Method Statement
1. SCOPE
The scope of this document is to outline the procedure for construction of Rigid Pavement Carriageway in order to ensure that it proceeds under controlled conditions and in a specified manner and sequence. All provisions of Specifications and other contract documents shall continue to apply. Where there is a conflict between this method statement and the Contract Documents, the Contract Document shall prevail.
2. FIELD OF APPLICATION
This Method Statement shall be applicable for construction of Rigid Pavement Carriageway, for Highway.
3. CONSTRUCTION SCHEDULE
Detailed program and time schedule for the construction of Rigid Pavement of Carriageway will be provided at time.
4. SAFETY PRECAUTIONS
Adequate steps shall be taken for the safety, health and welfare of persons and for the prevention of damage to work, material and equipment for the purpose of or in connection with the Contract.
5. SITE PREPARATION
General.
To start the work, first the site shall be prepared so that there is no obstruction or difficulty while executing the said work. Site preparation includes an easy access to working place of both men and equipment and clearance of site from asphaltic ripped material, stumps, roots, bushes, vegetation, rubbish and other objectionable material. Trees if any shall be removed as per Item 102 of Specifications.
Prior to commencement of work, all public traffic shall be diverted to old Carriageway. This diversion of traffic may take place in two or more segment depending upon the site conditions and permission to be granted by Motorway Police.
6. SETTING OUT
Setting out will be carried out by Surveyors before and after the excavation of the existing road structure entire / partial depending on the site condition to ensure that the pavement is located at its true position and grade. At each stage of the pavement, the axis and level will be marked out and checked by the Engineer’s Surveyor.
Existing carriageway is 2-lane. Rehabilitated carriageway shall be 3-lane. Third lane is to be constructed in the Median. As such, entire width of 3 lanes shall be constructed upto sub base level. In the rigid pavement portion, lean concrete (15 cm) shall be placed over the sub base to serve as base for concrete pavement (30 cm). Adjacent asphaltic pavement shall be of Agg. Base course (29 cm) overlayed with Asphaltic base course (11 cm). On outer side i.e. shoulder sub base shall be overlayed with Agg. Base course (43 cm) and finished with DST. Rigid pavement shall be 7.30 m wide, with Asphaltic pavement 3.65 m and shoulder 0.60 m. On outer side shoulder of 2.50 m wide shall be finished with DST.
7. CONCRETE PAVEMENT
7.1 DESCRIPTION
This work shall consist of a pavement composed of Portland cement concrete with reinforcement as specified on a prepared sub-grade or base course in accordance with these specifications and in conformity with the lines, grades, thickness and typical cross-sections shown on the drawings. This shall include deformed bars for contraction joints and dowel bars for expansion joints or as shown on the Drawings.
MATERIAL REQUIREMENTS
Concrete
Concrete material shall conform to the requirements indicated in item 401 and as specified hereinafter. In addition to it the contractor shall advise the Engineer of the source of all material to be used in proportioning concrete for the work. If the contractor later proposes to obtain materials from a different source, he shall notify the Engineer at least thirty (30) days before such materials are to be used.
Reinforcing Steel
Concrete reinforcement shall conform to item 404 or as indicated on the Drawings.
Polythene Sheeting
Polythene sheeting for placing immediately below concrete slabs shall be 0.065 mm thick or having a minimum weight of fifty (50) grams per square meter (whichever is greater) made from polythene or other approved hydrocarbon thermoplastic resin (produced by the polymerization of ethylene under high pressure and density) and given an anti-static treatment to reduce dust attraction and reduce friction.
Joint Filler
Joint filler shall consist of cane or other suitable long fibers of a cellular nature uniformly impregnated with asphalt. The asphalt content of the joint material shall be between thirty and fifty percent. Strips of the joint filler which do not conform to the specified dimensions within the tolerance ± two (2) mm for thickness and ± twelve (12) mm for depth are to be rejected.
Joint Sealing Compound
Joint sealing compound is to be as BS 2499 (1973) type A1 or A2, or as approved by the Engineer.
The compound is to be impermeable, is to withstand all weather conditions and is to be capable of adhering to the concrete without cracking, spalling or disintegrating and will not require an impracticable condition of dryness or cleanliness of the concrete slabs.
Where recommended by the manufacturer of the sealing compound, a primer supplied by him is to be used to improve adhesion.
Dowel Bars
Dowel bars shall be cut from mild steel and will be approved by the Engineer. The Contractor’s attention is directed to the requirement that one end of each dowel bar in all joints, except bonded construction joints shall be sawn and not sheared so that no irregularities likely to interfere with its sliding action in the concrete shall occur. The minimum length of the dowel bars spaced at one meter centre to centre or as shown on the drawings shall be thirty five (35) times the diameter of the bar used unless otherwise specified or as directed by the Engineer.
Expansion Caps
Expansion caps for dowel bars in expansion joints shall consist of pressed metal sleeves plugged at one end by punching the specified joint filler board of a wad of cotton waste of similar compressibility and sealed at the end against entry of mortar. The tube shall have an internal diameter permitting sliding on the dowel bar but close enough to prevent entry of mortar.
Cracks Inducing Battens
Cracks inducing battens shall be of wood or of any other suitable material proposed by the Contractor and approved by the Engineer. Battens of highly absorbent wood or other material shall be of cross-sectional dimensions shown on the drawings and treated to prevent adhesion between them and the concrete.
