710Concrete Structure Construction

- CONCRETE STRUCTURE CONSTRUCTION CONCRETE STRUCTURE CONSTRUCTION

710.1DESCRIPTION

Construct concrete structures according to the Contra ct 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 Concrete (*) (**) (***) (****) Cubic Yard Bridge Deck Grooving Square Yard *Grade of Concrete **AE (air-entrained), if specified ***Aggregate, if specified ****MPC (Moderate Permeability Concrete), if specified

710.2MATERIALS

Provide materials that comply with the applicable requirements. Concrete+ ............................................................................................................... SECTIONS 401 & 402 Aggregates for Concrete Not On Grade ................................................................ SECTION 1102 Concrete Curing Materials .................................................................................... DIVISION 1400 Joint Sealing Compounds ...................................................................................... DIVISION 1500 Type B Preformed Expansion Joint Filler ............................................................. DIVISION 1500 Preformed Elastomeric Compression Joint Seals .................................................. DIVISION 1500 Bridge Number Plates ........................................................................................... DIVISION 1600 + If Moderate Permeability Concrete (MPC ) is not specified, the concrete shall meet the requirements for Standard Permeability Concrete.

710.3CONSTRUCTION REQUIREMENTS

the Engineer the method and equipment used for deck placement; include the equipment for controlling the evaporation rate, procedures used to minimize the evaporation rate, and method to place saturated burlap within the specified 15 minute limit. Fogging using hand-held equipment may be required by the Engineer during unanticipated delays in the placing, finishing or curing operations. If fogging is required by the Engineer, do not allow water to drip, flow or puddle on the concrete surface during f ogging, placement of absorptive material, or at any time before the concrete has achieved final set. When needed, produce a fog spray fro m nozzles that atomize the droplets and a system capable of keeping a large surface area damp without depositing excess water. Use high pressure equipment that generates a minimum of 1200 psi at 2.2 gpm, or low pressure equipment having nozzles capable of supplying a maximum flow rate of 1.6 gpm. Use a method and sequence of placing concrete approved by the Engineer. Do not place concrete until the forms and reinforcing steel have been checked and approved. Before placing concrete, clean all forms of debris. Drive all foundation piling in any one pier or abutment before concrete is poured in any footing or column of that pier or abutment. On bridges skewed greater than 10º, place concrete on the deck forms across the deck on the same skew as the bridge, unless approved otherwise by State Bridge Office (SBO). Operate the bridge deck finishing machine on the same skew as the bridge, unless approved otherwise by the SBO. Maintain environmental conditions on the entire bridge deck such that the evaporation rate is less than 0.2 lb/sq ft/hr. This may require placing the deck at night, in the early morning or on another day. The evaporation rate (as determined in the American Concrete Institute Manual of Concrete Practice 305R, Chapter 2) is a function of air temperature, concrete temperature, wind speed and humidity. Just prior to and at least once per hour during placement of the concrete, the Engineer will measure and record the air temperature, concrete temperature, wind speed and humidity on the bridge deck. The Engineer will take the air - CONCRETE STRUCTURE CONSTRUCTION temperature, wind and humidity measur ements approximately 12 inches above the surface of the deck. With this information, the Engineer will determine the evaporation rate by using KDOT software or by using FIGURE 710-1 (Figure 2.1.5 from the American Concrete Institute Manual of Concrete Practice 305R, Chapter 2). When the evaporation rate is equal to or above 0.2 lb/ft 2/hr, take actions (such as cooling the concrete, installing wind breaks, sun screens etc.) to create and maintain an evaporation rate less than 0.2 lb/ft2/hr on the entire bridge deck. Place concrete to avoid segregation of the materials and displacement of the reinforcement. Do not deposit concrete in large quantities at any point in the forms, and then run or work the concrete along the forms. Deposit the concrete in the forms in horizontal layers . Perform the