460 Page 313460 STRUCTURAL CONCRETE
460.1DESCRIPTION
This work consists of falsework and form construction, and the furnishing, handling, placing, curing, and finishing of concrete for bridges, box culverts, and miscellaneous structures.
460.2MATERIALS
Materials will conform to the following Sections: A.Cement: Section 750. Type II cement will be used, unless otherwise specified. B.Fine Aggregate: Section 800. C.Coarse Aggregate: Section 820. D.Water: Section 790. E.Admixtures: Section 751 and Section 752. F.Reinforcing Steel: Section 1010 . G.Curing Materials: Section 821. H.Preformed Expansion Joint Filler: Section 860. I.Joint Sealer: Section 870. J.Fly Ash: Section 605 and Section 753. K.Grout: Grout will be a commercially available non-metallic, non-shrink grout capable of attaining a minimum compressive strength of 4500 psi and will conform to the requirements of ASTM C1107.
460.3CONSTRUCTION REQUIREMENTS
A.Concrete Quality and Proportion: The Contractor will design and be responsible for the performance of all concrete mixes used in structures. Mix designs will be modified during the course of the work when necessary to assure compliance with the requirements for strength and consistency. All mix designs and any modification thereto, including changes in admixtures, will be approved by the Concrete Engineer prior to use. Mix design data and test results will be recorded on a DOT-24 and submitted to the Engineer a minimum of 40 calendar days prior to anticipated use. The mix design will produce a concrete conforming to the following requirements: 460 Page 314Table 1 Class of ConcreteMinimum Cement Content*1 (Pounds / cubic yard)Maximum Water/ Cementitious Material Ratio*3Slump Range at Time of Placement*4Entrained Air Content Range*5 (%)Minimum Coarse Aggregate Content*6 (%)Minimum 28 Day Compressive Strength (PSI) A40 585 565 if well graded*2Field maximum listed on mix design1 - 5½ inches 5.0 to 8.0 50 4000 A45600 575 if well graded*2Field maximum listed on mix design1 - 5½ inches 5.0 to 8.0 50 4500 A50650 625 if well graded*2Field maximum listed on mix design1 - 5½ inches 5.0 to 8.0 50 5000 *1The maximum cementitious content (total cement, fly ash, and other cementitious admixture) content will be 800 pounds per cubic yard. The Contractor will substitute a portion of the cement with Class F modified fly ash in accordance with replaced will be 20% to 25% by weight. The ratio of substitution of fly ash to cement will be 1:1 by weight. *2 Well graded concrete mixes are those mixes conforming to the aggregate gradation shown in Chart A for size #15 coarse aggregate or Chart B for size #20 coarse aggregate. Size #20 coarse aggregate will only be allowed when specified in the plans *3The mix design will establish a maximum water/cementitious material ratio, which will not exceed 0.45 *4The slump of concrete used in bridge decks and bridge sidewalks poured with the bridge deck will be maintained between 2 and 4 inches at the time of placement. The slump of concrete used in cantilevered bridge deck sidewalks poured separately from the bridge deck will be maintained between 2 and 5½ inches at the time of placement. *5Concrete used in bridge decks, bridge sidewalks, and barrier curbs will contain 5.5% to 7.5% entrained air. *6The minimum coarse aggregate content is determined by the percent weight of the total aggregates. The absolute volume method as described in the American Concrete Institute Publication 211.1 will be used in selecting mix proportions. If a well graded concrete mix is used, the combined aggregate proportions submitted for mix design verification will conform to Chart A or Chart B. The mix design will be based upon obtaining an average concrete compressive strength 1200 psi above the specified minimum 28 day compressive strength. The Department may use laboratory trial batches to verify the concrete mix submitted. 460 Page 315Chart A Chart B1" 0.45 POWER GRADATION 05101520253035404550556065707580859095100 #100#200 #50 #30 #16 #8 #4 3/8 1/2 3/4 1 Upper Low er Seive Limit Limit 1" 100 92 3/4" 96 80 1/2" 81 65 3/8" 72 56 #4 55 39 #8 42 26 #16 33 17 #30 27 11 1.5" 0.45 POWER GRADATION 05101520253035404550556065707580859095100 #16 #8 #4 1/2" 1.5" 1" 3/4"#30#503/8"#200 #100 Upper Lower Seive Limit Limit 1.5" 100 92 1" 88.5 75 3/4" 81 65 1/2" 68 52 3/8" 61 45 #4 47 31 #8 37 20 #16 29 13 #30 23 7 460 Page 3161.Concrete Mix Design Performance: Satisfactory performance of the proposed concrete mix design will be verified by laboratory tests on trial batches. The trial batches must be performed by a testing facility approved by the Concrete Engineer. Trial batches will be conducted in accordance with the American Concrete Institute Publication ACI 211.1, ACI 318, ASTM C192 and the following: a.A minimum of three trial batches will be performed. b.The slump of each trial batch will be within ±3/4 inch of the maximum specified. c.The air content of each trial batch will be +0.5% to -1.0% of the maximum specified. The results of each trial batch test will be furnished by the Contractor to the Engineer at the time the proposed mix design is submitted. The as-batched results will include the following: material weights, aggregate moistures, fresh concrete test results (slump, air content, unit weight, and mix temperature), water cementitious material ratios, aggregate gradations, compressive strengths, and aggregate qualities. In addition, aggregate supplier production test results will be provided. 