513Structural Concrete

Structural Concrete

513.1DESCRIPTION

1 This section describes the requirements for furnishing and placing portland cement concrete for bridges, culverts, and other cast-in-place reinforced concrete structures.

513.2MATERIALS

1 Provide materials in accordance with the following:

Material Subsection Admixtures 801.4 Aggregate for Concrete 803 Curing Materials 802.1 Evaporation Retardant 802.2 Fly Ash 801.2

Slag Cement 801.6 Grout 819.1 Hardware Cloth for Drains 808.4.2 Joint Fillers and Sealers 807 Portland Cement 801.1 Water 814.1

2 Provide concrete consisting of portland cement, water, fine aggregate, coarse aggregate, and approved additives proportioned and mixed as specified or approved.

3 For the wearing surfaces of bridge decks, provide type 2, white-pigmented impervious curing compound. Elsewhere, provide and use type 1, clear or translucent.

4 Fabricate stay-in-place forms that will be exposed in the finished structure, including corrugated sheets spanning supports, closures, and accessories, from hot -dipped galvanized steel in accordance with ASTM Specification A 653Grade 50 with a minimum coating class of G165.

513.3EQUIPMENT

513.3.1 Batch Plant

1 Use a batch plant equipped with scales, bins, and weighing hopper as follows:

the accurate determination of the weight [mass] of each material. Ensure that

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poises can be secured in any position.

Ensure that the discharge chute is not suspended from the weigh hopper or arranged so that cement or fly ash lodges or leaks from the hopper.

209, Watering, using a calibrated measuring tank, or by weight [mass] on approved scales.

operated shutoff valve for introducing air-entraining agents into the mix.

2 Batch plants may be equipped to proportion aggregates and bulk cement by automatic weighing devices of an approved type.

513.3.2 Mixers

1 Provide stationary or truck mixers that are the revolving-drum or revolving- blade type, and operate them uniformly at the manufacturer’s recommended mixing speed. Before use, obtain a copy of the manufacturer’s operating guide showing dimensions and arrangements of blades in reference to the original height and depth. Do not use equipment or components made of aluminum or magnesium alloys that will come in contact with concrete during mixing, transporting, or pumping.

2 Equip mixers with adequate water storage and a meter for accurately measuring and controlling water used in each batch.

3 Equip stationary mixers with an automatic timing device that can be locked. Interlock the timing device and discharge mechanism to prevent discharging any part of the batch until the specified mixing time has elapsed.

4 If used, ensure the provision of revolving-drum truck mixers that are watertight and capable of distributing materials uniforml y. Equip with electrically - or mechanically - actuated, continuous-registering, accurate revolution counters mounted so that the dial can be easily read.

513.3.3 Placing and Finishing Equipment

1 Do not use aluminum equipment for placing concrete. Provide internal, high- frequency vibrators that produce at least 7000 pulses per minute.

2 Provide tremies consisting of a watertight tube with a hopper at the top and a minimum diameter of 10 in [250 mm]. Equip the tube with a device to prevent water from entering while the tube charges with concrete. Support the tremie to allow free movement of the

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discharge end and to allow rapid lowering, when necessary to slow or stop the flow of concrete.

3 Provide concrete pumping equipment of adequate capacity for the work and pumps that produce a continuous stream of concrete without causing air pockets.

4 Provide a finishing-machine that complies with the following:

equipped for raising screeds to clear the screeded surface when traveling in reverse.

of which is a pan-type vibrator and the other a device with two or more rotating cylindrical drums at least 4 ft [1.2 m] long. Ensure that the vibration frequency of the devices is variable, with positive control from 3000 to 6000 vpm, and that both devices have positive control of the vertical position.

edges.

machine and can be removed without damaging new concrete.

reinforcing steel.

5 Provide two portable, lightweight work bridges for touch-up work and placing curing materials behind the finishing machine.

513.3.4 Grinding Equipment

1 For corrective grinding, provide a diamond-saw cutting machine capable of cutting through mortar and aggregate without breaking or dislodging aggregate particles.

513.

3.5Grooving Equipment

1 Provide a multi-blade arbor with diamond blades on a self -propelled machine built for grooving concrete pavements. Provide grooving machine with the following:

adjusts the cutting head height to maintain the specified groove depth; and

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513.4CONSTRUCTION

513.4.1 General

1 Notify the engineer at least 24 hours before placing concrete. The engineer will hold a conference before the placement of concrete bridge decks and as otherwise deemed necessary.

513.4.2 Weather Limitations

1 Heat the water, aggregates, or both when air temperatures are at or below 35 °F [2 °C]. Provide heated enclosures during curing when the air temperature is at or below 35 °F [2 °C]. Maintain the concrete surface at a minimum temperature of 60 °F [15 °C] for at least 72 hours after placing and at 40 °F [5 °C] or higher for the remainder of the 7- calendar day curing period.

