Pipe

ADæÔ»¤ ædÚ <≤GD·Ò _™D¤· ß<Ë_™D Indian Railways Construction Bulletin‹x|> ëë, _¥™. î, GDY· íêêí Vol. 11, No. 4, March - 2002

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ECONOMIC DESIGNS OF HUME PIPES FORRAILWAY EMBANKMENTS AND UPGRADING OFEXISTING HUME PIPES DESIGNED FOR BGML

STANDARD (CONSTRUCTED IN 1970)TO HM LOADING STANDARD

(A CASE STUDY)

By

S. C. Gupta*

SYNOPSIS

Pipe culverts are most commonly used conduits for cross drainage throughRailway/Highway embankments, in addition to carrying of liquid under pressure.They are one of the most economical conduits because of circular structure.Circular structures are governed by the directed stress instead of bendingstress, therefore, are economical. The article deals with basic design conceptof pipe culverts and a case study showing advantage so obtained inupgrading the existing pipe culverts in embankments for higher grade ofloading by following basic concepts.

1.0 INTRODUCTION

There is a general thinking amongst the Rly. engineers that the existing humepipes provided for a lower standard of loading are not suitable for higherstandard of loading, therefore, decisions are taken to dismantle and replace theexisting pipe culverts with higher grade pipes without going into design details.A similar and interesting case study is provided here.

A Rly. line from Cuttack to Paradeep (82.9 km) long was to be executed as adoubling project. Since the entire line from Cuttack to Paradeep was plannedfor carrying axle load of Heavy Mineral Loading Standard, therefore, it wasplanned to upgrade the existing bridges from BGML to HMLS and to constructall new bridges for HMLS. The existing line was having 109 Hume pipe bridgesof dia varying 0.6 m to 1.2 m.

2.0 EXISTING DESIGN PRACTICES FOR RAILWAY EMBANKMENTS

The IS code provides thickness, amount and spacing of steel required for NP1,

NP2, NP3, NP4 type of pipes for different diameters ranging from 80 mm to

* Dy. CE/C/Designs, Bhubaneshwar


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2200mm. The pipes once casted as per the specification provided inIS 458-1988 need to be tested on 3 edge load bearing test for 0.25mm crackingload and ultimate load.

These designs provided irrespective of surcharge over the pipe. It was alsoclarified vide amendment slip no.2 of April, 1991, that the designs provided inIS-458-1988 are not suitable for Railway loadings. This aspect is discussed indetail in the subsequent paras.

Due to this reason, separate pipes are designed for loadings and variousdrawings are issued by RDSO from time to time for various types of loadings orsometimes designs are done by the field units as per the requirements. But inmost of the cases RDSO drawings are religiously followed.

However, RDSO’s drawing covered only up to MBG loading standards,therefore, for HM Loading standard there remains confusion amongst the designengineers and a general concept is that pipes for HM Loading standard shall beof higher thickness & provided with heavy reinforcement. But this is not the casealways, as will be revealed in subsequent paras.

RDSO drawings contain following shortcomings.

(i) Design are for a minimum surcharge cushion, but if cushion increasessubstantially then the design need to be reviewed from economy point ofview. This has not been considered & specified in RDSO’s drawings.

(ii) Design is probably made based on the working stress method assumingpipe behaviour as a doubly reinforced beam, but has not been checkedfor 0.25mm cracking load as prescribed in IS Codes and widelypracticed.

RDSO drg does not mention about at what load the pipes shall be tested. Theyhave defined that pipes are designed for wide trench, positive projection andtype ‘A’ beddings.

3.0 REVIEWING OF DESIGNSThe existing pipes in Cuttack-Paradeep BG line were laid in 1970 and musthave been designed for BGML Loading prevailing at that time as no detailswere available except NP3 type engraved on pipes, so as per normal practice,it was decided to dismantle all the existing pipes and to provide new type ofculverts either box or pipe. Most of the hume pipes bridges were alreadydismantled, meanwhile a problem was felt in replacing existing hume pipebridges having surcharge more than 5.0m on a busy running line. Thisrequires suspension of traffic, dismantling of existing bridge, providingrelieving girder and constructing new bridge. So execution becomes a realherculean task. Therefore, a detailed study and review of existing humepipe’s strength and suitability for HM Loading was made under theguidance of Dy. CE/C/Designs, Bhubaneswar.


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4.0 CRITERIA OF REVIEWING OF DESIGNS

4.1 Detailed design based on the basic concept

A design of hume pipe for HM Loading standard was checked theoreticallyfor simple bending and direct stresses with working stress method and alsoas per the method prescribed in IS-783 for 0.25mm CRACKING LOADS.The detailed calculations are available in Table I for different height of soilsurcharge. A sample calculation is enclosed in annexure. A similarcalculation for MBG Loading standard are given in Table II.

Table – I

Comparison of Hume pipe design parameters of internal dia 1200 mm withworking stress method vis-à-vis IS Code method (For HM Loading)

* It shows that NP4 pipes are safe for surcharge>0.5m* Figures in brackets shows reinforcement required as per RDSO

Drg. No.B-1609- R1 for MBG loading

1. Positive trench conditions (Described in IS 783) is a pipe laying condition,most widely practiced in Railways and recommended in RDSO Drawings.

