5-174
535.17 Accelerated Curing of Concrete (Optional) Cure the conc rete in accordance with
MNL 116, Section 4.19, except as modified herein. After initial set, the temperature gain of the concrete shall n ot exceed 40 F per hour. Initial set shall be determined in accordance with ASTM C403, Standard Test Method for Time of Setting of Concrete Mixtures by Penetration Resista nce; a strength gain of 500 psi indicates initial set. The maximum allowable concrete tempe rature shall be 160F. Concrete temperature shall be measured near each end of the casting bed and at intervals not to exceed 100 feet. In order to qualify for accel erated cure, the concrete temperature shall attain a minimum temperature of 120 F; that temperature shall be maintained for a minimum of 8 hours and the concrete shall achi eve a minimum of 80 percent of design strength. Detension precast/prestressed products immediately after the co mpletion of the curing cycle while the products are warm and moist. The accelerated c uring cycle shall be considered complete when the method of supplying heat is stoppe d and/or the concrete temperature drops below 120°F. Two cylinders shall be tested i mmediately upon completion of the accelerated cure cycle. Products that have n ot achieved all of the above criteria shall be moist cured until the concrete has achieved d esign strength. If the precast/prestressed concrete products have achieved 80 p ercent of design strength during the accelerated curing c ycle, no further curing will be required.
535.18 Prestressing Tension the strands in accordance with MNL 116 and this
Specification. Provide stressing calculations t o the QAI prior to tensioning s trands. Do not tension the strands until the QAI has reviewed the calculations. Apply ini tial force and final force to the strands in the presence of the QAI. The QCI shall be present t o monitor and document the application of initial force, final force and the elongation of the strands. Tension strands in an orderly sequence to avoid snags and entan glements. When strands from two, or more, coils are used, identify the locations of th e different strand lots. Calculate the elongation and adjusted gauge pressure readings f or each modulus of elasticity and cross sectional area of the strands. Prior to tensioning, cycle the hydraulic jacking devices until the hydraulic fluid reaches normal operating temperature. After initial tensioning, establish a permanent and clearly vis ible reference mark on the strand to determine strand elongation after final tensioning. Measure the strand elongation to the nearest 1/16 inch. If the strands have been tensioned for more than 48 hours witho ut concrete being placed in the forms, test a minimum of 10 percent of the strands, but not less than two strands in each row and not less than two strands in draped strand arrays, by applying the theoretical 5-175 force used during the final ten sioning to each of the strands. If additional elongation is gained, subtract the amount gained from the theoretical elongat ion. If the result of the theoretical elongation minus the gain in elongation is less tha n the minimum allowable elongation for any of the strands tested, apply the final force to all strands. Do not measure total elongation from the original reference mark. Accept prop erly tensioned strand based on the force applied to the strands. Measure and record the chuck-to-chuck distance on self-stressin g beds after tensioning the first set-up and at any time the number of strands or stran d array changes. Confirm that the measurement used in the stressing calculations is the same as the field measurement.
535.19 Detensioning Detension the strands in accordance with M NL 116 and this
Specification. Use a carburizing flame. Heat a minimum length of 6 inches of the strand slowly so that only one wire is released at a time. Cut both e nds and any intermediate points simultaneously. Failure to maintain symmetry of cutting or cau sing sudden shock to the product will make it subject to rejection. Detension the stran ds in the presence of the QAI and QCI. Measure any strand slippage on all precast/prestressed concrete products. Mark all strands prior to detensioning. Measure a minimum of four stran ds per row. The QAI will choose the strands to be measured.
535.20 Finishing Concrete and Repairing Defects Precast/prestr essed concrete products
fabricated under this Section shall meet Standard Grade finish requirements as defined in MNL 116, except that the Contractor shall rub fascia units in a ccordance with Section 502 of the Standard Specifications. Abrasive blast fascia surfaces prior to finishing. The Contractor may use alternative methods of achieving an acceptab le finish on fascia units, if approved by the Fabrication Engineer. Repair honeycombing, ragged or irregular edges and other non-st ructural or cosmetic defects using a patching material from the Department Qualified Products List (QPL). The repair, including preparation of the repair area, mixing and ap plication and curing of the patching material, shall be in accordance with the manufacturer 's product data sheet. Corners that are not exposed in the final product may be ground smooth with no further repair necessary if the depth of the defect does not exceed 1/2 inch. Remove form ties and other hardware to a depth of not less than 1 inch from the face of the concrete and patch the holes using a patching material from the Department QPL. Repair structural defects only w ith the approval of the Fabrica tion Engineer. Submit a nonconformance report (NCR) to the Fabrication Engineer with a proposed repair procedure. Do not perform struct ural repairs without an NCR th at has been reviewed by the Fabrication Engineer. Structural defects include, but are not be limited to, exposed reinforcing steel or strand, cracks in bearing areas, through c racks and cracks 0.013 inch in width that extend more than 12 inches in length in any directio n. Give the QAI adequate notice prior to beginning any structural repairs. 5-176 Make chamfers and drip notches smooth and uniform. Sandblast k eyways to remove mortar paste prior to shipping. Recess strand ends 1 inch and patch the holes with a patching material from the Department QPL. Coat the entire end s of the precast/prestressed concrete units with a bituminous protective coating unless othe rwise specified on the Plans or as directed by the Fabrication Engineer.
