wool plus 1.2% banana fibers showed higher peak strength (Sp), resilient modulus (MR) and California bearing ratio (CBR) as compared with cost.
Figure 7 shows that the Sp, MR and CBR of the clay (C)-wool (W)-banana (B) blends increase with the increase in wool and banana fiber contents and the optimal ratio of 0.6% wool (W) plus 1.2% banana (B) fibers show comparatively higher Sp, MR and CBR validating the cost-effective solution for agro-biogenic stabilization of subgrade clay.
4. Conclusions
The basic aim of this study was the sustainable eco-stabilization of the high-plasticity expansive clay of roads subgrade material by green agro-biogenic waste fibers. This research illustrates the optimized melioration of subgrade material by using waste wool, banana, and wool-banana fiber composites. Swell potential, peak strength (Sp), elasto-plastic strain (ԐEPT), resilient modulus (MR) and CBR of clay-fiber blends were evaluated in the study for remolded samples of untreated and clay-fiber blends prepared at maximum dry density (γdmax) and optimum moisture content (OMC). The following conclusions were addressed in this study:
- (1)
- The optimal composite blend of subgrade clay and waste fibers were observed as clay plus 0.6% wool fibers, 1.2% banana fibers. The outcome of this study clearly demonstrates that elastoplastic transition strain (ԐEP), peak strength (Sp), resilient modulus (MR) and CBR parameters were enhanced by 3.5, 2.7, 3.0 and 4.5-times, respectively for the optimal blend as compared with nontreated clay. This novel achievement of the enhancement of most significant geotechnical parameters up to 270% to 450% is a valuable addition to the existing literature for geotechnical and pavement engineers.
- (2)
- The optimal blend (clay + 0.6% wool + 1.2% banana fibers) evaluated showed the ratio of strain relating to the peak strength (ԐPS) to the strain relating to the residual strength (ԐRS), i.e., ԐPS/ԐRS as 2.99, which is highest among all fiber-clay blend depicting the ductile clay-fiber mixture.
- (3)
- The moisture content (MC) of optimal blend (i.e., clay + 0.6% wool + 1.2% banana fibers) was increased from 16.3% (OMC) to 26% (wet condition) which caused a decrease in peak strength from 128 kPa (at OMC) to 50 kPa (at 26% moisture). This aspect showed that the optimal blend works well in wet seasons. Hence, the “Moisture-Efficient Blend” was achieved in this research.
- (4)
- The study of the swell behavior shows the reduction of free swell potential up to 58%, depicting the feasibility of using optimal composite fibers dose in subgrades in response to wet season.
The study should be extended to different lengths of wool and banana fibers to explore the optimum length with optimum contents. The optimization of the strength and durability of blends is the function of fiber length. Exploring the strength and durability of clay with “two optimums i.e., content and length” will be another novel research.