Working Stress Load to Produce 0.25 Permissible Parameters for Parameters forMethod mm crack (Edge load (l/m) class NP4 RC Existing BGML NP4

Bearing Strength) as to produce pipes type RC Pipes (Diaper IS 783-1985 (ton/m) 0.25mm Thickness 1220mm, thickness

crack for 120 mm 125 mm)Ast(Kg/m) 1 2 class NP4 Ast (Kg/m) Ast (Kg/m)

Long Spiral Positive Imperfect RC pipes as Long Spiral Long Hoop Diag-Projection Trench per IS steel onaland wide Condition 458:1998 MeshTrench

Condition

0 165 8.679 63.615 11.408 11.402 9.001 6.04 53.07 - - -

1 0.5 145 7.89 62.825 8.497 8.537 9.001 6.04 53.07 7.103 41.06 2.17(7.89)* (61.71)*

2 1.0 140 7.89 62.546 7.219 7.252 9.001 6.04 53.07 7.103 41.06 2.17

3 2.0 135 7.89 62.36 5.875 5.781 9.001 6.04 53.07 7.103 41.06 2.17

4 5.0 140 7.89 62.593 4.922 4.364 9.001 6.04 53.07 7.103 41.06 2.17

5 10.0 155 8.679 63.243 5.059 4.216 9.001 6.04 53.07 7.103 41.06 2.17

6 15.0 160 8.679 63.522 5.170 4.138 9.001 6.04 53.07 7.103 41.06 2.17

7 20.0 165 8.679 63.615 5.129 4.039 9.001 6.04 53.07 7.103 41.06 2.17

8 25.0 180 9.47 69.822 5.260 4.098 9.001 6.04 53.07 7.103 41.06 2.17

9 30.0 200 10.26 76.169 5.404 4.177 9.001 6.04 53.07 7.103 41.06 2.17

Sl.

No

Sur

char

ge h

eigh

t (M

)

t(m

m)


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2. In imperfect trench condition embankment is first compacted then part of theembankment is excavated, pipe is laid and excavated portion is filled up withloose/compressible materials. The detailed procedure is described in IS 783.

Table – II

Comparison of Hume pipe design parameters of Internal Dia 1200mm withworking stress method vis-à-vis IS Code method (For MBG Loading)

4.1.1 Assumption in Calculations(a) Working stress calculations are based on the basic displacement equation

Ast (Kg/m) Load to Produce 0.25 m Permissiblecrack (t/m) load for NP4

Sl. Surcharge Thickness Long Spiral +ve Imperfect pipe toNo. ht (m) (mm) Projection trench produce

condition condtion 0.25mm

1 0.5 120 8.679 66.852 7.134 7.172 9.001

2 1.0 120 7.89 61.71 6.195 6.223 9.001

3 2.0 120 7.89 61.71 5.160 5.061 9.001

4 5.0 120 8.679 66.852 4.464 3.925 9.001

5 10.0 120 10.257 77.137 4.560 3.770 9.001

6 15.0 120 11.046 82.28 4.613 3.672 9.001

7 20.0 120 11.046 87.422 4.552 3.571 9.001

8 25.0 120 14.202 107.992 4.476 3.479 9.001

9 30.0 120 17.358 133.705 4.405 3.401 9.001

described in detail in various RCC design books for pressure and non-pressure pipes by neglecting relief due to side earth pressure.

(b) Pipes are checked for 0.25m cracking loads for two conditions

(i) Wide trench, +ve projection and A type bedding(ii) +ve projection, imperfect ditch condition and A type bedding

4.1.2 Analysis of Calculation(i) It is revealed from the calculations provided in Table II that existing

design of MBG Hume pipe are not suitable for surcharge less than 1.0 mand again surcharge more than 2.0m, if checked with basic bending andshear theory, which is contradictory to tested results. This may bebecause of two reasons.

(a) The above theory neglects the relief due to side earth pressure, which isabout 33%.


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(b) Simple bending and direct stress theories are absolutely not applicablein pipe designs for Rly. embankments. Because they are neitherundergoing direct stresses nor bending stresses.

(ii) If checked with IS 783’s method then not only RDSO’s BGML and MBGdrawings are safe for HM loading but also NP4 type pipes of IS 458 aresafe with a surchage > 0.5 m. The design concept prescribed in IS 783 isbased on Spangler’s theory and is more appropriate as it directly checksthe 0.25mm cracking load and ultimate load, This procedure is wellestablished and proven reliable and safe over the years, not only inIndia but all over the world in similar conditions (Ref.4,9,11)

(iii) It is also worth noting that even Spangler’s theory is on conservative sideas it does not take into account the full arching action of soil and IS-783has further gone on more conservative side by neglecting cohesiveelement of soil.

4.2 Based on Plate Load Test of Existing PipesIt was planned to check the loads carrying capacity of each pipe by directlyapplying the ultimate load in field conditions.