2 Ensure that concrete delivered in air temperatures below 40 °F [5 °C] arrives at the project at a temperature from 60 °F [15 °C] to 90 °F [30 °C].

3 Heat aggregates, water, or both to a temperature from 70 °F [20 °C] to 150 °F [65 °C]. Heat aggregates by steam or dry heat and ensure that they are free of frozen lumps, ice, and snow. Do not use equipment or methods that alter or prevent air entrainment or produce hot spots in the aggregate.

4 Do not place concrete against frozen ground or in contact with materials having a temperature less than 35 °F [2 °C] . If necessary, heat items such as forms, reinforcing steel, adjacent concrete, and foundation materials to above 35 °F [2 °C] before placing concrete. During placement, keep delivery chutes or buckets at or above 35 °F [2 °C]. Remove and replace concrete damaged by frost or over-heating at no additional cost to the department.

5 The department will use the critical rate of evaporation as a limiting factor for the placement of concrete on bridge decks during hot weather . Do not start work if the evaporation rate is greater than 0.2 lb/ft²/h [1 kg/m²/h]. Stop placing concrete if the evaporation rate rises above 0.2 lb /ft²/h [1 kg/m²/h], or take action to reduce evaporation, such as by providing shade, using ice or other cooling methods in the concrete mix, and providing wind barriers. The department will perform and record evaporation rates before and at 1 hour intervals, or if environmental conditions significantly change during the placement operations.

6 The engineer will determine the deck surface evaporation rate from Figure 513.4.2- 2, Evaporation Nomograph, by measuring relative humidity near the deck, wind velocit y, air temperature, and concrete deck temperature (concrete mix temperature). The engineer will determine the relative humidity from Figure 513.4.2-1, Relative Humidit y, using the wet-bulb and dry-bulb temperatures. Discuss cold or hot weather operations at the prepour conference.

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7 When the air temperature exceeds 90 °F [32 °C], cool the forms, reinforcing steel, steel beam flanges, and other surfaces contacting the concrete mix, with a water spray. When the air or surface temperature is below 30 °F [-1 °C], warm the forms, reinforcing steel, steel beam flanges, and other surfaces contacting the concrete mix.

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513.4.3 Shipping and Storage

1 Protect cement from moisture damage. Store cement of different brands, type, or from different mills separately. Deliver portland cement and fly ash, unless provided as a blended cement, separately, and store them separately at the plant site location.

513.4.4 Mix Design

1 At least 30 calendar days before concrete production, send a mix design request to the Materials Program that includes the following:

specified in the Materials Testing Manual.

2 The Materials Program will complete two mix designs per class of structural concrete at no cost to the contractor; however, the contractor will be char ged $1,500 for each additional mix design requested.

3 For the specified class of concrete (use class A or B when not specified), supply structural concrete in accordance with Table 513.4.4-1, Concrete Class Table.

Table 513.4.4-1 Concrete Class

Parameter Class A B S Ultimate Design Strength—f c @ 28 d (psi [MPa]) 4000 [28] 3500 [24] 4000 [28] Min. Cement Content (lb/yd3 [kg/m3]) 611 [362] 564 [335] 611 [362] Max. Water : Cement Ratio 0.45 0.45 0.45 Max. Water: (Cement + Fly Ash) Ratio

0.45 0.45 0.45 Percent Entrained Air Content— Range 4.5 - 7.5 4.5 - 7.5 4.5 - 7.5 Consistency— Max. Slump (in [mm])(1) 6 [150] 6 [150] 6 [150] Percent Fine Aggregate(2) 41 ± 3 41 ± 3 41 ± 3

4 For the class specified, the Materials Program will determine the material proportions to be used for producing a workable mix within the specified consistency and proportions of ingredients shown in Table 513.4.4-1, Concrete Class Table.

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5 Concrete mixes will be designed using a minimum cement content or minimum combined cement plus fly ash/slag content 564 lb/yd 3 [335 kg/m3] for Class B Concrete and 611 lb/yd3 [362 kg/m3] for Class A and ClassS Concrete.

6 For Mixes incorporating fly ash, a minimum cement content of 451 lb/yd 3 [268 kg/m3] for Class B Concrete and 489 lb/yd 3 [290 kg/yd3] for Class A and ClassS Concrete is required with 20 to 25 percent by weight of the total cementitious material consisting of fly ash. Do not allow the total combined weight [mass] of portland cement and fly ash to vary more than 1 percent from the approved trial mix.