Author Contributions
Conceptualization, A.H.K.; methodology, W.Q., A.H.K. and Z.u.R.; software, W.Q.; validation, W.Q., A.H.K. and Z.u.R.; formal analysis, W.Q., A.H.K. and Z.u.R.; investigation, W.Q., A.H.K. and Z.u.R.; resources, W.Q., A.H.K., Z.u.R. and Z.M.; data curation, W.Q. and A.H.K.; writing—original draft preparation, W.Q.; writing—review and editing, A.H.K., Z.u.R. and Z.M.; visualization, A.H.K. and Z.u.R.; supervision, A.H.K. and Z.u.R.; project administration, A.H.K. and Z.u.R.; funding acquisition, A.H.K. and Z.u.R. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Soltani, A.; Taheri, A.; Khatibi, M.; Estabragh, A.R. Swelling potential of a stabilized expansive soil: A comparative experimental study. Geotech. Geol. Eng. 2017, 35, 1717–1744. [Google Scholar] [CrossRef]
- Onyelowe, K.; Van, D.B.; Eberemu, A.; Xuan, M.N.; Salahudeen, A.B.; Ezugwu, C.; Van, M.N.; Orji, F.; Sosa, F.; Duc, T.T.; et al. Sorptivity, swelling, shrinkage, compression and durability of quarry dust treated soft soils for moisture bound pavement geotechnics. J. Mater. Res. Technol. 2019, 8, 3529–3538. [Google Scholar] [CrossRef]
- Ghorbani, A.; Hasanzadehshooiili, H.; Mohammadi, M.; Sianati, F.; Salimi, M.; Sadowski, L.; Szymanowski, J. Effect of selected nanospheres on the mechanical strength of lime-stabilized high-plasticity clay soils. Adv. Civ. Eng. 2019, 2019, 4257530. [Google Scholar] [CrossRef]
- Mirzababaei, M.; Karimiazar, J.; Sharifi Teshnizi, E.; Arjmandzadeh, R.; Bahmani, S.H. Effect of Nano-Additives on the Strength and Durability Characteristics of Marl. Minerals 2021, 11, 1119. [Google Scholar] [CrossRef]
- Karimiazar, J.; Sharifi Teshnizi, E.; Mirzababaei, M.; Mahdad, M.; Arjmandzadeh, R. California bearing ratio of a reactive clay treated with nano-additives and cement. J. Mater. Civ. Eng. 2022, 34, 04021431. [Google Scholar] [CrossRef]
- Galan-Marin, C.; Rivera-Gomez, C.; Petric, J. Clay-based composite stabilized with natural polymer and fibre. Constr. Build. Mater. 2010, 24, 1462–1468. [Google Scholar] [CrossRef]
- Hejazi, S.M.; Sheikhzadeh, M.; Abtahi, S.M.; Zadhoush, A. A simple review of soil reinforcement by using natural and synthetic fibers. Constr. Build. Mater. 2012, 30, 100–116. [Google Scholar] [CrossRef]
- Marino, C.; Nucara, A.; Nucera, G.; Pietrafesa, M. Economic, energetic and environmental analysis of the waste management system of Reggio Calabria. Int. J. Heat Technol. 2017, 35, S108–S116. [Google Scholar] [CrossRef]
- Giro-Paloma, J.; Formosa, J.; Chimenos, J.M. Stabilization Study of a Contaminated Soil with Metal(loid)s Adding Different Low-Grade MgO Degrees. Sustainability 2020, 12, 7340. [Google Scholar] [CrossRef]
- Türköz, M.; Umu, S.U.; Öztürk, O. Effect of Silica Fume as a Waste Material for Sustainable Environment on the Stabilization and Dynamic Behavior of Dispersive Soil. Sustainability 2021, 13, 4321. [Google Scholar] [CrossRef]
- Cristelo, N.; Rivera, J.; Miranda, T.; Fernández-Jiménez, A. Stabilisation of a Plastic Soil with Alkali Activated Cements Developed from Industrial Wastes. Sustainability 2021, 13, 4501. [Google Scholar] [CrossRef]
- Seco, A.; del Castillo, J.M.; Espuelas, S.; Marcelino-Sadaba, S.; Garcia, B. Stabilization of a Clay Soil Using Cementing Material from Spent Refractories and Ground-Granulated Blast Furnace Slag. Sustainability 2021, 13, 3015. [Google Scholar] [CrossRef]