Sampling and Testing
All material shall be approved by the Engineer prior to use in the work Additional samples will be taken and tested by the Employer during the progress of the work to check on the quality of the material being supplied and/or placed by the Contractor. The results of these tests will be available for the Contractor’s use; however they are not intended for construction control purpose. The contractor should set up his own test facilities or arrange the same from a private laboratory to assure that his materials and workmanship comply with the specification.
CONSTRUCTION REQUIREMENTS
Pavement Base
The base upon which the concrete pavement is laid shall be leveled compacted and true to the grades and cross-sections shown on the plans and shall be so maintained, throughout the period of placing concrete pavement.
To ensure the proper depth and section, a scratch template true to depth and section and resting on accurately set side forms shall be moved over the surface immediately before placing concrete and any irregularities shall be immediately corrected.
Forms
Side forms shall be made of metal of an approved section and construction/provided with adequate devices for secure setting so that when in place, they shall withstand the impact and vibration of the compacting and finishing equipment with settlement not exceeding 1.5 mm in three (03) meters from a true plane surface on the top of the forms and inside face shall not vary more than six (06) millimeter from a plane surface.
The depth shall be equal to the thickness of the pavement at the edge. The forms sections shall be tightly joined by each joint free from play in any direction. These forms shall be stacked with steel stakes and shall be of a length approved by the Engineer.
Side forms for machine placing shall have rolled section steel rails which shall be of adequate stiffness to carry the laying, compaction and finishing machines.
These machines shall not run on folded sheet metal form tops. The top faces of forms are to be carefully cleaned and maintained. The forms shall be without horizontal joints and with flange braces extending outward on the base not less than two-third the height of the forms. They shall be equipped with positive locking devices which will permit neat tight joints and do not deform under impact vibration by thrust.
Before placing forms the lean concrete shall be to the required grade. The forms shall have full bearing upon the lean concrete throughout their length and shall be placed with exactness to the required grade and alignment of the edge of the finished pavement.
Forms shall be set to the required lines and grades well in advance of placing concrete, preferably not less than two hundred (200) meters. Forms shall not be removed for at least twelve (12) hours after the concrete has been placed. Forms shall be carefully removed in a manner to avoid damage to the pavement. Pavement which in the opinion of the Engineer is damaged due to the careless removal of forms shall be repaved by the Contractor as directed by the Engineer at the Contractor’s own expense.
Forms shall be thoroughly cleaned and oiled each time they are used.
7.4 Composition and Compressive Strength of Concrete
1. Composition
(a) All concrete shall be proportioned by weighing and shall conform to the following strength and mix requirements
i) Compressive Strength, 28 days minimum 250 kg/sq. cm
ii) Cement content, sacks (50 Kg) iv) Slump 25-75 mm
v) Entrained air, percent 3 ± 0.6
vi) Nominal size of aggregate 11/2” Max.
(b) At least 35 days prior to the start of paving operations and after approval of all materials to be used in the concrete, the contractor shall submit for approval, the mix design he intends to use based on proportioned weights of cement, air entertainment agent, saturated surface dry aggregates and water. This mix design will be tested by the Engineer and approval will not be granted unless the average twenty eight (28) days compressive strength exceeds the minimum strength requirement by at least 15 percent. However the Engineer may allow paving operation on the basis of seven (07) days strength if he is satisfied with the result of seven (07) days strength.
(c) The cement content given in the foregoing table is minimum. If it is not sufficient to produce concrete of the compressive strength specified it shall be increased as necessary with out additional compensation under the contract.
(d) The compressive strength of the concrete will be determined by testing standard cylinders made from concrete taken from the mixer. The making, curing and testing of the specimens will be in accordance with AASHTO T23-73.
(e) During the course of construction, when the source of any material for the concrete is to be changed, or if there is any variation in the quality of the materials furnished, additional tests and necessary adjustments in the mix shall be made as required to obtain the specified strengths.
2. Consistency
The required consistency of the concrete mixture shall be such that the mixture will be cohesive, uniform and plastic permitting proper handling and finish. When deposited it shall not flow but shall remain in a conical pile. There shall be minimum of segregation and surplus water during the AASHTO T119-74.
The cement content shall be determined by means of a yield test in accordance with AASHTO T121-74.
3. Batching and Mixing
Concrete shall either be batched and mixed at a central batching and mixing plant or batched at a central batching plant for either mixing in field mixers adjacent to the forms for slabs or mixed in a truck mixer. When cement is supplied in bags, each batch of concrete shall contain a whole number of bags of cement.
i) Batching Equipment
All aggregates and cement for use in pavement shall be batched by weight by means of automatic devices of approved type conforming to the requirements specified below:
The batching shall consist of dividing the aggregates into three sizes, each stored in a separate bin of placing the cement in another bin and of recombining these ingredients as herein provided.
Material discharged from the several bins shall be controlled by gates or by mechanical conveyors. The means of withdrawal from the several bins and of discharge from the weigh box shall be so interlocked that not more than on bin can discharge at a time that the order of discharge can be changed as desired by the Engineer and that the weigh box cannot be tripped until the required quantity from each of the several bins has been deposited therein. Should a separate weigh box be used for each size of aggregate, all bins may be operated and discharged simultaneously. The discharged shall be so regulated that the amount of material discharged into the weigh hopper from any bin with weighing devices at rest will be within two (02) Kg of the weight called for by the scale setting for the bin.