4.2.1. Load Calculations

(i) Calculation of superimposed dead load (SIDL) and equivalent live load:Pipes are subjected to SIDL due to ballast, sleepers and Rails in addition todynamic loads. Dynamic loads were calculated for HM Loading. They werecoming as

Live Load - 15.8t/m as per Bridge Rules Amendment Slip No. 26Dt. 17.11.2000.

Live Load with CDA = 15.8 x 1.806 = 28.535t/m

SIDL = 5.5t/m

Live Load + SIDL = 28.535 + 5.5 = 34.035t/m

Total Load on plate of 1.5 x 3.0 = 34.035 x 1.5 x 3.0/2.745 (Sleeper Length)t

Ultimate load with FOS of 1.5 = 55.79 x 1.5 = 83.69t

4.2.2. Loading arrangements

(i) To test pipes under field condition a plate 1.5 x 3.0 x 10mm x 4 nos wereprovided on the bank coinciding with the underlying pipes centre line. Theabove dimension were chosen on the basis that at ballast soil interface theloading area over the 1.44m (external dia) pipe is approximately, 1.50 x3.0m.


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(ii) Thereafter a loading platform with the helps of rail pieces was made so as toobtain a dimension of 6.5 x 5.5m.

(iii) Remaining load was then applied with help of sand bags and loose sand.The arrangements are shown in Sketch – 1 and photographs No. 1 onpage no. 12.

(iv) Such load was applied for a surcharge of 1.0m and 3.0m.

4.2.3. Recording of deflection and settlement of pipe

(i) One meter scale was fixed at the bottom bed of the pipes centre andsupported with a plate.

(ii) To measure deflection in hume pipe a scale was fixed on the inside top ofthe hume pipe having a least count of 1.0mm.

(iii) Out side reference BM were fixed to measure relative settlement anddeflection of pipe.The details of measurement arrangement are shown in sketch No. 2 andphotograph No. 2 on page no. 13.

TABLE III RESULTS OF PLATE LOAD TEST

Sl. Surcharge Load Settlement of Pipe Deflection of Hume PipeNo. height Applied

in TonsPlate Ref. Diff Settle Invert Slump Add Defl.Read- Pt. ment pipe Plate In cming in cm top Reading

reading

14.76 91.7 83.9 7.8 0 37 75.2 112.2 0

1 3.0 84.88 91.2 83.0 8.2 0.4 21 91.2 112.2 0

131.68 93.2 85 8.2 0.4 19 93.2 112.2 0

14.76 91.3 83.3 8 0 19.8 91.3 111.1 0

2 1.0mt66.604 81.9 73.9 8 0 29.2 81.9 111.1 0

143.264 89.9 81.5 8.4 0.4 14.75 96.15 110.9 0.2

197.9 96.15 87.15 9 1.0 14.75 96.15 110.9 0.2

Note: Readings were taken at an increment of 20-25 ton of load, but same are notshown as there is no change in between readings.

The above load test indicates that the existing pipes are safe even HMLSLoading with a factor of safety of more than 2.25 to 3.0, which is much more than thecodal requirement of 1.5.


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4.3. Testing Pipes On Three Edge Bearing Load For 0.25m Crack as per IS3597-1998

Three pieces of 1.2m dia pipe, one piece each of 900mm dia and 600mm diapipes were taken to a factory about 100km away from the site at Bhubaneswar.The pipes were tested by three edge bearing test as prescribed in IS3597:1998. The results are given in the Table – IV below:

TABLE–IV THREE EDGE BEARING TEST RESULTS

0.25mm Crack Load in TonnesRequired for HM Loading

Required for StandardSl. Dia of NP4 pipe as per Without With 500mm ActualNo. pipe IS783 Cushion cushion load

1 600mm 11.1 12.699 11.664 21.0

2 900mm 15.90 18.141 16.663 25.0

3 1200mm 21.2 23.379 20.248 26.0

4 1200mm 21.2 27.379 20.248 26.0

5 1200mm 21.2 27.395 20.248 27.0

5.0. ECONOMICSAt this juncture it was decided not to dismantle about 9 No. of Hume pipebridges having higher (5-7m) cushion. The saving because of adoption ofexisting pipes was about 42.9 lakhs (Refer table V) excluding saving ofdisruption to traffic and inconvenience under traffic block.

Where as the saving could be unimaginable had there been clear and logicalguidelines on the subject. Such type of dismantling of Hume pipe bridges mustbe continuing all over the Indian Railways, such in depth study andreviewing certainly help in ease in construction apart from saving ofmoney and time.

Above saving includes only cost of extension portion of bridge for doubling, butthere is a plan to upgrade existing BGML bridge to HM loading standard in nextphase. Then the savings will almost be double. Entire savings for left overbridges may amount to several crores.