- Seco, A.; del Castillo, J.M.; Perlot, C.; Marcelino-Sádaba, S.; Prieto, E.; Espuelas, S. Experimental Study of the Valorization of Sulfate Soils for Use as Construction Material. Sustainability 2022, 14, 6609. [Google Scholar] [CrossRef]
- Cuisinier, O.; Auriol, J.C.; le Borgne, T.; Deneele, D. Microstructure and hydraulic conductivity of a compacted lime-treated soil. Eng. Geol. 2011, 123, 187–193. [Google Scholar] [CrossRef]
- Fatahi, B.; Le, T.M.; Fatahi, B.; Khabbaz, H. Shrinkage properties of soft clay treated with cement and geofibers. Geotech. Geol. Eng. 2013, 31, 1421–1435. [Google Scholar] [CrossRef]
- Kazmi, S.M.S.; Abbas, S.; Munir, M.J.; Khitab, A. Exploratory study on the effect of waste rice husk and sugarcane bagasse ashes in burnt clay bricks. Build. Eng. 2016, 7, 372–378. [Google Scholar] [CrossRef]
- Wang, Y.; Guo, P.; Li, X.; Lin, H.; Liu, Y.; Yuan, H. Behavior of fiber-reinforced and lime-stabilized clayey soil in triaxial tests. Appl. Sci. 2019, 9, 900. [Google Scholar] [CrossRef] [Green Version]
- Lemos, S.G.F.P.; Almeida, M.D.S.S.; Consoli, N.C.; Nascimento, T.Z.; Polido, U.F. Field and Laboratory Investigation of Highly Organic Clay Stabilized with Portland Cement. J. Mater. Civ. Eng. 2020, 32, 04020063. [Google Scholar] [CrossRef]
- Nasiri, H.; Khayat, N.; Mirzababaei, M. Simple yet quick stabilization of clay using a waste by-product. Transp. Geotech. 2021, 28, 100531. [Google Scholar] [CrossRef]
- Aygormez, Y.; Canpolat, O.; Al-mashhadani, M.M.; Uysal, M. Elevated temperature, freezing-thawing and wetting-drying effects on polypropylene fiber reinforced metakaolin based geopolymer composites. Constr. Build. Mater. 2020, 235, 117502. [Google Scholar] [CrossRef]
- Mejia Osorio, J.C.; Rodríguez Baracaldo, R.; Olaya Florez, J.J. The influence of alkali treatment on banana fibre’s mechanical properties. Ing. Investig. 2012, 32, 83–87. [Google Scholar]
- Mirzababaei, M.; Miraftab, M.; Mohamed, M.; McMahon, P. Unconfined compression strength of reinforced clays with carpet waste fibers. J. Geotech. Geoenvironmental Eng. 2013, 139, 483–493. [Google Scholar] [CrossRef]
- Arabani, M.; Haghsheno, H. The effect of water content on shear and compressive behavior of polymeric fiber-reinforced clay. SN Appl. Sci. 2020, 2, 1759. [Google Scholar] [CrossRef]
- Silveira, M.R.; Rocha, S.A.; Correia, N.D.; Rodrigues, R.A.; Giacheti, H.L.; Lodi, P.C. Effect of Polypropylene Fibers on the Shear Strength–Dilation Behavior of Compacted Lateritic Soils. Sustainability 2021, 13, 12603. [Google Scholar] [CrossRef]
- Taleb, T.; Unsever, Y.S. Study on Strength and Swell Behavioral Change and Properties of the Clay–Fiber Mixtures. Sustainability 2022, 14, 6767. [Google Scholar] [CrossRef]
- Yue, J.; Chen, Y.; Zhao, L.; Wang, S.; Su, H.; Yang, X.; Gao, H.; Zhang, Y.; Li, W. Effects of Aging on the Dry Shrinkage Cracking of Lime Soils with Different Proportions. Appl. Sci. 2021, 12, 145. [Google Scholar] [CrossRef]
- Abdi, M.R.; Ghalandarzadeh, A.; Chafi, L.S. An investigation into the effects of lime on compressive and shear strength characteristics of fiber-reinforced clays. J. Rock Mech. Geotech. Eng. 2021, 13, 885–898. [Google Scholar] [CrossRef]