When the discharge from the several bins is controlled by gates, each gate shall automatically lock in an open or partially open position until the required weigh is discharged into the weigh box, after which the gate shall automatically close and lock.
Scales utilised in the batching device may be of the springless dial type or of the multiple beam type.
The beams or dial of automatic scales shall be so arranged that the weighing units will be in a compartment that may be locked at the requirement of the Engineer.
It is the intension of this Specification that the device shall be automatic to the extent that the only manual operation required for combining the ingredients for one batch shall be a single operation of a switch or a starter.
Should separate supplies of aggregate material of the same size group, but of different moisture content be available at the batching plant withdrawal shall be made from one supply exclusively and the material therein completely exhausted before starting on another.
The moisture content of the aggregate shall be such that no visible separation of moisture and aggregate will take place during transportation form the batching plant to the point of mixing. Aggregates containing excess moisture shall be shockpiled prior to use until sufficiently dry to meet the above requirement.
The equipment for batching of concrete materials shall conform to the following requirements:
The batching equipment shall be substantially constructed on a firm foundation high enough above trucks being loaded to function properly. It shall have three (03) bins and a weighing hopper. The bins shall have a total capacity of not less than 100 tons and the
partition between them shall extend not less than one (01) meter above the bins. The bins shall be equipped with baffle boards so as to assist drainage of the aggregates and prevent the drained out water from passing through the outlet gate. A plateform shall extend around the weighing hopper for easy means of inspection, adjustment and weighing.
The weighing hopper shall have a single compartment with arrangements for ready removal of excess material and with a discharge gate opening parallel to the portion of receiving trucks. The amount of opening of the discharge gate shall be readily controlled. There shall be sufficient clearance at all points for the weighing hopper to function properly. The weighing scale shall be of the beam or springless dial type of standard design and make and shall be able to record the true weigh within two (02) Kg at maximum load. The beam type shall have separate beams for each size of aggregate and each beam shall have an easily operated locking device. A dial which will show the weight when the load is within forty five (45) Kg of that required an approved signal device shall be provided.
The weighing scales shall be arranged for ready standardization and with each scale shall be furnished a set of standard weights including seven 25 Kg, two 10 Kg, two 5 Kg and two (02) Kg weights. For batchers of capacity of half (1/2) cubic meter or less the standard weight to be furnished shall be as approved by the Engineer. The tolerance to these scales shall be within those listed in table 3 of US
In lieu of the automatic devices for controlling the weighing of the aggregates and bulk cement as described in the forgoing specification for batching equipment, the Contractor may be permitted to substitute manually controlled devices provided approval for such devices is granted by the Engineer.
ii) Truck Mixers
Truck mixer shall be used only when permitted by the Engineer in writing. Each transit mixer shall have a watertight drum, suitable mounted and fitted with adequate blades capable of properly combing the mixture. Measuring tanks equipped with outside taps and valves to facilitate checking their calibration shall be provided for the mixing water. All water added to the mixer shall be passed through an approved water meter, located between the water tank and mixer drum, equipped with indicating dials and totaliser and capable of measuring and discharging a specified amount of water within an accuracy one per cent. The device shall provide means of readily verifying the amount of water added to mixing shall be provided on each mixer. An inspection opening shall be provided to permit ready determination of the consistency of the concrete being placed in the forms.
4. Placing Concrete
a) General
The mixer shall be operated outside of the forms at all times expect at locations where the Engineer deems it not feasible to do so.
Concrete mixed in central plant shall be transported without delay from the mixing plant to the position for laying and any concrete which in the opinion of Engineer has been mixed too long before reaching, the work will be rejected and shall be removed from the site. The concrete shall be deposited on the lean concrete in successive batches for the full width between forms and in a manner which will require as little re-handling as possible. Spreading shall be done by an approved mechanical spreader in a manner that will prevent segregation and separation of the material. Necessary hand spreading shall be done with shovels not rakes. Workmen shall not be allowed to walk in the freshly mixed concrete with boots or shoes coated with earth or foreign substances the amount of material deposited shall be sufficiently in excess of that required form the pavement to the required cross-section after consolidation in order to provide a roll of concrete ahead of the front screed of the finishing machine for the full length of the screed.
Concrete shall be thoroughly consolidated against and along the faces of all forms and along the full length and on both sides of all expansion joint assemblies by means of vibrators inserted in the concrete. Vibrators shall not be permitted to come in contact with a joint assembly, the grade or a side form. In no case shall the vibrator be operated longer than fifteen (15) seconds. Concrete shall be deposited as near to expansion and contraction joints as possible without disturbing them but shall not be dumped from the discharge bucket or hopper on to a joint assembly. The hopper is well centered on the joint assembly. Damage to joint assemblies caused by dumped concrete shall be repaired immediately as directed by the Engineer at Contractor’s expense. Trucks delivering concrete shall not run on polythene sheeting nor shall they run on completed slabs until at least fourteen (14) days after placing the concrete.
Should any concrete materials fall on or be worked into the surface of completed slab, they shall be removed immediately by methods approved by the Engineer.
