utilization of plastic wastefor improving the subgrades in flexible pavements

22
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

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Technology


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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.

TRANSCRIPT

Page 1: Utilization of plastic wastefor improving the subgrades in flexible pavements

A.K.Choudhary1, J.N.Jha2, K.S.Gill3 

1Deptt. of Civil Engg., NIT, Jamshedpur, India2,3Deptt. of Civil Engg., GNDEC, Ludhiana, India

Page 2: Utilization of plastic wastefor improving the subgrades in flexible pavements

Thickness of flexible pavement depends upon subgrade strength and traffic intensity.

Soil reinforcement is an effective and reliable technique to improve the strength of soil subgrade.

Geotextiles and geogrids are commonly used in engineering practices.

Waste plastic can be a cheaper alternative of costly georids/geotextiles for construction of low cost roads.

Page 3: Utilization of plastic wastefor improving the subgrades in flexible pavements

Solid waste production in India: 39 million tons /year (2000) Expected production by 2010: 56 million tons /year

Typical %age of plastic in Municipal solid waste : 1% (India)

Best way to handle such waste :Utilization in engineering application

Application in Soil reinforcement : If found effective can be a significant secondary market for waste plastic

Possibility of replacing costly reinforcing material like geogrid

Page 4: Utilization of plastic wastefor improving the subgrades in flexible pavements

Effect of mixing different %age of high density poly ethelene (HDPE) strips on CBR value of subgrade soil .

Environment friendly disposal of non-biodegradable municipal waste.

To contribute towards the sustainable development of road infrastructure.

To reduce the construction cost.

Page 5: Utilization of plastic wastefor improving the subgrades in flexible pavements

SAND: Locally available sand(Jamshedpur,Jharkhand) (India) Specific gravity: 2.62, D50 : 0.55 mm,

Cu: 2.40, Cc: 1.67 Classification: ‘SP’, γmax : 16.5kN/m3

γmin : 14.6kN/m3

0

10

20

30

40

50

60

70

80

90

100

0.1 1 10Grain size (mm)

Perc

ent f

iner

(%)

Page 6: Utilization of plastic wastefor improving the subgrades in flexible pavements

HDPE: Purchased from a rag picker, at a price of INR 100 per kg

(approximately $2per kg). Width of HDPE : 12mm and Thickness: 0.40mm. Length of HDPE : 12mm [Aspect Ratio (AR=length/width) =1],

(Selected) 24mm (AR=2) 36mm (AR=3) Ratio of mould diameter to maximum strip length ≥ 4

(Ensures sufficient space for strip to deform freely and remains independent of mould confinement)

Ultimate tensile strength of this strip: 0.36kN and percent elongation at failure: 23% (ASTM D 4885)

Page 7: Utilization of plastic wastefor improving the subgrades in flexible pavements

Strip content (Defined in present case): Ratio of weight of strips to the weight of dry sand.

Strip content selected for the tests: 0.0%, 0.25%, 0.50%, 1.0%, 2.0% and 4.0%.

Preparation of specimens:

CBR mould of 150 mm diameter and 175 mm high Density and relative density of compacted sand: 16.2kN/m3 Dr= 85%No. of layers: Three

Page 8: Utilization of plastic wastefor improving the subgrades in flexible pavements

Density of HDPE strip reinforced sand layers kept equal to dry density of that of unreinforced sand.

Required amount of HDPE strips were randomly mixed with dry sand.

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).

Compaction of specimen: vibration for 2 minutes on a vibration table.

Page 9: Utilization of plastic wastefor improving the subgrades in flexible pavements

Tests performed: As per procedures described in IS-2720-Part XVI-1987

A surcharge plate of 2.44kPa placed on the specimen prior to testing.

Loads recorded as a function of penetration (up to a total penetration of 12.5 mm).

CBR and Secant modulus determined from Load vs Penetration curve

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).