7 Slag cement may be substituted for portland cement at a minimum of 20 percent to a maximum of 50 percent by weight [mass] at a 1:1 replacement ratio, when approved by the Materials Program based on a satisfactory trial mix. A set accelerator may have to be incorporated in the mix to control set times. Do not allow the total combined weight [mass] of Portland cement and slag cement to vary more than 1 percent from the approved trial mix. 8 Fine and coarse aggregates may be adjusted up to 2 percent based on total weight [mass] of aggregate without department requiring new mix design. Ensure fine aggregate fraction does not exceed 44 percent of total aggregate weight [mass]. 9 Do not change the material source, properties, or gradation specification without the engineer’s approval. Do not work with changed or new materials until the engineer has determined and designated an appropriate mix design based on the new or altered materials, including cement, fly ash, slag cement and admixtures. 10 To evaluate alkali silica reactivity, ASR, conduct the AASHTO T303 (ASTM C1260) test using a combined sample of fine aggregate and coarse aggregate, in the same proportions that will be used in the concrete mix design. If the test results indicate an expansion at 16 days from casting of 0.10 percent or less, the aggregate is considered non-reactive and mitigation measures are not required. If the test results indicate an expansion at 16 days from casting of greater than 0.10 percent, mitigate the aggregat e reactivity through the use of a class F fly ash approved for ASR mitigation in accordance with the Materials Testing Manual , silica fume, and/or lithium nitrate additive. Demonstrate adequate mitigation by conducting the ASTM C1567 test and ensuring the test results indicate an expansion at 16 days from casting of 0.10 percent or less. When conducting the ASTM C1567 test, use a combined sample of fine aggregate and coarse aggregate, in the same proportions that will be used in the concrete mix design and use the cementitious material that is to be used in the mix design. Ensure the AASHTO T303 (ASTM C1260), and ASTM C1567 tests have been performed within 12 months of the submittal date. The Materials Program maintains the option to conduct AASHTO T303 (ASTM C1260) and ASTM C1567 testing for verification.

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513.4.5 Forms

513.4.5.1 General

1 Use forms that are sufficiently rigid to prevent distortion from concrete pressure and other loads incidental to construction, including vibration. Construct and maintain forms mortar- tight and to prevent joints from opening. Ensure that forms produce smooth, even concrete surfaces in proper alignment. Keep forms free of dents and their surfaces free from foreign matter.

2 Clean previously used forms of all foreign material. Maintain the shape, strength, rigidity, water-tightness, and surface smoothness of reused forms.

3 Use forms that provide a smooth surface for forming exposed concrete surfaces. Chamfer corner angles measuring less than 120 degrees that will be exposed in the finished structure with a 1in [25 mm] triangular strip.

4 Countersink bolt and rivet heads on the inside of forms. Use clamps, pins, or other connecting devices designed to hold the forms rigidly together and allow removal without damaging the concrete.

5 To prevent the adherence of concrete, treat forms with a form-release agent before placing reinforcement, or saturate untreated wood forms with water immediately before concrete placement. Do not use agents that will adhere to or discolor concrete.

513.4.5.2 Stay-in-Place Forms

513.4.5.2.1 General

1 The department will allow the use of stay-in-place slab forms for bridge deck construction; however, the department will not pay for any increase in the quantity of concrete due to such use.

2 Store stay-in-place forms above the ground surface. Protect forms from moisture.

513.4.5.2.2 Design and Shop Drawings

1 Design stay-in-place forms and angle supports to support the dead load of the form, reinforcing steel and concrete, and an additional 50 lb/ft² [2.4 kPa] for construction live load. Ensure a unit working stress in the steel sheet of less than 0.725 times the specified minimum yield strength of the material furnished or 36,000 psi [248 MPa], whichever is less. Compute physical design properties in accordance with the latest published edition of American Ir on and Steel Institute Specification for the Design of Cold-Formed Steel Structural Members. Ensure a maximum dead load deflection of forms supporting slabs no greater than 1/180 of the span or ½ in [12 mm], whichever is less. Ensure a distance from the face of stay-in-place forms to the face of reinforcing steel of at least 1 in [25 mm].

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Do not exceed 15 psf [720 Pa] for the weight of the forms and additional concrete, including form deflection. Do not extend vertical legs of support angles past the bottom of the bottom reinforcing steel mat or use these legs to support the reinforcing steel.

2 Submit shop drawings to the State Bridge Engineer, in accordance with Subsection 105.2, Working Drawings. Ensure that the stay- in-place form fabricator verifies the appropriate girder dimensions with the girder fabricator before providing shop drawings so that the drawings are representative of actual girder dimensions.

513.4.5.2.3 Stay-in-Place Form Installation

1 Attach stay-in-place forms to concrete girders by welding or bolting to cast- in anchors. Ensure that the form fabricator supplies the anchors to the girder fabricator.

2 Use attachment devices from the form fabricator to attach stay -in-place forms to steel- girder bridge superstructures; do not weld or bolt.

3 When required, perform cutting with a sa w, gas torch, or shears. Do no damage adjacent girders or structural elements during cutting process.

4 Repair galvanized coating damaged during fabrication, shipping, storage, or installation of stay-in-place forms in accordance with Subsection 501.4.2.9, Repair of Galvanizing.

