CONTENTSI. IntroductionII. AdvantagesIII. Composition of the composite sleepersIV. Tests V. ConclusionVI. Reference

INTRODUCTIONComposite sleepers are new type of environment friendly

sleepers made of waste plastics. It has almost all the flexibilities of wooden or concrete sleepers. In many ways, it is even superior to any other sleepers.

Thermo-plastic based composite sleepers are eco-friendly. It is eco-friendly in the sense that it ensures reuse of the waste plastic in a better way by ensuring its usage in such a fashion, otherwise trees are required to be cut to have required number of wooden sleepers/turnout sleepers. The main constituents of composite sleepers are: used HDPE, plastics, polystyrene, polyethylene, PVC and so on.

ADVANTAGESThere are so many advantages of composite sleepers. Some of them are listed

below:

1.Composite sleepers being made of non bio-degradable material, its life is expected to be more than that of wooden sleepers. Life of wooden sleepers is normally 10 to 25 years. As compared to this, life of composite sleepers is assessed to be around 40 to 50 years.

2.Composite sleepers are impervious to insect and moisture damage, resistant to fungus, electrically non-conducive, resistant to chemical damage.

3.Property of the wooden sleeper is not uniform due to presence of knot and other defects available in the timbers. As compared to this, Property of composite sleepers is uniform in respect to shape and size.

4.The constituent material of the composite sleepers are thermo-plastic based. As such, its recycling is possible.

5.Composite sleepers consume the waste plastic which otherwise is posing its disposal problem. As such, it is fantastic case of reuse of waste resources.

6.More use of composite sleepers will ensure less destruction to the forests.

COMPOSITION OF THE COMPOSITE SLEEPERSComposition of such sleepers are mainly high-density

polyethylene (HDPE) based. Different manufacturers have patented their products based on different compositions.Tietek Sleepers– Composition of this sleeper is given below-

Recycled HDPE 55%

Crumbed rubber 12.5%

Glass reinforcement 12.5%

Fillers 20% (calcium carbonate, Mica etc.)

In addition to that, some other patented items are also there, which are the trade secret of the manufacturer.

COMPOSITION OF THE COMPOSITE SLEEPERSPolywood sleepers– Its composition is of mainly two items i.e. Polystyrene (PS) and High Density Polyethylene (HDPE).Its percentage is in the ratio of approximately 35% PS to 65% HDPE. In addition to that, some other patented items are also there, which are the trade secret of the manufacturer.

TEST CRITERIA FOR PASSING OF THE THERMO-PLASTIC BASED COMPOSITE SLEEPERS:

Indian Railways have developed certain test criteria to ascertain the desired mechanical properties and accordingly passing of such sleepers. The test criteria are –

1.Static Load Test

2.Impact Load Test

3.Dynamic fatigue test.

Static Load Test :– This test is carried out to assess the adequacy of design as per details given below –

1.Load - 50t on each rail seat

2.Loading area - As per size of the bearing plate to be provided.

3.Rate of loading - 5t/min.

4.Number of samples - 3

Acceptance criteria :– No visible cracks should be developed on the outer surface of the sleepers on holding the 50t load for 5 minutes. Deflection at any rail seat of sleeper under load should not exceed 20 mm at 50t.

Impact Load Test:– Impact load test is required to assess the shock absorption capacity of the sleeper, which the sleeper is about to bear during the train running as well as during derailment. The test scheme envisages dropping of wheel on sleeper placed at 30º slope to horizontal plane at following two locations:

1.294mm away from center line of rail toward center.

2.200mm away from sleeper end.

Wheel drop details are:

•Weight of wheel - 500kg.

•Height of drop - 75cm.

•No. of drops - 2 at the same location.

Acceptance criteria:– Only recess should form. No crack should appear on the surface of the sleeper.

TEST CRITERIA FOR PASSING OF THE THERMO-PLASTIC BASED COMPOSITE SLEEPERS:

Dynamic Fatigue Test :– This test is carried out to assess the rail seat abrasion, structural integrity for the product and to ensure absence of any void and other inherent manufacturing defects inside the composite sleeper.

PRESCRIBED TEST SCHEME

Load - 4 to 20t on each rail seat +5%

Horizontal - 40% of the vertical load +5%

No. of cycles - 2 million

Frequency - 5 Hz +5%

Acceptance criteria:– The sleeper shall not develop any cracks on the surface of the sleeper up to 2 million cycles. Hairline cracks may be permissible provided there is no reduction in the load carrying capacity of the sleepers.

TEST CRITERIA FOR PASSING OF THE THERMO-PLASTIC BASED COMPOSITE SLEEPERS:

OTHER TESTS1. AGEING TEST2. VOIDS TEST 3. INFLAMMABILITY TEST 4. SCREWING/UNSCREWING TEST 5. ELECTRICAL PROPERTIES

CONCLUSION• Literature survey, test results and performance of the sleeper

revels that composite sleeper may be one of the alternative for any other conventional sleepers that are in use today.

• Composite sleeper will ensure use of plastic waste, which is creating environmental hazard in the form of land pollution as well as choking of the sewerage system.

• Furthermore, adoption of composite sleeper will ensure less destruction to the forests.

• In case of import of such sleepers to be used as bridge timber, cost of the same is likely to be between Rs. 7000 to Rs. 8000 per sleeper. In case, the same is manufactured in this country itself, cost of the same may come to around Rs.5000/sleeper.

• As such, it would be better that such sleepers to the requirement of Indian Railways may be get manufactured here itself.

REFERENCE Rama Kant Gupta Executive Director (Bridge and

Structures) RDSO, Manak Nagar, Lucknow. TieTek official website (www.tietek.net) Patil Rail Infrastructures official website (

www.patilgroup.com) Wikipedia.com Wiki.iricen.gov.in

THANK YOU