239 (18) inches on each side of the base of the form, and thoroughly compacted. Imperfections or variations above grade shall be corrected by tamping or by cutting as necessary. 501.6.2 .2-Form Setting: Forms shall be set sufficiently in advance of the point where concret e is being placed. After the forms have been set to correct grade, the grade shall be thoroughly tamped, mechanically or by hand, at both the inside and outside edges of the base of the forms. Form sections shall be tightly locked, free from play or move ment in any direction. The forms shall not deviate from true line by more than ¼ in ch at any point. Excessive settlement or springing of forms under the finishing machine will not be tolerated. Forms shall be cleaned and oiled prior to the placing of co ncrete. 501.6.2 .3-Grade and Alignment: The alignment and grade elevations of the forms shall be checked and corrections made by the Contractor prior to placing the concrete. When any form has been disturbed or any grade has become unstable, the form sh all be reset and rechecked. 501.6.3 -Conditioning of Subgrade or Base: The base shall be brought to the proper cross section and plan grade within the tolerances specified for the final course underlying the pavement. The finished grade shall be mainta ined in a smooth and compacted condition until the pavement is placed. The grade shall be constructed sufficiently in advance of the paver to prevent delays. Unless waterproof subgrade or base course cover material is specified, the subgrade or base course shall be uniformly moist when the concrete is placed. 501.6.3.1 -Conditioning of Surfaces Receiving an Unbonded Concrete Overlay: If required, the bond breaker/leveling course for unbonded concrete overlays shall be constructed as shown on the Plans. Construct any specified hot -mix asphalt base, bond breaker, or patching and leveling course in accordance with Section 401. Remove a ll loose materials from the existing pavement prior to placing the asphalt. If required on the Plans, mill the surface before concrete placement in accordance with Section 415. After milling, tight blade the surface to remove ridges and loose material. Prior to placement of the overlay, the milled surface shall be swept clean. The Engineer shall be notified if milling operations expose underlying concrete pavement. All areas where the underlying concrete pavement is exposed shall be repaired, regardles s of size. The Contractor shall first determine, in the presence of the Engineer, if the remaining asphalt surrounding the area of exposed concrete is sound. This asphalt shall be considered sound if it cannot be easily removed by prying it loose with a shovel. If it can be easily removed in such a manner, the Contractor shall continue to remove all such unsound asphalt until sound asphalt is encountered. If the asphalt surrounding the exposed concrete area is less than two ( 2) inches thick, greater than 50 square feet or are wider than six (6) feet in the transverse direction, spray exposed concrete with tack coat meeting the requirements of Section 408 and cover with engineering fabric meeting the requirements of Section 715.1 1.8. If the asphalt surrounding the exposed concrete area is two ( 2) inches or more in thickness, repair the exposed concrete area with an asphalt patch of the same thickness as the surrounding asphalt with either a Base -II or 19 mm mix in accordance with Section 401. 240 501.7 -HANDLING, MEASURING, AND BATCHING MATERIALS : The batch plant site, layout, equipment and provisions for transporting material shall be such as to assure a continuous supply of material to the work. Stockpiles shall meet the requirements of 106.5. Aggregates shall be handled, hauled, and stored in such a manner which will minimize segregation, avoid contamination, and secure a uniform grading of the material within the specified gradation band. All aggregates produced or handled by hydraulic methods, and washed aggregates, shall be stockpiled or binned for draining a sufficient time to eliminate excess water. Aggregates which have dried below a saturated surface - dry condition shall be wet down the night previous to their use, and sprinkled during the day to obtain saturated surface -dry condition. The fine aggregate and each size of coarse aggregate shall be separately weighed into hoppers in th e respective amounts approved by the Engineer for the job mix. Cement shall be measured by weight. Separate scales and hoppers shall be used for weighing the cement, with a device to indicate positively the complete discharge of the batch of cement. Bul k fly ash shall be stored in weatherproof bins. Batching shall be so conducted as to result in weights within a tolerance of one percent (1%) for cement and two percent (2%) for aggregates. Water may be measured either by volume or by weight. The accurac y of measuring the water shall be within a range of error of not over one percent (1%) . All admixtures shall be measured into the mixer with an accuracy of plus or minus three percent (3%) . Admixtures shall be introduced into the mix simultaneously with the mixing water. When more than one type of admixture is used they shall be introduced into the mix separately. When cement or SCMs are being added in bag form, under no circumstances shall the packaging material be allowed to enter into the mix. Handling, measuring, and batching of materials for volumetric batching and continuous mixing shall, in addition to the preceding requirements, conform to the applicable requirements specified in AASHTO M 241. 