Placement of concrete ahead of the initial spreader strike off shall not be more than fifteen (15) minutes ahead of final spreader strike-off. If concrete is placed in one (1) layer only, the placement of concrete shall not be more than twenty (20) minutes ahead of the spreader strike-off.
In order to secure adequate compaction, the concrete is to be spread with a surcharge above the finished level of the layer. Spreading, compacting and finishing operations are to be completed without delay.
The total time taken from the addition of the water to the mix until the completion of the surface finishing operations shall not exceed thirty (30) minutes when the shade or mix temperature exceeds twenty seven (27) degree C or forty (40) minutes when less than twenty seven (27) degree C. The mixing and placing of the concrete shall progress only at such a rate as to permit proper finishing, protecting and curing of the pavement.
The additive shall be added to the concrete mix so as to ensure more setting time. The top of the forms shall be kept free from accumulation of concrete or foreign material. The Contractor shall not permit the accumulation of laitance along the edge of a slab poured adjacent to one previously placed. Any accumulation of laitance shall be removed and replaced with fresh concrete. As soon as the side forms are removed, the edges of the slab shall first be inspected by the Engineer and any minor honey combed areas shall then be filled with mortar composed of one part of cement to two parts of fine aggregate under the supervisor of the Engineer.
b) Weather Conditions
For concreting during hot/cold weather, requirements 401.3.6 (i) of the specifications will be followed.
5. Placing Reinforcement
All pavement reinforcement shall be placed as shown on the plans. All marginal bars, dowel bars, and tie bars required by the plans shall be held in proper position by sufficient number of metal bars supports or pins as approved by the Engineer. If the center joint is to be sawed in lieu of placing the metal center strip, the tie bars may be installed mechanically by means of equipment and methods approved by the Engineer. The satisfactory placement of the tie bars shall depend upon the ability of the mechanical device to place the tie bars in their true position. The Engineer may require, when satisfactory placement is not obtained by mechanical means, that the tie bars be installed ahead of placing of concrete and that they be securely staked and tied if necessary to hold them in their exact position. The use of removable devices, supporting the bars from the forms will not be permitted.
Following the placing of the concrete, it shall be struck off to conform to the cross section shown on the plans and to an elevation such that when the concrete is properly consolidated and finished, the surface of the pavement will be at the elevation shown on the plans.
Where two (02) layers of wire mesh reinforcement are required, as at bridge approaches the bottom layer shall be supported in the required position with bar chairs. Separators shall be used for the top layer if the strike off cannot be properly used for the operation. Laps in adjustment sheets or mats of reinforcement shall be shown on the plans. Laps parallel to the centerline of the pavement will not be permitted except for unusual width of pavement lanes or for irregular areas. If the plans do not show dimensions for laps, the minimum lap either perpendicular or parallel of the centerline of the pavement shall be fifteen (15) centimeters.
Reinforcement steel shall be free from detrimental amounts of dirt, oil, paints, grease, loose mill scale and loose or thick rust which could impair bond of the steel with the concrete.
6. Joints
Joints shall be constructed exactly in accordance with the details shown on the plans and specifications and with the best of workmanship. Failure to construct the joints as called for and in the best possible manner as determined by the Engineer will be cause for suspension of work until the cause of the defective work is remedied.
a) Expansion Joints
The lean concrete at Expansion Joints shall be accurately trimmed to the required cross section and to the proper depth of the pavement.
A string line shall be stretched between the pavement forms along the centerline of the joint. One half of the length of each dowel bar shall be painted in accordance with the directions shown on the plans and then thoroughly coated with hard grease or lubricant as approved by the Engineer to prevent the concrete from bonding to that portion of the dowel.
The entire joint assembly shall be of a type designated on the plans and shall be installed in such a position that the centerline of the joint assembly is perpendicular to the centerline of the pavement slabs and the dowels lie parallel to the centerline of the slab, Finished joints shall not deviate more than six (06) millimeters in the horizontal alignment from a straight line. No plugs of concrete shall be permitted any where within the expansion space.
A slip sleeve of the dimensions shown on the plans shall be placed on the greased end of each dowel. The greased ends shall be free to slide in the dowel holder and shall extend in the direction as indicated on the plans. Any excess grease on the dowel holder shall be removed.
The joint shall be securely staked or fastened in place prior to placing the concrete and in a manner to ensure the joint and the dowel bars will remain in their proper position after the concreting and finishing operations are completed.
Joints for pavement designed for two (02) or less lanes of traffic shall be assembled and installed in one (01) continuous piece or the connections between sections shall be made rigid and tight to prevent offsets in sections of the joints. The length of individual pieces of the expansion joint filler shall be not less than the width of one (01) traffic lane of the pavement.