2.Alternate Concrete Mix Design: A concrete mix design previously used will be considered in compliance with the mix design requirements provided all of the following conditions are met: a.The concrete mix proportions are in accordance with Section 460.3 A. b.The mix design, including all material and admixtures, are identical to those previously used and tested. c.The average 28 day compressive strength of 10 or more test results from an approved testing facility is at least 1.34 standard deviations above the specified strength. These test results and associated batch tickets will be submitted to the Engineer. No more than 1 in 10 compressive strength test results may be below specified strength. d.The Contractor submits all supporting information for the mix design, including but not limited to, fresh concrete tests and material properties. B.Determination of 28 Day Compressive Strength and Acceptance Criteria: The Engineer will be responsible for the sampling, preparing, properly curing, and breaking of all concrete cylinders for concrete compressive strength in accordance with the Materials Manual. The 28 day compressive strength will be determined in accordance with SD 420. The 28 day compressive strength acceptance criteria will be as follows: 1.Concrete Cylinder Testing: If the 28 day cylinder compressive strength is greater than or equal to the specified 28 day compressive strength, the quantity of concrete represented by the cylinder will be accepted. If the 28 day cylinder compressive strength is less than the specified 28 day compressive strength, the backup cylinder will be broken as soon as possible after breaking the 28 day 460 Page 317cylinder. The compressive strength for the backup cylinder will be the strength at the time it was broken and will not be corrected back to a 28 day strength. 2.Backup Concrete Cylinder Testing: If the backup cylinder compressive strength is greater than or equal to the specified 28 day compressive strength, the quantity of concrete represented by the cylinder will be accepted. If the backup cylinder compressive strength is less than the specified 28 day compressive strength by no more than 500 psi, the Department’s Bridge Construction Engineer will determine if the unit is structurally adequate at the average compressive strength of the 28 day and the backup cylinder. If structurally adequate, the concrete will be allowed to remain in place and will be subject to price adjustment based on the average compressive strength of the two cylinders. If the analysis shows the average cylinder compressive strength is not structurally adequate, the concrete will be removed and replaced at the Contractor’s expense. If the average compressive strength of the 28 day and the backup cylinder compressive strength is more than 500 psi, below the specified 28 day compressive strength, the concrete represented by the cylinders will be removed and replaced. 3.Suspect Test Results: If there is some reason to suspect that the compressive strength test results are not valid due to a damaged concrete cylinder, malfunction of testing equipment, etc. or that the test results are not representative of the in place concrete, the Department may core the concrete represented by the cylinders. When cores are deemed necessary by the Department and are required at no fault of the Contractor, the Department will arrange for the additional testing and all costs will be borne by the Department. The coring and compressive testing will be in accordance with the current edition of AASHTO T 24. If the average core compressive strength is greater than or equal to the specified 28 day compressive strength, the quantity of concrete represented by the cylinders will be accepted. If the average core compressive strength is less than the specified 28 day compressive strength by no more than 500 psi, the Department’s Bridge Construction Engineer will determine if the unit is structurally adequate at the lower compressive strength. If structurally adequate, the concrete will be allowed to remain in place and will be subject to price adjustment. If the analysis shows the average core compressive strength is not structurally adequate, the concrete will be removed and replaced at the Contractor’s expense. If the average core compressive strength is more than 500 psi below the specified 28 day compressive strength, the concrete represented by the cylinders will be removed and replaced. 