This page covers the method statement for the construction of plain cement concrete pavement in accordance with the drawings & specifications and in conformity with lines, grades and cross sections shown on the drawings.
All the joint details shall be as per the approved working drawing.
Concrete pavement installations shall be done in compliance with contractor agreement, Ministry of roads transport and highways specifications, relevant drawings and codes.
OPC 43 grade cement shall be used in the mix. Minimum quantity of cement shall be 400Kg/M3 of the Pavement quality concrete.
Pavement quality concrete shall be design mix concrete having characteristic flexural strength of 45 kg/cm2in field at 28 days.
Size of trial bay for PQC shall be min. 7.62m x 60m.
Concrete mix shall be as per the approved mix design.
Necessary Tools and Equipment:
Below is list of necessary tools and equipment’s required for the concrete road construction works.
- Batching & Mixing plant
- Joint cutting machine and blades
- Slip Form Paver & Fix Form Paver
- Finishing and Texturing equipments e Edging tools
- Water tanker
- Tippers/Dumpers/Transit Mixers
- Temporary movable collapsible tent
- Shuttering plates
- Survey Equipment
- Vibrators and needles
Coarse aggregate shall be produced from approved quarry in required sizes.
It shall consist of clean, hard, strong, dense, non-porous and durable pieces of crushed stone or a suitable combination thereof as specified.
Maximum nominal size of aggregate shall be 31.5 mm & shall confirm to the quality requirements as per roadwork specifications.
Fine aggregate shall be clean, hard, strong and durable natural sand meeting the project specifications.
It shall not contain dust, lumps, soft or flaky, materials, mica or other deleterious materials in such a quantity to reduce the durability and strength of concrete.
All the fine aggregate shall conform to the specifications.
Cement: Ordinary Portland cement of grade 43 confirming to specifications shall be used in the cement road construction.
Cement older than 60 days from date of manufacture shall not be allowed to use.
Water: Quality of the water shall conform to the project specifications.
Admixture: Admixture shall conform to the project specifications.
Synthetic Filler Board & Backup Rods:
Joint filler board for expansion joints shall be firm compressible material complying with the specifications.
It shall be 20 mm in thickness.
Backup rods shall be as per the specification requirements.
Joint Sealing compound: The joint sealing compound shall be as per the specification.
Separation Membrane: Separation membrane shall be impermeable plastic sheeting 400 micron thick as per specs.
Concrete Pavement Procedure
Preparation of sub base
The cement concrete pavement shall be laid over the DLC sub base with concrete mix with slip form Paver and Foam Fix Paver.
A plastic sheet of 400 micron over sand shall be placed flat without creases over the DLC.
Before placing the Sand and plastic sheet, the sub base shall be swept clean of all the extraneous material using air compressor.
If the subbase is found damaged at some places or it has cracks wider than 10 mm, it shall be repaired with fine cement concrete.
The plastic sheet shall be nailed to the DLC layer by patches of adhesives or appropriate tape or concrete nail with washer.
Damaged sheeting shall be replaced.
Mixing, Transportation, placing and compaction of Concrete
Concrete shall be mixed in approved proportions in batching and mixing plant having capacity 25 % higher than the proposed capacity of the paver.
Batching plant shall be capable of mixing the ingredients by weight, each type of material being weighed separately.
The weighing devices of the plant shall have an accuracy within 1% for cement, admixture and water and 2% for aggregates.
Mixing time shall be adjusted according to the efficiency of the mixer to ensure the uniform distribution and a uniform color of the entire batch.
In any case mixing time shall not exceed two minutes.
Mixer which has been out of use for more than 30 minutes shall be thoroughly cleaned before putting in a new batch.
Water cement ratio of the mix shall be maintained to the designed value by recording the moisture content of the ingredients frequently and adjusting the water quantity of the mix.
Suitable adjustment shall also be made in the weight of aggregate to allow for the variation in the weight of aggregate due to variation in their moisture content.
Aggregate shall be kept moist during summer to keep the temperature low and chilling water shall be used to control the temperature.
Mix design shall be done considering the degree of quality control as very good and minimum cement content of mix corresponding to 4.5 Mpa flexural strength shall not exceed 425 kg/cum.
Transportation of concrete mix:
Freshly mixed concrete from the batching plant shall be transported to the paving site by means of dumpers duly covered with tarpaulins.
The number of dumpers to be deployed shall depend on the distance of the paving site from the batching plant location so as to ensure a continues supply of material to paver.
Placing and Compaction of Concrete
The concrete shall be placed with a slip form paver with independent units designed for spreading, consolidating, texturing and curing of the concrete.
Paver shall be fitted with electronic sensor so as to control the lines and grade from either one side or both sides of the machine.
The transported concrete shall be placed in front of the PQC Paver.
Paver shall compact the concrete by internal vibration and shape it between the side forms by vibrating and oscillating finishing beams.
The concrete shall be deposited in front of paver across the whole width and to a height which at all times is in excess of the required surcharge.
Deposited concrete shall be struck off to the necessary average and differential surcharge by means of the strike off plate or a screw auger device extending across the whole width of slab.
The equipment for striking off the concrete shall be capable of being rapidly adjusted for changes of the average and differential surcharge necessitated by change in slab thickness or cross fall.
Level of the conforming plate and finishing beams shall be controlled automatically from the guide wires installed on both sides of the paving by sensors attached at the four corners of the paver machine.