- Tang, C.S.; Shi, B.; Zhao, L.Z. Interfacial shear strength of fiber reinforced soil. Geotext. Geomembr. 2010, 28, 54–62. [Google Scholar] [CrossRef]
- Wang, Y.-X.; Guo, P.-P.; Ren, W.-X.; Yuan, B.-X.; Yuan, H.-P.; Zhao, Y.-L.; Shan, S.-B.; Cao, P. Laboratory investigation on strength characteristics of expansive soil treated with jute fiber reinforcement. Int. J. Geomech. 2017, 17, 04017101. [Google Scholar] [CrossRef]
- Liu, J.; Li, X.A.; Li, G.; Zhang, J. Investigation of the Mechanical Behavior of Polypropylene Fiber-Reinforced Red Clay. Appl. Sci. 2021, 11, 10521. [Google Scholar] [CrossRef]
- Lang, L.; Chen, B.; Li, N. Utilization of lime/carbide slag-activated ground granulated blast-furnace slag for dredged sludge stabilization. Mar. Georesources Geotechnol. 2020, 39, 659–669. [Google Scholar] [CrossRef]
- Gu, K.; Chen, B. Research on the incorporation of untreated flue gas desulfurization gypsum into magnesium oxysulfate cement. J. Clean. Prod. 2020, 271, 122497. [Google Scholar] [CrossRef]
- Lang, L.; Chen, B.; Duan, H. Modification of nanoparticles for the strength enhancing of cement-stabilized dredged sludge. J. Rock Mech. Geotech. Eng. 2021, 13, 694–704. [Google Scholar] [CrossRef]
- Rahman, S.S.; Siddiqua, S.; Cherian, C. Sustainable applications of textile waste fiber in the construction and geotechnical industries: A retrospect. Clean. Eng. Technol. 2022, 6, 100420. [Google Scholar] [CrossRef]
- Galan-Marín, C.; Rivera-Gómez, C.; Petric-Gray, J. Effect of animal fibres reinforcement on stabilized earth mechanical properties. J. Biobased Mater. Bioenergy 2010, 4, 121–128. [Google Scholar] [CrossRef]
- Herrera-Franco, P.J.; Valadez-González, A. Mechanical properties of continuous natural fibre-reinforced polymer composites. Compos. Part A 2004, 35, 339–345. [Google Scholar] [CrossRef]
- Li, Q.; Chen, J.H.; Hu, H.X. The tensile and swelling behavior of cement-stabilized marine clay reinforced with short waste fibers. Mar. Georesources Geotechnol. 2019, 37, 1236–1246. [Google Scholar] [CrossRef]
- Mamunur Rashid, M.; Samad, S.A.; Gafur, M.A.; Qadir, R.; Chowdhury, A.M. Effect of reinforcement of hydrophobic grade banana (musa ornata) bark fiber on the physicomechanical properties of isotactic polypropylene. Int. J. Polym. Sci. 2016, 2016, 9017956. [Google Scholar] [CrossRef] [Green Version]
- Motaleb, K.Z.M.; Mizan, R.A.; Milašius, R. Development and characterization of eco-sustainable banana fiber nonwoven material: Surface treatment, water absorbency and mechanical properties. Cellulose 2020, 27, 7889–7900. [Google Scholar] [CrossRef]
- Wang, B.; Panigrahi, S.; Tabil, L.; Crerar, W.; Sokansanj, S.; Braun, L. Modification of flax fibers by chemical treatment. In Proceedings of the CSAE/SCGR Meeting, Montreal, QC, Canada, 6–9 July 2003; pp. 3–337. [Google Scholar]
- Yetimoglu, T.; Salbas, O. A study on shear strength of sands reinforced with randomly distributed discrete fibers. J. Geotext. Geomembr. 2003, 21, 103–110. [Google Scholar] [CrossRef]
- Ferreira da Costa, L.; Lucena, L.C.; Lucena, A.E.; Grangeiro de Barros, A. Use of Banana fibers in SMA mixtures. J. Mater. Civ. Eng. 2020, 32, 04019341. [Google Scholar] [CrossRef]
- ASTM D1557-12; Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort, Annual Book of ASTM Standards. American Society for Testing and Materials: Philadelphia, PA, USA, 2021; Volume 4.