4.Contractor Coring Option : If the Contractor disputes the accuracy of the 28 day cylinder compressive strength, the Contractor has the option to core the concrete represented by the cylinders. Upon notification of a deviation from the specified compressive strength, the Contractor will provide written notification of the intent to core the represented 460 Page 318concrete within 5 calendar days. Coring will be done in accordance with Section 460.3 B.5. If the average core compressive strength is greater than or equal to the specified 28 day compressive strength, the quantity of concrete represented by the cylinder will be accepted. If the average core compressive strength is less than the specified 28 day compressive strength by no more than 500 psi, the Department’s Bridge Construction Engineer will determine if the unit is structurally adequate at the lower compressive strength. If structurally adequate, the concrete will be allowed to remain in place and will be subject to price adjustment. If the analysis shows the average core compressive strength is not structurally adequate the concrete will be removed and replaced at the Contractor’s expense. If the average core compressive strength is more than 500 psi below the specified 28 day compressive strength, the concrete represented by the cylinders will be removed and replaced. 5.Coring & Compressive Testing: If the Contractor utilizes the option to core as specified in Section 460.3 B.4, the Contractor will arrange for an independent testing laboratory to perform the coring and compressive testing within 14 calendar days of notification of the failing compressive strength of the backup cylinder. The independent testing laboratory must be approved by the Department’s Concrete Engineer prior to starting the coring and compressive testing. The coring and compressive testing will be in accordance with the current edition of AASHTO T 24. The independent testing laboratory will take 3 cores of the area representing the cylinders in which the compressive strength is in question and test them for compressive strength. The coring and compressive testing will be witnessed by the Department’s Region Materials Engineer. The Contractor will be responsible to locate the reinforcing steel prior to coring. It is critical that the coring operation avoids all reinforcing steel. The core holes will be grouted with a grout that conforms to Section 460.2 . The average compressive strength of the 3 cores will be used for the determination of the concrete compressive strength. If the average core compressive strength is greater than or equal to the specified 28 day compressive strength, then no single core compressive strength may be more than 15% below the specified strength. ASTM E178 (Standard Practice for Dealing with Outlying Observations) will be used with the 10% significance level to deal with excessively high or low core strengths. If a core compressive strength is an outlier, then the set of cores will be averaged using the 2 remaining cores. The average compressive strength of the cores will prevail over all other compressive strength determination methods. If it is determined by the additional testing that the concrete is in compliance with the specified 28 day compressive strength, the Department will reimburse the Contractor for the cost of the coring and compressive testing. If it is determined by the additional testing 460 Page 319that the 28 day compressive strength is less than that specified, all costs for the coring and compressive testing will be borne by the Contractor and the concrete will be either accepted or rejected as per Section 460.3 B.4. The following information will be provided for each core taken: a.Include DOT project number, county, & PCN. b.Core identification number & location of each core (representing cylinder number, structure number, location of cores sketch, date concrete was cast, date cores taken, date cores tested) c.Age of the concrete at the time of testing. d.Length & diameter of each core tested. e.Unit weight of each core. f.End preparation (capped or neoprene). g.Date of last calibration of the compression machine. h.What, if any, correction factor was used to compute the compressive strength. i.Actual calculations including load & cross-sectional area. j.Type of fracture as per ASTM C39. Note if the bond to the coarse aggregate is not adequate due to cement adhesion. k.Any defects in either the core or the cap. C.Equipment: Equipment will be available in advance of the start of construction operations to allow for thorough examination by the Engineer. 