Performance of Plastic Waste for Soil Improvement PDF

Research Article Performance of plastic waste for soil improvement Rowad Esameldin Farah1 · Zalihe Nalbantoglu1 © Springer Nature Switzerland AG 2019 Abstract Recycling plastic waste from water bottles has become one of the main challenges worldwide. The aim of this study is to recycle empty plas...

Research Article Performance of plastic waste for soil improvement Rowad Esameldin Farah1 · Zalihe Nalbantoglu1 © Springer Nature Switzerland AG 2019 Abstract Recycling plastic waste from water bottles has become one of the main challenges worldwide. The aim of this study is to recycle empty plastic water bottles as reinforcing material for the improvement of sandy soil. The laboratory tests were performed on both natural and reinforced sands with different plastic waste percentages: 0, 0.5, 0.75 and 1.0 of the dry weight of sand at relative density states of 30% and 60%. Direct shear box and the California Bearing Ratio, CBR tests were performed to determine the effect of the plastic waste on the shear strength and the penetration resistance of the reinforced sand. Test results indicated that plastic waste reinforcement contributed to the improvement of the shear strength and the CBR number of the reinforced sand. Higher shear strength and higher penetration resistance were obtained with plastic waste reinforcement. The optimum percentage of plastic waste required for enhancing the shear strength and the CBR number was found to be 0.75%. With the optimum percentage of plastic waste, the improvement in the shear strength and the penetration resistance of the reinforced sand increased to at least 9% compared to natural soil at relative density states of 30% and 60%. Keywords Plastic · Recycle · Reinforcement · Shear strength · Waste Abbrevations 1 Introduction ASTM American society for testing and materials CBR California bearing ratio Literature review indicated that the usage of water bot- PET Polyethyethylene terephthalate tles has enlarged by around 500% throughout the previ- ous decade, and 1.5 million tons of plastic is utilized to List of symbols bottle water each year. Chen et al. stated that finding a c Cohesion way to reuse plastic waste is an environmentally friendly Cc Coefficient of curvature approach to reduce greenhouse gas (GHG) emission and Cu Coefficient of uniformity fossil fuel consumption. In some field conditions, soil sta- °C Celsius bilization techniques are required to agree with particular e Void ratio engineering projects in terms of soil properties. The emax Maximum void ratio most effective technique to improve the soft ground is emin Minimum void ratio insitu deep mixing [4–6], so the soil can be mixed with Gs Specific gravity plastic waste as reinforcing material. To enhance the envi- SP Poorly graded sand ronmental acceptability and decrease the construction ρd(max) Maximum index density cost of traditional stabilization such as cement and lime, ρd(min) Minimum index density the replacement of them by plastic waste can be one of ϕpeak Peak internal friction angle the alternatives. ϕcri Critical internal friction angle There are limited researches performed on the usage Dr Relative density of plastic bottle waste as a reinforcing material for soil * Rowad Esameldin Farah, [email protected]; Zalihe Nalbantoglu, [email protected] | 1Department of Civil Engineering, Eastern Mediterranean University, Via Mersin 10, Famagusta, North Cyprus, Turkey. SN Applied Sciences (2019) 1:1340 | https://doi.org/10.1007/s42452-019-1395-2 Received: 7 August 2019 / Accepted: 1 October 2019 / Published online: 5 October 2019 Vol.:(0123456789) Research Article SN Applied Sciences (2019) 1:1340 | https://doi.org/10.1007/s42452-019-1395-2 improvement. Researchers have focused on using the content on both shear strength and penetration resist- waste of plastic bottles as reinforcing material in the ance of reinforced sand soil. Consequently, the reinforced sand [1, 7]. The plastic waste has been added in the form soil with fiber requires more investigations. This research of chips in different percentages. The experimental out- aims to investigate the effect of introducing plastic waste comes have illustrated that the inclusion of plastic waste chips with various percentages on the shear strength and chips improved the shear strength of sandy soil due to penetration resistance of sand with two different relative the increase in friction between the soil particles and the densities, 30%, and 60%. plastic