- ASTM D2166-91; Standard Test Method for Unconfined Compressive Strength of Cohesive Soil, Designation D 2166-91: Annual Book of ASTM Standards. American Society for Testing and Materials: Philadelphia, PA, USA, 2017; Volume 4.
- AASHTO T307-03; Determining the Resilient Modulus of Soils and Aggregate Materials, Standard Specifications for Transportation Materials and Methods of Sampling and Testing. American Association of State Highway and Transportation Officials: Washington, DC, USA, 2013.
- ASTM D1883-16; Standard Test Method for California Bearing Ratio (CBR) of Laboratory-Compacted Soils, Annual Book of ASTM Standards. American Society for Testing and Materials: Philadelphia, PA, USA, 2016; Volume 4.
Figure 1.
Clay, wool and banana fiber materials.
Figure 2.
Clay material particle size distribution.
Figure 3.
The clay (C) and clay with wool (W), banana (B) and wool-banana (WB).
Figure 4.
UCS curves for optimal blends of clay, clay-wool (W), clay-banana (B) and clay-wool-banana (WB) blends.
Figure 4.
UCS curves for optimal blends of clay, clay-wool (W), clay-banana (B) and clay-wool-banana (WB) blends.
Figure 5.
Failure patterns in clay and clay-fiber composite samples.
Figure 6.
Fibers in a portion of C + WB sample after failure.
Figure 7.
Cost of clay-fiber blends compared with MR, Sp and CBR.
Table 1.
Properties of clay.
| Property/Constituent | Value ^ |
|---|---|
| Dry density (g/cm3) ASTM 1557 | 1.98 |
| OMC (%) ASTM 1557 | 16.3 |
| Liquid limit (%) ASTM 4318 | 77 |
| Plastic limit (%) ASTM4318 | 36 |
| Plasticity index (%) ASTM4318 | 41 |
| Free swell potential (%) ASTM 4546 | 31 |
| Swell pressure (kPa) ASTM4546 | 237 |
| Compression index ASTM4546 | 0.46 |
| Cohesion (kPa) ASTM 4767 | 59 |
| Friction angle (degree) ASTM4767 | 12 |
| Specific gravity (Gs) ASTM D854 | 2.69 |
| Clay (%) | 69 |
| Silt (%) | 28 |
| Sand (%) | 3 |
| USCS classification ASTM D2487 | CH |
^ Average value of three replicates.
Table 2.
Index properties of wool fibers.
| Property | Value |
|---|---|
| Breaking strain | |
| Dry | 19–38% |
| Wet | 32–53% |
| Specific gravity | 1.29 |
| Length (mm) | 23–31 mm |
| Color | white/brown |
| Moisture (%) | 21% |
| Recovery at strain | |
| 4% | 56% |
| 8% | 37% |
| Diameter (mm) | 0.136–0.214 |
Table 3.
Index properties of banana fibers.
| Constituent/Property | Value |
|---|---|
| Diameter (mm) | 0.245–0.311 |
| Natural moisture content (%) | 67 |
| Elongation at break (%) | 1.9–4.7 |
| Cellulose content (%) | 64 |
| Density (g/cm3) | 1.23 |
| Length (mm) | 28–46 |
| Ultimate strain (%) | 4.1–5.7 |
| Specific gravity | 1.17 |
| Color | brown |
Table 4.
(a)—matrix of tests on clay (C) plus wool (W) composite; (b)—matrix of tests on clay (C) plus banana (B) composite; (c)—matrix of tests on expansive clay (C) plus wool-banana (WB) composite.
Table 4.