As the finishing machine approaches the joint on the first trip, the excess concrete shall be shoveled ahead and the tamper and each screed in turn shall be lifted over the joint. On the second trip of the finishing machine, the screed may be operated over the joint.
b) Contraction Joints
Contraction joints shall be of the type and dimensions and the spacing shown on the plans. Sawed contraction joints shall be cut by means of as approved concrete saw. The joints shall not be sawed until the concrete has hardened to the extent that tearing and reveling is precluded. All joints shall be sawed during the initial curing period and the
sawing shall begin before the pavements starts shrinking and before uncontrolled cracking takes place. Any procedure which results in premature and uncontrolled cracking shall be revised immediately by adjusting the sequence of cutting the joints or the time interval involved between the placing of the concrete or the removal of the curing media and the cutting of the joints. In no case shall the pavement be left overnight without having the joints sawed. The joints shall be sawed at the depth, spacing and lines shown on the plans. Guidelines or devices approved by the Engineer shall be provided to ensure cutting the joint in a straight line and perpendicular to the centerline of the pavement. The dust resulting from sawing shall be completely removed from the joint and adjacent areas by means of an air jet or a combination of air and water applied under pressure immediately after the joint has been cut and before filing with joint compound. When the plans specify that dowel be installed through contraction joints, the lean concrete at the contraction joints shall be accurately trimmed to the required cross section and to the proper depth of the pavement. A string line shall be stretched between the pavement forms along the center line of the joint. Each dowel shall be painted and thoroughly coated with hard grease or lubricants, in accordance with the directions shown on the plans or as approved by the Engineer to prevent the concrete from bonding to that portion of the dowel. The entire joint assembly shall be of the type designated on the plans and shall be installed in such a position that the centerline of the joint assembly is perpendicular to the center line of the slab and the dowels lie parallel to the slab surface and parallel to the centerline of the slab. The greased ends of the dowels shall be placed in the direction as indicated on the plans and shall be free to slide in the dowel holder. Any excess hard grease on the dowel holder shall be removed.
c) Longitudinal Joints
Longitudinal joints shall be constructed in conformance with the details shown on the plans. When sawed joints are specified or used, suitable guidelines or devices shall beurnished to ensure cutting the longitudinal joint on the true lines as shown on the plans. The sawing of longitudinal joint shall be performed at a time that will preclude erratic or uncontrolled cracking. Sawed joints shall be filled with the type pf joint compound indicated on the plans. The dust resulting from sawing shall be completely removed from the joint and adjacent areas by means of air jet or a combination of air and water applied under pressure immediately after the joint has been cut and before filling with joint compound.
d) Construction Joints
A butt construction joint shall be made perpendicular to the centerline of the pavement at the close of each days work and also when the process of depositing concrete is stopped for a length of time such that, in the opinion of the Engineer, the concrete will have taken its initial set. This joint shall be formed by using a clean plank header having a nominal thickness of five (05) centimeters a width of not less than the thickness of the pavement and a length of not less than the width of the pavement. The header shall be cut true to the crown of the finished pavement and shall be accurately set and held in place in a plane at right angles to centerline and perpendicular to the surface of the pavement.
The top surface of the header shall be protected with steel as approved by the Engineer. On the face along with the center of the header there shall be fastened a trapezoidal piece of metal or wood the full length of the header, five (05) centimeters wide and at least
twenty five (25) millimeters in depth to form a grooved joint. The header shall have drilled holes to accommodate the dowel or tie bars hereinafter specified. Upon resumption of Work any surplus concrete remaining upon the subgrade shall be removed. The header shall then be carefully removed and fresh concrete deposited against the old in such a manner as to avoid injury to the edge of the old concrete. The fresh concrete shall be vibrated into the groove in a manner to ensure an interlocking joint.
Dowel bars or load transfer devices shall be used in all construction joints in accordance with the details shown on the plans. If no such details are shown on the plans, tie bars as provided for the longitudinal joint, and spaced at forty five (45) centimeter centers shall be placed across the joint in a plane parallel to the surface of the pavement approximately midway between the top and bottom surface of the pavement. The edges of the joint shall be grooved, edged and sealed with the material used for sealing expansion and contraction joints.
No construction joint shall be placed within three (03) meters of an expansion, contraction or other construction joint.
e) Sealing Joints
a) Materials: Joints shall be sealed with material of the type designated on the plans.
b) Hot poured Joints: The joints shall be sawed as provided in sub item 6 (b) and covered as provided in sub item 6 (c). After the fourteen (14) or seventeen (17) days curing period for the pavement has elapsed, the jute or other protective covering shall be removed from the joint and the joint thoroughly cleaned of all loose scale, saw dust, dirt, laitance or other matter. Cleaning may be accomplished with the compressed air jet, air and water under pressure, wire brushes or in extreme cases the joint shall, when directed by the Engineer, be resawed to ensure a completely clean joint. The joint surface and adjacent areas of the slab shall be thoroughly clean.
The hot poured joint material shall be heated in a heating unit approved by the Engineer to the temperature within the range required as shown by tests. The joint shall be filled from the bottom of the saw cut to the surface of the pavement. Any joint with the depth greater than twenty five (25) millimeters shall be filled with a minimum of two (02) layers, each layer being approximately equal in depth.
c) Cold Poured Joints: The joint shall be sawed as provided in sub-item 310.3.7 (b) & 310.3.7 (c) and cleaned of all loose saw dust, laitance, dirt, other foreign matter and free water.
The joints shall be filled immediately after cleaning. The nozzle used must be so designed that the joint is filled completely from bottom to top. The joint shall be filled so it is rounded on top about six (06) millimeters above the pavement surface. Immediately after the joints have been filled, they shall be covered with strip of nonabsorptive paper at least four (04) centimeters wide. Eleven (11) kilogram glassline or heavy craft is suitable. The paper shall remain on the joint it weathers or wears off.
