716 - POST-TENSIONING (Haunched Slab Bridges)
700-89 f. Grout. Provide the Engineer with a minimum of 3 days advance notice of the beginning of the grouting
operations to allow adequate time for ASBI-certifie d KDOT inspection staff to get to the job site. Grout the annular space between the duct and the te ndons after the tensioning of all tendons has been completed and the strands have been anchored. Weather permitting, begin grouting immediately or within 72 hours after stressing all tendons within an independent unit.
1.Equipment. Provide a grouting mixer capable of continuous mechanical mixing which shall produce grout free of lumps and undispersed cement. Batch all ma terials using batchi ng equipment which provides accurate solid and liquid measures. Provide grout equipment capable of continuously grouting the longest tendon on the project within a maximum of 20 minutes. Use grouting equipment utilizing gravity feed to the pump inlet from a hopper attached to and directly over it. Keep the grout hopper at least partially full of grout at all times during the pumping operation to prevent air from being drawn into the post-tensioning duct. Use positive displacement type pump s, capable of producing the outle t pressure required by the grout manufacturer. Use a pump with seals, adequate to prevent introduction of oil, air or other foreign substance into the grout, and to prevent loss of grout or water. Place a pressure gauge at some point in the grouting line between the pumping outlet and the duct inlet, and having a full scale reading of a maximum of 300 psi. Use grouting equipment containing a screen having clear openings of ⅛ inch maximum size to screen the grout prior to its introduction into the grout pump.
2.Mixing. Mix the grout accordin g to the manufacturer’s directions. The pumpability of the grout may be determined by the Engineer accordin g to ASTM C 939. When this method is used, do not exceed 11 seconds for the efflux time of the grout sample immediately after mixing. Do not use the flow cone to test grout which incorporates a thixotropic additive.
3.Grout Operations. Keep all grout inlets and high point outlets open when the grouting operation begins. Allow grout to flow from the first outlet past the inlet unt il any residual flushing water or entrapped air has been removed, at which time close the outlet. Close remaining outlets in the same manner and in the order shown on the plans. Perform normal grout pumping operations at 75 psi. Do not exceed 250 psi for pumping pressure at the inlet. Pump the grout through the duct and continuously waste at the outlets until there is no evidence of water or air being ejected. If the actual grouting pressure exceeds the maximum recommended pumping pressure , inject grout at any outlet that has been, or is ready to be closed as long as a one-way flow of grout is maintained. If this procedure is used, fit the outlet that is to be used for injection with a positive shutoff. When one-way flow of grout can not be maintained as outlined above, flush the grout immediately out of the duct with water. To keep the tendon filled with grout under pressure, close the outlets and inlets in the order shown on the plans, when the tendon duct section at the outlet and inlet is completely filled with grout. Do not remove or open positive shutoffs required at the inlets and outlets until the grout has set. In temperatures below 32°F, keep ducts free of water to avoid damage due to freezing. Maintain the temperature of the concrete slab between 35 and 85°F fr om the time grouting begins until jobsite cured 4 inch diameter cylinders of grout reach a minimum compressive st rength of 800 psi, when te sted according to AASHTO T22. The maximum grout temperature is 90°F, during mixing or pumping. When required, cool the mixing water. Remove ends of inlets and outlets a minimum of 1 ½ inches below the concrete surface after the grout has set and fill the recess in the concre te with an approved epoxy grout. Grout all anchorages, before the winter shut down.
g.Protection of End Anchorages. Clean exposed end anchorages, st rands and other metal accessories of rust, misplaced mortar, grout and othe r such materials as soon as possibl e after tensioning and grouting is completed. Immediately following the cleaning operation, apply a coat of zinc-rich epoxy paint, minimum thickness of 4 mils.
h.Recess Pocket Filling. Fill all longitudinal and transverse end an chorage recess pockets as shown in the Contract Documents. Apply an approved epoxy resin bonding agent according to the manufacturer’ prior to placing an approved non-shrink, non-metallic grou t. Apply grout according to the grout manufacturer’ s instructions. Finish the outside exposed surfaces of the recess pockets smooth an d flush with the surrounding concrete surface. Select grout to match the color of the surrounding concrete slab. 716 - POST-TENSIONING (Haunched Slab Bridges)
700-90 716.4 Measurement and Payment
The Engineer will compute the weight of the longitudinal post-tensioning tendons in pounds by measuring the theoretical plan length from end to end of wearing surface and for transverse post-tension tensions by measuring out-to-out of the bridge deck. Use a unit weight of 0.74 pounds per foot for 0.6 inch diameter strand. Payment for "Post-Tensioning for Slab Bridge" at the contract unit price is full compensation for the specified work. 717 - BRIDGE OVERLAYS
700-91 Section 717
BRIDGE OVERLAYS 717.1 DESCRIPTION Construct the portland cement concrete overla y as shown on the Contract Documents. When Bridge Deck Grooving is a bid item in the contract, perform the grooving as shown in the Contract Documents. B I D I T E M S U N I T S Portland Cement Concrete Overlay (*) Square Yard Material for Portland Cement Concrete Overlay (Set Price) Cubic Yard Bridge Deck Grooving Square Yard * Thickness 717.2 MATERIALS Provide materials that comply w ith the applicable requirements. Grade 4.0 (AE) Concrete+ ...................................................................................... SECTIONS 401 & 402 Aggregate for Concre te Not On Grade ................................................................... DIVISION 1102 Precure/Finishing Aid Material++ .......................................................................... DIVISION 1400 Concrete Curing Materi als .................................................................................... DIVISION 1400 Concrete Masonr y Coatin g .................................................................................... DIVISION 1700 +Use concrete that meets requirements for low permeability concrete (LPC) as specified in DIVISION 400 . ++When silica fume is used as an SCM, the use of Precure/Finish Aid may be used according to the manufacturer’s instructions. For overlays use Supplemental Cementitious Materials at allowable substitution rates as listed in TABLE
401-2 .
