DINDIGUL BYPASS TO SAMYANALLORE ON NH 7 IN THE STATE OF TAMIL NADU VOL - 2A(NS 82).pdf

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Volume 1 Concession Agreement ,Schedules and SPV Details for DS Toll Road Limited

Volume 2 RFP, Response to Queries and Addendum for DS Toll Road Limited

Volume 3 DPR for DS Toll Road Limited

National Highways Authority of India Consultancy Services for Feasibility study and Detailed Project Report for 46 Laning of Karur- Madurai section of NH-7 from Km 30518 to 42616

in the State of Tamil Nadu (Consuttancy Package Cmll Alll)

CONTRACT PACKAGE NS 82 (TN) I

VOLUME 11 (A) : APPENDIX D - BRIDGE REPAIR AND REHABILITATION REPORT

January 2005

BCEQM bint venture With F i w w ~ ~ c o H 6 u T ~ aarvee assoc~ates

4sD I ,. ,, , . . IFL E Z , " ' d Y E E ' H G Rol

REHABILITATION OF EXISTING BRIDGES FROM

KARUR TO MADURAI IN BANGALORE- KANNIYAKUMARI

SECTION OF NH7 IN TAMILNADU

PACKAGE 3

NS 82 (km 381 - km 426.6)

NH 7 (Karur - Madurai) Rehabilitation of Existing Bridges Package NS 82 (TN) (km 381 - km 426.6)

REPAIR, REHABILITATION, RETROFITTING AND WIDENING OF BRIDGES (NH7)

INTRODUCTION

The Ministry of Road Transport and Highways (MoRT&H), Govt. of India has decided

to take up the development of various National Highway Corridors where the traffic

intensity has increased significantly thereby necessitating capacity augmentation for safe

and efficient movement of traffic. One set of such corridors is North - South (From

Srinagar in J&K State to Kanyakumari in Tamil Nadu State) and East - West (Silchar in

Assarn to Porbander in Gujarat) for a total length of about 7300 Km. National Highways

Authority of India (NHAI) has been entrusted to implement the development projects for

these corridors. NHAI has accordingly taken up project preparation of certain stretches

on North - South, East - West corridors under Phase I1 of NHDP. NHAI issued RFP in

June 2003 for these stretches. The work of conducting Feasibility Studies and Preparation

of Detailed Project Report for Four / Six laning from Karur (Km 306) to Madhurai (Km.

427) in NH 7 has been entrusted to the Joint Venture of BCEOM - Aarvee Associates in

association with ORG.

The section has been divided into three packages as shown below:

Package 1 (NS - 80 ) from km 305.8 to krn 345

Package 2 (NS - 8 1 ) from km 345 to km 38 1

Package 3 (NS - 82 ) from km 38 1 to km 426.6

The existing 2-lane bridges are to be rehabilitated and widened to 3-lane, and a new 3-lane

bridge shall be constructed adjacent to the existing one. The following report pertains to the

rehabilitation and widening scheme that has been proposed for NS 82, the specifications for

the rehabilitation work and the schedule of work. The proposal can be summarized as follows:

1) Widening of existing 2-lane bridges to 3-lane.

2) Replacement of handrail with crash barrier, in the median side

3) Replacement of wearing coat.

4) Repair of the defects in the superstructures and the substructures


WIDENING METHODOLOGY:

It is intended to convert certain existing 2-lane bridges to 3-lane, the deck

widths of which are not the same. However, after widening it shall be 12.7m with a

carriageway of llm. The new camber provided after widening shall be 1 in 60 uni-

directionally. The profile of the deck slab after widening and application of the new wearing

coat shall be as shown in the figure. The thickness of the widened portion of the new slab will

be slightly more than the existing slab. The bottom of the new slab is to be kept flat as shown

in the figure. The new wearing coat is to be laid with a uni-directional camber of 1 in 60 with

the higher side towards the median side. Reference can be made to the detailed drawings for

better appraisal of the methodology.

REPLACEMENT OF HANDRAIL WITH CRASH BARRIER IN THE MEDIAN SIDE:

A new crash barrier solid type will be provided on the central verge side. The base

width of the crash barrier will be 450 mm instead of the standard 500 mm (change the

spacing of bars with the internal dimensions).

Step 1: Remove the railings along with post upto kerb level. The kerb is roughly 275 x

450 mm.

Step 2: The existing kerb of size, say 300 x 450mm, which is about 275 to 300mm above

the old concrete structural slab, is to be dismantled without breaking or removing the

vertical rebars which go inside the steel slab.

Step 3: The new kerb will be of (275 + 200) x 450 size and should have reinforcement of

16 dia bars 4 numbers on either side. These bars are vertical. In addition, the

reinforcement of the crash barrier should be provided inside the available depth of 475

mm. If required the end of the reinforcements of the crash barrier can be suitably bent

inside this depth of 475mm.

Step 4: Before concreting the new kerb, a suitable bonding coat should be provided

between the top of old structural slab and the new concreting of the kerb.

On the outer side, a safety kerb of 750 H x 250 V (clear) is to be provided.

NH 7 (Karur - Madurai) Rehabilitation of Existing Bridges Package NS 82 (TN) (km 38 1 - km 426.6)

RE-LAYING OF WEARING COAT:

The existing wearing coat of cement concrete is assumed to have been laid with a bi-

directional camber of 1 in 75, the condition of which is likely to be bad because of the age, and

the wncrete wearing coat might have been overlaid with bituminous material. In view of the

bad condition of the wearing course, it is proposed to remove completely, the old wncrete

wearing coat, so that the old structural slab can be exposed. On removal of the old wearing

coat, the top of the old concrete structural slab shall be examined to determine whether a cover

plate was provided or not over the expansion joint. This steel plate over the expansion joint is

to be replaced by means of 100 x 10 mm new cover plate. The new cover plate should have

diamond shaped BRC fabrics, welded on one side and the reverse side should have 10 mm dia

long 50mm long rods welded at the centre line.

REPAIR OF THE DEFECTS IN THE SUPERSTRUCTURES AND THE

SUBSTRUCTURES

The following defects have been detected in the existing bridges.

1) Cracking in superstructure and substructure,

2) Spalling of Concrete with/without exposure of reinforcement,

3) Leaching,

4) Honeycombing withiwithout exposure of reinforcement,

5) Loss of pointing,

6) Hollow sound in weblsoffit of girder.

7) Growth of vegetation.

The repair methodologies for the defects mentioned shall be as per MORTH specifications

and certain additional specifications brought for this project that have been given in the

'Specifications for Repair and Rehabilitation of Bridges' part of this document.