535.21 Precast/prestressed Deck Panels Produce precast/prestre ssed deck panels in
accordance with the Plans and Specifications. Cure the deck pa nels in accordance with Sections 535.16 or 535.17.
535.22 Tolerances Product dimensional tolerances shall be in c onformance with the
latest edition of MNL 116, Appendix B, as applicable to the pa rticular product (e.g., slab, I- girder. box beam), the Plans and this Specification. Use Box B eam fabrication tolerances for voided slabs and use Double T tolerances for NEXT beams. I n case of dispute, the Fabrication Engineer shall determine the allowable tolerance.
535.23 Transportation and Storage Handle and store material using lifting devices.
Handle and transport precast/prestressed units so that the reac tions with respect to the unit shall be approximately the same during transportation and stora ge as in its final position. Do not transport units until the 28 day design strength has bee n attained. Support stored precast/prestressed units above the ground on du nnage in a manner to prevent twisting or distortion. Protect the units from discolo ration and damage. Repair or replace precast/prestressed concrete units damaged by improper storing, hoisting or handling.
535.24 Installation of Slabs, Beams and Girders Finish bearing areas to the elevations
shown on the Plans and in accordance with Section 523, Bearings , as applicable. Lift the units using the lifting devices cast into them. Suppo rt I-Girders at the abutments and piers to prevent overturning. Place beams and slabs in the ir final location in a manner that assures that the keyways are spaced properly and the post- tensioning ducts are in alignment. Use compressible gaskets around duct openings withi n keyways to prevent blocking of the duct with grout. Prior to grouting, initially post-tension slabs or beams to 5,0 00 lbs. force, per strand. Make a permanent and clearly visible reference mark on each str and after it has been initially post-tensioned in order to determine strand elongatio n after final post-tensioning. Immediately prior to grouting, clean the keyways between slab o r box units and soak the keyways with water in order to pr event absorption of water from the grout. Seal the bottom of the keyways to prevent the loss of grout. Fill longitudinal keyways between slabs or beams with a non-shr ink, flowable, cementitious grout with a minimum design compressive strength o f 6,000 psi at 28 days. 5-177 The grout shall be a material for keyways from the Department Q PL. Mix, place and cure the grout in accordance with the manufacturer's product data sh eet. The Contractor may propose the use of an alternate grout material supplied from a Department approved ready mixed concrete batch plant. Ready mixed grout shall achieve a design compressive strength of 6,000 psi at 28 days, have an entrained air content of betwe en 6.0 and 9.0 percent, be non-shrink, flowable, and contain a non-shrink additive listed on the Department QPL for expansive cements. The proposed grout mix design shall be subm itted to the Department for approval. Do not perform final post-tensioning of slabs or beams less tha n 24 hours after completion of the grouting operation. Final post-tension preca st/prestressed concrete slabs or beams to 41,000 lbs. force per strand, unless otherwise spec ified on the Plans. Provide a jacking device that has been calibrated in accordance with MNL 116. Provide calibration documentation, a calibration curve and stressing calculations t o the Resident, allowing adequate time for review. Do not post-tension slabs or beams u ntil the documentation has been reviewed by the Department. Post-tension the slabs or bea ms in the presence of the Resident. No vehicular traffic , including the Contractor’s equ ipment, shall be allowed on the bridge until post-tensioning is complete. Saw cut or abrasive cut the post-tensioning strand of slabs or beams no closer than 1-¼ inches from the wedges after tensioning is complete. Coat the strand ends and wedges with a corrosion inhibiting grease and cap the ends with a watertigh t cover. Pack and neatly finish the post-tensioning recesses of slabs or beams with a grout made of the same brand and type of cement used to cast the slabs or beams. Clean the post- tensioning recesses prior to packing the grout.