work rapidly and continuously between predetermined planes. Vibrate through each plane. Fill each part of the form by depositin g the concrete as near to the final position as possible. If the chutes for placement of concrete are on steep slopes, equip them with ba ffle boards or assemble in short lengths that reverse the direction of movement. Do not drop concrete in the forms a distance of more than 5 feet, unless confined by clean, smooth, closed chutes or pipes. Work the coarse aggregate back from the forms and around the reinforcem ent without displacing the bars. After initial set of the concrete, do not disturb the forms, or place any strain on the ends of projecting reinforcement. If placing concrete by pumpi ng, place the concrete in the pipeline to avoid contamination or separation of the concrete, or loss of air by fitting the pump with a concre te brake (e.g. french horn or bladder valve) at the end of the pump boom. Obtain sample concrete for slump and air test requirements at the discharge end of the piping. Do not use chutes, troughs or pipes made of aluminum. Uniformly consolidate the concrete without voids. Accomplish consolidation of the concrete on all span bridges that require finishing machines by means of a mechanical device on which internal (spud or tube type) concrete vibrators of the same type and size are mounted (subsection 154.2). Observe special requirements for vibrators in contact with epoxy coated reinforcing steel as specified in subsection 154.2. Provide stand-by vibrators for emergency use to avoid delays in case of failure. Operate the mechanical device so vi brator insertions are made on a maximum spacing of 12-inch centers over the entire deck surface. Provide a uniform time per inse rtion of all vibrators of 3 to 15 seconds, or until the course aggregate settles below the surf ace of the concrete, unless otherwise de signated by the Engineer. Provide positive control of vibrators using a timed light, buzzer, automatic control. Smoothly extract the vibrators from the concrete at a rate to avoid leaving any large voids or holes in the consolidated concrete. Do not drag the vibrators horizontally through the concrete. Use hand held vibrators ( subsection 154.2) in inaccessible and confined ar eas such as along hubguards. When required, supplement vibrating by hand spading with suitable tools to provide required consolidation. Reconsolidate any voids left by workers. Deposit concrete in water, only with approval from the Engineer. Do not place concrete in running water. Use forms that are reasonably watertight to hold concrete deposited under water. Increase the minimum cement factor of the grade of concrete being deposited in water by 10%, obtaining approximately a 6-inch slump. Carefully deposit the concrete in place, in a compact ma ss, using a tremie pumped th rough piping, bottom-dumping bucket or other approved method that does not permit the concrete to fall through the water. Do not pump water from the inside of the foundation forms while concrete is being placed. Do not disturb the concrete after being deposited. If necessary to prevent flooding, place a seal of concrete through a closed chute or tremie, and allow it to set. Continuously place concrete in any floor slab until complete, unless shown otherwise in the Contract Documents. The method used for transporting concrete batches, ma terials or equipment over previously placed single pour (non-overlaid) floor slabs or floor units, or over units of structures of continuous design types is subject to approval by the Engineer. Do not operate bridge deck finishing equipment on previously placed concrete spans until: • A minimum of 72 hours on structures that are fully supported with falsework; • A minimum of 72 hours on structures with concrete girder spans with concrete decks; and • A minimum of 96 hours on structures with steel girder spans with concrete decks. The time delays begin after the day’s pour has been completed. Follow TABLE 710-2 for load limitations after concrete placement. Prior to permitting approved traffic on the bridge deck, construct temporary bridge approaches and maintain them in a condition to prevent damage to the bridge ends. - CONCRETE STRUCTURE CONSTRUCTION FIGURE 710-1: STANDARD PRACTICE FOR CURING CONCRETE 50 60 70 80 90 90F (32C) 80F (27C) 70F (21C) 60F (16C) 50F

(4C) 25 (40) 20 (32) 15 (24) 10 (16) 5 (8) 2 (3) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 10090 80 70 60 50 40 Air temperature, deg F 15 25 35 Rate of evaporation, lb/sq ft/hr 1.0 2.0 3.0 4.0 kg/m2/hr Deg C 5 To use this chart:

move up to relative humidity.