Pro osed Crash barrier 500 wide P Existin handraillkerb to be removed (16) B Existing handrail to be w a n t l e d with

4 Proposed Safety kerb 750 wide (Refer to Detailed drawing)

12 thk MA 50 thk BC\ 4- 1 in 60 - -

reinforcements intact MEDIAN SIDE

Profile corrective course (SDBC)

N concrete slab

11000 (Carriageway) 450 C,

12700 (Deck width) b

TYPICAL CROSS-SECTIONAL PROFILE OF DECK SLAB AFTER WIDENING

NH 7 (Karur - Madurai) Rehabilitation of Existing Bridges Package NS 82 (TN) (krn 38 1 - krn 426.6)

m Pic.1 Spalling of Concrete with exposure of reinforcement due to inadequate provision n of cover

,* Pie2 Spalling of Concrete with exposure of reinforcement near drainage spouts due to Z

a inadequate length of drainpipe

* /

n 1 .' . . . /'

n ' . C . .. '\ :. -4 1 .* T # -. ' - --

m

NH 7 (Karur - Madurai) Rehabilitation of Existing Bridges Package NS 82 (TN) (km 38 1 - km 426.6)

Pic3 Spalling of Concrete in pier caps due to growth of vegetation

Pic.4 Handrails missing


A .I-

The following table gives the details of existing bridges and the proposed rehabilitation h

works to be carried out. 6

CC -Camber Correction: WDN - Widening: NA -No Action

As indicated above, certain bridges are getting eliminated and no action is taken owing to

different reasons, which are mentioned in the remarks column. Bridge no: 40511 is a

single span slab bridge with a carriageway of 1 lm. This bridge need not be widened and

only camber correction is to be done. It shall be a uni-directional camber as indicated in

the drawings. The repair works to the defects found shall be canied out as mentioned in

the specifications. The schedule of the work for each bridge is given in the following

table.

Schedule of work

) ) I , ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) Z ) ) ) ) ) l ) N,%? (Karur Madural) Rehabll l tatlon of Exlstlng Bridgesi$ b h

Package NS 82(TN) km 381 - km426 6

BRlDGENo: SPAN ARRANGEMENT

38711 4 x 6.6

* *

*

*

Item I

l a

l b

2

3

3a

DESCRIPTION OF WORK Dlsmantllng the ra~l~nglparapet and kerb of the exlstlng br~dges for prov~dlng new crash barrler wthout causlng any structural damage to other parts of the br~dge lncludlng all labour tool and ~ t s d~sposal as per drawlng and MORTH spec~ftcat~ons 2802 and add~t~onal spec~f~cat~on 2814

Central Verge s~de

W~den~ng s~de

Removal of exlstlng b~tumtnous wearlng coat and concrete wearlng coat e~ther manually or w~th jack hammers lncludlng ~ t s dlsposal wlthout causlng any detr~mental effect to any part of the br~dge complete as per deta~ls glven and MORTH spec~f~catlo'l 2809 Careful cutt~nglremovalld~smantl~ng of exlstlng constructton mater~al In order to achleve proper connection between the exlstlng and new structure requlred for wdenlng the exlstlng br~dge and dlsposal of the dismantled materlal clearlng the area as per add~t~onal spec~flcat~on 2814

RCC ~n d~rt wall pler cap, abutment cap

5

.

' 6 ,

38Nl 1 3 8 W 2 x 5.7 1 3 x 5.1

Prov~d~ng pla~n cement concrete M I5 grade as levelling course (100mm thlck) below the new floor slab for wdened portlon of fpundatlon slablfloor slab cncludlng center~ng shuttering as per ,MQRTH cpec~f~cat~on 1700 Pla~n Cement Concrete MI5 grade In Open Foundat~on as per drawlng and MORTH spectflcattons 1500,1700,2100

390H 2 x 6.5

* *

*

t

* *

*

t

*

*

*

*

*

*

. *

39SH 2 x 7.2

* t

*

*

*

*

40311 2 x 3.4

* *

*

*

*

*

*

*

MI 1 x 10.6

* t.

*

*

*

*

*

t

*

40511 1 x 6.0

*

*

*

*

*

40512 2 x 5.8

* *

*

t

*

8

*

*

40611 4 x 8.7

*

*

*

*

*

*

*

40711 1 x 10.0

* *

*

*

*

*

*

*

*

40N1 2 x 8.4

* *

*

*

*

*

*

*

*

40812 2 x 8.4

1

t

*

*

*

*

41012

2 x 6.0

* *

*

*

*

*

*

*

*

*

*

*

*

*

*

*

. ) ) ) ) I \ ) ) J J ) ) ) ) ) ) ) ) ) ) ) ) ) ) I ) ) ~ ) ) ) ) ) ) ) ) i N)4? (Karur Madurai) Rehabilitation of Existing Bridges' 3

Package NS 82(TN) km 381 - km426.6

i ) ) ) ) ) ~ ) ) ~ ~ ) ) ) ) N%J (Karur Madurai) Rehabilitation of Existing Bridges' 3 L'

Packaae NS 82(TN) km 381 - krn426.6 ., \ ,

BRIDGE NO:^ 38711 1 38811 1 38911 1 390H I 3991 zm No1 SPAN ARRANGE MEN^ 4x6.6 1 2 x 5.7 I 3 x 5.1 1 2 x 6 5 1 2 x 7 2

I DESCRIPTION OF WORK I I I I I I

- -- -. ... . . -. . -. . . -. .~. I I I I I

21 [Plain Cement Concrete of M15 arade 100mm thick for levellinal I I I I - - course below approach slab complete as per drawing and * * * MORTH specification 1700

22 Providing RCC M30 grade approach slab including formwork and reinforcement complete as per drawing and MORTH * * t t

specification clauses 1500, 1700. 2700 and addditional lspeclfication 2828 I I I I I

23 IHYSD bars in approach slabs confirming to MORTHI * I * I * I * I * specification I600

24 Providing and fixing in position "Buried" type of Expansion joints to be installed under supervision of the approved manufacturer * * x

complete as per drawing and MORTH specifications 2600 and additional specification 2830

25 Providing profile corrective course of semidense bituminous concrete in specified thickness and camber at the appropriate points over the slab along the transverse direction of the bridge * * * deck after application of tack coat as per drawing and MORTH specifications 503,508 and additional specification 2815 I I I I I I

26 Bituminous wearing coat 62 mm thick consisting of 50 mm thic bituminous concrete (BCI laid in two lavers, overlaid by 12 m thick mastic asphalt 'layer with a prime coat as per-^^^^^ * t * specifications 515, 2700 and additional specification 2815

27 Reinstating the existing handrail In the damaged portion as per specifications 2816

28 Repairs to leached1 honey combed and spalled concrete surface and exposed reinforcement complete as per drawing, MORTH * * * * * * t t t * * * specifications 2804, additional specification 2818 and special

lons 1.1.4 and 1.1.5 I I I I I I I I I I I I I I 29 IGunitina for repair of substructures as per specification 2821 1 * I * I * I * I * I + I ~ * ~ * ~ * ~ * ~ d X ~

and spiclal specification 1.1.6a) 30 Sealing of fine cracks (less than 0.5mm) by application of PMC

mortar after making grooves 10 x 20mm in size complete as per * * * * * t * l * t

