TRACK BED AND METHOD OF STABILIZING A TRACK BED

Abstract

A track bed for a railroad track, includes track ballast made from particulate matter and a multitude of railroad ties supported on the track ballast, wherein at least one region of the track ballast is stabilized by a bonding agent that bonds together particles of the particulate matter, wherein the bonding agent is based on a hydraulic binder, in particular cement, and the bonding agent leaves free voids between the bonded particles so that the track ballast has a water draining capability in the at least one stabilized region.

Claims

1. A track bed for a railroad track, comprising track ballast made from particulate matter and a multitude of railroad ties supported on the track ballast, wherein at least one region of the track ballast is stabilized by means of a bonding agent that bonds together particles of the particulate matter, wherein the bonding agent is based on a hydraulic binder, and the bonding agent leaves free voids between the bonded particles so that the track ballast has a water draining capability in said at least one stabilized region.

2. The track bed according to claim 1, wherein the bonding agent is a hardened cement slurry.

3. The track bed according to claim 1, wherein the hydraulic binder is a Portland cement binder.

4. The track bed according to claim 1, wherein the track ballast comprises a central region located below said railroad ties and side regions arranged on both sides of said central region, wherein only the side regions are stabilized by said bonding agent.

5. The track bed according to claim 1, wherein the stabilized region has a mass ratio of bonding agent to track ballast of 1:10-1:20.

6. A method of stabilizing a track bed for a railroad track, said track bed comprising track ballast made from particulate matter and a multitude of railroad ties supported on the track ballast, wherein particles of the particulate matter are bonded together by means of a bonding agent that is based on a hydraulic binder, said bonding agent being applied to the particles of the particulate matter so as to leave free voids between the bonded particles so that the track ballast has a water draining capability.

7. The method according to claim 6, wherein the bonding agent comprises or consists of a cement slurry.

8. The method according to claim 6, wherein the hydraulic binder is a Portland cement binder.

9. The method according to claim 6, wherein the bonding agent is poured or sprayed onto the track ballast in at least one region to be stabilized.

10. The method according to claim 6, wherein the bonding agent is mixed with the particles of said particulate matter and the resulting mixture is placed as track ballast on a track formation.

11. The method according to claim 6, wherein the track ballast comprises a central region located below said railroad ties and side regions arranged on both sides of said central region, wherein the bonding agent is only applied to the particles of the side regions.

12. The method according to claim 6, wherein a flowability of the bonding agent, at the time of application, is 2-7 seconds, when measured according to a spread test method inspired from the method described in ASTM D6910/D6910M-09, where the dimensions of the funnel are adapted for slurries (internal top cone diameter: 149 mm, internal bottom cone diameter: 17.3 mm, bottom tube height: 30.3 mm, total height: 190 mm (comprising cone and bottom tube)) and where the time measured to characterize the flowability corresponds to the flow of 0.6 L of the product.

13. The method according to claim 6, wherein the bonding agent has an initial slump of at least 90 mm, measured according to a spread test method inspired from EN 12350-8 referring to the testing of fresh concrete/self-compacting concrete, wherein the dimensions are adjusted for slurries (height 57 mm, internal diameter at top: 21 mm, internal diameter at bottom: 37 mm) 5 min after mixing.

14. The method according to claim 6, wherein the Portland cement has a specific surface of 3000-10000 cm.sup.2/g.

15. The method according to claim 6, wherein the bonding agent comprises a water reducer.

16. The method according to claim 6, wherein the bonding agent is poured or sprayed onto the track ballast in an amount of 40-70 litres per m.sup.2 of track ballast surface and per m of track ballast thickness.

17. The method according to claim 6, wherein the bonding agent is poured or sprayed onto the track ballast in such an amount that a homogeneous bed of said bonding agent is formed at the bottom of the track ballast.

18. The track bed according to claim 1, wherein the hydraulic binder is cement.

19. The track bed according to claim 2, wherein the bonding agent is a hardened cement paste or cement mortar.

20. The track bed according to claim 3, wherein the Portland cement binder is a cement of the type CEM I, CEM II, CEM III, or aluminate cement.

21. The method according to claim 7, wherein the bonding agent is a cement paste or cement mortar.

22. The method according to claim 8, wherein the Portland cement binder is a cement of the type CEM I, CEM II, CEM III, or aluminate cement.

23. The method according to claim 12, wherein the flowability of the bonding agent, at the time of application, is 2-4 seconds.

24. The method according to claim 14, wherein the specific surface (Blaine) is 3500-6000 cm.sup.2/g.

25. The method according to claim 15, wherein the water reducer is a plasticiser or a superplasticizer.

26. The method according to claim 25, wherein the water reducer is a polycarboxylate based or a polynaphthalene sulfonate based water reducer.

27. The method according to claim 16, wherein the bonding agent is poured or sprayed onto the track ballast in an amount of 50-70 litres per m.sup.2 of track ballast surface and per m of track ballast thickness.