7. Consolidating and Finishing
After being spread and struck-off as provided in sub item 310.3.5 “Placing Concrete” the concrete shall be further struck-off and consolidated with an approved finishing machine to such an elevation that when finishing operations are completed, the surface will conform to the required grade and crown. The finishing machine shall operate over the entire surface at least twice, the first time with the finishing machine tamper and both screeds in operation. A uniform roll of concrete approximately fifteen (15) centimeters above the pavement grade shall be maintained ahead of the front screed for its entire length during the first trip over with the finishing machine. Excessive temping or finishing resulting in bringing an excess of mortar to the surface will not be permitted.
After the last pass of the finishing machine, a mechanical longitudinal finisher shall be operated over the concrete surface. The forward motion of the longitudinal finisher shall be so adjusted that the screed will pass over each portion of the surface at least twice. The longitudinal finisher shall be operated in manner that will prevent excessive slumping of the concrete at the form lines or the metal centre strip or the loss of the crown of the pavement. If necessary or when ordered by the Engineer, the finisher shall be operated in one direction only or shall be operated from only the form to the centerline in order to ensure that the proper cross section of the pavement is obtained. The leading edge of the screed shall clear the forms upon completion of each transverse pass in order to clear the pavement surface of any laitance or thin mortar.
In general, the addition of superficial water to the surface of the concrete to assist in finishing operation will not be permitted. If the application of water to the surface is permitted by the Engineer, it shall be applied as a fog spray by means of approved spray equipment.
As an alternative to the longitudinal finisher, the contractor may use a machine composed of a cutting and smoothing float, or floats, suspended from and guided by a rigid frame. The frame shall be carried by four (04) or more visible wheels riding on and constantly in contact with, the side forms.
When directed by the Engineer, following one of the preceding methods of longitudinal finishing, long-handled floats having blades not less than one and one half (1.5) meters in length and fifteen (15) centimeters in width shall be used to smooth and fill in open-textured areas in the pavement, Long-handled floats shall not be used to float the entire surface of the pavement in lieu of or supplementing, one of the preceding methods of longitudinal finishing.
When the longitudinal finishing has been completed, the entire surface shall be tested with straightedges not less than three (03) meters in length. The straightedges shall be operated parallel to the pavement centerline starting at the center and progressing toward the forms. Advance along the pavement shall be in successive stages of not more than one half (1/2) the length of the straightedges. All laitance, surplus water and inert material shall be removed from the surface. All high places shall be worked down and all low places filled by combined operation of floats an straightedges until no irregularities exist. The proper crown of the pavement shall be maintained throughout the operations.
After floating and straightening has been completed, the concrete shall be finished by using a belt made of canvas, rubber or other approved belting not less than fifteen (15) centimeters in width, nor less than sixty (60) centimeters longer than the width of the pavement. This belt shall be worked with a longitudinal and crosswise motion. Care shall be exercised in the use of the belt to ensure that the edges of the belt do not dig into the surface of the concrete or work the crown out of the pavement. Either machine belting or hand belting will be permitted.
As soon as all excess moisture has disappeared and while the concrete is still plastic enough to make a granular surface possible, a drag shall be used which shall consist of a seamless strip of damp burlap or cotton fabric, which shall produce a uniform surface of gritty texture after dragging it longitudinally along the full width of pavement. For pavement (05) meters or more in width, the drag shall be such that a strip or burlap or fabric at least one and one half (1.5) meters wide is in contact with the full width of pavement surface while the drag is used. The drag shall be maintained in such condition that the resulting surface is of uniform appearance and reasonably free from grooves over two (02) millimeters in depth, as determined by the Engineer. Drags shall be maintained clean and free from encrusted mortar. Drags that cannot be cleaned shall be discarded and new drags substituted.
After dragging the surface with burlap, the concrete over the expansion joint filler shall be completely removed and the joint finished. The edge of the concrete at expansion joints shall be finished with an edger to the radius shown on the plans. The exposed edge of the pavement shall be finished with an edger to a radius of six (06) millimeters. Any tool marks appearing on the slab adjacent to the joints or edge of slab shall be eliminated by dragging the surface. In doing this, the rounding of the corner of the slab shall not be disturbed.
Hand Finishing
Unless otherwise specified, hand finishing methods will not be permitted except under the following conditions:
i. In the event of breakdown of the mechanical, hand methods may be used to finish the concrete already deposited on the grade when the breakdown occurs, and no additional concrete shall be placed until such equipment is repaired to the satisfaction of the Engineer.
ii. Narrow widths or areas of irregular dimensions where operations of mechanical equipment is impractical as determined by the Engineer may be finished by approved hand methods.
iii. Short lengths of pavement, such as bridge approach pavement where the operation of mechanical equipment is impractical may be finished by approved hand methods.
Concrete, as soon as placed shall be struck-off and screed. An approved portable screed shall be used.
The screed for the surface shall be at least one (01) meter longer than the maximum width of the slab to be struck-off. It shall be of approved design, sufficiently rigid to retain its shape and be constructed either of metal or other suitable material shod with metal
Consolidation shall be attained by the use of a suitable vibrator or other approved equipment.