.. MORTH specification 2803 additional specification 2819 and l s ~ e c ~ a ~ spec~f~cat~ons 1.1.1 I I I I I I I I 1 I SBollng of wde cracks (more than 0 5mm) wlth cement grout b lnlectlon process through nipples complete as per MORT * * * * * * *

&eclflcatlbns 2803 aditlonal spec~f~cat~ons 2819, 2823 and1 I I I I I I I I I I I I I 32 , IRepalrs to volds In glrders as per speclficatlon 2822 and speclall

Schedule of work 'T

) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) I ) \p N , s (Karur Madurai) Rehabilitation of Existing Bridges ' 3 L A

Package NS 82(TN) km 381 - km426.6

I I I I Providing plain cement concrete M15 grade as levelling cours f100mm thick) below the new floor slab for widened oortion A A , ~~

foundat~on slablfloor slab including centering, shuttering as pe . MORTH spectfication 1700 6 IPlain Cement Concrete MI5 grade in Open Foundation as per( I . I *

drawing and MORTH speclficatlons 1500, 1700,2100 l " 1 - 1 - - 7 /Pr&vldlng new substructure of plain cement concrete M20 grad!

in oler abutment return walllwna wall ~otned to old exlsttna sub

II labour, tools,scaffolding as per drawing an

Schedule of work

1 j ) ) > ~ ) j ) ) ) j ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) i Nr?$ (Karur Madurai) Rehabilitation of Existing Bridges , b 1

Package NS 82(TN) krn 381 - km426.6

eat, and or straightening of bar, cutting of reinforcement and

Schedule of work

l ) ~ ) ) ) , ) ) ) ) ) j ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) 'I NVL7 (Karur Madurai) Rehabilitation of Existing Bridges LI

Package NS 82(TN) km 381 - krn426.6

concrete in specified thickness and camber at the appropriat

ck after application of tack coat as per drawing and MORT

ituminous concrete (BC) laid in two layers, overlaid by 12 rn

Schedule of work

SPECIFICATIONS FOR REPAIR AND

REHABILITATION OF BRIDGES

416 Laning of Kamr-Maduni Section of NH-7 Consultancy Services for Feasibility study and P~.cparation of DPR

Clause

SECTION 2800 - REPAIR OF STRUCTURES

2809 DISMANTLING OF CONCRETE WARING COAT

Rename the clause as:

Dismantling of Existing Concrete/Bituminous Wearing Coat, Expansion Joints

2809.1 Commencement of dismantling

Add as sub para (i) as below

(i) The concrete wearing coat as well as the bituminous overlay shall be removed from the existing bridges.

Renumber the sub para (i), (ii), (iii) as (ii), (iii) & (iv)

2809.2 This Clause shall read as follows:

The removal operations shall be carried out mechanically using pavement breakers and compressors. Removal shall be done carefully to avoid damage to any part of the existing structure. In delicate locations for example around spouts, which will continue to serve as rain water spouts, removal shall be done by manual methods. After removal, the concrete deck surface shall be closely inspected for identifying any distress such as cracks, pockets of loose or honeycombed concrete etc. The deck surface shall be thoroughly cleaned with special efforts to remove any loose material. Expansion joints and spouts shall be removed carefully so that deck concrete is not damaged.

2809.3 Precautions during dismantling work

Add the following at the end.

Dismantled material shall not be stacked on the deck nor shall it be thrown below the bridge. It shall be neatly piled at points designated by the Engineer with all lifts and lead upto 1000m. Materials, which can be used or auctioned, shall be stored in neat piles at locations designated by the Engineer with all lifts and lead upto 2000m.

Measurement for Payment

Add the following to the end of the Clause.

g) Dismantling of wearing coat shall be measured in cubic metre of volume of the wearing coat dismantled.

Rate

Add the following to the end of the Clause.

The contract unit rate for dismantling the wearing coat shall include the materials, labour, tools and plant, traffic management, signage, safety

- - i

T e c h n ~ ~ a l Spec~ficat~ons \A/

Rchab~llbt~on.& W ~ d & ~ n g o'f Exlstlng %dgs , ,.A' / Contract Package NS 82 1 d

4/6 Laning of Karur-Madurai Sectionof NH-7 Consultancy Services for Feasibility study and Preparation of DPR

Clause and other incidental expenses including removal of existing expansion joints for the satisfactory completion of the work as per these specifications.

The following new clauses shall be added.

2814 DISMANTLING OF DAMAGED STRUCTURES AND/OR PART OF EXISTING STRUCTURES

The work shall be executed in accordance with Standard Specifications section 200 clause 202. All damaged concrete brick worMstone work in coping wing walls, returns, piers and abutment and caps shall be thoroughly inspected to identify the extent of dismantling. The decision of the Engineer shall be final. Care shall be taken to avoid damage to any part of the existing structure. Dismantling work for part of deck slab railing and kerbs shall be done carefully such that the existing reinforcement, which will project into the new work, is not damaged or lost. Reinforcement shall be cleaned thoroughly.

Dismantled material shall not be stacked on the deck nor shall it be thrown below the bridge. It shall be neatly piled at points designated by the Engineer with all lifts and lead upto 1000m. Materials, which can be used or auctioned, shall be stored in neat piles at locations designated by the Engineer with all lifts and lead upto 2000m.

Water shall be sprayed to reduce the dust while the dismantling work is in progress. Dismantling work shall not be carried out at night, during storms or heavy rain.

Goggles and gas masks shall be worn at the time of dismantling. Leather gloves shall be worn by the workers. Screens made of G.I. sheets shall be placed wherever necessary to prevent the disintegrated pieces from flying.

Damage caused to any component of the bridge structure during removal operations shall be restored by the Contractor at his cost. The service lines, if any, shall be disconnected/diverted before dismantling work commences.

2814.1 Dismantling of existing railings, kerbs, footpath slabs, approach slabs and damaged concrete in wing wallslreturns, piers and abutments

Railing, kerbs, concrete (P.C.C.) parapet erected in place of damaged railing, footpath slabs, approach slabs and damaged concrete in wing walls/retums, piers and abutments of the existing structures shall be dismantled as shown in drawing or as directed by the Engineer.

2814.2 Dismantling of existing deck slab

The depth of cutting of the existing deck slab shall be as shown in the drawings. Dismantling shall be done in accordance with Standard Specification section 200.

Technical Specifications

Contract Package NS 82 2

416 Laning of Ka~r-Madurai Section of NH-7 Consultancy Services for Feasibility study and Prepamtion of DPR ' 4

Clause

2814.3 Dismantling of existing damaged stonelbrick masonry in pier, abutment, wing wallslreturns, parapet, etc.

Damaged stonebricks masonry in pier, abutment, wing wallslreturns and all stonebrick parapets shall be dismantled as shown in drawings or as directed by the Engineer.