5 Place concrete in accordance with Subsection 513.4.11, Placing Concrete. Do not dump concrete near laps in forming, at mid-span of corrugated sheets, or in any manner causing excessive concentrated construction loads.

6 When required by the engineer, remove sections of stay- in-place forms to examine concrete surfaces for cavities, honeycombing, and other defects. If defects are found, repair them or replace the concrete, as approved by the engineer. The department does not require the replacement of removed forms; however, repair adjacent forms to present a neat appearance and ensure their satisfactory retention.

513.4.6 Falsework

1 Build falsework on a firm foundation and strong enough to carry the superimposed load without excessive deflection, settlement, or stress. Design falsework to allow for normal settlement so that the final position of the parts of the structure will meet specified dimensions and elevations. Leave falsework in place during placement of the entire superstructure, except curbs. Remove supports to allow the concrete to uniformly and gradually take the stresses of its own weight [mass]. Remove falsework piling to at least 24 in [600 mm] below the original ground or finished surface, whichever is lower. Remove and replace any part of the structure damaged or not true to line and grade because of sag, settlement, or failure of the falsework, at no additional cost to the department.

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513.4.7 Deck Drains, Weep Holes, and Eye Bolts

1 If specified, install deck drains along the front face of the curb. If specified, provide and install structural steel drains in accordance with Section 501, Structural Steel.

2 Provide and install weep holes in abutment walls, wingwalls, and retaining walls, as specified.

3 When specified for attaching fence to box culverts and bridges, anchor eye bolts in the concrete.

513.4.8 Batching

1 Control weight [mass] of components including cement, fly ash and aggregates to within 1 percent of requirements.

sack unless the fractional weight [mass] is known. Do not use cement damaged by moisture. Weigh bulk cement and fly ash on approved scales in accordance with Subsection 109.1.4, Weighing Procedures and Equipment.

Do not use segregated aggregates or those mixed with earth or foreign material.

Stockpile or bin aggregates that have been washed, produced, or handled hydraulically to drain at least 12 hours before batching. The department will accept rail shipment lasting more than 12 hours as adequate binning if the cars allow free drainage. The department may require longer storage if aggregates have a high or nonuniform moisture content.

containers, and protect them from freezing. Before use, mix the admixture thoroughly with a mechanical stirring device. Except as indicated below, introduce air-entraining admixtures with a calibrated dispenser into the stream of mixing water. Fully discharge the required quantity before all the mixing water has entered the drum.

A dd air-entraining and other approved admixtures to the concrete mix separately and do not intermingle them before entering the concrete batch. Before adding admixtures other than those for air- entraining, obtain the engineer’s approval for the proposed methods and equipment.

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513.4.9 Mixing and Delivery

513.4.9.1 General

1 Use a concrete plant with sufficient capacity and hauling vehicles to ensure continuous concrete delivery at the rate required for uninterrupted placement and without allowing intervals between batches longer than 20 minutes.

1 Mix and deliver concrete to the site by one of the following:

agitators.

3 Clean mixers to prevent build-up of materials. Repair or replace the pick-up and throw- over blades in the drums when worn 1 in [25 mm] or more. Repair or replace mixers and agitators with accumulated hard concrete or worn blades. When blade wear or mixing uniformity is questionable, the engineer will take consistency tests. If the measured consistency falls outside limits specified, do not use the concrete, and repair or replace the mixing unit. The engineer will conduct uniformity tests for mixing time or mix consistency in accordance with AASHTO M 157.

4 Use a mixer drum speed in accordance with the manufacturer’s plant operating directions. Do not mix a volume of concrete greater than the mixer’s rated capacity or greater than the amount needed for immediate use. Do not use concrete that has developed an initial set or retemper concrete by adding water or additives.

5 Empty the mixer, including rinse water, at the plant before charging a batch of concrete.

6 Before charging the mixer, wet the inside of the drum thoroughly and eject free water. Charge the batch into the mixer so that some water enters before the cement and aggregates. If approved, a portion of the mixing water may be withheld from the batch materials in order to adjust the consistency of concrete at the placement site. Charge into the drum the water that is used in batching within the first one-quarter of the specified mixing time. Batch and charge cement into the mixer with no loss of cement.

7 Ensure that concrete is homogeneous and mixed thoroughly with no evidence of lumps or undispersed cement. Mix admixtures uniformly throughout the batch.

8 When the concrete temperature is from 50 °F [10 °C] to 70 °F [21 °C], place within 90 minutes of introducing the cement to the aggregates or water. For each one degree increase in concrete temperature above 70 °F [21 °C], reduce the 90-minute placing time by 2 minutes [4 minutes for one degree Celsius]. Other conditions that speed the stiffening

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of the concrete may warrant shortening the placing time to 45 minutes or less.