Page 10: Utilization of plastic wastefor improving the subgrades in flexible pavements

Increase in CBR value due to the presence of HDPE strip content: Expressed by California Bearing ratio Index (CBRI)

CBRI = CBRr/CBRu

CBRr: California bearing ratio (CBR) value of reinforced soil

CBRr: California bearing ratio (CBR) value of unreinforced soil

Secant modulus: Defined as the ratio of load in kPa at a penetration of 5.0 mm to the penetration of 0.005m

(obtained from load penetration curve)

Page 11: Utilization of plastic wastefor improving the subgrades in flexible pavements

Variation of load-penetration curves (AR=1) with different strip content (0.025% to 4.0%)

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2

4

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0

0.5 1

1.5 2

2.5 3 4 5

7.5

8.5 10

12.5

Penetration (mm)

Load

(kN

)

0%

0.25%0.50%

1%2%

4%

Strip content AR = 1

Page 12: Utilization of plastic wastefor improving the subgrades in flexible pavements

Variation of load-penetration curves (AR=2) with different strip content (0.025% to 4.0%)

0

2

4

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0

0.5 1

1.5 2

2.5 3 4 5

7.5

8.5 10

12.5

Penetration (mm)

Loa

d (k

N)

0%0.25%0.50%1%2%4%

Strip content AR = 2

Page 13: Utilization of plastic wastefor improving the subgrades in flexible pavements

Variation of load-penetration curves (AR=3) with different strip content (0.025% to 4.0%)

0

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0

0.5 1

1.5 2

2.5 3 4 5

7.5

8.5 10

12.5

Penetration (mm)

Load

(kN

)0%

0.25%

0.50%

1%

2%

4%

Strip content AR = 3

Page 14: Utilization of plastic wastefor improving the subgrades in flexible pavements

0

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0.25 0.5 1 2 4

Strip Content (%)

CB

R (%

) AR = 0

AR = 1

AR = 2

AR = 3

Page 15: Utilization of plastic wastefor improving the subgrades in flexible pavements

15

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25

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55

10 20 30 40

Strip length (mm)

CB

R (%

)

0%

0.25%

0.50%

1%

2%

4%

Strip content

Page 16: Utilization of plastic wastefor improving the subgrades in flexible pavements

1.5

1.7

1.9

2.1

2.3

2.5

2.7

2.9

0 1 2 3 4

Strip Content (%)

CBRI

AR=1

AR=2

AR=3

Page 17: Utilization of plastic wastefor improving the subgrades in flexible pavements

350

450

550

650

750

850

950

1050

1150

1250

10 20 30 40

Strip length (mm)

Seca

nt m

odul

us,

(Mpa

)

0%

0.25%

0.50%

1%

2%

4%

Strip content

Page 18: Utilization of plastic wastefor improving the subgrades in flexible pavements

After completion of each test: Specimens were dissected and strip examined

Many of the strips showed elongation, thinning and clear impression of sand particles

As soil sheared during penetration, strip fixed in the sand by friction elongated as the soil deformed

CBR value of HDPE strip reinforced sand at 5.0mm penetration were found to be higher than those at 2.5 mm penetration

At higher deformation HDPE strip reinforcement is more effective in improving the strength of sand by increasing the resistance to penetration

Page 19: Utilization of plastic wastefor improving the subgrades in flexible pavements

Situation (a) plunger pushes down particle ‘C’ to occupy position in between particle ‘A’ and ‘B’

The strips resist the downward movement of particle ‘C’ until slippage between soil and strip occur resulting into a development of situation (b)

Interaction between soil and strips causes the resistance to penetration of the plunger resulting into higher CBR values

S trip

(a ) (b )

Page 20: Utilization of plastic wastefor improving the subgrades in flexible pavements

The addition of reclaimed HDPE strips a waste material to local sand resulted in an appreciable increase in the CBR and the secant modulus

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.

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.

Page 21: Utilization of plastic wastefor improving the subgrades in flexible pavements

Small size of CBR mould limits size & amount of fibre inclusion

End effects in small sample size is more pronounced

Despite these limitations large experience base and satisfactory design method are in use based on CBR test results

Further study needed (a) to optimise the size, shape of strips

(b) to assess the durability and aging of strips

Page 22: Utilization of plastic wastefor improving the subgrades in flexible pavements