(a)—matrix of tests on clay (C) plus wool (W) composite; (b)—matrix of tests on clay (C) plus banana (B) composite; (c)—matrix of tests on expansive clay (C) plus wool-banana (WB) composite.
| Sr No. | Mixtures ID | Swell Potential ^ | UCS ^ | Resilient Modulus ^ | CBR ^ |
|---|---|---|---|---|---|
| (a) | |||||
| 1 | C | * | * | * | * |
| 2 | C + 0.2% W | * | * | ||
| 3 | C + 0.4% W | * | * | ||
| 4 | C + 0.6% W | * | * | * | * |
| 5 | C + 0.8% W | * | * | ||
| (b) | |||||
| 1 | C + 0.4% B | * | * | ||
| 2 | C + 0.8% B | * | * | ||
| 3 | C + 1.2% B | * | * | * | * |
| 4 | C + 1.6% B | * | * | ||
| (c) | |||||
| 1 | C + 0.2% W + 0.4% B | * | * | ||
| 2 | C + 0.2% W + 0.8% B | * | * | ||
| 3 | C + 0.2% W + 1.2% B | * | * | * | * |
| 4 | C + 0.2% W + 1.6% B | * | * | ||
| 5 | C + 0.4% W + 0.4% B | * | * | ||
| 6 | C + 0.4% W + 0.8% B | * | * | ||
| 7 | C + 0.4% W + 1.2% B | * | * | * | * |
| 8 | C + 0.4% W + 1.6% B | * | * | ||
| 9 | C + 0.6% W + 0.4% B | * | * | ||
| 10 | C + 0.6% W + 0.8% B | * | * | ||
| 11 | C + 0.6% W + 1.2% B | * | * | * | * |
| 12 | C + 0.6% W + 1.6% B | * | * | ||
| 13 | C + 0.8% W + 0.4% B | * | * | ||
| 14 | C + 0.8% W + 0.8% B | * | * | ||
| 15 | C + 0.8% W + 1.2% B | * | * | * | * |
| 16 | C + 0.8% W + 1.6% B | * | * | ||
^ Average value of three replicates, UCS—unconfined compression test, CBR—California bearing ratio test. * tests performed.
Table 5.
(a)—matrix of test results for clay and clay plus wool; (b)—matrix of test results for clay plus banana; (c)—matrix of test results for clay plus wool and banana.
Table 5.
(a)—matrix of test results for clay and clay plus wool; (b)—matrix of test results for clay plus banana; (c)—matrix of test results for clay plus wool and banana.
| Sr No. | Mixtures ID | Free Swell Potential (%) | UCS Test Parameters | CBR (%) | Resilient Modulus, (MPa) | |||
|---|---|---|---|---|---|---|---|---|
| Elastoplastic Strain (%) | Peak Strength (kPa) | SCF/SC | ԐPS/ԐRS | |||||
| (a) | ||||||||
| 1 | C | 31 | 1.51 | 48 | - | 1.41 | 3.4 | 80 |
| 2 | C + 0.2% W | 29 | 1.75 | 51 | 1.06 | 1.57 | ||
| 3 | C + 0.4% W | 27 | 2.16 | 61 | 1.27 | 1.78 | ||
| 4 | C + 0.6% W | 26 | 3.05 | 66 | 1.38 | 2.02 | 7.5 | 116 |
| 5 | C + 0.8% W | 23 | 3.16 | 57 | 1.19 | 1.95 | ||
| (b) | ||||||||
| 1 | C + 0.4% B | 30 | 1.62 | 50 | 1.04 | 1.46 | ||
| 2 | C + 0.8% B | 29 | 1.73 | 55 | 1.15 | 1.59 | ||
| 3 | C + 1.2% B | 27 | 2.32 | 58 | 1.21 | 1.87 | 5.4 | 101 |
| 4 | C + 1.6% B | 26 | 2.53 | 53 | 1.10 | 1.75 | ||
| (c) | ||||||||
| 1 | C + 0.2% W + 0.4% B | 27 | 1.82 | 57 | 1.19 | 1.62 | ||
| 2 | C + 0.2% W + 0.8% B | 25 | 2.61 | 64 | 1.33 | 1.86 | ||
| 3 | C + 0.2% W + 1.2% B | 23 | 3.32 | 78 | 1.63 | 2.03 | 13.6 | 156 |
| 4 | C + 0.2% W + 1.6% B | 21 | 4.21 | 72 | 1.50 | 1.94 | ||