9 Ensure that the mixed concrete temperature immediately before placing is from 50 °F [10 °C] to 90 °F [32 °C]. If ice is used as part of the mixing water, do not discharge concrete from the mixer until the ice melts.

10 When stabilizers are used, use in accordance with manufacturer's recommendations to increase maximum placing time, not to exceed additional 90 minutes. Apply an evaporation retardant after placement to exposed concrete surfaces which cannot be protected immediately with the curing medium.

11 As applicable, admixture dosage rates in the approved mix design may be adjusted within the manufacturer’s normal dosage range without requiring a new mix design.

513.4.9.2 Mixing Time

materials are in the drum and ending with the start of the discharge. For central mixers with a capacity of 10 yd³ [8 m³] or less, mix for at least 60 seconds. For larger mixers, mix for the time recommended by the mixer manufacturer.

blades, at the manufacturer’s recommended mixing speed. At the plant, record the number of revolutions at mixing speed on the concrete batch ticket. Actuate the revolution counter after all materials, including mixing water, are in the mixer drum. After mixing, rotate the drum at the agitating speed recommended by the manufacturer. Do not exceed a total of 300 revolutions.

1 Adjust mixing time as necessary to obtain a uniform mix.

513.4.9.3 Transporting

1 Transport mixed concrete in truck agitators or mixers operating at the agitating speed designated by the manufacturer. Provide mixed concrete at the delivery point suitable for placement and meeting specified requirements.

2 Deliver each load of concrete with an accompanying department-furnished “Concrete Batch Ticket” (Form E-1 17) or with a computer-generated ticket providing the same information.

513.4.9.4 On-Site Mix Adjustment

1 Do not add mixing water to the concrete while hauling; if necessary to increase the slump, add remaining mixing water at the placement site. Accurately meter added water. Do not exceed the allowable ratios of water-to-cement or water- to-cement-plus-fly-ash specified

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in T able 513.4.4-1, Concrete Class T able. If water is added on-site, use up to 30 additional mixing revolutions, if necessary.

2 The engineer may approve the use of on-site admixtures for slump and air enhancement; if used, mix additionally in accordance with the admixture manufacturer’s recommendations. 3 Do not make more than two on-site mix adjustments, defined as the addition of water or an on-site admixture. Do not redose partial loads. Adjust the mix on-site while the concrete is plastic and within 45 minutes of starting the initial mixing if no stabilizers are used. Do not add water or other materials to concrete that has started to set.

513.4.10 Testing

1 The engineer may test for consistency of individual loads at approximately the beginning, midpoint, and end of the load. If slump tests on any one load vary by more than 1½ in [38 mm], do not use the mixer until the condition is corrected.

2 The engineer will take concrete samples for slump and air content tests at the outlet of the mixer truck. For pumped concrete, slump and compressive strength samples will be taken either after pumping and before screeding or before pumping. Air content samples for pumped concrete will be taken after pumping and before screeding. Samples represent the entire batch.

513.4.11 Placing Concrete

513.4.11.1 General

1 Place concrete after forms and reinforcing steel have been checked, with the engineer present, after forms have been cleaned, and immediately after wetting surfaces on which concrete will be placed.

2 Place unsegregated concrete without displacing reinforcement. Do not deposit a large quantity at any point and run, work, or drop concrete into or along forms for a distance of more than 5 ft [1.5 m], unless confined by closed chutes or pipes. Fill forms by depositing concrete as near final position as possible. Work coarse aggregate back from the forms and around reinforcement without displacing the bars. After the concrete obtains initial set, do not jar forms or place stress on reinforcing steel.

3 Incline chutes to allow the free flow of concrete. Do not add water to concrete to promote flow in chutes.

4 Place concrete continuously in each section of the work to complete integral placements. Place and consolidate concrete in horizontal layers no deeper than 18 in [450 mm] for beams and slabs or 30 in [750 mm] for footings, walls, or columns. Place layers before the previous layer obtains an initial set. Do not taper the ends of layers;

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place with nearly square ends and level tops. Consolidate each layer to prevent separation planes between layers.

5 Consolidate the external surface of concrete during placement with spading tools and vibrators. Place concrete to force coarse aggregate from the surface and bring mortar against the forms producing a dry, smooth finish, without air pockets or honeycombs.

6 For pumped concrete, arrange equipment to protect fresh concrete from vibrations. After pumping, dischar ge remaining concrete in the pipeline without contamination or segregation.

7 Keep chutes, troughs, and pipes clean by flushing with water after each run. Discharge flushing water away from the placed concrete.

513.4.11.2 Consolidation

1 Consolidate concrete with mechanical vibrators operating in the concrete; supplement by hand spading as necessary. Provide at least two vibrators at the site when placing more than 10 yd³ [8 m³] of concrete. Work the concrete around the reinforcement and embedded fixtures and into form corners and angles. Do not use vibrators to flow or run concrete into position. Vibrate concrete for a period long enough to compact but do not cause segregation.