501.8 -MIXING CONCRETE : Concrete may be mixed at the site or a central mix plant, or it may be produced by volumetric batching and continuous mixing as designated in AASHTO M 241. When permitted in the Contract, concrete may be mixed in a truck -mixer. Ready -mixed concrete shall be mixed and delivered in accordance with the requirements of AASHTO M 157 paragraphs 10 and 11, or AASHTO M 241 paragraphs 7 and 8, except as otherwise specified. The required minimum mixing time for an individu al mixer may be specified as that which, as shown by tests made at the Contractor's expense, will result in satisfactory mixing. Performance tests and the acceptable ranges in test results within each batch from the three different samples are given in Ta ble 501.8. The mixing time shall not be less than 75 seconds. Where mixer performance tests are not made, minimum mixing time shall be 60 seconds plus 15 additional seconds for each cubic yard of concrete being batched in excess of one cubic yard. The m ixer shall be operated at a drum speed recommended by the manufacturer. Any concrete mixed less than the specified time shall be discarded and disposed of by the Contractor at his expense. The mixer shall not be operated in excess of its nominal capacity as shown on the manufacturer's rating plate. The mixing of concrete shall continue for the required mixing time after all ingredients, except water and admixture if added with water, are in the mixing compartment of the mixer before any part of the batch is released. The batch shall be so charged into the drum that a portion of the mixing water shall enter in advance of the cement and aggregates. The flow of water shall be 241 uniform and all water shall be in the drum by the end of the first 15 seconds of the mixing period. The throat of the drum shall be kept free of such accumulations as may restrict the flow of materials into the drum. The time elapsing from the time water is added to the mix until the concrete is deposited in place at the site of the work shall not exceed 30 minutes when the concrete is hauled in non - agitating trucks, nor shall it exceed 60 minutes when hauled in transit -mix trucks or truck agitators. The addition of water after the completion of the initial mixing operation will not be permitted, except that when concrete is delivered in transit -mix trucks additional water may be added to the batch materials and additional mixing (minimum of 20 revolutions at mixing speed) performed to modify the consistency to meet the specified requ irements, provided all these operations are performed within 45 minutes after the initial mixing operation and provided the maximum number of revolutions at mixing speed is not exceeded. Concrete that is not within the specified consistency limits at the time of placement shall not be used. No concrete shall be mixed, placed or finished when the natural light is insufficient unless an adequate artificial lighting system is used. TABLE 501.8 PERFORMANCE TESTS AND ACCEPTABLE RANGES FOR CENTRAL MIXED CONCRETE *Test Criteria **Permissible Ranges Within Batch From Three Samples Plant Slump, in inches 2.25 Air content, percent by volume of concrete sample. 2.0 Weight per cu. ft. of plastic concrete, in lbs. 4.0 Coarse aggregate retained on No. 4 sieve expressed as a percent of three -sample average weight retained 11.0 * Tests to be made in accordance with applicable AASHTO or ASTM Methods. ** Each property measured shall not exceed the permissible range in more than one out of seven batches NOTE: Mixer performance data shall be based on three concrete samples per test batch, taken at the mixer during discharge from approximately 1/6th, 1/2 and 5/6th points of the batch discharge. Determination of coarse aggregate uniformity within the batch where concrete ingredients are batched from separate stockpiles of more than one size of coarse aggregate shall be made using sieves of appropriate size to identify the quant ity of coarse aggregate coming from each of the separate stockpiles. A minimum of seven production batches of concrete shall be tested for the proposed minimum mixing time unless the Engineer determines, on the basis of prior tests on concrete produced wi th the equipment and materials to be used, that a different number of batches is adequate for the purpose. When any change occurs in size of the batch, the operating process, conditions affecting mixing or hauling, the ingredients of the concrete, or othe r conditions which will affect the quality of the concrete incorporated in the pavement, an additional seven production batches of concrete shall be tested. 501.9 -PLACING CONCRETE : The conc rete shall be deposited on the grade in such manner as to require as little rehandling as possible. Unless transit -mix trucks, agitators, or other hauling equipment units are 242 equipped with means for discharge of concrete without segregation, the concrete shall be unloaded into a spreading device and mechanically spread on the grade in such manner as to prevent segregation of the materials. Placing shall be continuous between transverse joints without the use of intermediate bulkheads. Necessary hand spre ading shall be done with shovels, not rakes. Workers shall not be allowed to walk in the fresh concrete with boots or shoes coated with earth or foreign substances. The pavement shall be constructed by placing two longitudinal traffic lanes full width in one operation unless otherwise indicated in the Contract. Lane -at-a-time construction will be permitted in variable width sections or other sections designated by the Engineer. When the Contract permits lane -at-a-time construction and concrete is to be placed adjoining a previously constructed lane of pavement and mechanical equipment other than finishing equipment will be operated upon the existing lane, that lane shall first meet the requirements of 501.18. If only finishing equipment is carried on the existing lane, paving in adjoining lanes may be permitted after three days. 