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TABLE V-SAVING DUE TO REVISED DESIGNS

Sl. No. Br.No. Value of BOX Value of Net SavingHume Pipe

1 3 707000 127000 5800002 21 707000 127000 5800003 22 850000 200000 6500004 23 850000 200000 6500005 25 850000 200000 6500006 26 707000 127000 5800007 243 550000 250000 3000008 244 550000 250000 300000

TOTAL 5771000 1481000 4290000

6.0. CONCLUSION/RECOMMENDATIONS

I. From the above calculations, laboratory tests and field test itbecomes quite clear and evident that Hume pipes designed andcasted as per NP3 standard requirement for BGML loading are safefor HMLS with strength factor more than 2 – 3. Therefore, shall beadopted as it is, without any modification.

II. For all new construction of HM/MBG loading standards, present NP4pipes (given IS 458-1998) shall be used with a minimum cushion of600 – 900 mm.

III. The study so conducted caused a immediate saving of Rs. 42.90 lakhsfor Rlys in addition to time saving, easier execution, avoiding ofsuspension of running lines.

IV. It shall also be kept in mind that calculations and formulae developed byMortson and Spangler for pipes are itself on very much conservativeside, as they ignores the full arching benefits of soil. In addition to thisIS 783:1985 has further gone on safer side by ignoring cohesive elementof soil in calculating dead load factor.

V. Construction in field can be easily and shall be done as per para A-4 ofIS 783:1985 for imperfect ditch conditions than load factors will furtherincrease and requirement of pipe thickness and reinforcement will furtherdecrease.

VI. Special design Hume pipe with simple bending and shear stresstheory for HM loading with 85kg per meter spiral reinforcement(1200mm internal dia, 120mm thickness, M-30 concrete) are alsocasted and tested on three edge bearing load. The pipes shown


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0.25mm crack on 30 ton load where as an NP3 pipe (design forBGML) with a spiral reinforcement of 43kg per meter found safe for26 ton crack load, therefore, the increase in the reinforcement doesnot increase the relative strength of pipe. Hence, there is no use inincrease of reinforcement for higher loading.

VII. There is no need for separate RDSO’s drawings for Hume pipes, ratherthey shall only prescribe the requirement of test load for three edgebearing test for present NP4 type of pipes. As this method is wellestablished, proven and tested all over the world as discussed by variousauthors. The clause provided in IS – 458 i.e., NP4 pipes shall not beused for Rly loadings shall not be mistaken as those calculations areprovided irrespective of minimum cushion.

ACKNOWLEDGEMENT:

1. I acknowledge my gratitude to Sri S.P. Sahu, CE/C/I/BBS, who inspired, helpedand encouraged in conducting load tests.

2. I acknowledge my thanks to Sri. I.B. Jha, Dy. CE/C/CTC and Sri. N.S. Uikey,Dy. CE/C/D-IV/BBS for helping in making arrangements for necessary loadtesting.

3. I acknowledge my thanks to Sri PK Patra, AXEN/C/Designs/BBS, Sri RC Sethi,JE/I/Drg, Sri DK Choudhury, JE/I/W for helping in making calculations andsupervising load tests.

REFERENCES:1. IS-783-1985 “Indian Standard Code of Practice For Laying of Concrete Pipes”,

(First Revision), Bureau of Indian Standard, New Delhi.2. Is-458-1988 “Indian Standard Specification for Precast Concrete Pipes (With &

Without Reinforcement)”, (Third Revision), Bureau of Indian Standard,New Delhi.

3. IS-3597-1998 “Concrete Pipes – Method of Tests”, Bureau of Indian Standard,New Delhi.

4. A. Rico Rdgrighez, H.del Castrilo and G.F. Seweres “Soil Mechanics inHighway Engineering”, Trans Tech Publication.

5. G.Annamalai, J Shammujesunderam & others “Earthfill Load on Burred Pipes”.Journal of Insitute of Engineers, India

6. N.Krishna Raju “Advanced RCC Design”. Tata Machrawhill Publication.7. O.P. Jain & Jai Krishna “Plain and Reinforced Concrete –Vol.II” Nem Chand

and Brothers, Roorkee8. Merlin G.Spangler “Culverts and Conduits”.9. Bernard E.Butler “Structural Design Practice of Pipe Culverts”, Highway

Research Record No.413/197210. A.Martson & A.O. Anderson “Theory of Loads on Pipes in Ditch”.


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ANNEXURE I

DESIGN EXAMPLE OF HUME PIPE BRIDGE FOR RAILWAY EMBANKMENTS

VARIOUS FORCES ACTING ON A HUME PIPE

Type of Loading HMLSFormation Level 9.54 mBed Level 7.22 mInternal diameter of pipe 1.2 mGrade of concrete M30Grade of Steel Hard drawn wireDia of Longitudinal bar 8 mmDia of Spiral bar 10 mmNo. of longitudinal bar 22 Nos.Spacing of Spiral bar 80 mm

STANDARD DATA

Depth of ballast cushion 0.35 mDead load 5.5 T/mLive load 15.8 T/mAngle of repose 30 degreeUnit Wt of soil 1.8 T/cumUnit Wt of water 1 T/cum


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A) Design with basic bending moment & shear force theory, assuming pipe as doublereinforced beam.