waste [1, 7]. Consoli et al. used polyethylene fib- ers extracted from plastic wastes for reinforcing cemented and uncemented sand. The findings of the study illustrated 2 Materials and sample preparation that plastic waste improved the stress–strain response of both cemented and uncemented sands. Boter et al. In the study, all the laboratory tests were performed on dry studied the effect of the plastic waste material on the shear sand. Before testing, the sand was kept in an oven at 110 strength of silty soil. The test results indicated that the degree Celsius for at least 24 h. The sieve analysis was car- increase in plastic waste material decreased the internal ried out to determine the particle sizes of the sand, and the friction angle, whereas an increase in the cohesion value results were used for the classification of the sand. Direct was obtained. Researchers concluded that the inclusion of shear tests have been conducted on natural and plastic plastic waste (fiber reinforcement) enhances the strength chips reinforced sand to determine the shear strength and stability of soils [10–12]. Yetimoglu and Salbas parameters before and after reinforcement. The CBR tests have conducted an experimental study to evaluate the were performed for the evaluation of the effect of plastic effectiveness of randomly distributed discrete fibers on waste on the subgrade strength of pavements by deter- shear strength of sand by conducting direct shear tests. mining the maximum penetration of the natural and the Test results indicated that the introduction of fibers into plastic chips reinforced sands. the soil has enhanced the residual strength taking place after peak stress and decreased the brittle character of soil. 2.1 Beach sand Dos Santos et al. have investigated the effect of Poly- propylene fiber on the shear strength of sandy soils under In this study, the sand was taken from the sea coast of different confining stresses. The test results exhibited that Famagusta in North Cyprus. The particle size distribution the shear strength of soil mainly depended on testing curve of this sand was given in Fig. 1. According to the Uni- confining stresses. Moreover, the inclusion of fibers has fied Soil Classification System (ASTM D 2487-00), the coef- appealed a reduction in shear strength of fiber-reinforced ficient of curvature (Cc) was 0.91 which is less than 1, the soil with an increase in confining stress. coefficient of uniformity ­(Cu) was 1.78 which is less than Nagrale et al. conducted a study on the improve- 6, ­D60, ­D30 and ­D10 were 0.32, 0.23 and 0.18, respectively. ment of CBR value of subgrade soil (fine sand and clay The result of soil classification is mentioned in the results soil) with the addition of polypropylene fibers, and they and discussion section. The physical properties of the sand concluded that the fiber enhanced CBR value of soils. were given in Table 1. Choudhary et al. have performed California Bear- ing Ratio (CBR) tests on soil that has been reinforced by 2.2 Plastic bottles highly density polyethylene strips (HDPE). The high den- sity polyethylene strips were randomly distributed with The empty plastic water bottles were collected from vari- the soil with different percentages and lengths. The CBR ous cafeterias in Eastern Mediterranean University campus test results showed that the introduction of waste HDPE in North Cyprus. The plastic bottle waste used in this study strips in soil with suitable amounts improved the strength was polyethylene terephthalate (PET). After collecting the and deformation character of subgrade soils remarkably. plastic bottles, they were first cut into small sizes and then All the previous investigations have presented that the into strips. By using a scissor, these strips were then cut introduction of fiber caused a significant enhancement into small chips. in shear strength of fiber-reinforced soils. The randomly In the literature, different sizes of plastic chips were spread fiber could be considered as a good enhancement used in correspondence to aspect ratios (length/width). material which leads to a remarkable improvement in the Benson and Khire have used plastic strips with a width engineering index properties of sand. While efforts have of 6 mm and lengths of 24, 48, and 72 mm (aspect ratios of also been made to examine the influence of fiber on the 4, 8 and 12) to study the effect of them on shear strength penetration resistance of reinforced soil (CBR test). Never- of the soil. Babu and Chouksey used a plastic chip size theless, there is limited literature on the influence of fiber of 12 mm long and 4 mm in width to see the response of Vol:.