In operation the screed shall be moved forward on the form with a combined longitudinal and transverse shearing motion, moving always in the direction in which the work is progressing and so manipulated that neither end is raised from the side forms during the striking of process. If necessary, this shall be repeated until the surface is of uniform texture true to grade and cross section and free from porous areas.
After the concrete has been struck-off, it shall be further smoothed, trued and consolidated by means of a longitudinal float. The hand operated longitudinal float shall be not less than three and one-half (3.5) meters in length and fifteen (15) centimeters in width, properly stiffened to prevent flexing and warping. The longitudinal float, operated from foot bridges resting on the side forms and spanning but not touching the concrete shall be worked with a sawing motion, while held in a floating position parallel to the road centerline and passing gradually from one side of the pavement to the other Movement ahead along the centerline of the pavement shall be in successive advances of not more than one half (1/2) the length of the float. Any excess water or soupy material shall be wasted over the side forms on each pass.
At the option of the Engineer, the long-handled floats having blades not less than one and one half (1.5) meters in length and fifteen (15) centimeters in width may be substituted for the hand operated longitudinal float.
All other operations after this substitution for the mechanical equipment shall be performed in the manner previously described.
Concrete operation shall be performed only in daylight. Under no circumstances shall concrete pavement placed or finished at night.
Removing Forms
Unless otherwise provided, forms shall not be removed form freshly placed concrete until it has set for at least twelve (12) hours, except auxiliary forms used temporarily in widened areas. Forms shall be removed carefully so as to avoid damage to the pavement. After the forms has been removed, the sides of the slab shall be cured as specified for the surface. Major honeycombed areas will be considered as defective work and shall be removed and replaced at the Contractor’s expense, as directed by the Engineer. Any area or section so removed shall not be less than three (03) meters in length nor less than the full width of the lane involved. When it is necessary to remove and replace a section of pavement, any remaining portion of the slab adjacent to the joints that is less than three (03) meters in length, shall also be removed and replaced.
Protection and Curing of Concrete Pavement
a) Initial Curing
As the surface of newly-laid pavement is progressively finished, the initial curing and protection operations shall be started.
Upon completion the finishing operation and while the surface of concrete is still moist, but no free water remains a liquid curing membrane approved by the Engineer shall be applied to the exposed surface of the pavement at the rate not less than one (01) litre per three and two third (3-2/3) square meters of surface area when mechanical pressure distributors are used. The curing membrane, except on irregular areas shall be applied by means of approved self-propelled mechanical pressure distributors or approved hand sprays. Satisfactory means shall be provided for thoroughly mixing the curing membrane compound before and during its use. The mechanical spraying equipment may be either a full width spray bar equipped with multiple nozzles or a traversing spray which travels from one edge of the pavement to the other. In either case the path of adjacent nozzles or passes of the traversing spray shall overlap a minimum of one-half (1/2) the width of the spray pattern so that all portion of the surface shall receive double applications from adjacent nozzles or passes. The pumping, pressure and distribution arrangement shall be correlated with the forward speed to provide adequate and uniform coverage of the pavement at not less than the minimum rate required. Irregular areas to which the mechanical distributor cannot be adapted may be covered with hand sprays.
When hand sprays are used, the curing membrane shall be applied in two (02) applications each at a rate of not less than one (01) litre per five (05) square meters of surface areas so as to provide a total rate of application of one (01) litre per two and one half (2-1/2) square meters of surface areas. The path of the spray on the second application shall be at right angles to the path of the spray on the first application. When hand operated sprays are permitted, the equipment supplying the pressure to the spray nozzle shall be capable of supplying a constant and uniform pressure to provide uniform and adequate distribution of the curing membrane compound at the rate required. If from any cause, such as rain-fall soon after its applications the curing membrane is damaged, the Contractor shall immediately apply another application of curing membrane to the surface of the pavement. The rate of application for the replacement membrane shall be the same as for the original membrane.
When forms are removed, whether during the initial or the final curing period, the edges of the pavement shall receive curing membrane at the rate of coverage specified for the pavement surface.
The curing membrane may be applied to the vertical edges of the pavement by means of hand sprays or by nozzles attached to the mechanical distributor, but the edges of the pavement shall be covered with curing membrane at the rate specified within thirty (30) minutes after removal of the forms.
When hot poured joint compound is used, the joints shall be sawed, cleaned, and filled with jute or other acceptable protective material.
In no case shall any portion of the concrete pavement be exposed to the direct rays of the sun for more than one (01) hour.
Following jointing operations, curing membrane shall be applied to the joint area at the rate of specified for the pavement surface.
b) Final Curing
Upon completion of the initial curing period and jointing operation has been completed, the pavement shall be completely covered with White Opaque Polythene Film as specified in AASHTO M171. Adjoining sheets shall be lapped a minimum of forty five (45) centimeters. The sheeting shall be held in place in a manner approved by the Engineer.
Final curing shall be continued until the concrete reaches an age of fourteen (14) days. During the period, the curing membrane and polythene film shall be protected from damage from any cause. Any damage from any cause shall be immediately repaired by the Contractor at his expense. No traffic, including workmen and pedestrian shall be allowed on the surface of the pavement until the expiration of the fourteen (14) days curing period.