1.Batching Equipment: Batching equipment will be automatic, or a Department inspector will be present during batching operations. The Contractor will provide satisfactory means for obtaining material samples from the batching plant. Batching plant structures will be leveled so the accuracy of the weighing mechanism is maintained. Hoppers will fully discharge without jarring the scales. Clearances between scale parts, hoppers, and bin structure will be maintained to avoid displacement of, or friction between, parts due to materials accumulations, vibration, or other cause. Exposed fulcrums, clevises, and similar working parts will be kept clean. To maintain accuracy, weighing hoppers and other parts which are affected by wind action will be protected by shelters or wind breaks. The scale display will be completely enclosed in weather proof cases and provided with glass opening to permit observation and reading. The equipment for weighing aggregates, cement, water, and admixtures will be an integral part of the batching equipment. The scales/load cells will be accurate within 0.5% at any point throughout the range of the scale/load cell. Graduations will be not greater than 0.1% of the capacity of the scale/load cell. The scales/load cells will be sensitive to the weight indicated by one graduation. 460 Page 320The batching equipment will operate within a delivery tolerance of 1.5% of the net weight for each aggregate weighed. The hopper inlet mechanism will be interlocked against opening when the discharge gate is open. The hopper discharge mechanism will be interlocked against opening while the hopper is being charged. The hopper discharge mechanism will be interlocked against opening if any material in the hopper is either overweight or underweight by more than 1.5% of the specified weight. The cement batching equipment will operate within a delivery tolerance of 1% of the net weight of the cement per batch. The cementitious material (cement and fly ash) batching equipment will also operate within a delivery tolerance of 1% of the net weight of the total cementitious material per batch. Water may be measured by volume or weight. The measuring equipment will operate within a delivery tolerance of 1% of the net weight or volume of water. When water is measured by volume, means for determining the accuracy of the measuring device will be provided. Air-entraining or other admixtures may be measured by volume or by weight. The measuring equipment will operate within a delivery tolerance of 3% of the net weight or volume per batch. 2.Computerized Batching Equipment: The following provisions will apply to all Class A or Class M concrete batched by computerized batching equipment: A printed, computer generated, ticket will be automatically produced for each load of concrete batched. The printed computer ticket will accompany each load of concrete to the project and will be presented to the Engineer prior to discharging the load at the project site unless the Engineer approves an alternate procedure. The printed ticket must contain the following minimum information: Truck Number Date and Time batched Total volume of the load, in cubic yards DOT Mix Design Number Actual weight (mass) or volume of each component of the mix: Coarse Aggregate Fine Aggregate Cement Fly ash Water (batch water) Admixtures Air Entraining Admixtures 460 Page 321Water Reducers Retarders Accelerators Others % Moisture in Aggregate (either % free moisture or % total moisture) Maximum Water Allowed (maximum water allowed = weight of mix design water - weight of free water) W/C ratio (as batched) The final W/C ratio, for acceptance, will be calculated using the following formula and rounded to the nearest 0.01: 𝑊/𝐶 𝑟𝑎𝑡𝑖𝑜 =𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑓𝑟𝑒𝑒 𝑤𝑎𝑡𝑒𝑟 +𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑏𝑎𝑡𝑐ℎ 𝑤𝑎𝑡𝑒𝑟 +𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑎𝑑𝑑𝑒𝑑 𝑤𝑎𝑡𝑒𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑐𝑒𝑚𝑒𝑛𝑡 +𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑢𝑝𝑝𝑙𝑒𝑚𝑒𝑛𝑡𝑎𝑟𝑦 𝑐𝑒𝑚𝑒𝑛𝑡𝑖𝑡𝑖𝑜𝑢𝑠 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 % free moisture =% total moisture in aggregate - % absorption of aggregate weight of free water =% free moisture x weight of aggregate weight of batch water =total weight of water added to the batch either at the plant or in the truck weight of added water =total weight of water added after batching process (typically added at point of delivery) The weight of free water will be calculated for both the fine aggregate and the coarse aggregate. The above information must be automatically printed in such a manner that the Engineer may verify the mix adheres to the proportions specified by the design mix. 3.Mixing and Hauling Equipment : Mixers and agitators will have attached in a prominent place, a manufacturer plate or plates showing the various uses for which the equipment is designed and the capacity of the drum or container in terms of volume of mixed concrete. The pick-up and throw-over blades in the drum will be restored or replaced when any part or section is worn 3/4 inch or more below the original height of the manufacturer’s design. The Contractor will maintain a copy of the manufacturer’s design, showing original dimensions and arrangement of blades. Mixers that have an accumulation of hard concrete or mortar will not be used. Mixers, except truck mixers, will be equipped with an approved timing device to track the total mixing time of the concrete batch. Truck mixers will be equipped with counters to record the number of revolutions of the drum or blades. The revolution counter on the truck mixers will be set to zero as each new load is batched. Mixers will be capable of combining the concrete ingredients into a thoroughly mixed and uniform mass and will uniformly discharge the concrete. 