The alignment and level of ancillary machines for finishing, texturing and curing of the ‘concrete shall be automatically controlled relative to the guide wire or to the surface and edge of the slab.
Slip form paver shall have vibrators of variable output.
The machines shall be of sufficient mass to provide adequate reaction during spreading and paving operations on the traction units to maintain forward movements during the placing of concrete in all situations.
Dowel bars and tie bars shall be inserted at the required locations and to the required depth, as mentioned in the drawings, by the dowel bar inserter and tie bar inserter integrally fitted in the paver.
There shall be some area (Short straight length area, link area) where Slip form paver shall not work properly, in that case foam fix paver shall be used.
In which after spreading sand and polyethene sheet, shuttering plate shall be fixed.
Shuttering plate shall be in proper alignment, line and levelling.
Foam fix paver shall rest on rails.
Rails shall be in levels according to shuttering levels.
Concrete shall be placed in front of foam fix paver.
Concrete shall be spread.
Vibrators shall be used for vibrating concrete and then foam fix paver shall be used to achieve proper levels.
This processing shall be followed at each 5 to10 meter length continuously.
The produced concrete shall be spread, compacted and finished within two hours of production if the temperature is less than 25°C or within 90 minutes of production if the concrete temperature is between 25°C to 30°C.
If necessary, chilling water shall be used for mixing in concrete so as to reduce the concrete temperature.
There are two types of joints:
1) Transverse joints
2) Longitudinal Joints
1) Transverse Joints
Contraction joints: Contraction joints shall be constructed by forming in the surface of slab, a slot of 4 mm wide and having a depth 1/3rd the depth of the slab + – 5 mm or as stipulated in the drawing.
The groove shall be formed by a joint cutting saw which shall be cut as soon as the concrete has undergone initial hardening and hard enough to take the load of groove cutting machine.
Groove is subsequently widened to seal with sealant.
Contraction joints shall be provided at spacings as shown in the approved joint layout drawing.
The Expansion joints shall consist of’ a joint filler board as per details in the drawings.
Approved filler board shall be positioned vertically with the prefabricated joints assemblies along the line of the joints and kept within +10 mm.
The best fit straight line through the joint grooves shall not be more than 25 mm from the intended line of joint.
Height of the filler board shall be such that its top is minimum 25 mm below the surface of the pavement.
Transverse construction joints shall be provided whenever concreting is completed after a day work as per details shown in approved layout, except in the case of emergency, construction shall always be suspended at the site of expansion or contraction joints.
2) Longitudinal Joints
The longitudinal construction/ contraction joints shall be provided as per details shown in approved joint layout drawing.
Groove shall be cut in longitudinal contraction joint after the final set of the concrete.
Joints shall be sawn to at least 1/3 depth of the slab +5 mm.
After the final floating and finishing of the slab and before the application of the curing membrane, the surface of the concrete slabs shall be textured in transverse direction.
The texturing shall be done by tinning the finished concrete surface by using rectangular steel ties.
Texturing unit is an integral part of the paver and texturing will be started after a gap of 1-2 hours of finishing of slab so as not to damage the freshly finished surface.
The Texturing depth shall be measured by sand patch method as mentioned in specifications.
Texture depth should not be more than 1.5 mm.
Immediately after texturing, the surface the sides of the slab shall be sprayed with the approved resin based aluminized reflective curing compound which hardens into an impervious film, with the help of mechanical sprayer.
After the curing compound loses its tackiness, the slab will be covered with moist hessian laid in two layers and same shall be kept damp for a minimum period of 14 days and maximum 28 days time periods.
Saw Cutting of Joints
The finished concrete slab shall be saw cut at transverse/Longitudinal joints with diamond studded blades soon after the concrete has hardened to take the load of the sawing machine and crew members without damaging the texture of pavement.
Such time difference will be determined for the first time of saw cutting and for further works the same duration shall be adopted for saw cutting of transverse/Longitudinal Joints.
The contraction joint shall be of the dimensions as shown in the drawing and subsequently widened accommodate the sealant at the time of sealing of joints.
Sealing of grooves: Grooves shall be cleaned using compressed air and water jet, primed and filled with polyurethane as shown in the drawing.
- Edge of the carriage way shall be within ± 10 mm.
- Level tolerance shall be ±5mm.
- Surface regularity shall be ±3mm.
- Thickness of the slab shall be -5mm and +10mm.
- Average 28 days flexural strength of the batch of beams shall exceed the specified characteristics flexural strength plus 1.65 times the standard deviation of the batch.
- There is no honey combing in concrete.
- Tolerance level factor is 1.5.
- The 28 days Strength of more than one test beam should not be less than specified characteristic flexural strength in the same batch.
During the construction of the cement concrete pavement, adequate safety and traffic signs shall be installed adjacent to the work area to protect the ongoing work.
Visible safety and road signs shall be provided adjacent of the work area.
Flagmen with reflective vests and holding a red flag each shall be deployed to control the traffic which may be effected by the construction operations.
The safety officer shall make frequent patrols of the construction site to ensure that the safety equipment and signs are operational at all time and workmen deployed are equipped with personal protective equipment.
Other safety arrangements shall be as per approved project safety manual.
All debris shall be disposed off at designated locations.
Site shall be kept clean of all oil spills, grease etc. and disposing these off as per the safety procedures given in safety manual.
Provisions given in the contract agreement, specifications, drawings, approved mix designs & ITP shall get precedence over this roadwork method statement.