BENDING MOMENT AND FORCE TABLE(Unit – All bending moments in ton metre and all Forces in ton)

Loading Type Bending Moment Direct ForceTop Side Bottom Top Side Bottom

Wt. of Pipe 0.045 -0.051 0.058 0.033 -0.311 -0.033Wt. of Water 0.05 -0.056 0.063 0.254 0 -0.254Earth of 0.012 -0.022 0.024 0.014 -0.168 -0.014haunchesUDL from top 0.924 -0.924 0.924 0 -5.602 0Earth pressure -0.101 -0.108 -0.116 0 0 0Total sagging 1.031 0.108 1.07Total hogging -0.101 -1.054 -0.116Net moment 0.93 -0.946 0.954Critical moment 1.031 1.054 1.07 0.301 -6.082 -0.301

*Bending moment due to side earth pressure are neglected, while considering criticaldesign moments

Design moment 1.07 TmDesign force 0.301 TonThickness of pipe provided 0.12 mStandard thickness 0.12 mStress in Steel 13744.769 ton/sqmPermissible Stress in Steel 14000 ton/sqm i.e. SAFEStress in Concrete 744.922 ton/sqmPermissible Stress in Concrete 1020 ton/sqm i.e. SAFEWeight of spiral reinforcement 66.852 kg/mWeight of longitudinal reinforcement 8.679 kg/m

B) Checking with IS-458-1988, methodi.e. With ultimate load theory for 0.25 mm crack load

Steel as per NP4 pipesEdge bearing strength for positive projection, wide trench condition 10.52 ton/mEdge bearing strength for imperfect ditch condition 10.563 ton/mLoad to produce 0.25mm crack for positive projection 7.013 ton/mLoad to produce 0.25 mm crack for imperfect ditch condition 7.042 ton/mPermissible load to produce 0.25mm crack for NP4 pipe 9.001ton/m i.e.NP4 pipes of IS-458-1988 are SAFE

Sign for force +ve is Tension,-ve is Thrust

Total


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Photo 1, Load test arrangement at site

Sketch 1, Load test arrangement at site


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Photo 2, Load arrangement and deflection measuring arrangement

Sketch 2, Deflection measuring arrangement

ARRANGEMENT FORHUME PIPE SETTLEMENT READING

NOT TO SCALE

BANK HEIGHT 1.00M

SCALE 0.30M

SCALE 1.00M

H. P. 1.2MØINSTRUMENT NO. 1

REFERENCEPOINT


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Photo 3, Deflection measurement with the help of auto level


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WATER PROOFING TREATMENT

ON RCC/FLAT SLAB BYCHINA MOSAIC PROCESS

BY

Vardhman Jain*D. S. Yadav**P. K. Vyas***

1. Introduction :

The problem of leakage from roof of building is experienced by all the zonal railways.Various methods / Techniques have been tried to arrest the leakages. Most of the timethe treatments adopted proves to be effective only for a short duration.This report is covering the details of prevention of leakage through R.C.C. New/old orflat slabs terrace by China mosaic treatment.

2. Reason of leakage through slabs :

The following are the probable causes of leakage through flat slab.

(a) Deterioration of slabs (i) Due to age

(ii) Weathering actions

(iii) Debonding

(b) Improper Supervision (i) Honey combing / porus concrete.

(ii) Inadequate compaction.

(iii) Excess water addition.

(iv) Improper cover.

(v) Inadequate slope

(vi) Bad workman ship

(c) Water stagnation

(d) Provision of less number of discharge / down take pipes.

*AXEN (CS) CCG, **AXEN (TP) CCG, ***ADEN (W) DHD


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(e) Leakage through cold joint, construction joints, expansion joints, cracks, junction ofwall joints of different materials etc.

3. Basic requirements of arresting leakage of roofs

The following are the basic requirements of water proofing of roofs.

1. Provision of adequate slope - gravitational flow (1 in 100)

2. Provision of adequate openings for drainage of water pipe - spacing of Down takepipes - not more than 6 meter (as per clause 5.3.2 of IS 2527 year 1984).

3. Proper detailing of junction at roof with parapet wall - (as per IS 3067 -1988).

4. Proper treatment of expansion joint

5. Provision of effective water proofing system over the roof.

In order to arrest leakage of water through RCC roofs. It is necessary that roofs areprovided with suitable water Proofing system.

4. Different process of water proofing system

The various methods adopted at various part of country are given below :

1. Lime concrete terracing.

2. Water proofing using bitumen felts

3. Mud - phuska treatment.

4. Water proofing using polyethylene films.

5. Water proofing using polymer modified bitumen members.

6. Water proofing by polymer cementitious slurry coating and then china mossaictreatment.

5. Water proofing by China Mossaic process

In order to overcome the leakage problems the china mosaic treatment is very effectiveto prevent leakage from slabs. And most widely used in W. Railway in BCT Division.

Surface Preparation :


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1. Surface preparation is most important step before application to get best resultsand to avoid failure.

2. The surface must be free from dust, dirt, coatings loose particle, fungus, oils,greases etc.

3. Clean the surface by scrapping sand blasting, grinding to remove dust and looseparticles.

4. Treat the surface with 5 to 10% hydrochloric acid followed by completeneutralization with water which will improve bonding of the coating.