2814.4 Dismantling of existing wing wall for construction of adjacent one lane bridge - a) StoneIBrick masonry, b) Concrete

Part of existing stonebrick masonrylconcrete wing wall shall be dismantled for construction of adjacent 1 lane bridge as shown in drawings and Specification clause 2814 above or as directed by the Engineer.


The work of dismantling structures shall be paid for in units by taking measurements before and after as applicable

1) Railing and kerb together linear metre ii) Footpath slab square metre ii) Approach slab cubic metre iii) Dismantling bricWstone masonry/

concrete (plain & reinforced) cubic metre Rate

The contract unit rate for the various items of dismantling shall be paid in fill for canying out the required operations including full compensation for all labour, materials, tools, equipment, safeguards and incidentals necessary to complete the work. These will also include excavation and backfilling where necessaq to the required compaction and for handling, salvaging, piling and disposing of the dismantled materials within all lifts and up to a lead of lOOOm

PROVIDING NEW WEARING COAT WITH PROFILE CORRECTIVE COURSE FOR NEW CROSS CAMBER 1/60

In order to have a cross slope of 1/60 in all existing bridges whether the cross- section is retained or widened, profile corrective course of Semi-Dense Bituminous Concrete (SDBC) shall be laid over the structural deck slab after the top has been exposed by removing the existing wearing coat (refer to clause 2809). The existing wearing coat will be basically of PCC with or without surface reinforcement, but can also have top bituminous overlay, which had been provided subsequently as a leveling course.

The profile corrective course of SDBC of variable thickness has to be laid over the existing caniageway. For T girder bridges, which are not being widened, the maximum thickness of profile corrective course will be at the existing Centre Line. For slab bridges, which are being widened, the maximum thickness of profile corrective course will be at the kerb toward the cent-ge because of

.. . . .. .i. - .. unidirectional camber. . ,' . .,


Contnct Package NS 82

416 Laning of Kamr-Madurai Section of NH-7 Consultancy Services for Feasibility study and Preparation of DPR

Clause Slab bridges are being widened with slab extensions. The top of extended slab will have a cross slope of 1/60 and no profile corrective course will be required for the widenedlextended portion of the slab bridge.

A tack coat confuming to standard specification clause 503 shall be applied over the exposed surface of deck slab before the application of SDBC. In addition, tack coat has to be provided on new concrete surface of widened portion.

The SDBC shall follow standard specification clause 508.

Bituminous concrete confirming to standard specification clause 509 shall be laid as component of wearing coat over the SDBC in the existing bridge portion and directly over concrete on the new widened concrete slab. Tack coat has to be provided on new concrete surface.

The Mastic Asphalt (MORTH specification clause no. 515) shall be overlaid as the other component of wearing coat on the bituminous concrete.


The profile corrective course (PCC) shall be measured in cubic metres, as running continuously through. The tack coat shall not be measured. The work of wearing coat shall be measured in square metres.

Rate

The contract unit rate for profile corrective course shall include the cost of tack coat and shall also cover cost of all materials, labour, tools, plant and equipment required for mixing, transporting and placing in position, vibrating and compacting and finishing as per this section or as directed by the Engineer, including all incidental expenses, sampling and testing, quality assurance and supervision.

2816 REINSTATING THE EXISTING DAMAGED HANDRAILS, KERBS, etc

For repair of kerb, railhailing post etc., cement sand mortar (1 :3) shall be applied. Missing reinforcement if any shall be compensated before application of mortar.

Damaged rails of the railing shall be replaced by rails of same size and reinforcement as given in MORTH drawings. Both the above operations shall be done as per relevant provisions of MORTH specification clause 27033 & 2703.4


The measurement shall be done in linear metres of railings repaired.

Rate The contract unit rate shall include the cost of all labour, materials, tools and plant, scaffolding and all incidental expenses, supervision as described in these specifications.

Technical Specifications Rehabilitation &wjdi,q+"gqf;~x&ting Bridges

4 .._._.I

Contract Package NS 82

416 Laning of Kamr-Madurai Sectioli of NH-7 Consultancy Services for Feasibility study and Preparation of DPR

Clause

2817 PROVISION OF NEW DRAINAGE SPOUTS AND REPAIR OF EXISTING DRAINAGE SPOUTS

a) Provision of new drainage spouts:

For all existing bridges that are being widened and changed to uni-directional camber drainage spouts shall be provided as shown in the drawings.

The work of new drainage spout shall be executed in accordance with Standard Specification Section 2700 Clause 2705

Measurement for payment The measurement for provision of new drainage spouts shall be done in number of drainage spouts provided.

Rate The contract unit rate for each drainage spout shall include the cost of all labour, material, tools and plant required for completing the work as per the specifications. It shall also include the cost of closure of existing drainage spouts and providing flow drainpipes with all fixtures up to the point of ground drains wherever shown on the drawings.

b) Closure and sealing of existing drainage spouts:

The work shall be done after the wearing coat is removed. The grating shall be dismantled and the existing spouts shall be removed carefully with minimum damage to surrounding concrete.

The pocket formed shall be sufficiently large to ensure good flow and compaction of concrete in the hole. The area around the spout covered by the grating shall be provided with PMC slurry.

Before commencing application of PMC slurry brush topping, the prepared concrete substrata shall be thoroughly soaked with clean water. Before priming it should be ensured that any free surface water is removed. The material shall be applied in accordance with manufacturer's recommendations. Suitable steel rods shall be placed vertically in the drainage spout and then concreting shall be done in the hole. And then the steel shall be embedded in the concrete poured over the grating area.

The specifications for polymer modified cementitious topping & mortar shall be as per of Special Specifications A-3 (1.7)

Measurement for payment The closure of drainage spouts shall not be measured.

Rate The rate for such closing shall be deemed to have been included in the cost of new drainage spouts provided in the widened portion. ,.;--<---- ..

Technical Spscifications


416 Laning of Ka~r-Madurai Section of NH-7 Consultancy Smices for Feasibility study and Prepantion of DPR

Clause c) Extension of existing drainage spouts

For bridges that are not being widened, the existing drainage spouts are to be retained with minor repairs. The work shall be carried out as shown in the drawing. The concrete surrounding the spout in the soffit of the slab shall be chipped out. An extension collar of specified size shall be attached to the existing pipe as shown in the drawing. The chipped out area shall then be filled with 1 :4 cement sand mortar over which a lOmm thick layer of PMC repair mortar shall be applied.


Drainage spout repair shall be measured in numbers.

Rate

The contract unit rate for each drainage spout shall include the cost of all labour, material, tools and plant required for completing the work as per these Specifications. It shall also include the cost of providing flow drainpipes in girder bridges with all fixtures up to the point of ground drains wherever shown on the drawings.