to concrete temperature.

to wind velocity.

rate of evaporation. Effect of concrete and air temperatures, relative humidity, and wind velocity on the rate of evaporation of surface moisture from concrete. This chart provides a graphic method of estimating the loss of surface moisture for various weather conditions. To use the chart, follow the four steps outlined above. When the evaporation rate exceeds 0.2 lb/ft2/hr (1.0 kg/ m2/hr), measures shall be taken to prevent excessive moisture loss from the surface of unhardened concrete; when the rate is less than 0.2 lb/ft2/hr (1.0 kg/m2/hr) such measures may be needed. When excessive moisture loss is not prevented, plastic cracking is likely to occur. humidity, percent Relative Wind velocity mph (km/hr) Concrete temperature 100F (38C) 100

construction joints as shown in the Contract Documents. If construction joints are not shown in the Contract Documents, submit proposed locations for approval by the Engineer. - CONCRETE STRUCTURE CONSTRUCTION If the work of placing concrete is delayed and the concrete has taken its initial set, stop the placement, saw the nearest construction joint approved by the Engineer and remove all concrete beyond the construction joint. On post-tensioned structures construct a stepped joint as shown in the Contract Documents. When the Contract Documents show a construction joint in the wall of the RCB 3 inches above the floor, the Contractor has the option of constructing the joint as shown on the Contract Documents, or constructing the joint level with the floor of the RCB. When the Contract Documents show a construction joint in the wall of the RFB 2 inches above the floor haunch, the Contractor has the option of constructing the joint as shown on the Contract Documents, or even with the top of the floor haunch of the RFB. If dowels, reinforcing bars or other tie devices are not required by the Contract Documents, make a key in the construction joint. Construct keyed joints by embedding water-soaked beveled timbers of a size shown on the Contract Documents, into the soft concrete. Remove the timber when the concrete has set. When resuming work, thoroughly clean the surface of the concrete previously placed, and when required by th e Engineer roughen the key with a steel tool. Before placing concrete against the keye d construction joint, the joint shall be cleaned of surface laitance, curing compound, and all other foreign material, use of abrasive blasting may be required to achieve the level of cleanliness required. Thoroughly wash the surface of the keyed joint with clean water, and allow the joint to dry to a saturated surface dry condition immediately prior to placing fresh concrete against the joint key.

inch) bolts to hold a header board for each traffic lane into the vertical surface of the EWS. Finish the surface of the EWS using an edging tool with a ¼ inch radius. Immedi ately after the vertical forms on the EWS are removed, protect the exposed EWS by bolting a wooden header (minimum dimension of 2 ⅝ inches by 7 ½ inches) to the exposed vertical surface of the EWS. Extend the header board the full width of the EWS, or use 1 section of header board for each lane of traffic. Shape th e header board to comply with the crown of the brid ge surface, and install it flush with the concrete wearing surface. Do not bend the reinforcing steel which will tie the approach slab to the EWS or damage the concrete at the EWS.

approach slab away from the EWS place bolts and attach a header board in the same manner required for bridges with tied approaches. If the Contractor needs to drive on the bridge before the approach slabs can be placed and cured construct a temporary bridge from the approach over the EWS capable of supporting the anticipated loads. The method of bridging must be approved by the Engineer.

