248 In operation the screed shall be moved forward on t he forms in the direction the work is progressing, using a combined longitudinal and transverse shearing motion, so manipulated that neither end is raised from the side forms during the striking process. This shall be repeated until the surface is of unif orm texture, true to grade and cross section, and free from porous areas.
501.12.5 Floating: After the concrete has been struck off and consolidated, it shall be
further smoothed, trued, and consolidated by means of a mechanical longitudinal float, exc ept when waived by the Engineer. If necessary, following one of the methods of floating described, long -handled floats may be used to smooth and fill in open textured areas in the pavement. Care shall be taken not to work the crown out of the pavement du ring the operation.
501.12.5 1-Mechanical Method: The mechanical longitudinal float shall be
maintained in proper working order. At the beginning of each day's operation the float shall be checked and adjusted to the design crown of the pavement. A sm all amount of mortar shall be carried ahead of the float at all times. The forward speed shall be adjusted so that succeeding strokes of the float shall overlap on each transverse trip. The float shall pass over each area of pavement sufficient number of times until the surface shows no variation from straightedge requirements, but excessive operation over a given area will not be permitted. All excess water, laitance, or other foreign material shall be wasted over the side forms on each pass. Pipe float devices may be used for longitudinal floating when slipform paving.
501.12.5 2-Alternative Mechanical Method: As an alternate to the above method,
the Contractor may use a machine composed of a cutting and smoothing float, or floats, suspended fro m and guided by a rigid frame. The frame shall be carried by at least four visible wheels riding on, and constantly in contact with, the side forms.
501.12.5 3-Hand Method: The hand -operated longitudinal float shall be not less than
twelve ( 12) feet in length and six ( 6) inches in width, properly stiffened to prevent flexibility and warping. The float shall be operated from foot bridges resting on the side forms and spanning but not touching the concrete. The float 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 the length of the float. Any excess water, laitance, and other foreign material shall be wasted over the side forms on each pass.
501.12.6 Straightedge Checking and Surface Correction: After the floating has been
completed and the excess water removed, but while the concrete is still plastic, the surface of the concrete shall be tested for trueness with a ten (10) foot straightedge. The Contractor shall furnish and use a ten (10) foot straightedge swung from handles at least three ( 3) foot longer than one -half the width of the slab. The straightedge shall be held in contact with the surface in successive positions parallel to the road centerline and the whole area gone over from one side of the slab to the other as necessary. Advance along the road shall be in successive stages of not more than one -half the length of the straightedge. Any depressions found shall be immediately filled with freshly mixed concrete, struck off, consolida ted, and refinished. High 249 areas shall be cut down and refinished. Special attention shall be given to assure that the surface across joints meet the requirements for smoothness. Straightedge testing and surface corrections shall continue until the entir e surface is found to be free from observable departures from the straightedge and the slab conforms to the required grade and cross section.
501.12.7 Final Finish: Use a burlap drag or other method approved by the Engineer,
which spans the entire widt h of pavement being placed, as soon as all excess moisture has disappeared and while the concrete is still plastic enough to make a granular surface possible. Drag the burlap longitudinally along the pavement surface after finishing to enhance the pavemen t texture. Clean or replace the drag material as necessary to prevent it from getting plugged with grout. Measures should be taken to produce a surface of uniform appearance that is free from deep striations. Following the dragging operation, the surfa ce of the mainline pavement, acceleration and deceleration lanes, ramps, and all travelled ways shall be given a final tined groove finish. This grooved finish shall be a longitudinally tined texture parallel to the pavement centerline. A three ( 3) ± 1/2 inch wide strip of pavement surface shall be protected from tining for the length of and centered about the longitudinal joint(s). The longitudinal tining shall extend to within six (6) inches of the outside edge of the pavement. The equipment used for longitudinal tining shall have automated horizontal and vertical controls to ensure straight, uniform depth tined grooves. It shall be mounted on a device which is driven by tracks (wheel -driven equipment will not be permitted) and shall be controlled by the same grade alignment method as the concrete paver. The tool used for tining shall have a single row of tines and shall produce a groove that is 1/8 in ch wide and 1/8 to 1/4 in ch deep. The grooves shall be spaced uniformly apart at a center to center distance of 3/4 in ch. Tining shall be performed when the concrete surface is of such plasticity as to prevent excessive raveling (concrete too dry) or to prevent mortar from flowing back into the grooves (concrete too wet). All tin ing shall be accomplished with a single pass of the tool. Tines should be cleaned and replaced as necessary. Transverse tining shall be permitted in areas requiring hand finishing and consolidation, including shoulders, as required in Section 501.12.4.