(1234567890) SN Applied Sciences (2019) 1:1340 | https://doi.org/10.1007/s42452-019-1395-2 Research Article Fig. 1  Particle size distribution D60=0.32, D30=0.23, D10=0.18 curve for natural beach sand Cc=0.91, Cu=1.78 100 80 Passing (% ) 60 40 20 0 0.01 0.1 1 10 Grain Size (mm) Table 1  Physical properties of the natural beach sand (10 mm × 1.25 mm) to see the effect of them on compac- Physical properties Values tion characteristics and consolidation behavior of soil. Since, there is no specific size in the literature the size of Minimum void r­ atioa, ­emin 0.55 approximately 12 mm length, 4 mm width and thickness Maximum void ­ratioa, ­emax 0.73 of 0.3 mm (aspect ratio f 3) with specific gravity of 1.0 were Minimum index d ­ ensitya, ρd(min) (g/cm3) 1.57 utilized in this study. A photo of the plastic chips used in Maximum index d ­ ensitya, ρd(max) (g/cm3) 1.76 this study was given in Fig. 2. b Specific ­gravity , (Gs) 2.72 Coefficient of ­uniformityc, ­Cu 1.78 Coefficient of c­ urvaturec, Cc 0.91 3 Methods Soil ­classificationd SP a According to Impact method, Joseph E Bowles 1986 3.1 Minimum index density and maximum void b According to ASTM D 854-06 ratio, ρd(min) and ­emax c According to ASTM D 2487-06 d This test was conducted according to the impact method According to ASTM D 2487-00 (Unified Soil Classification System) suggested by Bowel. Also, to obtain the maximum void ratio of the sand at the loosest condition, the dry sand it in bearing capacity improvement and settlement reduc- was poured into a mold by using a small funnel. With the tion. Plastic bottle fibers have been used in three different known weight and the volume of the mold, the maximum aspect ratios 2 (10 mm × 5 mm), 4 (10 mm × 2.5 mm) and 8 void ratio, ­emax of the sand was determined. Fig. 2  Plastic bottles chips used as a reinforcing material in this study Vol.:(0123456789) Research Article SN Applied Sciences (2019) 1:1340 | https://doi.org/10.1007/s42452-019-1395-2 3.2 Maximum index density and minimum void slightly shaken and tamped to reach the desired rela- ratio, ρd(max) and ­emin tive density state. For the reinforced soil, the specified weight of plastic waste percent by dry weight of soil According to Bowel , the impact method was also was distributed uniformly over the soil and mixed uni- used for finding the maximum index density of the sand. formly, and same procedure as for natural soil was then The oven-dried sand was poured into the mold by using followed. The sand specimens were subjected to three the small funnel in five successive layers. Each layer was different normal stress values: 20, 30, and 50 kPa and the compacted according to the impact method proposed by shear strength parameters were determined. The rate of Bowel , from the known volume of the mold and the shear displacement applied in the study is 1.06 mm/min, weight of the compacted sand inside the mold, the maxi- according to Prakash. mum index density, ρd(max), and the minimum void ratio, The shear stress versus horizontal displacement ­emin, of the sand was determined. curves obtained for the natural beach sand under dif- ferent normal stress values was given in Figs. 3 and 4. The 3.3 Direct shear box test curves in Fig. 3 represented the values of the sand pre- pared at 30% relative density value whereas, in Fig. 4, the In this study, the sand specimens were prepared at 30% sand specimens were prepared at 60% relative density. and 60% relative density values using Eq. 1. From the curves obtained in Figs. 3 and 4, the peak and emax − e the critical friction angles of the natural beach sand were Dr = (1) determined at 30% and 60% relative density values by emax − emin using the maximum and critical shear stress values. Then, where ­Dr: relative density, ­emax = maximum void ratio, these values were used with the corresponding normal ­e min = minimum void ratio, e = void ratio of the sand stresses values to get the shear strength parameters. specimens. The sand specimens were compacted in the direct shear box at 30% and 60% relative density values. The 3.4 California bearing capacity ratio, CBR test void ratio of the sand prepared at 30% (loose state) and 60% (dense state) relative density values were calculated The CBR test is a penetration test for evaluating the bear- to be 0.676 and 0.622, respectively. For 30% relative den- ing capacity of subgrade soil for