wooden float by tamping and floating, flushing the mortar to the surface a nd provide a uniform surface, free from pits or porous places. Trowel the surface producing a smooth surface, and brush ligh tly with a damp brush to remove the glazed surface. Strike off bridge decks with a self-propelled finishing machine, which may be manually operated by winches to reach a temporary bulkhead when approved by the Engineer. 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 decks skewed greater than 10º, operate the finishing machine on the same skew as the bridge, unless approved otherwise by the SBO. Befo re placing concrete, position the finisher throughout the proposed placement area allowing the Engineer to verify the reinforcing steel positioning. Irregular sections may be finished by other methods approved by the Engineer. Reinforced concrete box bridges that will be under fill may be struck off by other approved methods. Float and straightedge the wearing surface so the finished surface is at the cross-section shown in the Contract Documents. Do not add water to the surface of concrete, unless approved by the Engineer, and when approved apply as a fog spray. 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. Straightedge decks that are to receive an overlay, leaving them with an accep table float or machine pan finish. For decks not receiving an overlay, and without the bid item Bridge Deck Grooving, finish the deck with the rough burlap drag. For decks not receiving an overlay, and wi th the bid item Bridge Deck Grooving, see subsection 710.3f. for grooving requirements. - CONCRETE STRUCTURE CONSTRUCTION Obtain reasonably true and even concrete surfaces, free from stone pockets, excessive depressions or projections on the surface. Strike off w ith a straightedge and float the concrete in bridge seats and walls flush with the finished top surface. As soon as the forms are removed and the concrete is ready to hone, rub the conc rete surfaces that are not in an acceptable condition, or are designated in the Contract Documents to be surface finished to a smooth and uniform texture with a carborundum brick and clean water. Remove the loose material formed on the surface, due to the rubbing with a carborundum brick as soon as it dries. The finished surface shall be free from all loose material. Do not use a neat cement wash. Give handrails, handrail posts, the deck side, and the top and end of all curbs, except curbs of structures having the top of curb below the final sh oulder elevation of the road, an acceptable troweled or floated finish. This includes the back of the inside rails of side by side structures, or any rails easily viewed by the traveling public. Remove the forms as early as possible, and perform the float finish while the concrete is still green. Use mortar during the float finish operation to fill in air and wa ter voids and supplement the float finish. Keep surfaces requiring a rubbed finish moist before and during the rubbing. Do not use a mortar coating after the concrete has cured. Unless otherwise provided in the Co ntract Documents, all reasonably tr ue and even surfaces, obtained by use of a form lining, which are of a uniform color, free from stone pockets, honeycomb, excessive depressions or projections beyond the surface, are considered as acceptable surfaces, and a rubbed surface finish is not required. The Engineer may require the use of a dry carborundum brick for straightening moulding lines, removing fins or requiring a rubbed surface finish on all portions of the structure that do not present an acceptable surface even though a form lining is used.

the same manner as the bridge deck. The determination of the time requirement for curing commences after all the concrete for the placement is in place and finished. During cold weather, the specified time limits may be increased at the discretion of the Engineer, based upon the amount of protection and curing afforded the concrete. Maintain a damp surface until the wet burlap is placed. Fully saturate burlap before placing on concrete surface. Cover all concrete surfaces with saturated burlap within 15 minutes after finishing the concrete, do not mar concrete during placement of the wet burlap . Maintain the curing so that moistu re is always present at the concrete surface. Place and weight down the burlap so it will remain in intimate contact with the surface covered. When an impermeable sheeting material is used, lap each unit 18 inches with the adjacent unit. Place and weight down the impermeable sheeting material so it will remain in intimate contact with the surface covered. When any burlap or impermeable sheeting material becomes perforated or torn, immediately repair it, or discard and replace it with acceptable material. - CONCRETE STRUCTURE CONSTRUCTION TABLE 710-1: MINIMUM CURE TIMES AND CURING MEDIUMS Type of Work Minimum Cure Time (days) Curing Medium and Use Bridge decks (full-depth decks with multi-layer polymer overlays) Bridge subdecks (decks with overlays) Wet Wet burlap covered with white polyethylene sheeting during the 14-day period. Bridge decks (full-depth decks with no overlay) Bridge Overlays Wet Plus Curing Membrane Wet burlap covered with white polyethylene sheeting during the 14-day period. After the wet cure period, apply 2 coats of Type 2 white liquid membrane forming compound. Place the first coat within 30 minutes of removing the sheeting and burlap. Spray the second coat immediately after and at right angles to the first application. Protect the curing membrane against marring for a minimum of 7 days. The Engineer may limit work during this 7-day period. Other unformed or exposed surfaces Curing Membrane Apply 2 coats of Type 2 white liquid membrane forming compound. Place the first coat immediately after completion of the concrete finish just as the surface water disappears. Spray th e second coat immediately after and at right angles to the first application. Protect the curing membrane against marring for a minimum of 7 days. The Engineer may limit work during this 7-day period. Should the compound be subjected to continuous damage, the Engineer will require wet burlap, white polyethylene sheeting or other approved impermeable material to be applied at once for the remainder of the cure time. Formed sides and ends of bridge wearing surfaces and bridge curbs Other formed surfaces Formed Formed surfaces will be considered completely cured upon the Engineer’s permission to remove the forms, providing the forms have been in place for a minimum of 4 days. If forms are removed before the end of the 4-day cure period, cure the surface with an application of Type 1-D liquid membrane forming compound.

