Pavement Quality Concrete

Construction of Pavement Quality Concrete

TABLE OF CONTENTS Description

Clause No

Pages

1.0

PURPOSE

2

2.0

SCOPE

2

3.0

DEFINITION

2

4.0

REFERENCE

2

5.0

CONSTRUCTION METHODOLOGY

3-8

5.1

Manpower deployed

3

5.2

Equipment deployed

3

5.3

Materials for PQC

5.4

Proportions of material &mix design

4

5.5

Site trials

4

5.6

Construction methodology

5

3-4

5.6.1

Clearing and under laying surface

5

5.6.2

Placing of separation membrane

5

5.6.3

Joints

5

5.6.3.1

Transverse contraction joint

5

5.6.3.2

Transverse expansion joint

5

5.6.3.3

Longitudinal joint

6

5.6.4

Batching and mixing

6

5.6.5

Laying and compaction

6

5.6.6

Texturing

7

5.6.7

Curing

7

5.6.8

Joint cutting

7

5.6.9

Sealing the joints

7

5.6.10

Weather and seasonal limitations

8

5.6.11

Tolerance of material

8

5.6.12

Quality control of works

8

6.0

TESTING AND ACCEPTANCE PROCEDURES

8

7.0

OCCUPATIONAL HEALTH & SAFETY MANAGEMENT PLAN

8

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1.0

PURPOSE: This submittal pertains to methodology adopted by H.C.C. for “Laying of Pavement Quality Concrete”. This statement describes the construction methodology and covers production patterns, personnel involved, equipments used, testing frequencies and quality control methods planned to be executed for this work. The statement subject to the client’s approval will be used as a guide by the field staff, engineers etc. for the construction of the pavement quality concrete layer to the satisfaction of the Engineer.

2.0

SCOPE: The scope of this methodology covers following activities: Survey and setting out works Identification of sources, selection of materials of PQC and other materials & storage, handling & testing of all materials Laying of pavement quality concrete Recording of all results / inspection data etc. in relevant inspection and test formats and controlling of all inspection / test records / files as per existing internal document control system for identification and t raceability.  

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3.0

DEFINITION: Definitions of various terms used in this methodology will have the same meaning as described in the DEFINITIONS as given below. MoRTH: Ministry of Road Transport & Highways specification IS: Indian standards PQC: Pavement Quality concrete DLC: Dry Lean concrete

4.0

REFERENCE:  

MoRTH: Ministry of Road Transport & Highways specification (Fourth revision) Additional Technical Specification

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5.0

CONSTRUCTION METHODOLOGY:

5.1

Manpower Deployed: Section in charge will be responsible for execution and Quality Control Manager will be responsible for quality of all works for laying of pavement quality concrete. Both will liaise with Engineer. Further, surveyors and supervisors will assist field engineer whereas lab technicians will assist quality control engineer.

5.2

Equipment Deployed: Following Equipments will be deployed for laying of pavement quality concrete. Batching plant of capacity 30cum/hr with automatic controls, for making concrete. Transit mixer of required capacity to carry the concrete from batching plant to work spot. Screed, to spread the concrete to required dimensions and initial compaction of concrete. Needle vibrators for compaction of concrete. Joint cutting machine, to provide the joints to required dimensions in concrete. The saw machine having sufficient no. of diamond-edge saw blades and machine shall be either electric or diesel driven type. 

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5.3

Materials For Pavement Quality Concrete: Crushed coarse aggregate: Coarse aggregate from approved source, Pali stone Quarry confirming to IS: 383 shall be used. Fine Aggregate (Sand): Sand from Approved sources confirming to IS: 383 will be used. Cement Source: Approved OPC 53 grade cement, stocked at Batching plant. Admixture: From Fosroc, BASF, SIKA , conforming to IS: 6925 and IS: 9103. Concrete: Batched and mixed at the batching plant. Lead-time to stretch will vary along the stretch; maximum time to reach extreme points being 30 – 40 minutes.

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Water: Water for mixing and curing of concrete shall be clean and free from oil, salt, acid, vegetable matter or other substances harmful to concrete. Water shall conform to relevant specifications stipulated in IS: 456. Water from approved Bore well near batching plant will be used. Mild steel bars for dowels and tie bars: These shall conform to the requirements of IS: 432, IS: 1139 and IS: 1786 as relevant. The dowel bars shall conform to grade S240 and tie bars to grade S415 of IS. Pre-moulded joint filler: Joint filler board for expansion joints is of firm compressible material and complying with the requirements of IS: 1838. Joint Sealing Compound: Polysulphide type sealant from Approved sources conforming to BS: 5212: 1990 shall be used. Separation Membrane: Separation membrane shall be impermeable plastic sheeting 125 microns thick. 5.4

Proportion of materials and mix design: The minimum cement content in PQC is 350kg/M3 and Maximum cement content is 425kg/M3 of concrete. The compressive strength of 28 days will not be less than 45Mpa & Flexural strength not less than 4.7Mpa as per contract specification. The proportioning of material and the design mix shall be carried our as per IS: 10262 and SP: 23 & to be submitted for Engineers approval.