460 Page 322The hauling bodies of non-agitating equipment will be smooth, mortar-tight metal containers equipped with gates and vibrators that will permit uniform control of the discharge of the concrete. 4.Forms and Falsework: Forms and falsework will conform to Section 423. D.Handling, Measuring, and Batching Materials: The separate aggregate components will not become intermixed prior to being weighed and the weigh hopper or hoppers will be charged so the batched weights are within the tolerances of Section 460.3 C.1 1.Cement will be measured by the sack or by weight. When cement is weighed, separate scales and hoppers will be used with a device to indicate positively the complete discharge of the batch of cement into the mixing drum. 2.Admixtures will be used in accordance with the manufacturer’s recommendations. When multiple types of admixtures are being used, the admixtures will be individually dispensed. Compatibility of the admixtures will be verified prior to use. 3.The amount of batch water and aggregates added to the mix will be adjusted accordingly using the results of the most recent two hour moisture tests. If automatic moisture sensing equipment is used, the Engineer may allow the use of the automatic moisture sensing results to make adjustments. E.Mixing Concrete : Concrete will be mixed at a central stationary plant site or in truck mixers. Mixing and agitating speeds will be as designated by the manufacturer of the equipment. Mixers will not be charged in excess of the rated capacity. When a concrete batch is 60% or less of the rated capacity of the drum on a central plant, drum on a truck mixer, or agitator; the Contractor may pre coat the drum or agitator or incorporate additional cementitious materials to the batch. 1.Central Plant Mixing: The batch will be charged in the drum so a portion of the mixing water enters in advance of the cement and aggregates. The flow of water will be uniform and all water will be in the drum by the end of the first 15 seconds of the mixing period. Concrete will be mixed for a period of not less than one minute after all materials, are in the mixer. Concrete mixed less than the specified mixing time will be discarded and disposed of. 2.Truck Mixing: Original mixing time for truck mixed concrete will be not less than 70 or more than 100 revolutions of the drum at mixing speed after all ingredients, including water, are in the drum. Additional revolutions beyond 100 will be done at agitating speed. The mixing water will be added at the time of batching. Additional water, cement, or admixtures may be added to the full load after completion of the original mixing, provided that slump, entrained air, and water cement specifications are adhered to. Addition of water, cement, or admixtures to partial loads is not allowed (partial loads of concrete are defined as loads that have been partially discharged). Admixtures will be added in 460 Page 323accordance with the manufacturer’s recommendations. When additional water, cement, or admixture is added, the batch will be mixed an additional 30 revolutions at mixing speed. The Contractor will provide means to accurately measure the amount of additional materials added. 3.Water/Cementitious Material Ratio: The water/cementitious material ratio of the concrete placed will not exceed the maximum water/cementitious ratio established for the mix design. F.Limitations of Mixing : Concrete will be mixed in the quantities required for immediate use and will be placed before initial set has occurred. Concrete in which initial set has begun prior to beginning placement will be wasted at the Contractor's expense. Retempering of concrete after initial set has occurred will not be allowed. Concrete will not be mixed and placed unless the natural light is sufficient for finishing operations, or an adequate artificial lighting system is provided. Mixing water will not be heated above 160°F. Aggregates will not be heated above 100°F and will be free of frozen lumps, ice, and snow. G.Delivery Requirements : When concrete is continuously agitated in the hauling unit, the concrete will be discharged within 90 minutes after the cement has been placed in contact with the aggregates and discharged and screeded within 105 minutes after the cement has been placed in contact with the aggregates. When the concrete temperature is 80°F or above, the time limitation will be reduced to discharged within 45 minutes and discharged