28. The method according to claim 27, wherein the bonding agent is poured or sprayed onto the track ballast in an amount of 55-65 litres per m.sup.2 of track ballast surface and per m of track ballast thickness.

29. The method according to claim 17, wherein the bed has a height of 5-20 mm.

Description

[0058] The invention will now be described in more detail with reference to an exemplary embodiment illustrated in FIG. 1.

[0059] FIG. 1 shows a cross section of a track bed 1 for a railroad track. The track bed 1 comprises a sub-ballast layer 2 and track ballast 3 made from particulate matter. A multitude of railroad ties 4 are supported on the track ballast 3, wherein rails 5 are fixed to the railroad ties 4. In side regions 6 of the track ballast a bonding agent based on a hydraulic binder has been applied so that the particles of the track ballast are bonded together.

[0060] The invention will also be described in more detail with reference to the following examples.

Example 1

[0061] This example illustrates the bonding capacity of the bonding agent of the present invention and the possibility to bond a specific given thickness of the track ballast by depositing the suitable quantity of bonding agent per unit area of ballast.

[0062] The following materials were used for the test: [0063] Bonding agent: A Portland cement mortar with the following composition: [0064] CEM I 52.5 R (Lafarge France Le Teil plant): 750 parts by weight [0065] Limestone filler (BL 200): 375 parts by weight [0066] Sand with a particle size of 0-1 mm: 833 parts by weight [0067] Water: 420 parts by weight [0068] The cement mortar was prepared by mixing the cement, the filler and the sand in a Perrier planetary mixer during 15 sec. Thereafter, water was added to the mixture during a time period of 30 sec and the mortar was mixed during 2 minutes at a slow speed. [0069] The fresh cement mortar has the following properties: [0070] Slump flow (method inspired from EN 12350-8 referring to the testing of fresh concrete/self-compacting concrete, wherein the dimensions are adjusted for slurries (height 57 mm, internal diameter at top: 21 mm, internal diameter at bottom: 37 mm) 5 min after mixing): 110 mm [0071] Modified Marsh Funnel: 2.5 seconds [0072] The cement mortar once hardened had a 24 h compressive strength of 6 MPa and a 24 h flexural strength of 1 MPa (measured on prisms having a dimension of 4*4*16 cm according to EN 196-01 24 h after mixing). [0073] Ballast: Glensanda Ballast 35-65 having particle sizes of 35-65 mm.

[0074] 23+/1 kg of ballast was placed in a bucket (30 cm deep, 30 cm diameter) and compacted 30 seconds on a vibrating table. The ballast height after compaction was obtained by the average value of 4 height measurements (H1). The effective mass of ballast was measured (M1). The apparent specific weight of the ballast (R1) and the ballast porosity (P1) were calculated.

[0075] A given mass of bonding agent (M3) was deposited homogeneously at the top surface of the ballast and then sealed in order to prevent any water loss which may cause weight measurement artefacts. This sealing was done purely for the purpose of this test. 24 hours after the application, the bonded ballast was unmoulded and the mass of the bonded ballast (including the bonding agent) was measured (M2). The fraction of the ballast bonded was evaluated first by calculating (M2M3)/M1.

[0076] If any, the excess of bonding agent was quantified by determining the height of the bonding agent layer (H2) at the bottom of the bucket. The volume of excess bonding agent per surface unit was calculated: H2/P1

[0077] Three tests were performed, wherein the test differed primarily in the mass of the bonding agent (M3) used.

[0078] The results are shown the following table:

TABLE-US-00001 Test Test 1 Test 2 Test 3 Ballast Mass M1 (kg) 22 23.55 22.44 Ballast Height H1 (cm) 22 23 22 Specific weight R1 (kg/m3) 1415 1449 1443 Porosity () 46% 44% 44% Mass of treated ballast M2 (kg) 23.06 25.78 25.56 Mass of bonding agent applied 1.06 2.23 3.12 M3 = M2 M1 (kg) Volume of bonding agent per 7.5 15.7 22 unit area of ballast (L/m.sup.2) Mass of bonded ballast with 10.32 25.52 25.34 bonding agent M4 (kg) Mass of bonded ballast without 9.26 23.29 22.22 bonding agent M5 = M4 M3 (kg) Wt.-% of ballast bonded 42 99 99 Depth of bonding (cm) 9 23 22 Thickness of excess bonding 0 0.5 2 agent H2 (cm) Volume of excess bonding agent 0 0.13 0.63 in the bucket (L) Volume of excess bonding agent 0 1.8 8.9 per surface unit (L/m.sup.2)

[0079] Test 2 shows that with the application of 15.7 L/m.sup.2 of bonding agent a thickness of 23 cm of ballast is bonded. An homogeneous layer of 5 mm of bonding agent is found at the bottom of the bucket.

[0080] Test 1 shows that with a lower amount of bonding agent per surface unit the depth of bonding is reduced to 9 cm. The percentage of ballast bonded is surprisingly closely proportional to the amount of bonding agent deposited (42% versus 47%=7.5/15.7).