2818 REPAIR TO HONEYCOMBED, SPALLED CONCRETE

Honey combed, spalled concrete should be cleaned and cleared (plaster removed) before the start of repair operation. If necessary, should be cleaned vigorously with wire brush.

The work shall be executed in accordance with standard Specification Section 2800 and special Specification A-3 (1.4 & 1.5).


Measurement for application of PMC mortar for specified thickness shall be per square metre of surface area of application.

Rate

The contract unit rate for application of PMC mortar for specified thickness including cement mortar 1:4 wherever required, shall include cost of all materials, labour, tools and plant, placing in position, testing and other incidental expenses including surface preparation for the satisfactory completion of the work as per these specifications and as shown in the drawings.

2819 SEALING OF CRACKS IN CONCRETE

The work is to seal all cracks in slab, girders and substructures.

The work shall be executed in accordance with 2800 Clause 2803,2804 and Special

. , . .. \



416 Laning of Kamr-Madurai Section of NH-7 Consultancy Sewices for Feasibility study and Preparation of DPR

Clause Measurement for Payment

Fine Crack: Measurement for sealing of fine crack by application of PMC mortar for specified thickness along with application of PMC slurry for proper bondage of old concrete and PMC mortar shall be linear metre of crack.

Wide crack: Measurement for sealing of cracks and injection shall be made by weight of cement consumed in kg for cement grouting.

For provision of nipples required for grouting, the payment shall be for number of nipples inserted.

Rate

Fine crack:The contract unit rate for application of PMC mortar for specified thickness shall include cost of all materials, labour, tools and plant, placing in position, testing and other incidental expenses including surface preparation for the satisfactory completion of the work as per these specifications and as shown in the drawings.

Wide crack: The contract unit rate for sealing of cracks and injection of cement grout shall include cost of all materials, labour, tools and plant, placing in position, testing, curing and other incidental expenses for the satisfactory completion of the work as per these specifications.

Injection nipples are being paid separately.

VOIDS IN SOFFIT OF GIRDER

Portions of the soffits of the girder wherever voids are anticipated shall be chipped off so that films forming external soffit surface are removed exposing the reinforcement. Loose concrete sticking with the reinforcement shall be removed using appropriate tool and equipment. Polymer modified concrete 15- thick shall be applied and after that cement plaster 1 :4 shall be applied so as to have the entire soffit in one straight line.

The work shall be executed in accordance with Special Specification A-3 (1.3)


Measurements for reshaping of soffit of girder with PMC and Cement Plaster (1 :4) shall be square metre of surface area of application.

Rate

The contract unit rate for application of PMC mortar for specified thickness shall include cost of all materials, labour, tools and plant, placing in position, testing and other incidental expenses including surface preparation for the satisfactory completion of the work& per these sp&ifications-and as-n the

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Technical Specifications Rehabilitation m n i n g of Existing Bridges


416 Laning of Karur-Madurai Section of NH-7 Consultancy Services for Feasibility study and Preparation of DPR

Clause 2821 SEALING OF WIDE CRACKS AT JUNCTION OF WING WALL AND

ABUTMENT WITH BRICK BATS AND FINISHING WITH 1:3 CEMENT MORTAR

Wide cracks of different degreelextent due to separation of masonryPCC substructure such as wing wall abutments etc. shall be sealed by cement grout after filling the gap followed by the application of sealing material. The work shall be executed in conformity with Standard Specification Section 2800 Clause 2806 and Special Specification A-3 (1.2). Gaps shall be sealed by filling sized stones/brick bats and finishing with cement plaster (1:3).


Measurements for sealing of cracks and injection shall be made by weight of cement consumed in kg for cement grouting. For provision of nipples required for grouting, the payment shall be for number of nipples inserted.

Rate

The contract unit rate for sealing of gap, cracks and injection of cement grout shall include cost of all material including the gap filling material, labour, tools and plant, placing in position, testing, curing and other incidental expenses for the satisfactory completion of the work as per these specifications.

The work is to repair spalls or loss of cover in abutment, pier substructure and gaps. This shall be executed in accordance with standard Specification Section 2807 and special Specification A-3 (1.6 (a) & @)) and 1.7

Measurement for Payment Measurement for guniting shall be square metre of area of application.

Rate The contract unit rate for guniting shall cover cost of all materials, labour, tools, plant, placing in position, testing, curing and surface preparation and other incidental expenses for the satisfactory completion of work as per specification. It shall also include the cost of the provision of steel weld mesh as per specification.

2823 PROVIDING AND INSERTING NIPPLES FOR CEMENT INJECTIONS

The work shall include providing and inserting nipples with approved fming compound after drilling holes, and after operation, cutting and removing nipples and sealing the holes.


Measurement for Payment for making provision of nipples reqGed for grouting shall be for number of nipples inserted. 6 . .. . .

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T ~ h n i c a l Specifications Rehabilitation & Widening of Existing Bridges Contract Package NS 82 8


Clause Rate

The rate will include cost of cement nipples, admixture fixing compound, all material and labour in drilling fixing and cutting after the job and removal and sealing the holes including the cost of drilling equipment, cost of drill, bits and spares wastage etc.

CASTING OF APPROACH SLAB WITH M-30 GRADE CONCRETE

Approach slabs are to be provided for the new widened carriageway of bridges. In addition, approach slabs, which are cracked or otherwise damaged, shall be recast.

The work shall be executed in accordance with Standard Specification Section 2700 Clause 2704. The approach slab shall be laid over lean concrete as per drawing. The base shall be consolidated by ramming with water.


The measurement shall be in cubic metre.

Rate

The contract unit rate for approach slab shall include the cost of all labour, material, tools and plant and other cost necessary for completion of the work as per these Specifications. The rate for base shall include cost of all labour, material, tools and plant required, including preparation of surface and consolidation complete in all respects

EXPANDED METAL SHEET

Expanded metal sheet of size 75 mm x 200 mm, 3.25 mm wide and 3.15 rnrn thick @ 2.141 kg1sq.m shall be provided over the steel plate placed at the expansion joint and welded.

Measurement for Payment This provision of expanded metal sheet shall not be measured and shall be deemed to have been included in the cost of provision of expansion joints.

Rate The contract unit rate shall include provision, placing in position of the sheet as per drawing and specifications, and welding also.

Technical Specifications Rehabilitation & Widening of Existing Bridges



Clause

SPECIAL SPECIFICATIONS

A-3 REPAIR PROCEDURE, UPGRADATION AND MATERIAL SPECIFICATION.

Various types of distress in concrete superstructure and substructure manifesting in the formation of horizontal cracks, vertical cracks and spalling are generally observed. The constructional inadequacy in the form of honeycombing and spalling of soffit concrete near drainage spout outlet are also found.

Apart from these, the bridges are to be provided with uni-directional camber, crash barriers in lieu of railing and new expansion joints specially when the slab bridges are widened.

For various types of defects, the repair methodology, its procedure and the material specification and the specification and procedure for providing new expansion joint, crash barrier and wearing coat are outlined in the succeeding Para.