717.3 CONSTRUCTION REQUIREMENTS
a.Equipment. Use a finishing machine consisting of a mech anical strike-off capable of providing a uniform thickness of concrete slightly above finish grade in front of an oscillating screed or screeds. The finishing machine will be insp ected and approved by the Engineer before work is started on each project. Use a minimum of 1 oscillating screed capable of cons olidating the concrete by vibration to 100% of the vibrated unit weight with the following features: Install identical vibrators so a minimum of 1 vibrator is provided for each 5 feet of screed length; Bottom face a minimum of 5 inch es wide with a turned up or rounded leading edge; Effective weight a minimum of 75 pound s for each square foot bottom face area; Positive control of vertical position, the angle of tilt and the shape of the crown; Design together with appurtenant equipment to obtain positive machine screeding of the plastic concrete as close as practical to the face of the existing curb line; Length sufficient to uniformly strike-off and consolidate the width of the lane to be paved; Forward and reverse motion under positive control; Supporting rails which are fully adjustable (not shimmed) to obtain the correct profile, unless otherwise approved by the Engineer. Provide supports which are sufficiently rigid and do not deflect under the weight of the machine. Anchor the supporting rails to provide horizontal and vertical stability; and Equip to travel on the completed lane when placing concrete in a lane abutting a previously completed lane. Manufacturer’s specifications or certification may be used as verification of the oscillating screed requirements. A drum roller equipped to perform all functions outlined for the oscillating screed above, may be used for finishing the overlay concrete in lieu of an oscillating screed . Equip the drum roller to vibrate by either a factory or 717 - BRIDGE OVERLAYS
700-92 field adaptation. The drum roller must be able to compact the concrete to a minimum of 100% of the consolidated
unit weight. Provide an overall combination of labor and equipment with the capability for proportioning, mixing, placing and finishing new concrete at the following minimum rates shown in TABLE 717-1 . TABLE 717-1: PORTLAND CEMENT CONC RETE OVERLAY PRODUC TION REQUIREMENTS Total Placed Surface Area per Bridge (Square Yards) Minimum Cubic Yards per Hour 0-328 1.0 329-492 1.5 493-656 2.0 Over 656 2.5
b.Preparation of Surface. Prior to placement of concrete, sand or shot blast the surface followed by an air blast to the bottom 3 inches of hubguard, and edges agains t which concrete is to be placed to remove all dirt, oil, pavement marking and other foreign material, as well as any unsound concrete, laitance and curing material from the surface. Wet sand blasting may be used only with approval of the Engineer. It is desired that the surface be roughened by the sand or shot blast to provide satisfactory bond with the surfacing concrete. Protect metal deck drains and areas of the curb or railing above the proposed surface from the sand or shot blast. Check the finish machine clearance above the prepared surface before concrete is placed to obtain the thickness specified in the Contract Documents. A minimum of 2 hours before the placing of the concrete overlay, use clean water to thoroughly wet any concrete surfaces to which the concrete is to bond agains t. Blow or broom away all free water immediately ahead of the placing operation. Bonding su rfaces should be mainta ined in a damp conditio n with no free water.
c.Placing Concrete. Place and fasten the screed rails in position to obtain finished concrete at the required profile. Place the supporting rails upon which the finishing machine travels outside the area to be concreted. A hold-down device shot into concrete is prohibited, unless the concrete is to be subsequently overlaid. Hold-down devices of other types leaving holes in exposed areas will be approved provided the holes remaining are grouted full. Methods for anchoring and supporting the rails and the concre te placing procedure require approval by the Engineer. Locate longitudinal joints along lane lines, or as approv ed by the Engineer. Keep the joints clear of wheel paths as much as practical. Placing of the overlay is prohibited when conditions on th e bridge deck are such that the evaporation rate is estimated to equal or exceed 0.2 pounds per square foot pe r hour, or is predicted to exceed that rate during the course of the placement, unless corrective measures listed in subsection 710.3b. are taken to reduce the evaporation rate to below 0.2 pounds per square foot per hour. Fogging may be necessary during placement of the overlay. Accomplish fogging according to subsection 710.3b . The evaporation rate will be recheck ed with the measures in place, using the procedures outlined above. The elapsed time between depositing the concrete on the deck and final screeding may not exceed 15 minutes, unless otherwise authorized by the Engineer. Manipulate and mechanically conso lidate new concrete to a minimum of 98% of the consolidated unit weight and screed to final grade. In irregular areas or along the curb where the finishing screed does not reach, hand tamp with a 6-inch by 6-inch metal plate device to assist in consolidation and bonding of the concrete. When concrete for partial depth patches is placed with the overla y, apply additional vibration or hand tamping in the patch areas to assist in consolidation and bonding of the concrete.