2 Insert the vibrator vertically with a distance between insertions of approximately 1 ½ times the radius of influence, defined as the area visibly af fected by the vibrator. Overlap adjacent radii of influence by approximately 2 in [50 mm]. With the vibrator, penetrate rapidly to the bottom of the layer and hold in place from 5 to 15 seconds. Stop vibrating in one location when lar ge aggregate is embedded and escaping air bubbles stop appearing.

513. 4.11.3 Joints

1 Locate construction joints as specified or approved by the engineer. For an emergency joint, form a keyway or insert dowel bars to provide adequate bond across the joint.

2 Rough-float horizontal joints to consolidate the concrete surface; do not key. When placing new concrete on the joint, draw the forms tight against existing concrete. Clean the joint surface of foreign matter with wire brushes, brooms, or sand- blasting, and wet immediately before placing concrete.

3 Key vertical joints; form with oiled, beveled timber.

4 Do not make joints with concrete sloping to a thin feathered edge. Use bulkheads for nonhorizontal joints and for horizontal joints that would otherwise lead to a feathered edge

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in the next layer. Form such joints with a temporary bulkhead so that the next layer will end in a body of concrete at least 6 in [150 mm] thick.

5 Sandblast construction joints at the tops and bottoms of T- girder stems, box girder webs, and box culvert side walls to remove foreign matter , including laitance and curing compound, and to expose clean aggregate. Sandblast or otherwise clean openings for joint materials before placement to ensure proper bonding with concrete. Let joints dry before placing joint material.

513.4.11.4 Grout Work

1 Prepare areas to be grouted in accordance with manufacturer’s recommendations. Fill completely and pack grout into recesses and holes on surfaces, under structural members, and at other locations specified. Ensure that locations where grout could escape are mortar-tight before placing. For at least three calendar days after placement, cure grout surfaces by the water method and keep free of loads. Remove and replace improperly cured or otherwise defective grout at no additional cost to the department.

513.4.11.5 Footings

1 When approved by the engineer, forms may be omitted on sides of concrete footings not exposed in the finished structure; if doing so, place concrete directly against the sides of the footing excavation.

513.4.11.6 Cofferdam Seals

1 If excavations cannot be dewatered before placing concrete, construct an underwater concrete cofferdam seal at least 24 in [600 mm] thick from concrete containing 25 percent extra cement. Do not build the top of the seal higher than the specified bottom of the footing. Place the concrete in a compact mass, in its final position, using a tremie. Maintain still water at the point of deposit, and use watertight cofferdam forms. Do not place concrete other than that for cofferdam seals underwater. Fill the tremie by a method that prevents washing of the concrete. Submerge the discharge end completely in concrete to prevent water entry. With a batch in the hopper, start the flow of concrete by slightly raising the dischar ge end but still keeping it subme rged in deposited concrete. Continue the flow until completion of a monolithic, homogeneous seal.

2 Cure the concrete at least five calendar days before dewatering. Increase the time if the seal is to withstand hydrostatic pressure and the seal has been placed in water less than 45 °F [7 °C]. Exclude from the counted curing time periods when water temperature is continuously below 40 °F [5 °C]. Take concrete test cylinders and cure in similar conditions to determine strength. After sufficient time to ensure adequate seal strength, dewater the cofferdam, and clean the concrete top of scum, laitance, and sediment.

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513.4.12 Finishing Concrete Surfaces

513.4.12.1 Finish Types

immediately after form removal. Finish horizontal surfaces while concrete is plastic.

Do not add water to concrete surfaces for finishing operations. If approved by the engineer and applied in accordance with the manufacturer’s recommendations, a commercial evaporation retardant may be used.

Remove fins and irregular projections from exposed surfaces. Clean cavities and other defects thoroughly, saturate with water, and carefully point and true with a mortar of cement and fine aggregate mixed in the proportions of the concrete being finished. Use mortar for pointing within 30 minutes of mixing. Use commercial patching mixtures only when approved by the engineer. Cure patches in accordance with Subsection 513.4.13, Curing Concrete. Tool construction and expansion joints in completed work, and free from mortar and concrete.

Ensure the mortar used in pointing is set before wetting . Rub surfaces with a medium-coarse carborundum stone faced with a small quantity of mortar composed of cement and fine sand mixed in proportions of the concrete being finished. Rub until form marks, projections, and irregularities have been removed; all voids are filled; and a uniform surface is obtained. Leave the paste produced by rubbing. After placing concrete above the treated surface, obtain the final finish by rubbing with a fine carborundum stone and water until the entire surface is smooth and uniform in color. After final rubbing, and when the surface is dry, rub with burlap to remove loose powder.

oat Finish. Obtain a float finish for horizontal surfaces by placing an excess of material in the form and removing or striking off the excess with a template, forcing coarse aggregate below the mortar surface without creating a concave surface. After striking-off, work and float the surface with a floating tool. Do not use aluminum floats. Before the finish sets, remove the surface cement film with a fine brush, leaving a fine-grained, smooth, sanded texture.

