Utilization of plastic wastefor improving the subgrades in flexible pavements

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Waste plastic strip reinfofced soil can be used in low cost embankment/road construction leading to significant cost advantage as well as safe disposal of these waste in a environment friendly manner.

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Utilization of plastic wastefor improving the subgrades in flexible pavements

  1. 1. A.K.Choudhary 1 , J.N.Jha 2 , K.S.Gill 3   1 Deptt. of Civil Engg., NIT, Jamshedpur, India 2,3 Deptt. of Civil Engg., GNDEC, Ludhiana, India
  2. 2. <ul><li>Thickness of flexible pavement depends upon subgrade strength and traffic intensity. </li></ul><ul><li>Soil reinforcement is an effective and reliable technique to improve the strength of soil subgrade. </li></ul><ul><li>Geotextiles and geogrids are commonly used in engineering practices. </li></ul><ul><li>Waste plastic can be a cheaper alternative of costly georids/geotextiles for construction of low cost roads. </li></ul>
  3. 3. <ul><li>Solid waste production in India: 39 million tons /year (2000) </li></ul><ul><li>Expected production by 2010: 56 million tons /year </li></ul><ul><li>Typical %age of plastic in Municipal solid waste : 1% (India) </li></ul><ul><li>Best way to handle such waste :Utilization in engineering application </li></ul><ul><li>Application in Soil reinforcement : If found effective can be a significant secondary market for waste plastic </li></ul><ul><li>Possibility of replacing costly reinforcing material like geogrid </li></ul>
  4. 4. <ul><li>Effect of mixing different %age of high density poly ethelene (HDPE) strips on CBR value of subgrade soil . </li></ul><ul><li>Environment friendly disposal of non-biodegradable municipal waste. </li></ul><ul><li>To contribute towards the sustainable development of road infrastructure. </li></ul><ul><li>To reduce the construction cost. </li></ul>
  5. 5. <ul><li>SAND: Locally available sand(Jamshedpur,Jharkhand) (India) </li></ul><ul><li>Specific gravity: 2.62, </li></ul><ul><li>D 50 : 0.55 mm, </li></ul><ul><li>C u : 2.40, C c : 1.67 </li></ul><ul><li>Classification: ‘SP’, </li></ul><ul><li>γ max : 16.5kN/m 3 </li></ul><ul><li>γ min : 14.6kN/m 3 </li></ul>
  6. 6. <ul><li>HDPE: </li></ul><ul><li>Purchased from a rag picker, at a price of INR 100 per kg (approximately $2per kg). </li></ul><ul><li>Width of HDPE : 12mm and Thickness: 0.40mm. </li></ul><ul><li>Length of HDPE : 12mm [Aspect Ratio (AR=length/width) =1], </li></ul><ul><li>(Selected) 24mm (AR=2) </li></ul><ul><li>36mm (AR=3) </li></ul><ul><li>Ratio of mould diameter to maximum strip length ≥ 4 </li></ul><ul><li>(Ensures sufficient space for strip to deform freely and remains independent of mould confinement) </li></ul><ul><li>Ultimate tensile strength of this strip: 0.36kN </li></ul><ul><li> and percent elongation at failure: 23% (ASTM D 4885) </li></ul>
  7. 7. <ul><li>Strip content (Defined in present case): Ratio of weight of strips to the weight of dry sand. </li></ul><ul><li>Strip content selected for the tests: 0.0%, 0.25%, 0.50%, 1.0%, 2.0% and 4.0%. </li></ul><ul><li>Preparation of specimens: </li></ul><ul><li>CBR mould of 150 mm diameter and 175 mm high </li></ul><ul><li>Density and relative density of compacted sand: 16.2kN/m 3 D r = 85% </li></ul><ul><li>No. of layers: Three </li></ul>
  8. 8. <ul><li>Density of HDPE strip reinforced sand layers kept equal to dry density of that of unreinforced sand. </li></ul><ul><li>Required amount of HDPE strips were randomly mixed with dry sand. </li></ul><ul><li>Mix transferred to the mould and a surcharge (base plate 148 mm in diameter) weighing 25 N placed over the sample (to avoid segregation of the strips during vibration). </li></ul><ul><li>Compaction of specimen: vibration for 2 minutes on a vibration table. </li></ul>