5. Oils, greases and mould release agents can be cleaned with solvents.

Provision of Slope :

A minimum slope of 1 in 100 with M 15 concrete and water proofing admixture onprepared surface. The thickness of layer is kept between 25 to 40 mm. the size ofaggregate should be down 10 mm. The w/c ratio 0.45 should be maintained.It is better if slope is 1 in 60.

6. Detail of NS items adopated in Western Railway (BCT Division)

Providing water proofing treatment with china mosaic on terrace slab as per under inaddition to specifications enclosed along with tender documents. Preparing the surfacefor water proofing treatment by scrapping and brushing the surface so as to remove allloose material after removing old tarfelt bitumen fiber glass tissues etc. and completewashing to the surface with. Only dismantling of concrete if any will be paid separatelyunder SOR item. Providing cement concerete to proper slope as directed by theRailway Engineer or his representative. However, cost of providing cement concretewill be paid for separately under SOR items.

Applying one coat of polymer based water proofing compound of approved qualitymixed with cement (OPC). 1 kg of polymer based water proofing compounds and 2 kgof cement (OPC) should cover an area of 2.80 sq. m.

Providing and laying broken China Mosaic (Broken pieces of China glazed tiles) ofapproved colour set in 20 mm thick cement mortaral 1 : 3 mixed with water proofingpowder of approved quality at correct level and slope and joints finished by pouringcement slurry and brooming them down. The tiles shall be closely packed such thatchina mosaic covers atleast 90% of slab area.

The above treatment shall be provided on the parapets / any other wall upto 30 cmabove the floor level and the junction between the wall and parapet round offin theshape of area of a curve.

Curing of the flooring continuously for 10 days so as to render the surface hard.


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Cleaning the China mosaic tiles of all dust and stains.

The rate shall also exclude cost of cement, which will be paid for separately, but shallinclude disposal debris released from this work.

7. Salient features of polymers

1. Bonds (adhesive) strongly to most of the building materials.

2. Can be applied to uniform thickness coating on horizontal and vertical surface.

3. Allows trapped water vapours to escape and prevents blistering and adhensionfailure.

4. It is unaffected by UV light and prevents discolouration of concrete. It will notcorrode reinforcing steel.

5. Coating is highly durable even in continuous contact with water.

6. It is resistant to water, dilute acids and alkali solution.

7. It is non-flammable, non hazardous, does not evolve toxic gasses when exposed tofire.

8. Non-toxic to human being.

9. Most properties improve an aging.

10. Resistant to fungus and micro organism growth.

8. Typical characteristics fo different polymers of the water proofing compoundsand admixtures

A) Tech. coat - 61 (p) white polyurethane water proofing coating.

(a) Mixing ratio - 10 to 15% of cement.

(b) Consistency of mix - ready to use brushable.

(c) Application time (portlife) at 300 C - 3 to 4 hours.

(d) Surface dry time at 300 C - 15 to 30 minute on concrete surface

(e) Complete curing time - 72 hours min.

(f) Recoatibility time - 10 to 12 hours.


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(g) Coverage : on concrete surface - 45 to 50 sq. f / lit / coat.

(h) Packing - 1, 4, 20 lit.

B) Master - Crete

(a) PH Value - 9 to 10

(b) Consistency - free folwing thin / liquid

(c) Mixing ratio - 18 to 20 % by weight or cement quality

(d) Intitial setting time - 24 hours

(e) Initial curing time - 72 hours

(f) First coat - 4 to 4.5 sqm / 3 lit mix

(g) Second coat - 4.5 to 5.5 sqm / 3 lit mix

(h) Package 1, 5, 20 lit.

C) Chemistik - clean water proofers

(a) Colour - Clear liquid

(b) Film properties - flexible tack free. Clean film

(c) Coverage - first coat - 60 to 70 sq.f/ lit

(d) Second coat - 75 to 80 sqf / fit

(e) Flash point - 400 C

D) Polcrete admixture : Used as admixture to control w/c ratio generally 2% ofcement dose prepared with water. Admixture available in packing - 1, 4, 10, 20 kgand 100 gms.

E) Chemicrete integers water proof admixture.

doses - 250 gm. per kg.

It can be used with all types of cement including the sulphate resistance type. It is


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chloride free hence will not have any harmful effect on the reinforcement steel,prestressed tendon.

F) Xypex : Water proofing by crystallization when mixed with water and applied as acementitious coating, the active chemical in X Y P E X cause a catalytic reactionwith generates a non-soluble crystalline formation of dendristic fibers within thepores and capillary track of concrete. Thus the concrete becomes permanentlysealed against the penetration of water or liquids from any direction.

Before applying wet the surface.

G) S B R Polymer latexes based n styrene butadiene (SBR) acrylics or polyvinylacetate can be used

Properties :

(a) Solid contents mini 40% max. 50%

(b) pH 7.5 to 8.5

(c) 14 days bond strength at 250C-7.5 to 10 mpa

(d) Maximum shrinkage conefficient on cure (linear)- 0.005.