1.1 FINE CRACKS

There can be fme visible cracks in bridges. If the cracks are 0.5mm wide or less, these cracks are to be repaired with PMC mortar. The location of the cracks can be seen during repair and widening works. , In order to avoid increase in corrosion, rectification of the cracks by cutting grooves in the concrete and sealing the grooves with PMC repair mortar after cleaning and applying PMC slurry on the freshly cut surfaces at all locations is recommended.

Procedure

The size of the groove, which should be cut along the whole length of visible cracks, shall be 20 x 1Omm. Depth of the groove is lOmm while the width of the groove is 2 0 m n which however, should be symmetrically placed along the crack. In case reinforcement is met within a depth of 6mm, the depth should be limited to the depth of the reinforcement from the surface. It is preferable to cut the groove perpendicularly to the surface but a deviation of 15 degrees in either direction may be permitted.

After cutting the groove it shall be cleaned properly to ensure a dust free clean surface and a coating of PMC sluny be applied over the freshly cut surfaces.

The PMC repair mortar shall be used to fill the 20 x lOmm groove while the sluny coating is still wet, after a lapse of 30 minutes from the time of application of the slurry, the PMC repair mortar shall be applied and compacted to ensure complete filling of the groove.' The filling up of the groove shall be finished flush with the existing concrete surface. After the finishing operation, the filled up groove should be properly covered with impermeable sheet whose edges are to be sealed by taping.

Curing of the finished surface will be the same as that stated for curing of PMC mortar (See C1.1.7). Care should be taken to cut the groove with sharp instrument to avoid damage to the structure.

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Clause

Material Specification

Specification of PMC material is provided at 1.1.7.

1.2 WIDE CRACKS

Wide cracks having width more than 0.5 mm have been found in some of the bridge components. Moreover, these wide cracks are also found in MasonryPCC substructure, such as wing walls, abutments and piers. While locating them and to repair specially the wing walls, it is to be decided whether the old wing wall will be functional after widening, if so they need to be repaired.

The basic repair methodology consists of injection of cement grout in the wide cracks after most of the visible gaps have been sealed by applying sealing mortars. The repair should be in conformation with clause 2806 of MORTH specification. However, the general procedure is briefly described.

Procedure

The wide gaps should be chased so that grooves are formed which may be 10 x 5 mm in size. AAer cleaning the surface with wire brush and compressed air, 15mm dia nipples are to be fixed in 150 - 200mm deep holes with suitable sealing material. The nipples should have maximum spacing 500 - 600mm. The chased groove also should be filled up with suitable sealing material. Neat cement along with soluble glass (Sodium Nitrate) forms excellent quick setting sealing compounds.

Grouting of cement slurry should be done by mechanical pumps. The details of procedure should be in conformity with clause 2806 of MORTH specification except for sub clause 2806.6.

Material Specification

- Material specification should be in accordance with clause 2806.1 of MORTH specification.

1.3 REPAIR OF VOIDS IN GIRDER SOFFIT

In case of voids in the girder soffits are identified, the repair technique shall be as follows. The repair shall be done by low permeability polymer modified cement repair mortar. The thickness of the PMC repair mortar shall be limited to 15 mm. For repairing voids more than 15 mm, the lowerlinner layer should be filled with cement- sand mortar 1 :4 prior to application of PMC repair mortar.

Portions of the soffits of the girders to be repaired are to be chipped off, so that the film forming the external soffit surface are removed exposing the reinforcement. All loose concrete sticking with the reinforcement shall be removed using appropriate tools and equipment.

Depending on the depth of voids, cement sand mortar 1:4 is to be applied, application of PMC mortar 15mm thick so that the soffit of the girder is line i.e., the soffit should not have protrusion or depressions.

All concrete film in the soffit of girders and weak c reinforcement will be removed by using appropriate tools anif-

Technical Specifications Rehabilitation, & Wi ,.y &"" Bridges

Contmct Package NS 82 11 \.:>, . ., . . ,. . . .. . . . .. , . , - _


Clause reinforcement bars are exposed, the breaking shall continue so as to expose half the diameter prior to further treatment.

Reinforcement Preparation

All exposed reinforcement shall be cleaned in accordance with the following:

a) Where exposed reinforcement is sound and does not show any signs of heavy corrosion or pitting other than typical rusting, it shall be mechanically cleaned to remove rust and loose mill scale.

b) Where exposed reinforcement shows signs of heavy corrosion deterioration, it shall be cleaned by grit blasting or by proprietary rust removing compound.

Reinforcement Priming

Within one hour of preparing and cleaning, the reinforcement shall be coated with a primer. The primer shall be PMC slurry using Tapecrete PI51 as polymer latex or approved equivalent polymer latex.

The primer shall be brush applied on to the cleaned reinforcement ensuring that the full surface area is in accordance with the manufacturer's recommendation.

Concrete Su$ace Priming for Bond

Before commencing to apply PMC repair mortar or the inner cement sand mortar, the prepared concrete substrata shall be thoroughly soaked with clean water. Free surface water shall be removed before priming. The primer shall be PMC slurry using M/s CICO Technologies Ltd.'s Tapecrete P151 polymer latex or approved equivalent.

The priming agent shall be well worked into the irregularities according to the manufacturer's recommendations.

The repair material should be applied before the priming agent sets. The area coated as one time must be restricted to allow for this provision and any area, which becomes set shall be recoated as per manufacturer's instruction.

Cementitious Repair Mortar

The repair mortar shall be high build polymer modified cementitious repair mortar. The PMC repair mortar shall be of appropriate general specification for use in vertical and overhead application.

The total thickness of mortar shall be applied in one layer not exceeding lSmm without sagging or slumping. The material shall be applied in accordance with the manufacturer's recommendations.

The mixing shall be carried out using forces action mixes or with slow speed drive mixer (400 - 500 rpm) fitted with a spiral paddle. In no circumstances shall water be used in the PMC repair mortar mix. Re-mixing and re-tampering shall not be permitted.

The material shall be applied by gloved hand or trowel to the prepared and surface of the substructure and be well worked inside paying pakicular

. Technical Specilications

12 Conttact Package NS 82

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416 Laning of Kamr-Madumi Section of NH-7 Consultancy Services for Feasibility study and Preparation of DPR

Clause packing behind and between the reinforcement. In order to make up the total height of the girder up to the original soffit level, the balance portion of the girder depth shall be made up with 1:4 cement sand plaster. Refer to Para 1.7.1 for specifications of PMC mortar i.e., special specification 1.7

1.4 SPALLING OR HONEYCOMBING IN DECK SLAB WITH LIGHT EXPOSURE OF REINFORCEMENT (Less than half the diameter of reinforcement visible or discolouration of soffit)

For some bridges, spalling and honeycombing have been observed specially near the drainage waterspout. The basic repair for this defect is to provide a 5 to 8 mm thick PMC repair mortar layer after removing the loose concrete, plaster etc. The peripheral edge may be cut upto lOmm deep and the material removed to give a proper demarcation line. If such spalling or honeycombing is observed in the cantilevered portion of deck of girder bridges, a drip course covered with PMC repair mortar may be provided to stop the back flow of rainwater.