road and pavement. sity state, the soil mass was poured in one layer with a In this study, the CBR test was performed to assess the slight vibration and tamped to reach the required den- effectiveness of plastic waste on the penetration resist- sity state in the box. For 60% relative density state, the ance of the 0.75% plastic chips reinforced sand. The sand soil was poured in three successive layers, each layer was specimens were prepared at relative density values of 30 and 60%. Fig. 3  Shear stress versus 50 horizontal displacement curves for the natural beach sand pre- 20 kPa pared at 30% relative density 40 30 kPa 50 kPa Shear Stress (kPa) 30 20 10 0 0 2 4 6 8 10 12 Horizontal Displacement (mm) Vol:.(1234567890) SN Applied Sciences (2019) 1:1340 | https://doi.org/10.1007/s42452-019-1395-2 Research Article Fig. 4  Shear stress versus 50 horizontal displacement curves for the natural beach sand Pre- 20 kPa pared at 60% relative density 40 30 kPa 50 kPa Shear Stress (kPa) 30 20 10 0 0 2 4 6 8 10 12 Horizontal Displacement (mm) Table 2  The internal friction angles for natural and reinforced sand Table 3  The internal friction angles for natural and reinforced sand at 30% relative density at 60% relative density Internal friction angle Plastic percentage Friction angle Plastic percentage 0 0.50 0.75 1.0 0 0.50 0.75 1.0 Peak internal friction angle, ϕp 33° 34° 36° 34° Peak internal friction angle, ϕp 34° 35° 37° 34° Critical internal friction angle, ϕcri 18° 30° 33° 32° Critical internal friction angle, ϕcri 30° 30° 33° 30° 4 Results and discussion test results indicated an increase in the peak and critical friction angles of the plastic chip reinforced sand due to According to the Unified Soil Classification System (ASTM the increase in the frictional strength between the sand D 2487-00), the soil was classified as poorly graded sand particles. Test results also indicated that mixing of sand (SP). with 0.5% and 0.75% plastic waste caused an increase in the peak and the critical friction angles, in all cases of reinforced sand soil the cohesion was about 1 kPa and 4.1 Direct shear box test no changes were confronted. The results also indicated that with increasing relative density, the peak inter- From the curves obtained in Figs. 3 and 4, the peak and nal friction angles were increased due to the increase the critical friction angles of the natural beach sand in the interlocking of the sand particles. In addition to were determined at 30% and 60% relative density val- that, the increase in the shear strength of reinforced soil ues. The peak internal friction angle, ϕ p of the natural with strips could be explained because of the generated beach sand prepared at 30% relative density gave a tension in the shear region due to the occurred anchor- value of ­33◦ whereas the peak internal friction angle at age at the soil/reinforcement interface outer the shear 60% relative density was found to be ­34◦. Also, the criti- region. The generated tension in the strips adds to the cal internal friction angles of the natural beach sand at shear strength of soil. Moreover, the strips are retained 30% and 60% relative densities were found to be ­18◦ and in tension even after reaching the peak strength. There- ­30◦, respectively. fore, the post-peak loss in shear strength is lesser than The shear strength parameters of the natural and the would be noticed in unreinforced specimens. As it plastic waste reinforced sand obtained from the direct can be seen in Fig. 5. On the other hand, the comparison shear box tests were given in Tables 2 and 3. The values in of the results in Tables 2 and 3 on reinforced soil of loose Tables 2 and 3 presented the peak ϕp and the critical fric- and dense states (30% and 60%) showed that the plas- tion angle, ϕcri of the sand specimens prepared at 30% tic inclusion contributed in a slighter or marginal role in and 60% relative density values, respectively. Generally, the critical internal friction angle in the densely packed soil (60% relative density) compared to loosely packed Vol.:(0123456789) Research Article SN Applied Sciences (2019) 1:1340 | https://doi.org/10.1007/s42452-019-1395-2 Table 6  CBR numbers for natural, 0.75% plastic waste reinforced sand and its percent of increase Relative CBR number of CBR number of % increase in density (%) natural sand 0.75% reinforced CBR number sand 30 9 10 11 60 11 12 9 percentage of plastic chips with 30% and 60% relative Fig. 5  Mechanism of soil reinforcement, Gray and Ohashi density states. 