(e) Mini compressive yield strength at 7 days- 55mpa.

(f) Absorption: 24 hours maxi. 1% .

(g) Tensile strength 7 days mini - 40 Mpa.

(h) Elongation at break mini 1% .

(I) Doses- depends upon use-10 to 15 lit/bag

for cover replacement-7%

core replacement-10%

Applied in 3 Croat first two coat perpendicular to each other.

H) Roff Super Crete : Acrylic polymer based designed for use with cementformulation.

50 kg cement + 125 kg zone II sand + 10 lit roff super create + 5 to 7 lit water.

9. Conclusion


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China mosaic process is the best process of all available methods in followingway.

1. It Completely prevent the leakages from slab for long duration.,

2. Terrace give good out look appearances. Hence can be used for commercialpurpose.

3. The 90% area of top surface is covered by the Broken tiles which reducedweathering effects.

4. The method reduce unnecessary dead load.

5. The minimum effective life is 5 years. However it is effective more than 12 years.

6. The further maintenance cost in NIL

7. It prevents the leakage through RCC roof or terrace in three way,

(i) The china clay tiles pieces give the impervious surface which do not allow topenetrate the water through top surface.

(ii) If due to any cause water passes through the china clay top layer then thedense M 15 layer of concrete with admixtures and in proper slope do not permitthe water to further penetrate the slab. The penetrated water flow outside theslab due to gravitational flow. Hence, water is not sustain above the slab.

(iii) Even though, if water penetrates through the both surfaces, then the third(i. e. bottom most) layer of polymers do not allow to penetrate the water throughthe slab.

Hence, the china mosaic restrict the percolation of water in three stages thusproving to be the most effective method of water proofing.

10. Suggestions :

Inspite of water proofing treatment of the leaky roofs, in some of the cases, wateragain starts leaking from the roofs after passing one or two years, due to poorworkmanship or in adequate supervision, causing hardship to the occupants.Therefore the water proofing treatment shall be guaranteed for a minimum period of5 years from the date of completion of the work. For this purpose special conditionshould be included in all tenders regarding water proofing treatment work. Acertain amount say about 5% of the cost of work shall be kept deposit from thecontractor which shall be released only after successful completion of 5 years. Inthe meantime if leakage occurs the contractor should be bound to rectify the same.


22/

In case contractor fails to rectify the leakages the deposited amount should beforfeited. This will ensure 100% water proofing of the leaky roofs.

Annexure - I

Standards & codes of practice dealing with water proofing to roofs.

Following is the list of various I S codes which deals with water proofing of roofs.

(a) I S 1322 : 1993 specification for bitumen felts for water proofing and damp proofing(Forth revision)

(b) I S 1346 : 1991 code of practice for water proofing of roofs with bitumen felt (Thirdrevision)

(c) I S 1580 : 1991 specification for bituminous compound for water proofing andcaulking proposes (First revision)

(d) I S 2115 : 1980 code of practice for flat roof finish mud phuska.

(e) I S 2527 : 1984 code of practice for fixing rain water gutters and down pipes fordrainage.

(f) I S 3036 : 1992 code of practice for laying lime concrete of a water proofing rooffinish (second revision)

(g) I S 3037 : 1986 specification of bitumen mastic for use in water proofing of roofs(First revision)

(h) I S 3067 : 1988 code of practice for general design details and preparatory work fordamp proofing and water proofing of buildings (First revision)

(i) I S 3384 : 1986 specification for bitumen primer for use in water proofing and dampproofing (first revision)

(j) I S 4365 : 1967 code of practice for application of bitumen mastic for water -proofing of roofs.

(k) I S 4911 : 1968 glossary of terms relating to bituminous water proofing and dampproofing buildings (first revision)

(G) I S 7193 : 1974 specification for glass fiber base - bitumen felt.

(m) I S 7290 : 1979 Recommendations for use of polyethylene film for water - proofingof roofs (first revision)


23/

(n) I S 9981 : 1981 Code of practice for in situ water proofing and damp -proofingtreatments with glass fiber tissue reinforced bitumen.

(o) I S 13182 : 1991 Recommendations for water proofing of wet areas in building.

(p) I S 13826 ( P + 1) 1993 Bitumen based felts - method of test part 1 breakingstrength test,.

(q) I S 13826 (P + 2) Bitumen based felts method of : 1993 test part 2 pliability test

(r) I S 13826 Bitumen based felts - method of test (P + 3) : 1993 Part 3 storagestocking test.

(s) I S 13826 Bitumen based felts - method of (p + 4) 1993 test part - 4 pressure headtest.,

(t) I S 13826 Bitumen based felts - method of test (P + 5) 1993 Part-5 head resistancetest.

(u) I S 13826 Bitumen based felts - method of test (P + 6), 1993 Part - 6 waterabsorption test.

(v) I S 13826 Bitumen based felts - method of test (P + 7) 1993 Part-7 determination ofbinder content.