and screeded within 60 minutes. When concrete is not continuously agitated in the hauling unit, the concrete will be discharged within 45 minutes after the cement has been placed in contact with the aggregates and discharged and screeded within 60 minutes. When the concrete temperature is 80°F or above, the time limitation will be reduced to discharged within 30 minutes and discharged and screeded within 45 minutes. The rate of delivery of concrete will be uniform. The interval between batches will not exceed 30 minutes. For delivery of concrete in remote locations where the preceding concrete delivery requirements will be difficult to meet, the Contractor may be allowed to use a set retarding admixture to control initial set when approved by the Engineer. When set retarding admixtures are allowed, the concrete delivery requirements may be adjusted with approval from the Department’s Concrete Engineer. H.Construction Tolerances: Construction tolerances will be in accordance with the latest edition of ACI 117, Standard Tolerances for Concrete Construction and Materials. I.Pre-pour Inspection Requirements for Concrete Bridge Decks: Pre-pour inspections will be conducted for all new concrete bridge decks. The Contractor will advise the Engineer 24 hours in advance of the time when deck preparation will be complete and ready for inspection. The following items of work will have been completed at the time of inspection: 460 Page 3241.Formwork: Formwork and decking will be complete and joints made mortar tight. 2.Reinforcing Steel: Reinforcing steel will be accurately placed in accordance with the tolerances of ACI 117, secured, and tied according to specifications. 3.Screed: Screed rails will be set and adjusted for final grade. 4.Finishing Machine: Finishing machine will be adjusted for crown slope and placed upon the screed rails. 5.Safety: Necessary walkways and safety railing will have been installed. 6.Inspections: A responsible Contractor employee will be designated to accompany the Engineer during the pre-pour inspection. Following the pre-pour inspection, any corrective work required will be completed during the normal work shift and will not extend past the normal project work hours. Violation of this provision will be cause to postpone the scheduled deck placement. J.Placing Concrete: The Contractor will give sufficient notice before starting to place concrete to permit inspection of forms, reinforcing steel, and preparation for placing. Concrete will not be placed without approval of the Engineer. Placement of concrete on a frozen foundation will not be permitted. The surface temperature of forms, steel, and adjacent concrete which will come in contact with the concrete being placed will be raised to a temperature above freezing prior to placement. The temperature of concrete immediately after placing will not be less than 50°F or more than 90°F. The top limit for bridge deck concrete will be 80°F except as indicated below. During periods of extreme and sustained hot weather it may become extremely difficult to maintain the 80°F maximum concrete temperature for bridge deck concrete. When such conditions exist the Engineer may authorize the maximum concrete temperature to be raised to 85°F provided the following conditions are met: 1.The coarse aggregate piles must be flushed with water for a minimum of 24 hours. 2.A minimum rate of pour of 40 cubic yards per hour, or as listed in the plans, must be maintained. 3.Wet curing blankets and polyethylene sheeting must be placed as soon as possible after the pour. 4.If the ambient temperature is 80°F or less the concrete will be cured as specified in Section
M. Whenever the ambient temperature exceeds 80°F, a continuous fogging will be applied
from the time of initial strike off until the curing process specified in Section 460.3 M is in place. This continuous fogging will be in addition to the curing process specified in Section 460.3 M. 460 Page 325Fogging equipment will be capable of applying a fine mist, not a spray, under pressure through an atomizing nozzle. The fogging option will not be allowed when wind conditions preclude complete coverage. Placement of concrete for bridge decks will not be permitted during the period from November 1 to April 1 (inclusive), without written authorization from the Engineer. Authorization will be given only if there is a distinct advantage to the Department. Barrier curbs will not be allowed to be placed with slipform paving equipment. Before placing concrete, sawdust, chips, debris, and extraneous matter will be removed from the interior of forms. Temporary struts, stays, and braces holding the forms in the correct shape and alignment, will be removed when the fresh concrete has reached an elevation rendering their service unnecessary. These temporary members will not be buried in the concrete. The slope of chutes for concrete placement will allow the concrete to flow slowly without segregation. The