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 onto a joint as sembly unless the bucket is well centered on the joint assembly. When using a slip -form paver, or combination of pavers, they shall be designed to spread, consolidate, screed and float -finish the freshly placed concrete in one complete pass of the paving train in such manner that a minimum of hand finishing will be necessary to provide a dense and homogenous pavement in conformance with the Plans and Specifications. The equipment shall vibrate the concrete for the full width and depth of the strip of pave ment being placed. Such vibration shall be accomplished with vibrating tubes or arms working in the concrete or with a vibrating screed or pan operating on the surface of the concrete. No appreciable edge slumping of the in -place concrete will be allowed , and, if necessary, forms shall be trailed behind the paver to prevent slumping. If training forms are used, they shall be rigidly supported laterally. Slip-form pavers shall be operated with as nearly a continuous forward movement as possible and all o perations of mixing, delivering and spreading concrete shall be so coordinated as to provide uniform progress. If, for any reason, it is necessary to stop the forward movement of the paver, the vibratory and tamping elements shall also be stopped immediat ely. No tractive force shall be applied to the machine, except that which is controlled from the machine. Placement to essential full width is required when slip -form paving methods are used. However, the Engineer may permit lane -at-a-time placement on variable width, small, or otherwise restricted sections using standard forming methods detailed elsewhere in these Specifications. Concrete shall be thoroughly consolidated against and along the faces of all forms and along the full length and on both sid es of all 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 equipment mounted vibrators be operated when the equipme nt is not moving in the forward direction. All equipment mounted vibrators shall be stopped, either manually or automatically, when the equipment stops its forward progress. Should any concrete materials fall on, or be worked into, the surface of a compl eted slab, they shall be immediately removed. When placing an unbonded concrete overlay, place the concrete when the base temperature is below 115°F. Reduce the temperature by spraying a fine water fog on the base. Ensure water does not pond in front of the plastic concrete. The application of white curing compound or a lime slurry shall be permitted as temperature control measures when waterproof bases are encountered. Concrete shall not be placed if frost exists in the base or if the base temperature is below 35°F. 243 When placing unbonded concrete overlays, concrete should be placed on the grade to the nominal thickness shown on the Plans. Any deviations for profile adjustments, and/or cross section adjustments, should be above the nominal thickness. When adjustments are necessary for grade or yield improvement, the thickness shall not, in any case, be less than the minimum thickness shown on the Plans. 501.9.1 -Safety Edge: Concrete safety edge shall be constructed on the outside paveme nt edge using a wedge shape meeting the requirements of the plan details. Safety edge is not to be used through intersections, against curb or barrier, or when directed by the Engineer. The paving operation shall allow for automatic and/or manual transi tions at cross roads, driveways, and intersections. The Engineer may allow short sections of handwork for transitions at driveways, intersections, interchanges, and bridges.
501.10 Strike -Off of Concrete and Placement of Reinforcement :
Following placing, the concrete 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 consoli dated and finished, the surface of the pavement will be at the elevation shown on the Plans. When reinforced concrete pavement is placed in two layers, the entire width of the bottom layer shall be struck off to such length and depth that the sheet of fab ric or bar mat may be laid full length on the concrete in its final position without further manipulation. The reinforcement shall then be placed directly upon the concrete, after when the top layer of the concrete shall be placed, struck off, and screede d. All portions of the bottom layer which have been placed more than 30 minutes without being covered by the top layer shall be replaced at the Contractor's expense. When reinforced concrete pavement is placed in one layer, the reinforcement may be posit ioned in advance of concrete placement, or it may be placed in the plastic concrete, after spreading, by mechanical or vibratory means. When reinforcement is specified, it shall be placed in the center portion of the pavement. Variation in the depth of r einforcement is permitted, but the minimum concrete cover shall be one -third of the plan depth of the pavement. Reinforcement shall be as designated on the Plans and shall be free from dirt, oil, paint, grease, and loose rust which could impair bond of the steel with the concrete.
501.11 Joints :
Joints shall be constructed of the type and dimensions and at the locations shown on the approved Joint Layout Plan(s). The Contractor shall submit for ap proval a Joint Layout Plan for all intersections on the project in general accordance with the following: “Street Jointing Criteria: Ten Rules Of Practice” as suggested by the Portland Cement Association (PCA), Skokie, Illinois; the American Concrete Pavem ent Association’s Intersection Joint Layout Guidelines; the latest issue of the West Virginia Division Of Highways’ Standard and Supplemental Specifications; the West Virginia Division Of Highways’ “Standard Details Book Volume 1 – Drainage, Guardrail, Pavement, Fence, and Markers” hereinafter referred to as “Standard Details Volume 1”; or as directed by the Engineer. The “Street Jointing Criteria: Ten Rules of Practice” suggested by the PCA are paraphrased and revised for the West Virginia D ivision of Highways’ needs as follows: i Joints are used in concrete pavement to aid construction and to minimize random cracking. Avoid odd -shaped areas of pavement. ii Space longitudinal joints not to exceed twelve ( 12.0) feet. The contractor shall decide on the type of longitudinal joint as shown on Standard Detail Sheet PVT1 of “Standard Details Volume 1” needed depending on the type of construction. Type D joints will