uniform pressure to provide uniform distribution at the rates required. Agitate the liquid membrane forming compound continuously during application. The surface must be kept wet from the time it is finished until the liquid membrane forming compound is applied. Apply liquid membrane forming compound at a minimum rate per coat of 1 gallon per 200 square feet of concrete surface. Give marred or otherwise damaged applications an additional coating. If rain falls on the newly coated concrete before the film has dried sufficiently to resist damage from the rain, or if the film is damaged by any other means, apply a new coat of the membrane to the affected portion equal in curing value to the original application.

Maintain the curing so that moisture is always present at the concrete surface. Maintain the wet burlap in a fully wet condition using misting hoses, self-propelled, machine-mounted fogging equipment with effective fogging area spanning the deck width, moving continuously across the entire burlap- covered surface, or other approved devices until the concrete has set sufficiently to allow foot traffic. At that time, place soaker hoses on the burlap, and supply running water continuously to maintain continuous saturation of all burlap - CONCRETE STRUCTURE CONSTRUCTION material to the entire concrete surface. For bridge decks with superelevation, place a minimum of 1 soaker hose along the high edge of the deck to keep the entire deck wet during the curing period. If the concrete surface temperature is above 90ºF, do not use polyethylene sheeting in direct sunshine during the day for the first 24 hours of the specified curing period ( TABLE 710-1). White polyethylene sheeting may be used at night to maintain the required damp condition of the burlap. When polyethylene sheeting is used over the burlap at night during the first 24 hours and the concrete surface temperature is above 90ºF, place the polyethylene sheeting a maximum of 1 hour before sunset, and remove the polyethylene sheeting within 1 hour after sunrise. After the first 24 hours, the polyethylene sheeting may be left in place continuously for the remainder of the curing period provided the burlap is kept damp. Construction loads on the new bridge subdeck, new one-co urse deck or any concrete overlay are subject to the limitations in TABLE 710-2. The use of supplemental cementitious materials will require additional time before specified loading is allowed. *Maintain the specified wet cure at all times (TABLE 710-1). ** All haunched slab structures. *** Submit the load information to the appropriate Engineer. Information that will be required is the weight of the material and the footprint of the load, or the axle (or truck) spacing and the width, the size of each tire (or track length and width) and their weight. ****An overlay may be placed using pumps or conveyors until legal loads are allowed on the bridge. Δ Increase time period by 3 days when supplemental cementitious materials are used October 1 thru April 30.

after the surface is completed, and while the concrete is still damp.