delivery point of the chute will be as close as possible to the point of deposit. Chutes and spouts will be kept clean and will be thoroughly flushed with water before and after each run. The flush water will be discharged outside the forms. Free fall of concrete will not exceed 5 feet. In thin walls or columns where the reinforcement prohibits the use of chutes the method of placement will prevent objectionable separation of coarse aggregate. The sequence of placing concrete, including the location of construction joints, will be as specified. Concrete will be placed in continuous horizontal layers. Each subsequent layer will be placed before the preceding layer has attained its initial set. The concrete will be consolidated by vibrating internally, externally, or both without displacement of reinforcing or forms. The vibration will be of sufficient duration and intensity to thoroughly consolidate the concrete without causing segregation; localized areas of grout; or damage to concrete, forms, and reinforcement. Vibration will not be applied directly to reinforcement which extends into sections or layers of concrete which are not plastic under vibration. Vibrators will not be used to move concrete over distances or to transport concrete in the forms. Accumulations of mortar splashed upon the reinforcing steel and the surfaces of forms will be satisfactorily removed. Care will be exercised not to injure or break the concrete to steel bond at and near the surface of the concrete while cleaning the reinforcing steel. Dried mortar chips and dust will be removed and not left in the unset concrete. K.Underwater Concrete Placement: Concrete placed under water will be placed as per Section
465.3K.
L.Surface Finish : The surfaces of all structural concrete will be worked during placing. The working will force all coarse aggregate from the surface and thoroughly work the mortar against the forms to produce a smooth finish relatively free of water, air pockets, and honeycombing. 460 Page 326As soon as the concrete has set in accordance with Section 460.3 O, the forms on all exposed surfaces will be carefully removed and all depressions including, but not limited to; air pockets, bug holes, honeycombing, and voids from the removal of metal ties will be carefully pointed with a mortar of sand and cement in the same proportions as the concrete being treated. All fins and rough corners on the surfaces will be removed to present a neat and uniform appearance. Additional finishing will be required as follows: 1.Rubbed, Brushed, and Commercial Texture Finishes : One of these three finishes will be required for all railing, curbs, parapets, wing walls, and other surfaces not subject to wear which are visible from the travelled way unless otherwise designated in the plans. The selected finish will be used throughout the entire structure, except the finish for the top and inside of the curb may be different than that used for the other parts of the structure. a.Rubbed Finish: As soon as the pointing has set sufficiently, the surfaces to receive a rubbed finish will be thoroughly wetted with a brush and rubbed with a medium coarse carborundum stone or an abrasive of equal quality using a small amount of mortar on stone face. The rubbing will be continued until all form marks and projections are removed, producing a relatively smooth clean surface free from pits or irregularities. The final finish will be obtained by rubbing with a fine carborundum stone or an abrasive of equal quality. This rubbing will continue until the entire surface has a smooth texture and a uniform color. b.Brushed Finish: This finish will be permitted only if it is accomplished within 12 hours of concrete placement. The forms will be removed as soon as the concrete is able to stand firm without slumping. The surface will be worked with a rubber float which may be dipped in a very wet three parts sand to one part cement grout mixture. Immediately after the surface is worked into a lather, a soft bristle brush will be used to smooth the surface, leaving a fine grained, smooth but sanded texture. A "plastering" job resulting from the use of an excess of grout on the surface will not be permitted. c.Commercial Texture Finish: The objective is to obtain a surface that is reasonably smooth and uniform in texture and appearance. Repairing surface blemishes (bug holes, form lines, etc.) to prevent "show through" prior to application of the commercial texture finish is required. The commercial texture finish will be performed using an approved system from the Department’s Approved Products List. The Department’s Approved Products List contains two separate classes (Class A and Class B) for commercial texture finish. Unless otherwise specified on the plans, either Class A or Class B systems may be used. The Contractor is required to provide a copy of the manufacturer's recommendations to the Engineer prior to performing any commercial texture finish work.