513.4.12.2 Finishing Bridge Decks

513.4.12.2.1 General

1 Finish bridge decks with a deck finishing machine on rails. Use hand tools only where necessary. Set up finishing machines 24 hours before use to allow inspection by the engineer in daylight before each placement.

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2 Before placing concrete, and under the engineer’s inspection, verify the adjustment and operation of deck finishing machines by moving the machine over the full length of the deck section and traversing the float completely across end bulkheads. Check the specified cover over reinforcing steel and make necessary adjustments. 3 The engineer will randomly check the depth of fresh concrete immediately behind the screed and over reinforcing steel across the full width and length of the bridge deck. If depth checks indicate variations greater than ½ in [12 mm], take corrective action immediately, which may involve additional tie downs for reinforcing steel or adjusting screed elevations. Provide a working bridge behind the screed that can be used for depth checks.

4 Immediately after screed floating and while concrete is plastic, test the slab surface for irregularities using a 10-foot [3 m] straightedge. Hold the straightedge in successive positions parallel to the road centerline and in contact with the slab surface for the entire area of the slab. Move the straightedge in stages of no more than half its length. Correct variations immediately; fill depressions with freshly-mixed concrete or strike off projections. Consolidate and refinish corrected areas. Repeat straightedge testing and refloating until the slab surface has no deviations greater than ¼ in [6 mm]. Use a commercial evaporation retardant approved by the engineer and applied in accordance with the manufacturer’s recommendations

5 After finishing the slab surface and allowing water sheen to evaporate, finish the concrete surface by dragging a seamless strip of damp burlap over the full width of the surface. Use a drag consisting of burlap layers with sufficient length in contact with the concrete to slightly groove the surface. Move the drag forward with a minimum bow of the lead edge. Keep the drag damp, clean, and free of hardened concrete particles.

6 Grooved deck in accordance with Subsection 513.4.15, Grooving of Hardened Concrete.

513.4.12.2.2 Tine Finish---Vacant

513.4.12.2.3 Surface Tolerance

1 When concrete has set sufficiently to allow walking, and no later than the day after placement, the engineer will check the surface with a straightedge and mark variations in excess of ¼ inch in 10 ft [6 mm in 3 m]. Grind high spots with a diamond- saw cutting machine. Repair low spots as approved by the engineer. Grind or patch to smooth the surface. At no additional cost to the department, remove portions or all of the deck if corrective work is not satisfactory.

2 Protect concrete against damage until it obtains final set.

Structural Concrete SECTION 513

513.4.13 Curing Concrete

1 If forms are removed in less than five calendar days, cure concrete immediately with water or impervious compound methods after removal of forms; curing is not necessary if concrete is protected by metal or treated wooden forms for five calendar days or more. Keep untreated wood forms moist during curing period.

2 When the weather would otherwise cause concrete mixing water to evaporate rapidly, apply a fine mist to concrete surfaces until curing is complete. Alternatively, use a commercial evaporation retardant approved by the engineer and applied in accordance with the manufacturer’s recommendations.

3 When using the water method, keep concrete continuously damp for at least five calendar days by applying water with an atomizing nozzle that produces a fog mist; do not direct water under pressure on the concrete or allow water to accumulate, causing concrete to flow or wash. Keep surfaces damp throughout curing, and use burlap or other covering approved by the engineer to retain moisture.

4 When using impervious curing compound, give surfaces the required surface finish before applying compound. Apply curing compounds in accordance with Table 513.4.13- 1, Impervious Curing Compound Applications. During finishing, protect concrete by the water curing method. Mix compound thoroughly an hour or less before use, and apply uniformly. Apply twice, each time at a rate of 1 gal per 300 ft² [1 L per 7 m²] of surface area. For concrete bridge decks and other exposed concrete, apply the first time immediately after the disappearance of free water from the surface. For formed concrete, apply immediately after removing forms. If the concrete surface is dry, spray with a fine water mist, and apply curing compound immediately after the disappearance of free water from the surface. Apply compound the second time after the first application has set and at right angles. During curing, spray any uncovered surfaces with a fine water mist. Protect the coating against marring for at least ten calendar days after application. Recoat marred surfaces at the specified rate. Stop using compound if it leaves a streaked or blotchy appearance; cure with water until the cause of the problem is corrected.