  9. 9. <ul><li>Tests performed: As per procedures described in IS-2720-Part XVI-1987 </li></ul><ul><li>A surcharge plate of 2.44kPa placed on the specimen prior to testing. </li></ul><ul><li>Loads recorded as a function of penetration (up to a total penetration of 12.5 mm). </li></ul><ul><li>CBR and Secant modulus determined from Load vs Penetration curve </li></ul><ul><li>CBR values reported in the present investigation are those of 5.0 mm penetration (CBR value at 5.0 mm penetration observed higher than that of 2.5 mm penetration even on repetition). </li></ul>
  10. 10. <ul><li>Increase in CBR value due to the presence of HDPE strip content: Expressed by California Bearing ratio Index (CBRI) </li></ul><ul><li>CBRI = CBR r /CBR u </li></ul><ul><li>CBR r : California bearing ratio (CBR) value of reinforced soil </li></ul><ul><li>CBR r : California bearing ratio (CBR) value of unreinforced soil </li></ul><ul><li>Secant modulus: Defined as the ratio of load in kPa at a penetration of 5.0 mm to the penetration of 0.005m </li></ul><ul><li>(obtained from load penetration curve) </li></ul>
  11. 11. <ul><li>Variation of load-penetration curves (AR=1) with different strip content (0.025% to 4.0%) </li></ul>
  12. 12. <ul><li>Variation of load-penetration curves (AR=2) with different strip content (0.025% to 4.0%) </li></ul>
  13. 13. <ul><li>Variation of load-penetration curves (AR=3) with different strip content (0.025% to 4.0%) </li></ul>
  14. 18. <ul><li>After completion of each test: Specimens were dissected and strip examined </li></ul><ul><li>Many of the strips showed elongation, thinning and clear impression of sand particles </li></ul><ul><li>As soil sheared during penetration, strip fixed in the sand by friction elongated as the soil deformed </li></ul><ul><li>CBR value of HDPE strip reinforced sand at 5.0mm penetration were found to be higher than those at 2.5 mm penetration </li></ul><ul><li>At higher deformation HDPE strip reinforcement is more effective in improving the strength of sand by increasing the resistance to penetration </li></ul>
  15. 19. <ul><li>Situation (a) plunger pushes down particle ‘C’ to occupy position in between particle ‘A’ and ‘B’ </li></ul><ul><li>The strips resist the downward movement of particle ‘C’ until slippage between soil and strip occur resulting into a development of situation (b) </li></ul><ul><li>Interaction between soil and strips causes the resistance to penetration of the plunger resulting into higher CBR values </li></ul>
  16. 20. <ul><li>The addition of reclaimed HDPE strips a waste material to local sand resulted in an appreciable increase in the CBR and the secant modulus </li></ul><ul><li>The reinforcement benefit increases with an increase in strip content and the aspect ratio and maximum improvement in CBR and secant modulus of a reinforced system is around three times to that of an unreinforced system. </li></ul><ul><li>Though the maximum improvement in CBR and secant modulus is obtained when the strip content is 4% and the aspect ratio 3, but even at 2% strip content the improvement in CBR is also appreciable. </li></ul>
  17. 21. <ul><li>Small size of CBR mould limits size & amount of fibre inclusion </li></ul><ul><li>End effects in small sample size is more pronounced </li></ul><ul><li>Despite these limitations large experience base and satisfactory design method are in use based on CBR test results </li></ul><ul><li>Further study needed (a) to optimise the size, shape of strips </li></ul><ul><li>(b) to assess the durability and aging of strips </li></ul>

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