Procedure

The honeycombed/spalled surface after removing plaster, if any, should be cleaned vigorously with steel wire brush. PMC sluny coat should be provided on the prepared surface after the surface has been pre-wetted with water. The surface should be moist but without any free water. For further details refer to "Concrete surface priming for Bond" and "Cementitious Repair Mortar" under Para 1.7 ante.

A drip course 10 x 12 mm size is to be formed at the outer edge of the soffit of the cantilevered deck slab. PMC repair mortar 5mm thick shall be applied on the drip course. Refer to Para 1.7 for details of specification of PMC materials.

1.5 SPALLING OR HONEYCOMBING IN DECK SLAB WITH HEAVY EXPOSURE OF REINFORCEMENT (More than half the diameter of reinforcement visible)

This type of distress has been observed in couple of bridges. The large spalling might have been initiated due to honeycombing, a bad construction defect. In many cases, inadequate length of drainage spout has been responsible for wetting the locality with drained rainwater and in addition due to the growth of vegetation. This happens particularly in pier caps.

The repair technique suggested is the application of Cement Sand mortar 1 :4, before the application of PMC mortar 15mm thick so that the soffit is in a straight line.

Procedure for Repair

All concrete film in the soffit and weak concrete sticking to the reinforcement shall be removed by using appropriate tools and equipment. Where the reinforcement bars are exposed, the breaking shall continue so as to expose half the diameter prior to further treatment. PMC slurry shall be applied over the prepared surface. After application of PMC slurry, the repair shall be canied out as per section 1.3

Techn~cal Speclficatlons ~ehab~hdl& & w n g of Exlstlng Bndges Contract Package NS 82 13

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Clause 1.6 PIER AND ABUTMENT SUBSTRUCTURE AFFECTED BY WEATHERING

AND LOSS OF POINTING/PLASTER

Generally, there are no cases where these defects have been identified. However, during the construction period, if the defects are noticed, the following methodology shall be used for repairing the same.

Case (a) Weathering

Basic Principles

Guniting or shotcreting of affected portion of masonry of abutment and pier is being suggested in such cases. (Guniting and shotcreting are the two different names for the same operation)

The purpose of guniting of the bridge is to increase its life from general weathering and for counteracting weathering effects also. There are distinct weathering signs in the old masonry/cement concrete substructure portion.

The guniting thickness for vertical faces of substructure should be at least 40mm and should be strengthened by providing a steel weld mesh 50 x 50 x 10 gauge all along vertical faces of substructure.

Procedure

The steel wire mesh has to be placed in position keeping the mesh within 10 - 15mm from the surface, which will be curved for the cutwater portion. Suitable fixing pins are to be inserted between the masonry mortar joint so that the mesh can be kept in proper position. The inserts can even be spaced quite apart but ensuring that the weld mesh is not disturbed during guniting, which is also termed as shotcreting.

Depending on the expertise of the guniting personnel, the thickness of 40mm may be built in one layer but it must be ensured that no void is created behind the gunite built up thickness. The presence of void can be found by hollow hammering sound after the gunite has attained strength say after 3 days.

Material Specijkation

For details and specification of gunite refer to clause 1.8

Case (b) Loss of PointingIPlaster

For loss of pointinglplaster cement mortar 1 :3 will be used on exposed surface after removal of old plasterfpointing and preparation of surface thereof.

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Clause 1.7 SPECIFICATION FOR MATERIALS AND MIX FORMULATIONS FOR

PMC MATERIAL SYSTEM

The acrylic polymer latex to be used for system shall be TAPECRETE P 151 manufactured by MIS CICO Technologies Ltd. Equivalent products of MIS FOSROC and MIS SIKA are also acceptable.

1.7.1 Specification for Acrylic Polymer Latex

The polymer latex, which is to be used, should consist of water based acrylic and copolymer dispersion and special purpose chemicals. (TAPECRETE P151 of M/s FRC Composites (I) Pvt. Ltd. or any approved equivalent may be used for this purpose). The polymer solid contents shall be 30 + 1 percent. The particles shall be nearly spherical shape with a diameter of 0.35 + 0.05 micrometer. The manufacturer shall certify to the above requirements about solid content and grain size. In order to keep control over the quality, the manufacturer shall provide infrared absorption spectrum analysis for the materials (polymer latex) to be supplied to them.

The integral waterproofing compound which is to be used for underlying layer of cement sand mortar shall conform to IS: 2645 No. 1 manufactured by M/s Structural Waterproofing Co. Pvt. Ltd. or approved equipment.

Portland Cement conforming to IS: 81 12 shall be used for production of polymer modified cement repair mortar and polymer modified cementitious coating system, which is to be used as a bonding medium with concrete substrate.

Tapecrete P151, an acrylic polymer latex shall be used as the polymer for modifying and improving the properties of cement. The same product is to be used for various purposes such as in a sluny form with cement to form a bondinglpriming medium and with sand to firm PMC repair mortar. However, no additional water is to be added to PMC slurry or PMC repair mortar as the water which is present in the latex is sufficient for cement hydration and for this reason the latex cement ratio remains constant for all applications.

The sand, which is to be used for constituting the PMC repair mortar, should be Silica sand as the basic material, which is categorized in two groups:

a) Coarse Silica Sand b) Fine Silica

The grading of the above groups should follow the limits provided below: -

IS Sieve No. Percentage Passing by weight Coarse Fine Combined

10 mm 100 100 100 4.75mm 95 - 100 100 98 - 100 2.361nm 90 - 100 100 80 - 100 1.18mm 40 - 60 100 70 - 80 600 micron 0 - 10 90 - 100 45 - 55 300 micron 0 - 4 40 - 60 150 micron 0 - 3 0-10 0 - 5 75 micron 3 max 0 - 3

Techn~cal Specificat~ons

15 -. _ _ Contract Package NS 82

416 Laning of Kamr-Madurai Section of NH-7 Consultancy Services for Feasibility study and Preparation of DPR 12,

Clause In the event of using local sand, the sand to be used must satisfy the limits of deleterious materials and the requirements of soundness as given in Clause. 3.2.1 and 3.6 of IS: 383 respectively. Confirmatoly tests shall be conducted by the contractor and sample kept for comparison by the Public Works Department.

Cement - Sand Mortar

For repair of spallings, where the depth of spalling exceeds 15mm cement-sand mortar 1 :4 layer have been recommended after the application of PMC repair mortar, 15mm thick.

The composition of the cement sand mortar shall be as follows:

COMPOSITION Cement Sand CICO No. 1 or equivalent Water

PARTS BY WEIGHT 100 400 3 Variable

The amount of water will depend on the environment condition and is therefore variable.