d.Finishing. Strike off overlays with a self-propelled fini shing machine. The screed on the finish machine must be self-oscillating, and operate or finish from a position either on the skew or transverse to the bridge roadway centerline. On overlays skewed greater than 10 º, operate the finishing machine on th e same skew as the bridge, unless approved otherwise by the State Bridge Office. Irregular sections may be finished by other methods approved by the Engineer. Float and straightedge the wearing surface so the finished surface is at the cross-section shown in the C ontract Documents. Do not add water to the surface of concrete, unless approved by the Engineer, and when approved apply as a fog spray. 717 - BRIDGE OVERLAYS
700-93 Secure a smooth riding bridge deck , correcting surface variations exceeding ⅛ inch in 10 feet by use of an
approved profiling device, or other method approved by the Engineer. For decks without the bid item Bridge Deck Grooving, finish the deck with the rough burlap drag. For decks with the bid item Bridge Deck Grooving, see subsection 710.3f. for grooving requirements.
e.Curing and Protection. Cure and protect according to subsection 710.3e .
f.Weather Limitations. See SECTION 401 . Also, discontinue concreting operations when a descending air temperature in the shade and away from artificial heat falls below 45ºF except with written approval from the Engineer. Do not start or resume operations until an as cending air temperature reaches 40ºF, or if night time temperatures are expected to fall below 35ºF.
g.Limitations of Operations. When a new deck is involved, do not commence work on the wearing surface until the lower course meet s the time requirements of SECTION 710 , unless specified otherwise. Do not place concrete adjacent to a surface course, less than 36 hours old. This restriction does not apply to a continuation of placement in a lane or strip be yond a transverse joint in the same lane or strip. In areas where there is no traffic, preparation of the area may be started in a lane or strip adjacent to newly placed surface the day following its placemen t. If this work is started before the end of the 7- day curing period, restrict the work as follows: Sawing or other operations may interfere with the curing process in the immediate work area for the minimum practical time only; Resume the curing promptly upon completion of the work; Keep the exposed areas damp until such time as curing media is replaced; and Do not use power driven tools heavier than a 15-pound chipping hammer.
h.Construction Joints. Make construction joints (either longitudinal or transverse) by placing and finishing the overlay approximately 6 inches beyond the desired location of the construction joint. After the overlay is cured, make a vertical saw cut at the location of the construction joint and chip away the excess overlay.
i.Sealing Vertical Faces of the Overlay. Seal all construction joints and vertical faces (such as the edge at the curb line) of th e overlay. Sand or shot blast the construction joints and vertical faces, and apply a concrete masonry coating to the cleaned vertical surfaces according to SECTION 726 . This work is subsidiary to the overlay.
j.Correction of Unbonded Areas. If during construction of the project, newly overlain areas are discovered to be unbonded by tapping or chaining, outline the concrete from such areas by sawing, remove it with small air tools (15-pound maximum) and replace it at no additional compensation. 717.4 METHOD OF MEASUREM ENT AND BASIS OF PAYMENT The Engineer will measure portland cemen t concrete overlay by the square yard. The Engineer will measure material for portland cement concrete overlay by the cubic yard according to the following:
1.When approved by District on repair of existing bridges, this pay item will be used to compensate the Contractor for the additional overlay material that will be required to fill the areas greater than the thickness of overlay shown in the Contract Documents. The Contractor is responsible for maintaining adequate quality control of the demolition process to minimize deviations from the plan grades.
2.The Engineer will keep a running account of the volume of overlay material that is produced and delivered to the deck. When approved, the Contractor will be paid, at the set price per cubic yard, for all overlay material in excess of 110% of the theoretical volume to cover the deck area with the thickness of overlay shown in the Contract Documents. When shown as a bid item in the contract, the Engineer will measure for payment bridge deck grooving by the square yard. Payment for "Portland Cement Concrete Overlay" and "Bridge Deck Grooving" at the contract unit price and "Material for Portland Cement Concrete Overlay (Set Price)" at the contract set unit price (when approved by the District Engineer) is full compensation for the specified work.
Source: Kansas Standard Specifications for State Road and Bridge Construction, 2015 Edition. Pages 420–424 of 978.