[0081] Test 3 shows that with an amount of 22 L/m.sup.2 of bonding agent all ballast is fully bonded. A homogeneous layer of 2 cm of bonding agent is measured at the bottom of the bucket.

[0082] It is observed that in tests 2 and 3 the bonding agent was deposited in excess. When subtracting this excess volume and normalize it by the thickness of ballast bonded, one can calculate the minimal volume of bonding agent needed per ballast layer thickness unit: [0083] For Test 2: (15.71.8)/0.23=60.7 L/m.sup.2/m, i.e. 60.7 litres of bonding agent per surface unit and per metre (depth) of ballast. [0084] For Test 3: (228.9)/0.22=59.7 L/m.sup.2/m, i.e. 59.7 litres of bonding agent per surface unit and per metre (depth) of ballast.

Example 2

[0085] In example 2 a number of different cement slurries were prepared that are suitable as bonding agent according to the invention.

[0086] Table 1 illustrates the impact of different types of binder:

TABLE-US-00002 TABLE 1 Raw material (kg) Mix1 Mix2 Mix3 Mix4 Mix5 Mix6 Mix7 CEM I 52.5 R 750 375 487 CEM II/A 42.5 R 750 CEM III/A 42.5 N 750 Finer CEM I 52.5 R 375 Aluminate Cement 375 Limestone Filler 375 375 375 Fly Ash 262 0-1 Sand 805 833 833 833 833 833 Water 460 420 420 420 420 460 420 Slump-Flow (mm) 105 105 100 110 95 105 110 Modified Marsh 2.4 2.5 2.5 2.5 3 2.6 2.5 Funnel 24 h compressive 17 12 6.7 6 4.8 8.4 5.7 strength (MPa) 24 h flexural 5.5 3.5 2.2 1 1.6 2.9 2.2 strength (MPa)

[0087] Table 2 illustrates the impact of different types of sand:

TABLE-US-00003 TABLE 2 Raw material (kg) Mix 4 Mix 8 Mix 9 CEM I 52.5 R 375 375 550 Limestone Filler 375 375 550 0-1 Sand 833 0-2 Sand 833 Water 420 420 620 Slump-Flow (mm) 110 105 115 O'Funnel 2.5 2.4 2 24 h compressive 6 6.1 5 strength (MPa) 24 h flexural 1 2.3 2 strength (MPa)

[0088] Table 3 illustrates the impact different types of admixtures:

TABLE-US-00004 TABLE 3 Raw material (kg) Mix10 Mix11 Mix12 Mix13 Mix14 Mix15 CEM I 52.5 R 375 375 375 375 375 375 Limestone 375 375 375 375 375 375 Filler 0-1 Sand 833 1048 833 833 833 736 Super- 2 plasticizer Accelerator 7.5 Fibres 2.25 Latex 40 Thickening 0.2 agent Water 420 330 420 420 401 450 Slump-flow 110 115 110 105 100 95 (mm) O'Funnel 2.5 6 2.7 2.6 2.9 2.6 24 h 6 12 6.8 6.2 4.5 4.3 compressive strength (MPa) 24 h flexural 1 4 2.4 2.3 1.1 0.9 strength (MPa)

[0089] In the above examples, the following materials were used:

TABLE-US-00005 Materials Source CEM I 52.5 R Lafarge France, Le Teil plant CEM II/A 42.5 R Lafarge France Val D'Azergues plant CEM III/A 42.5 N Holcim Croatia, Adria Cement Koroma{hacek over (c)}no plant Finer CEM I 52.5 R Lafarge France, Le Teil plant, blaine fineness 6000 m.sup.2/g Aluminate Cement Mixture of 50 wt.-% CEM I 52.5 R, 25 wt.-% gypsum, 25 wt.-% calcium aluminate cement (Ciment Fondu from Kerneos) Limestone Filler Omya BL 200 Fly Ash Cordemais plant 0-1 Sand Sibelco BE 01 0-2 Sand EN Normalized sand Superplasticizer Chrvso Premia 180 Accelerator CaCl.sub.2 Fibres Chryso Syntec 12 Latex Water Etonis Thickening agent CP Kelco - Kelco-crete

[0090] In the above examples, the bonding agent was prepared by the following method: The cement mortar was prepared by mixing the cement, the filler and the sand in a Perrier planetary mixer during 15 sec. Thereafter, water and additives were added to the mixture during a time period of 30 sec and the mortar was mixed during 2 minutes at a slow speed.

[0091] The material properties were measured as follows: The slump flow was measured with a method inspired from EN 12350-8 referring to the testing of fresh concrete/self-compacting concrete, wherein the dimensions are adjusted for slurries (height 57 mm, internal diameter at top: 21 mm, internal diameter at bottom: 37 mm) 5 min after mixing. The flow time was measured by the modified Marsh funnel test, using the protocol described above.

[0092] The compressive strength and the flexural strength were measured on prisms having a dimension of 4*4*16 cm according to EN 196-01 24 h after mixing.