501.12.8 Edging at Forms and Joints: Before the concrete has taken its initial set, the
edges of the pavement along each side of the slab and on each side of all formed joints, except joints initially formed that will be later widened by second -step sa wing, shall be rounded. A ¾ inch radius edging tool shall be used for rounding outside edges and a ¼ in ch radius tool for other edges. A well-defined and continuous radius shall be produced and a smooth, dense mortar finish obtained. The surface of the slab shall not be unduly disturbed by tilting the tool during use. Any tool marks shall be eliminated by brooming the surface without disturbing the radius. All concrete on top of the joint filler shall be removed. All joints shall be checked with a str aightedge before the concrete has set and all necessary corrections made if one side is higher than the other or if they are higher or lower than the adjacent slabs.
501.12.9 Station Numbers: The Contractor shall impress station numbers into the
pavement before it takes its final set. The complete station number is to be marked each 100 feet. Where equalities in alignment occur, they shall be marked in the pavement in the same manner as they are shown on the Plans. The numerals shall be three ( 3) to four ( 4) inches in height and ¼ inch in depth. The station numbers shall be placed parallel to the transverse 250 joints, approximately twelve ( 12) to twenty -four ( 24) inches from the outside edge o f the pavement. Station numbers shall be placed along the right edge of a two -lane highway, readable in the direction of increasing stations. On multi -lane highways, numbers shall be placed along the outside edge of the two outside lanes of the roadway, readable in the direction of travel.
501.12.10 Protection Against Rain: In order that the concrete may be properly protected
against the effects of rain before the concrete is sufficiently hardened, the Contractor shall have available at all times mate rials for the protection of the edges and surface of the unhardened concrete. Such protective materials shall consist of metal forms or wood planks having a nominal thickness of not less than two ( 2) inches and nominal width of not less than the thickness of the pavement at its edge for protection of the pavement edges, and covering material such as burlap or cotton mats, curing paper, or plastic sheeting for protection of the surface. When rain appears imminent, all paving operations shall stop and all a vailable personnel shall begin placing forms against the sides of the pavement and covering the surface of the unhardened concrete with the protective covering.
501.13 Surface Tests :
The smoothness of the riding surface will be determined using the procedures outlined in Section 720. When corrective action is needed, the diamond grinding operations shall be in accordance with section 508.
501.13.1 Sampling Units: The pavement will be divided into sampling Lots of 0.1 lane
mile each. Each Lot shall exhibit a smoothness measurement, expressed in inches per mile.
501.13.2 Smoothness Requirement: Each sampling unit shall exhibit a smoothne ss equal
to or less than sixty -five ( 65) inches per mile. Sampling units exhibiting smoothness values greater than sixty -five ( 65) inches per mile shall be paid for at an adjusted price as follows: Revised Unit Price = UBP – [(1.00 -{127.86 -0.429S }) (0.18 UBP)] Where: UBP = Unit Bid Price S = Smoothness in inches per mile When the measured smoothness value exceeds the specified value by 50 percent (50%) or more, the Lot shall be corrected to comply with these specifications.
501.13.3 Grinding Requirements: When the pavement requires corrective action as
noted above, the diamond grinding operations shall be in accordance with section 508, except that the final pavement smoothness requirements shall be in accordance with section 501.
501.14 Curing :
Immedia tely after the finishing operations have been completed and as soon as marring of the concrete will not occur, the entire surface of the newly placed concrete shall be cured in accordance with one of the methods described.