535.25 Installation of Precast/Prestressed Deck Panels Erect d eck panels as shown on
the Plans or reviewed Working Drawings, as applicable. Adjust the bottom-of-slab elevation using threaded jacking devices cast into the panels, or by other means approved by the Resident. Fill the voids between the top of the beam and the bottom of th e panels, as shown on the Plans, reviewed Working Drawings or Standard Details, as applic able, with a non-shrink, flowable, cementitious grout with a minimum design compressive strength of 6,000 psi at 28 days. The grout shall be a material for keyways from the Depar tment QPL. Mix, place and cure the grout in accordance with the manufacturer’s published product data sheet. Provide vent holes at 3-foot intervals to avoid air locks. The Contrac tor may propose the use of an alternate grout material supplied from a Department approved re ady mixed concrete batch plant. Ready mixed grout shall achieve a design compressive str ength of 6,000 psi at 28 days, have an entrained air content of between 6.0 and 9.0 perc ent, be non shrink, flowable, and contain a non shrink additive listed on the Department QPL for expansive cements. The proposed grout mix design shall be submitted to the Department for approval. Prevent concrete leakage between the deck panels using caulking , backer rod or other methods approved by the Resident. 5-178 Remove all visible contaminants from the deck panels and protru ding reinforcing steel by abrasive blast cleaning or high pressure (minimum of 8,000 p si) water cleaning, prior to placing the deck concrete.
535.26 Method of Measurement Prestressed structural concrete i tems will be measured
by the lump sum, except that precast deck panels will be measur ed as part of the structural concrete slab Pay Item(s).
535.27 Basis of Payment Acceptable work done under Precast, Pr estressed Concrete
Superstructure will be paid for at the Contract lump sum price for the respective Pay Item; all work associated with precast deck panels will be considered incidental to the structural concrete slab Pay Item(s). Payment will be full compensation f or furnishing all materials, labor and equipment in the precast/prestressed work, including concrete, strand, reinforcing steel, anchor dowels and related items. Related items will inc lude, but not be limited to: Working Drawings, preformed pads, transportation, erecting the units, drilling and grouting of anchor dowels, grouting of keyways, panels and ducts, tensio ning and post-tensioning operations, and required concrete admixtures. Payment will be made under: P a y I t e m P a y U n i t
535.60 Prestressed Structural Concrete Slab L u m p S u m
535.61 Prestressed Structural Concrete I-Girders L u m p S u m
535.62 Prestressed Structural Concrete Box Beams Lump Sum 535.622 Prestressed Structural Concrete NEXT Beam Lump Sum
6-1 Chapter 6 DIVISION 600 - MISCELLANEOUS CONSTRUCTION SECTION 601 - GABIONS AND MATTRESSES
601.01 Description This work shall consist of furnishing, ass embling, filling with
stones and lacing wire mesh baskets, hereafter called gabions o r mattresses, constructed in accordance with these specifications and placed in conformity w ith the lines, grades and dimensions shown on the plans or established.
601.02 Materials Materials shall conform to the requirements specified in the
following Sections of Division 700 - Materials. G a b i o n 711.02 S t o n e s f o r G a b i o n s 711.03 M a t t r e s s e s 711.07 S t o n e s f o r M a t t r e s s e s 711.08
601.03 Fabrication Gabions and mattresses shall be manufactur ed so that their sides,
ends, lid, and diaphragm(s) can be assembled to form rectangula r units of the specified dimensions. Gabions shall be of a single unit construction. The front, ba se, back and lid shall be woven into a single unit. The ends and diaphragm(s) shall be f actory connected to the base. The base, sides, and two ends of mattresses shall be of a sing le unit construction woven into a single unit. Diaphr agm(s) shall be factory connec ted to the base. The lid may be a separate unit. Perimeter edges of the mesh forming the gabion or mattress sha ll be securely fastened so that joints have at least the same strength as the wire mesh itself. The wire mesh shall be fabricated to be non-raveling. Non-rav eling is defined as the ability to resist pulling apart at any of the twists or connect ions forming the mesh when a single wire in a section of mesh is cut and the section of mesh then subjected to the load test described in the materials specification. The gabion length shall be 1½, 2, 3, or 4 times its horizontal width. The horizontal width shall not be less than 36 i n. However, all gabions furni shed by the manufacturer shall be of uniform width. Where the gabion length exceeds 1½ times its horizontal width, the gabion shall be equally divided into cells by diaphragm(s) of t he same mesh and gauge as the gabion body. Mattresses shall be at least 6 ft by 6 ft and equally divided by transverse diaphragms.