If concrete is placed and the ambient air temperature is expected to drop below 40ºF during the entire specified curing period, provide suitable measures such as straw, additional burlap or other suitable blanketing materials or housing and artificial heat to maintain the concrete temperature between 40 and 90ºF as measured on the surface of the concrete. Keep the surface of the concrete moist by the use of an appr oved moisture barrier such as wet burlap or polyethylene sheeting or both as defined in TABLE 710-1 . Maintain the moisture barrier in intimate contact with the concrete during the entire specified curing period. After the completion of the required curing period, remove the curing and protection to prevent rapid cooling of the concrete.

conditions are waived providing the surface of the water does not freeze.

profiling device, or other methods approved by the Engineer after the curing period. Perform grinding on hardened concrete after the specified curing membrane period (TABLE 710-1) to achieve a plane surface and grooving of the final wearing surface as shown in the Contract Documents. Apply the corrective measure to the full width of the lane. The corrected areas shall have uniform texture and appearance. The beginning and endi ng of the corrected areas shall be squared normal to centerline of the paved surface. TABLE 710-2: CONCRETE LOAD LIMITATIONS ON BRIDGE DECKS Days after concrete is placed Element Allowable Loads 1* Subdeck, one-course deck or concrete overlay Foot traffic only. 3* One-course deck or concrete overlay Work to place reinforcing steel or forms for the bridge rail or barrier. 7*, Δ Concrete overlays Legal Loads; Heavy stationary loads with the Engineer’s approval.*** 10 *, Δ (15)**, Δ Subdeck, one-course deck or post- tensioned haunched slab bridges Light truck traffic (gross vehicle weight less than 5 tons).**** 14 *, Δ (21)**, Δ Subdeck, one-course deck or post- tensioned haunched slab bridges Legal Loads; Heavy stationary loads with the Engineer’s approval.***Overlays on new decks. 28 Bridge decks Overloads, only with the State Bridge Engineer’s approval.*** - CONCRETE STRUCTURE CONSTRUCTION If at least 25% of the traveled way of the deck needs ground to correct surface variations, grind the entire deck. Use a self-propelled grinding machine with diamond blades mounted on a multi-blade arbor. Avoid using equipment that causes excessive ravels, aggregate fractures or spalls. Remove from the project and properly dispose of the material. Do not allow the grinding slurry to flow across lanes being used by traffic, onto shoulder slopes, into streams, lakes, ponds or other bodies of water, or gutters or other drainage facilities. Do not place grinding slurry on foreslopes. After any required grinding is complete and after the specified curing membrane period (TABLE 710-1), give the surface a suitable texture by transverse grooving. Use diamond blades mounted on a self-propelled machine that is designed for texturing pavement. Transverse grooving of the finished surface may be done with equipment that is not self-propelled providing that the Contractor can show proficiency with the equipment. Use equipment that does not cause strain, excessive raveling, aggregate fracture, spalls, disturbance of the transverse or longitudinal joint, or damage to the existing concrete surface. Make the grooving approximately 3/16 inch in width at ¾ inch centers and the groove depth approximately ⅛ inch. Terminate the transverse bridge deck grooving approximately 2 feet in from the base of the rail, and 1 foot from any deck drains or other appurtenances. If after corrective measures are made, more than ½ inch of the deck was gr ound at any location, the Engineer may require a multi-layer polymer conc rete overlay over the whole deck, according to SECTION 729, at no additional cost to KDOT.