| 5 | C + 0.4% W + 0.4% B | 25 | 1.97 | 63 | 1.31 | 1.71 | ||
| 6 | C + 0.4% W + 0.8% B | 23 | 2.82 | 79 | 1.65 | 1.93 | ||
| 7 | C + 0.4% W + 1.2% B | 19 | 3.81 | 94 | 1.96 | 2.09 | 14.6 | 183 |
| 8 | C + 0.4% W + 1.6% B | 17 | 4.62 | 88 | 1.83 | 1.81 | ||
| 9 | C + 0.6% W + 0.4% B | 22 | 2.24 | 84 | 1.75 | 1.88 | ||
| 10 | C + 0.6% W + 0.8% B | 17 | 3.89 | 92 | 1.92 | 2.14 | ||
| 11 | C + 0.6% W + 1.2% B | 13 | 5.29 | 128 | 2.67 | 2.99 | 15.4 | 236 |
| 12 | C + 0.6% W + 1.6% B | 12 | 4.78 | 108 | 2.25 | 2.34 | ||
| 13 | C + 0.8% W + 0.4% B | 23 | 2.18 | 75 | 1.56 | 1.81 | ||
| 14 | C + 0.8% W + 0.8% B | 21 | 3.02 | 84 | 1.75 | 1.98 | ||
| 15 | C + 0.8% W + 1.2% B | 20 | 4.14 | 117 | 2.44 | 2.73 | 11.2 | 216 |
| 16 | C + 0.8% W + 1.6% B | 18 | 3.89 | 97 | 2.02 | 2.13 | ||
Table 6.
ANOVA results for all mixtures.
| Sr No. | Statistic | Free Swell Potential (%) | UCS Test Parameters | CBR (%) | Resilient Modulus, (MPa) | |||
|---|---|---|---|---|---|---|---|---|
| Elastoplastic Strain (%) | Peak Strength (kPa) | SCF/SC | ԐPS/ԐRS | |||||
| 1 | F | 118.846 | 92.112 | 94.542 | 82.596 | 77.058 | 102.070 | 81.697 |
| 2 | p | 2.913 × 10−20 | 6.652 × 10−19 | 4.836 × 10−19 | 2.525 × 10−18 | 5.891 × 10−18 | 1.865 × 10−6 | 4.009 × 10−6 |
All measurements’ p values indicate significant difference at p < 0.01.
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |
© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Share and Cite
MDPI and ACS Style
Qamar, W.; Khan, A.H.; Rehman, Z.u.; Masoud, Z. Sustainable Application of Wool-Banana Bio-Composite Waste Material in Geotechnical Engineering for Enhancement of Elastoplastic Strain and Resilience of Subgrade Expansive Clays. Sustainability 2022, 14, 13215. https://doi.org/10.3390/su142013215
AMA Style
Qamar W, Khan AH, Rehman Zu, Masoud Z. Sustainable Application of Wool-Banana Bio-Composite Waste Material in Geotechnical Engineering for Enhancement of Elastoplastic Strain and Resilience of Subgrade Expansive Clays. Sustainability. 2022; 14(20):13215. https://doi.org/10.3390/su142013215
Chicago/Turabian StyleQamar, Wajeeha, Ammad Hassan Khan, Zia ur Rehman, and Zubair Masoud. 2022. "Sustainable Application of Wool-Banana Bio-Composite Waste Material in Geotechnical Engineering for Enhancement of Elastoplastic Strain and Resilience of Subgrade Expansive Clays" Sustainability 14, no. 20: 13215. https://doi.org/10.3390/su142013215
APA StyleQamar, W., Khan, A. H., Rehman, Z. u., & Masoud, Z. (2022). Sustainable Application of Wool-Banana Bio-Composite Waste Material in Geotechnical Engineering for Enhancement of Elastoplastic Strain and Resilience of Subgrade Expansive Clays. Sustainability, 14(20), 13215. https://doi.org/10.3390/su142013215
Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.