4.2 California bearing capacity ratio, CBR Table 4  shows the percentage of increase in internal friction angles in case optimum percentage of plastic chips with 30% relative den- In the CBR tests, the optimum percentage of plastic waste: sity state 0.75% was used, and the sand specimens were prepared Internal friction angle % increase in in the CBR mold at 30% and 60% relative density values. internal friction The CBR numbers obtained for the natural and 0.75% rein- angle forced sand at 30% and 60% relative densities were given Peak internal friction angle, ϕp 9 in Table 6. The values in Table 6 indicated that 0.75% plastic Critical internal friction angle, ϕcri 83 waste reinforcement caused a slight increase in the CBR number. The slight increment in the CBR number can be attributed to the strong binding between the sand parti- Table 5  shows the percentage of increase in internal friction angles cles and the plastic chips, resulting in higher penetration in case optimum percentage of plastic chips with 60% relative den- resistance of the reinforced sand. This result was in good sity state agreement with the findings of Poweth et al. as the Internal friction angle % increase in 0.75% of plastic increased the CBR number of soil, even internal friction though in their study the plastic was in the form of gran- angle ules but same behavior was confronted. The same table, Peak internal friction angle, ϕp 9 Table 6, shows the percent of increase in CBR number of Critical internal friction angle, ϕcri 10 reinforced sand compared to natural sand. According to Bowel , the obtained CBR numbers indicated that the reinforced sand could be used as sub-base materials for soil (30%). In the densely packed soil, sliding of particles road and pavement constructions. likely happens on the smooth surface of plastic chips. This sliding prevents bending-stretching of plastic chips and leads to a restricted generation of plastic chips ten- 5 Practical implications of the study sile stress and, therefore, shearing resistance. However, no further improvement in the friction In this study, the cutting of plastic bottles into small angle of the sand was obtained above 0.75% plastic chips was time-consuming and very difficult to attain waste. Above this value, there was no contribution to the the required size as described in materials and methods improvement of the shear strength parameters of the section. reinforced sand. The reinforcing effect of plastic waste In this study, the distribution of higher percentages diminished. The reinforcement effect can be explained of plastic chips with sand was difficult to attain uniform due to the breakage of the frictional bond between the mixtures. sand particles and the plastic chips above 0.75% plastic For further studies, it is better to search for recycling waste. Weaker bonding between the sand particles and industries, which most probably may help to get the the plastic chips resulted in lower internal friction angle. required material in different shapes and sizes. In this study, the optimum percentage of plastic chips For further studies, different percentages and sizes of to improve the shear strength was found to be 0.75%. plastic waste should be used. Besides, another cementing This result was in good agreement with the findings of material can be blended with plastic chips such as lime Poweth et al.. Tables 4 and 5 show the percentage and cement to increase its effect on geotechnical proper- of increase in internal friction angles in case of optimum ties of soils. Vol:.(1234567890) SN Applied Sciences (2019) 1:1340 | https://doi.org/10.1007/s42452-019-1395-2 Research Article 6 Conclusions 3. Rogers CDF, Glendinning S, Roff TEJ (1997) Lime modification of clay soils for construction expediency. In: Proceeding of the institution of civil engineers: geotechnical engineering, vol 125, Based on the experimental work carried out on natural and p4 plastic waste reinforced beach sand, the test results of this 4. Kawasaki T (1981) Deep mixing method using cement harden- study indicated that recycling of plastic waste bottles is ing agent. In: Proceedings of 10th international conference on SMFE, pp 721–724 possible. The improvement in the shear strength and the 5. Bruce DA. Bruce MEC, Dimillio AF (1999) Dry mix methods: a CBR number of plastic waste reinforced sand is encour- brief overview of international practice. In: Proceedings of inter- aging. Based on results of tests the following conclusions national conference on dry mix methods for