5.5

Site Trials: The trial paving will be carried out on the road alignment under the supervision of the Engineer. The trial will be carried out to demonstrate the suitability of plant, equipments and work procedures to provide and compact the concrete to the specified proportions, density, void contents and to confirm that, any other specified requirements as per contract specification be achieved. Trial will be carried out over two days with a minimum of 30-meter stretch each day and all longitudinal and transverse joints will be constructed as per the approved drawing. Tests on trial will be carried out as specified vide clause 602.10.5 of MoRTH

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specification. Three numbers of core from each trial stretch will be taken not before 7 days to determine the density of the concrete, thickness, air voids and to check segregation by visual inspection. The temperature development in the concrete slab during hardening will be recorded. All data retrieved from the trial stretches i.e; In-situ density, air void, pavement thickness, texture depth, surface regularity, alignment of dowel bars etc will be submitted separately.

5.6

Construction Methodology:

5.6.1

Cleaning The Underlying Surface After marking to the required widths and lengths on DLC surface, cleaning of DLC surface shall be done with manual brooming and / or compressed air.

5.6.2

Placing Of Separation Membrane A separation membrane of 125-micron thick white in colour, transparent & impermeable in nature shall be placed between the DLC and PQC layer. Before placing the membrane DLC layer shall be swept clean of all extraneous material. Where overlap is required it shall be of 300mm minimum. The membrane shall be nailed to the DLC with nails and no standing water on or under the membrane shall be allowed before placing concrete.

5.6.3

Joints Both transverse and longitudinal joints have been discussed here. All the joints shall be made in accordance with approved drawing. Transverse joints are further classified as contraction joints, expansion joints and construction joints.

5.6.3.1 Transverse Contraction Joint Contraction joints shall be provided at 4.5m c/c in the longitudinal direction except at expansion joint locations. 32mm dia MS dowel bars of length 500 mm shall be placed at 150 mm from the top of the separation membrane layer, spacing between bars will be 180mm c/c. Dowel bar shall be supported on a cradle in a pre-fabricated joint assembly that will be positioned prior to the laying of the PQC layer. The cradle consists of 8mm MS bar bent in the shape of a “U” and supported by 8mm MS rods. Dowel bar shall be painted with corrosive paint and covered by a thin plastic sheath for a minimum length of 300mm from one end. A groove of 11mm thickness and 110mm depth runs all along the transverse direction just above the center of the dowel bar arrangement. 5.6.3.2

Transverse Expansion joint Expansion joints are consisting of joint filler board and 32mm plain MS bars of length 500 mm covered by a thin plastic sheath for a minimum of 275 mm length of the bar placed at 150 mm from the top of the separation membrane. The bars are

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placed at 180mm c/c and the expansion joint is spaced at 30mtr c/c in the longitudinal direction or at end of the day’s work. On the other end of the dowel bar, a 300mm long closely fitted PVC cap filled with sponge for a length 30mm will be provided. A similar cradle arrangement as above for supporting the dowel bar is followed. To separate the slabs adjacent to the expansion joint completely, a joint filler board of thickness 20mm is positioned vertically along the line of the joint. A groove of thickness 20mm and 25mm deep is made all along the centerline of the expansion joint while the concrete is still green. Space around the dowel bar, between the lower concrete layer and the filler board is packed with a suitable compressible material to block the flow of cement slurry. 5.6.3.3 Longitudinal joint The longitudinal joints shall be saw cut as per details in approved drawing. Tie bars will be used in longitudinal joints. These are of HYSD with minimum strength 415Mpa or Fe500 TMT. 12mm dia 640mm long will be provided at a spacing of 560 mm c/c, A start end and stop end is fixed at the position where concrete is to begin for the day and is expected to close for the day. At the stop end position, the dowels of 25mm are capped along with sponge inserted so as to facilitate the easy movement of the dowel while expansion of concrete. The groove shall be cut after final set of concrete. 5.6.4

Batching and Mixing Batching and mixing of the concrete shall be done at batching and mixing plant. Proportioning of materials shall be done in the batching plant by weight as per approved mix design.