Table 513.4.13-1 Impervious Curing Compound Applications Application Material Concrete Pavement Premium White Approach Slabs Premium White Bridge Decks Premium White Silica Fume Concrete Premium White Curb and Gutter, Double Gutter Premium White or Premium Clear Sidewalks and Bike Paths Premium White or Premium Clear Median Paving Premium White or Premium Clear

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Table 513.4.13-1 Impervious Curing Compound Applications Application Material Concrete Pavement Repair Premium White or Premium Clear Concrete Barrier Premium White or Premium Clear Cast-in-Place Drainage Elements Premium White or Premium Clear Decorative Concrete Premium Clear Slope Paving Basic Ditch Paving Basic Erosion Control Basic Culvert Boxes Basic Exposed Horizontal Surfaces of Formed Structures Basic Surfaces Exposed After Form Removal Basic

5 Polyethylene sheeting meeting the requirements of AASHTO M 171 may be used along with the preceding methods. Overlap sheets at least 18 in [450 mm] and extend at least 12 in [300 mm] beyond the outer edges of the concrete. Seal, weight, cover, or tie sheet edges to prevent premature removal.

6 Cure all concrete at least five calendar days. Do not use the water method in temperatures below 35 °F [2 °C].

7 Do not allow vehicles on any span until concrete has obtained at least 80 percent of its ultimate design compressive strength (f'c). Do not allow loads greater than 6000 lb [2700 kg] on any span until the concrete obtains f'c.

513.4.14 Removal of Forms and Supports

1 Do not remove structural forms until concrete is strong enough to withstand damage once forms are removed. Remove forms and supports such that concrete gradually and uniformly takes stresses due to its own weight. Remove forms by methods that do not mar, gouge, or chip concrete surfaces; overstress concrete members; or distort formwork. Leave surfaces clean and umblemished.

2 Forms and their supports may be removed and subsequent loads, excluding backfill, may be placed when both conditions of Table 513.4.14- 1, Form and Support Removal and Loading of Concrete, are met, as approved by the engineer.

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3 Backfill when the requirements of Subsection 206.4.5, Backfilling, or Subsection 212.4.7, Backfill, are met.

513.4.15 Grooving of Hardened Concrete

1 Straightedge and repair the bridge deck before grooving. Do not groove the deck before the end of the concrete curing period.

2 Cut grooves parallel or perpendicular to the centerline of the roadway.

3 Begin grooving 12 in [300 mm] from the gutter line or face of rail and run in a continuous pattern to 12 in [300 mm] from the opposite gutter line or face of rail. The Contractor may increase the 12 in [300 mm] dimension on one side of the deck to as much as 24 in [600 mm], if the cle arance of the grooving machine does not allow a closer approach to the railing. Table 513.4.14-1 Form and Support Removal and Loading of Concrete Structural Element Form and Support Removal Subsequent Loading Strength of Concrete Based on % of Design Strength Time(1) Strength of Concrete Based on % of Design Strength Time in Days (1) Footings/Sleeper slabs 60 12 h 80 2 Drilled shafts 60 12 h 80 3 Columns/Pier Walls 60 1 d 100 5 Abutment/Sills/ Diaphragms 60 12 h 80 3 Bent Caps/Pier Caps 80 7 d 100 14 Concrete superstructures (T-beam, flat slab) 80 7 d 100 14 Bridge Decks 80 7 d 80 7 Floor and wingwall footings of box culverts 60 12 h 80 2 Walls of box culverts 60 1 d 80 3 Top slab of box culverts 80 7 d 80 7 Wingwalls / Retaining Walls 60 12 h 80 3 Approach Slabs 100 3 Other vertical surfaces not carrying load 60 12 h - - (1)From time of the last placement in the forms and without counting days when air temperature is below 40 °F [5 °C].

Structural Concrete SECTION 513

4 Provide grooves that begin and end within 2 in to 4 [50 mm to 100mm] in of expansion joints, contraction joints, and ends of the slab.

5 Lay out the grooving accurately before cutting begins. Provide grooves that are ⅛ in [3 mm] wide and from ⅛ in to ¼ in [3 mm to 6 mm] deep.

6 Space grooves in a random pattern from ½ in to ⅞ in [12 mm to 19 mm] centers.

7 Continuously remove resulting slurry or residue immediately following grooving operations. Clean the lands and the grooves and leave the surface free of slurry residue and other deleterious material. Remove grooving residue by flushing, vacuuming, or other methods approved by the engineer.

513.5MEASUREMENT and PAYMENT

1 The engineer will measure Class A Concrete, Class B Concrete, and ClassS Concrete as one complete unit or by the cubic yard [cubic meter]. The engineer will compute volumes from the neat lines specified.

2 The department will pay as follows:

Pay Item

Pay Unit Measure to the Nearest Pay to the Nearest Class A Concrete LS, CY [LS, m3] LS, 0.1 ft [LS, 0.5 m] LS, 0.1 CY [LS, 0.1 m3] Class B Concrete LS, CY [LS, m3] LS, 0.1 ft [LS, 0.5 m] LS, 0.1 CY [LS, 0.1 m3] ClassS Concrete LS, CY [LS, m3] LS, 0.1 ft [LS, 0.5 m] LS, 0.1 CY [LS, 0.1 m3]