In case where two layers of cement-sand mortar are to be used, the second layer shall be provided after a lapse of 24 hours from the time of application of the first layer. Conventional practice or surface preparation for good bonding shall be adopted for all layers.

Conventional curing of the cement sand mortar layer by application of water spray should be followed for at least 2 days.

Mix Formations PMC SLURRY

Component Parts by Weight Cement 100 Tapecrete P 15 1 or equivalent 50

PMC BRUSH TOP COATING Cement 100 Tapecrete P 15 1 50 Fine Silica Sand 100

PMC REPAIR MORTAR Cement 100 Tapecrete P 1 5 1 50 Coarse Silica Sand 150 Fine Silica Sand 150

PMC FILLER Cement 100 Tapecrete P15 1 50 Concrete Sand

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Clause Curing of PMC Work

This specification describes the curing procedures to be followed for various PMC systems.

The curing procedures outlined apply to normal weather conditions. Take precautions to avoid drymg. PMC work should be carried out a temperature below 35°C.

Under unusual weather conditions e.g. high humidity and/or high wind velocity or imposed constraints special curing procedures shall be followed. Approval, therefore, shall be obtained from the Engineer-in-charge.

Air-drying shall be considered to take place only during unfavourable uninterrupted weather conditions existing throughout the recommended drying period. Some judgement shall be made in this respect and if conditions are deemed unfavourable for drying to occur, then drying must be prolonged for the full-recommended period after the weather clears.

Curing of PMC Repair Mortar and Filler

As PMC work proceeds, precautions shall be taken to prevent rapid drying of the PMC repair mortar and PMC filler. This is usually accomplished by covering the filled surfaces with an impermeable sheet shortly after the work has been done. The edges of the impermeable sheet should be suitably taped.

The sheet shall be kept in place until further work is carried on over the filler or in the case where the filler will be exposed to heavy abuse, the sheet shall be kept in place for 24 hours.

No foot traffic or m h e r work shall be allowed over the filler until 12 hours from the time of the completion of the work.

All the areas repaired using cementitious materials specified above shall be fully cured in accordance with good practice for PMC application as given under general specifications for PMC material systems.

No curing compound shall be used as a curing membrane. Care shall be taken to ensure complete coverage particularly around the interface with the host concrete.

For the first day the repaired concrete patch shall be protected from harsh environment by laying a polythene sheet over it taping down the edges.

Curing PMC Brush top Coatings and PMC Slurry

In unexposed and exposed areas the initial air-drying of 2 to 12 hours shall be followed by moist curing for 24 hours by spraying or another approved curing method. No curing compound is to be used.

be allowed to air dry for at least 3 days

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Following moist curing, the coating shall to the application of finishing coat.

Technical Specifications Contract Package NS 82 17

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Clause

1.8 SPECIFICATION FOR GUNITING (SHOTCRETING)

The gunite is a mixture of cement, sand and water. It comprises 100 parts by weight of cement, 300 parts by weight quartz sand, 35-50 parts by weight water and 2 parts by weight approved quick setting compound. In general, dry mix shotcrete shall be used.

Ordinary Portland cement conforming to IS: 269 shall be used for guniting.

Sand for guniting shall comply with the requirements stipulated in IS: 383. In general, sand should neither be too coarse to increase the rebound nor too fine to increase the slump. Sand should preferably have a moisture content between 3 and 6%.

The grading of sand shall lie within the limits given below:

IS Sieve Designation 4.75 mm 2.36mm 1.18mm 600 microns 300 microns 150 microns

% Passing the Sieve 95 - 100 65 - 90 45 - 75 30 - 50 10-22 2 - 8

For thick sections it may be advantageous to incorporate coarse aggregate in the mix provided adequate guniting equipment is available. Coarse aggregate, when used shall conform to grading given in Table 1 of IS 9012. The percentage of coarse aggregate may normally be kept as 20 to 40% of the total aggregate and the mix shall be suitably designed. Waterlcement ratio for guniting shall fall within the range 0.35 to 0.50 by mass, wet enough to reduce the rebound. Drying shrinkage may be between 0.06% and 0.1%. The quick setting compound shall be added at the nozzle with water just before guniting.

The cement and sand shall be batched and mixed and conveyed through a hosepipe with the help of compressed air. A separate line shall bring the water under pressure. The cement, sand water mix shall be passed through and intimately mixed in a special manifold and then projected at high velocity to the surface being repaired. The density of gunite shall not be less than 2000 kglcum. The strength of gunite shall not be less than 25 Mpa. For effective guniting the nozzle shall be kept 60 to 150 cm away from the surface, preferably normal to that surface. While enclosing reinforcement bars during repairs the nozzle shall be held closer at a slight angle and the mix shall be wetter than the normal.

Test panels simulating actual field conditions shall be fabricated for conducting pre- construction testing. The procedure for testing the cubes or cylinders taken from the panels stipulated in clause 6 of IS: 9012 shall be followed. It should be ensured from tests that a strength of about 30 MPa at 28 days is available for the mortar/concrete mix.

The defective concrete shall be cut out to the full depth till sound concrete reached. Under no circumstances should the thickness of concrete to be less than clear cover to the main reinforcement. No square shoulders the perimeter of the cut-off portion and all edges shall be tapered. Thereafter, loose and foreign matenals should be removed and the surface be

. . ,. Technical Specifications Rehabilitation & of E 'ng Bridges Contract Package NS 82 18 . .

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Clause make it rough to receive shotcrete after applying a coat of bonding epoxy as per recommendation of the manufacturer @ 1.0 kg per 1.5 sqm of surface area.

The exposed reinforcement shall be thoroughly cleaned free of rust etc. by wire brushing. Wherever the reinforcements have been corroded the same shall be removed ad replaced by additional reinforcement. Before application of gunite a coat of neat cement slurry should be applied on the surface of the reinforcement. Sufficient clearance shall be provided around the reinforcement to permit encasement with sound gunite. Care shall be taken to avoid sand pockets behind the reinforcements.

A thickness of 25 to 40mm of gunite can normally be deposited in one operation. It would always be necessary to apply guniting on a damp concrete surface.

Where required, welded wire fabrics 5 an x 5 cm x No. 10 gauge shall be provided in the first layer of guniting. The fabric shall be tied properly. In case the damage to the concrete member is too deep, the specifications for guniting as well as requirement of placement of wire mesh has to be decided as per field conditions.

The stipulations given in IS: 9012 regarding applications of gunite should be followed so as to keep the rebound to the minimum. The quality of guniting and workmanship shall be such that the percentage of rebound mentioned in IS: 9012 can be adhered to. In no circumstances shall the rebound material be reused in the work. It would be desirable that green gunite is moistened as curing requirement for at least 7 days. Guniting work shall not be done during windy or rainy conditions.


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