5.6.5

Laying and Compaction In case of screed operations for outer lanes of 3.5m, the side shutters are fixed along the lane that is to be concreted, taking lines and levels from the surveyor. The gaps between the bottoms of side shutters shall be plugged with wedges/ foam sheets to prevent escape of slurry. In case of inner lanes of 3.5m, the existing outer lanes serve the purpose of side shutters. In both cases a pair of masons behind the screed take care of any irregularities etc. The concrete from batching plant shall be transported in transit mixers to the work spot. Concrete shall be dumped to position in front of screed. The screed moves at a speed of approximately 0.2 m/min in an even manner without segregation, so that after compaction the layer will be of specified thickness of 300mm. Before the paving starts for a particular stretch, form / shutter panels are fixed with marking on them to specify the depth of concrete at that end of the stretch. The screed is to be set to lay the PQC layer of width 3.5m. The lead of the tipper from the batching plant to the paving site is so timed that the entire operation of spreading, compacting and finishing the concrete from a particular tipper is completed within

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90 minutes when the concrete temperature is between 25 and 30 degrees Celsius. The slumps required at site will be kept between 50 and 75. Compaction shall be carried out immediately after the material is laid and leveled. The concrete is given a rough level of paveable thickness & the screed is passed to give further surface vibrations and achieve the accurate finish level. Initial compaction during laying of concrete will be achieved by the tamping bars of the screed. In order to ensure thorough compaction, needle vibrators will be used on the full width of the lane till there is no further visible movement.

5.6.6

Texturing Wire brush or other suitable means of appropriate size as described in MoRTH Clause: 602.9.8.2, shall be used for texturing the surface evenly across the slab in transverse direction, immediately after the finishing of the concrete surface and before the application of curing compound. A labour on the working platform shall brush the surface. The texture depth will be measured by sand patch test as described in clause 602.12 of MoRTH. An average of 5 measurements will be taken for each day of paving between 24 hours and 7 days after the construction of the slab.

5.6.7

Curing Immediately after surface texturing, the surface and sides of the slab shall be cured by the application of approved curing compound with the help of a manual sprayer. Curing compound shall be stable and impervious to evaporation of water from the surface of the concrete within 60 minutes of application. The compound shall not react with the underlying concrete layer or the film will not crack, peel or disintegrate and have a water retention efficiency index of 90%.In addition to spraying of the curing compound, the fresh concrete surface will be protected from adverse atmospheric conditions by warping with polythene tents for a minimum period of 3 hours, and then it will be covered with moist hessian cloth till completion of curing.

5.6.8

Joint cutting On well-cured concrete, after a gap of 6 hours from the start of concreting the transverse joints namely contraction and expansion joints shall be cut as per approved drawings. Contraction joints shall be 11mm wide and 110mm deep. The Expansion joints are cut initially in a fashion similar to the contraction joints whereas they are widened as 20mm wide and 25mm deep. Curing with thick hessian cloth will be done immediately after the joints are cut. These will be kept continuously moist by sprinkling water as per specification.

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5.6.9

Sealing the joints After the grooves are widened to the required widths and depths, joints will be sealed with polysulphide sealants. A preliminary preparation of the groove in the way of cleaning off the dirt, by air compressor or in some cases by pressurised water jets. The groove will then be dried. To break the bond between the bottom of the groove and the sealant, a highly compressible and heat resistant paper backed depending strip of width greater than the width of the groove is inserted so that the sealant does not leak through the cracks in concrete.

5.6.10

Weather & Seasonal limitations During monsoon required number of tarpaulin and shall be provided along the line of work. In case of rains during concreting using tarpaulin sheets shall adequately protect all the freshly laid concrete, which had not been covered for. Any concrete damaged by rain during laying shall be removed and replaced. If the damages are limited to textures only, it shall be re textured in consultation with the Engineer. In hot whether precautionary measure shall be taken to maintain the temperature of concrete below 30 0C at the paving site.

5.6.11 Tolerances for materials Joint filler board used in transverse expansion joint to be within +/- 1.5mm. For paving works, the slump value in the range of 50 to 75 mm is reasonable. For bars supported on cradles: All bars to be within (+/-3) mm per 300mm length. 2/3rd of the bar to be within (+/-2) mm per 300mm length. No steel bar of the cradle assembly shall be continuous across the joint.      

5.6.12 Quality control of works Surface levels: Surface regularity of pavement courses:

+5/-6mm as per table 900-2 of MOST Cl. 902.4

Rectification of regularity of the surface: The defective length of the course shall be removed to the full depth and replaced with conforming material. The area shall be at least 3m long, not less than 1 lane width and will extend to the full depth. Before laying this course, the disturbed sub base layer is corrected by leveling, watering and compacting. 6.0

TESTING AND ACCEPTANCE PROCEDURES:

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All the Inspection and Test requirements will be carried out as per Technical Specifications and other Codes/Standards as mentioned in References Chapter. All the Records shall be properly controlled and maintained in easily identifiable and traceable manner. Any Non-Conformity observed during Field Inspection and also during Testing of Materials the same Non-Conformity shall be recorded in the specified Format and necessary Corrective/Preventive actions shall be initiated to prevent such things in future. All Product Non-Conformities shall be observed, recorded, corrective/preventive actions and closing of NCR’s shall be as per the procedure. 7.0

OCCUPATIONAL HEALTH & SAFETY MANAGEMENT PLAN: The OH & Safety Management Plan for the Project has been prepared to meet the various Safety requirements as mentioned in Contract Documents and also as per the established OH & Safety Management Systems and Procedures of HCC.

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Pavement Quality Concrete

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