___


24/

CLEANING OF SURFACE IN PROGRESS

SURFACE AFTER APPLYING POLYMERCEMENTITIOUS SLURRY COAT


25/

FINAL VIEW AFTER LAYING CHINA MOSAIC ON ROOF SLAB

FINAL VIEW AFTER LAYING CHINA MOSAIC ON PARAPET

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Volume 11, Number 4 March 2002

ADæÔ»¤ ædÚ <≤GD·Ò _™D¤· ß<Ë_™D

INDIAN RAILWAYS CONSTRUCTION BULLETIN

ÙxßDj_™ Gx|>ÚEDITORIAL BOARD

o» Ãw ß¥_™Dm <≤jdm_™ / ΩRæÙd≤ Í¡¤±Shri Budh Prakash Director / IRICEN Chairman

o» e≤ Ù» mDæjD „RæŸfl> ß¥D¡¤Dß_™ / ΩRæÙd≤ Ùjy¤Shri N. C. Sharda Sr. Professor / IRICEN Member

o». ÙÃwDxmÃ mGD· ß¥D¡¤Dß_™ / ΩRæÙd≤ Ùjy¤Shri Sudhanshu Sharma Professor / IRICEN Member

o». ß¥„»Ò _Ã™GDæ ß¥D¡¤Dß_™ / ΩRæÙd≤ Ùjy¤Shri Praveen Kumar Professor / IRICEN Member

o» e. _d™. ¤Dj„ „Ræ˛> ß¥D¡¤Dß_™ / ΩRæÙd≤ _™D¤·_™Dæ» ÙxßDj_™Shri A. K. Yadav Sr. Professor / IRICEN Executive Editor


28/

FROM THE DESK OF EXECUTIVE EDITOR

The March 2002 issue of the Construction Bulletin features twoarticles. The first article by Shri S.C. Gupta Dy CE/C/ DesignsBhubaneshwar deals with basic design concept of Pipe Culverts with acase study showing advantages obtained in upgrading the existing pipeculverts for higher grade of loading by following basic concepts. Thoroughanalysis, and field laboratory tests author has observed that, hume pipesdesigned as per NP3 standard for BGML loading are safe for H.M.loadingstandards with strength of factor 2-3.

The second article authored by Shri Vardhman Jain AXEN (CS)CGE, Shri D.S. Yadhav AXEN (TP) CCG and Shri P.K.Vyas ADEN (W)DHD, Western Railway deals with water proofing treatment on RCC/FLATSlab. The authors have detailed water proofing by Chaina Mosaic. Variousadvantages of this treatment has been highlighted.

It is hoped that these articles will be useful to the field Engineers.

The field engineers and other readers are requested to send articleson various issues, which they feel important enough to be shared withothers through this common forum of Indian Railway Construction Bulletin.The articles may be sent on diskette or through E-mail so that editing at ourend can be done quickly.

With best wishes,

- EDITOR

( ii )

ADæÔ»¤ ædÚ <≤GD·Ò _™D¤· ß<Ë_™D

INDIAN RAILWAYS CONSTRUCTION BULLETIN

<„ Q ¤ „ yÔÃC O N T E N T S

Page No.

1. Economic Designs of Hume Pipes for Railway Embankments and Upgrading (1)of Existing Hume Pipes Designed for BGML Standard (Constructed in 1970)to HM Loading Standard (A Case Study)

By

S. C. Gupta. Dy. CE/C/Designs, Bhubaneshwar

2. Water Proofing Treatment on RCC/FLAT Slab by (15)China Mosaic Process

By

Vardhman Jain, AXEN (CS) CCGD. S. Yadav, AXEN (TP) CCGP. K. Vyas, ADEN (W) DHD

Ô_™≤»_™” ßdßÙ· _d™ Úd‹_™Dd* VDæD @¤⁄Ô <_™e ‘e <„YDæ Í<≤„D¤· L™ß Ùd ΩRæÙd≤ _d™ <„YDæ ≤´»* ´I $

The views expressed by the authors of Technical Papers are notnecessarily the views of IRICEN.

( i )

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Volume 11, Number 4 March 2002

Edited Published By :The DirectorIndian Railways Institute Of Civil Engineering,Pune - 411 001.

DESIGNED & PRINTED by :M/S. M. R. & Co.1552 Chimanbaug,P. Jog Classes Lane,Pune - 411 030.Phone : 4330449

THIS IS YOUR BULLETIN, SHOULDN'TYOU BE CONTRIBUTING TO IT?

Editor, Indian Railways Construction Bulletinextends an invitation to all its readers to take activepart in the publication of the Bulletin.

Do send any articles, experiences, notes andsuggestions which you think would make interestingand informative reading to other readers of ourBulletin.

You could also give us some ideas on howto improve the Bulletin, its contents and itspresentations.

Any reader can contribute articles, but theyshould be about your work environment andexperiences on maintnance & construction of worksand Bridges.

Please send your articles to:The executive Editor,Indian Railways Construction Bulletin,Director,Indian Railways institute of Civil Engineering,Pune 411 001.Fax: (020) 6128677e-mail : [email protected] : www.iricen.gov.in

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