approval. During cold weather, the specified time limits may be increased at the discretion of the Engineer, based upon the amount of protection and curing afforded the concrete. Do not remove forms and falsework until the minimum amount of time required for strength gain has elapsed regardless if the concrete is fully cured per TABLE 710-1. If forms are removed before expiration of the cure period, maintain the cure as provided in DIVISION 700. Remove forms on handrails, ornamental work and other vertical su rfaces that require a rubbe d finish as soon as the concrete has hardened sufficiently that it shall not be damaged. Under normal conditions, the Engineer will allo w removal of forms and falsework according to TABLE 710-3. The determination of the time requirement for the removal of forms commences after all the concrete for the placement is in place and finished. If high early strength concrete is used, the specified time limits may be decreased as determined by the Engineer, and agreed upon before placing the concrete. - CONCRETE STRUCTURE CONSTRUCTION TABLE 710-3: MINIMUM STRENGTH GAIN TIME BEFORE REMOVAL OF FORMS & FALSEWORK (DAYS) Type of Work Span Length (feet) Less than 10 or less Greater than 10 10 to 20 + to 30 Greater than 20 Greater than 30 Cantilevered Piers - Formwork (supporting the pier beam) supported on column 7 Δ [4]* 10 Δ [6]* Column Bent Piers - Falsework supporting pier beam** 4 Δ 7 Δ [4]* 10 Δ [6]* Forms and Falsework under slabs, beams, girders, arches and brackets*** 4 Δ 7 Δ [4]+ 10 Δ [6]+ 15 Δ [10]+ RCB and RFB top slabs not re-shored 7 Δ [4]+ 7 Δ [4]+ 10 Δ [6]+ Type of Work Time (Days) Walls, Wing Walls and vertical sides of RCB and RFB structures Do not backfill according to SECTION 204, until 3 days after forms are removed. 4 Δ [3]* Footing Supported on Piles - minimum cure before erecting forms and reinforcing steel for columns 4 Δ [2]* Spread Footing founded in rock – minimum before erecting forms and reinforcing steel for columns 2 Δ Footing supported on piles - minimum cure before erecting forms and reinforcing steel for columns 4 Δ [2]* Columns for cantilevered piers -

column.

4 Δ [2]+ 7 Δ [4]+ Columns for bent piers -

2 Δ 4 Δ [2]* Drilled shafts - minimum before erecting forms and reinforcing steel for the columns 2 Δ Floors for RCB and RFB structures on rock or a seal course - minimum before erecting forms and reinforcing steel 2 Δ Floors for RCB and RFB structures on soil or foundation stabilization - minimum before erecting forms and reinforcing steel 4 Δ [2]* Do not remove forms or falsework from post tensioned elements until all applied post tensioning forces are transferred. NA * Contractors may reduce the time required before form remova l to the number of days shown in brackets, provided the concrete is shown to have attained a minimum strength of 65% of the specified f 'c. To accomplish this, prepare the necessary cylinders, obtain the services of an approved laboratory to br eak them at the appropriate time and provide a report to the Engineer. Field cure the cylinders alongside and under the same curing conditions, as the concrete they represent. ** Do not set girders or beams on the pier beams until the falsework under the pier beams is removed. *** Remove the formwork from subdecks or one-course decks within 6 weeks after the deck has been placed. + Contractors may reduce the time required before form removal to the number of days shown in brackets, provided the concrete is shown to have attained a minimum strength of 75% of the specified f 'c. To accomplish this, prepare the necessary cylinders, obtain the services of an approved laboratory to br eak them at the appropriate time and provide a report to the Engineer. Field cure the cylinders alongside and under the same curing conditions, as the concrete they represent. Δ Increase the time period 3 days when supplemental cementitious materials are used October 1 thru April 30. - CONCRETE STRUCTURE CONSTRUCTION Reshoring of RCB and RFB (classified as culverts or br idges) top slab will be permitted if the Contractor uses traveling forms or to reduce the minimum time shown in TABLE 710-2. At the Preconstruction Conference, submit calculations, sealed by a Professiona l Engineer, to the Engineer that show that the concrete tensile stress is below 0.23 √f 'c (ksi) and the shoring has sufficient capacity. In determining the time for the removal of forms, give consideration to the location and character of the structure, weather and other conditions influencing the set ting of concrete. If forms are removed before expiration of the cure period, maintain the cure as provided in DIVISION 700. For additional requirements regarding forms and falsework, see SECTION 708.

bridges by the use of plates recessed in the concrete during construction, using plates constructed as shown in the Contract Documents. The date placed on the plates is the year in which the structure is completed.

710.4MEASUREMENT AND PAYMENT

The Engineer will measure the various grades of conc rete placed in the structur e by the cubic yard. No deductions are made for reinforcing steel and pile heads extending into the concrete. When shown as a bid item in the contract, the Engineer will measure for payment bridge deck grooving by the square yard. Payment for the various grades of "Concrete" and "Bridg e Deck Grooving" at the contract unit prices is full compensation for the specified work.