deep soil stabiliza- could be drawn: tion. Balkema, Rotterdam, pp 15–25 6. Saitoh S, Suzuki Y, Shirai K (1985) Hardening of soil improved The inclusion of plastic chips of waste bottles into by deep mixing method. In: Proceeding of 11th international the sand increased the shear strength of the sand. The conference on soil mechanics and foundation engineering, San optimum percentage of the plastic chip was found to Francisco, Publication of: Balkema (AA), pp 12–16 be 0.75%. The values of the peak and the critical internal 7. Dutta RK, Dutta K, Jeevanandham S (2015) Prediction of deviator stress of sand reinforced with waste plastic strips using neural friction angles increased with an increase in the percent network. Int J Geosynth Ground Eng 1(2):11 of plastic chips up to 0.75%. The addition of plastic chips 8. Consoli NC, Montardo JP, Prietto PDM, Pasa GS (2002) Engineer- beyond 0.75% decreased the peak internal friction angle. ing behavior of a sand reinforced with plastic waste. J Geotech That means the reinforcing effect of plastic waste on the Geoenviron Eng 128(6):462–472 9. Botero E, Ossa A, Sherwell G, Ovando-Shelley E (2015) Stress– shear strength of sand diminished. strain behavior of a silty soil reinforced with polyethylene tere- The 0.75% plastic chip reinforcement resulted in a posi- phthalate (PET). Geotext Geomembr 43(4):363–369 tive improvement in the CBR number. With 0.75% plastic 10. Gray DH, Ohashi H (1983) Mechanics of fiber reinforcement in chip reinforcement, the reinforced sand showed higher sand. J Geotech Eng 109(3):335–353 11. Vijayasingam B, Heng GY (2003) The laboratory study of granu- resistance to penetration, leading to an increase in the lar soils reinforced with randomly oriented distributed flexible CBR number. fibres. Major Research Project University of Bristol, p 45 In the case of 30 and 60% relative densities, the inclu- 12. Kar RK, Pradhan PK, Naik A (2012) Consolidation characteris- sion of the optimum plastic percentage (0.75%) improved tics of fiber reinforced cohesive soil. Electron J Geotech Eng 17:3861–3874 the peak, critical internal friction angles and CBR numbers 13. Yetimoglu T, Salbas O (2003) A study on shear strength of sands of sand soils by at least 9%. reinforced with randomly distributed discrete fibers. Geotext In this study, only one percentage of plastic chips were Geomembr 21(2):103–110 used (optimum percentage in case of shear strength) to 14. Dos Santos AS, Consoli NC, Baudet BA (2010) The mechanics of fibre-reinforced sand. Geotechnique 60(10):791 study the CBR values. For future studies, different per- 15. Nagrale PP, Chandra S, Viladkar MN (2005) Behaviour of flexible centages and sizes of plastic waste should be utilized to pavements resting on fiber reinforced subgrade soils. In: Pro- indicate whether the 0.75% of plastic chips is an optimum ceedings of Indian geotechnical conference, Ahmedabad India percentage also for resistance penetration in reinforced 185-188 16. Choudhary AK, Jha JN, Gill KS (2010) A study on CBR behavior of sand as in the case of shear strength. waste plastic strip reinforced soil. Emirates J Eng Res 15(1):51–57 17. Benson CH, Khire MV (1994) Reinforcing sand with strips Acknowledgements The support and facilities of this research to be of reclaimed high-density polyethylene. J Geotech Eng accomplished returning to Eastern Mediterranean University, Civil 120(5):838–855 Engineering Department. 18. Laskar A, Pal SK (2013) Effects of waste plastic fibres on compac- tion and consolidation behavior of reinforced soil. Electron J Compliance with ethical standards Geotech Eng 18:1547–1558 19. Bowel JE (1986) Engineering properties of soils and their meas- urements, 3rd edn. McGraw-Hill, Inc, New York Conflict of interest The authors declare that they have no conflict of 20. Prakash S (1995) Fundamental of soil mechanics. Shamsher interest. Prakash Foundation 21. Poweth MJ, Haneef FM, Jacob MT, Krishnan R, Rajan S (2014) Effect of plastic granules on the properties of soil. Int J Eng Res References Appl 4(4):160–164 Publisher’s Note Springer Nature remains neutral with regard to 1. Babu GS, Chouksey SK (2011) Stress–strain response of plastic jurisdictional claims in published maps and institutional affiliations. waste mixed soil. Waste Manag 31(3):481–488 2. Chen X, Xi F, Geng Y, Fujita T (2011) The potential environmental gains from recycling waste plastics: simulation of transferring recycling and recovery technologies to Shenyang. Waste Manag 31(1):168–179 Vol.:(0123456789)