When concrete is being placed during the time that the air temperature may be expected to drop below fifteen (15) degree C, a sufficient supply of burlap, straw, hay or other suitable blanketing material shall be provided along the work to protect the concrete and maintain a minimum temperature of fifteen (15) degree C in the concrete as measured on the surface of the pavement. An approved moisture barrier such as wet burlap or plastic sheeting shall be placed on the concrete prior to placing the blanketing material. The type of cure shall be maintained for a period of seventy two (72) hours as the initial cure. After the initial cure as specified above, a final cure as specified above may be used. The final cure shall be maintained for a period of fourteen (14) days, thus making a seventeen (17) days curing period for cold weather concreting.
Surface Tolerance
As soon as the concrete has hardened sufficiently, the pavement surface shall be tested with a three (03) meter straightedge or other specified devices. Areas showing high spots of more than three (03) millimeters, but not exceeding twelve (12) millimeters in three (03) meters between any two contact points shall be marked and immediately ground down with an approved grinding tool to a tolerance of less than three (03) mm as described above. Where the departure from correct cross section exceeds twelve (12) millimeters, the pavement shall be removed and replaced by and at the expense of the Contractor.
Any area or section so removed shall be not less than three (03) meters in length or less than the full width of the lane involved. When it is necessary to remove and replace a section if pavement, any remaining portion of the slab adjacent to the joints that is less than three (03) meters in length shall also be removed and replaced at the Contractor’s expense.
8. Tests for Thickness of Pavement and Degree of Compaction
i) Thickness of Pavement
The Employer will not be liable for payment of any excess in thickness of depth of pavement. During the progress of the work, the thickness or depth of pavement will be determined by the Engineer from cores cut from the concrete pavement by the Contractor. The cost of cutting and recovering all the cores described in this clause and the following paragraph shall be deemed to be included in the rates and prices for Portland Cement Concrete Pavement.
Unsatisfactory work shall be replaced, or will be paid for at an adjusted price, as follows:
a) One 15 cm diameter core will be removed by the Contractor from each lane at such locations as the Engineer may direct and shall represent not more than 1000 SM of pavement area. A lane shall be considered the pavement surface between longitudinal joints or a longitudinal joint and pavement edge.
b) If any core measurement is deficient more than 6.5 mm form the required thickness a core measurement shall be taken at each 30m interval in both directions longitudinal from the first deficient core in the same lane, as defined herein, until the thickness of the pavement is found to be not more than 6.5 mm deficient from the required thickness. Each deficient core shall be considered as representing the condition in the same lane or longitudinal section, as above defined, for a distance of 15 m in each direction longitudinally from the core.
c) Sections of pavement which are deficient in thickness, as determined by cores, by an amount more than 1.3 cm shall be removed and replaced with pavement of the specified thickness at the expense of the Contractor. The removal and replacement shall start at the determined point of deficiency and proceed longitudinally as hereinafter specified, until the pavement is to be not more than 6.5 mm deficient from the required thickness. The old reinforcing steel shall be left extended a sufficient distance so as to allow the new reinforcement steel to be lapped with the old, the required distance to be welded to the satisfaction of the Engineer.
d) The removal and replacements of pavements shall extend transversely the full width each lane in which such deficiency is found.
e) All pavements within two (02) meters of the deficiency spot shall be removed, except that when any joint is more than two (02) meters, all pavements shall then be removed to the next joint.
f) Sections of pavement which are deficient in thickness, as determined by measurement of cores in accordance with AASHTO T148-49 by an amount more than 6.5 mm, but nor more than 1.3 cm will be paid for at an adjusted price as specified in Table below:
DEFICIENCY IN THICKNESS AS DETERMINED
FROM CORES
Thickness
|
Proportional Part of Contract of Contract Price to be allowed.
|
3.00 mm to 6.5 mm
6.5 mm to 13 mm
|
95 %
75%
|
ii) Degree of Compaction
The cores that have been cut from the concrete pavement according to the requirements of (i) above shall be examined by the Engineer’s Representative to check the degree of compaction achieved through the slab and to check the effectiveness of the bond between the top and bottom course concrete.
Should any core reveal that any part of the slab has not been adequately compacted by revealing honeycombed or segregated concrete, then additional cores shall be taken to check the areas of defective concrete pavement according to the procedure laid down in (i) above for determining the areas of concrete pavement deficient in compaction.
Ant areas of defective pavement concrete so found shall be replaced with new concrete in accordance with this section at Contractor’s own expense.
The Engineer reserves the right to carry out crushing tests on any or all of the concrete cores taken in accordance with this clause and should these tests show that any area of pavement concrete has failed to meet the strength requirements of the specifications then such areas of concrete shall be removed and replaced with new concrete, mixed, laid, compacted and finished to the requirements of this section at Contractor’s own expense.
iii) Refilling of Holes
Holes in the pavement created by the cutting of cores shall be thoroughly coated on the inside with a neat cement grout and shall then be filled with concrete of the same mix as shown in the pavement. The filling shall be in two equal layers and each shall be rodded 25 times to its full depth. The surface shall be finished flush and broomed. The surface shall be kept thoroughly wet for 72 hours thereafter.
Replacement of Defective Concrete
Any concrete not complying with the specifications shall be cut out and replaced in accordance with the specification over the full width of the slab between longitudinal construction joints and over a length extending between two transverse joints each of a type other than a warping joint.