Unless otherwise noted in the manufacturer's recommendations, commercial texture finish will not be applied to any surface until the concrete is a minimum of 28 days old. The surfaces to receive commercial texture finish will be abrasive blast cleaned to 460 Page 327break the surface film, to remove all laitance and other foreign material, and to provide an absorptive surface. When allowed in the manufacturer's recommendations, pressure washing may be used to prepare the surface in lieu of abrasive blast cleaning. The commercial texture finish mixture will be mixed in accordance with the method specified in the approved list for the system being used. The same materials and application method will be used for all surfaces on any one structure. Commercial texture finish mixtures may be applied by a brushing, rolling, or by spraying, as per the manufacturer’s recommendations. The mixture will cover the original surface with a one coat application. The one coat application will not be too thick to cause runs, sags, or a plastered effect. After drying, the final surface will be uniform in color and texture with no laps or breaks in continuity. The color of the system will closely simulate the color of the original concrete, unless otherwise specified on the plans. The application of the commercial texture finish will not be started until all other work that could damage the finish has been completed. The finishing operations will be continuous until completion of the finish application on any one surface. Corrective work, at the Contractors expense, will be required on any surfaces which have not been satisfactorily finished or on finished surfaces that have been damaged during subsequent work. The repair work will include as much adjacent surface area as necessary to achieve a uniform appearance. 2.Special Surface Finish: Special surface finish will be required on the concrete surfaces designated on the plans. The special surface finish will be performed using an approved Class A or Class B system from the Department’s Approved Products List of materials/mixes for commercial texture finish. Surface preparation will be in accordance with the requirements of Section 460.3 L.1.c except that abrasive blast cleaning is required for all in place concrete surfaces. Pressure washing is not an acceptable method of surface preparation on these surfaces. Mixing and application of the special surface finish will be in accordance with Section 460.3 L.1.c for commercial texture finish. 3.Float Finish: Unformed surfaces, except bridge decks, approach slabs, and sleeper slab top surfaces poured with the approach slab will be given a float finish. After the concrete has been struck off, the surface will be thoroughly worked and floated with a suitable floating tool. Before the finish has set, the surface cement film will be removed with a fine brush in order to have a fine-grained, smooth but sanded texture. 4.Bridge Deck, Approach Slab, and Sleeper Slab Top Surface Poured with the Approach Slab Finish : Immediately after the concrete has been placed and consolidated as required by Section 460.3 J, the surface will be struck off and finished with an approved finishing machine. For bridge decks the finishing machine will meet the following minimum requirements: 460 Page 328The finishing machine will be a self-propelled rotating cylinder type, with one or more rotating steel cylinders and augers. The machine will span the concrete placement width. The cylinders and augers will spread and consolidate the concrete to the established profile by traversing the placement width, transverse to the roadway centerline. The machine will be capable of forward and reverse motion under positive control and be capable of raising all cylinders and augers to clear the surface when traveling in reverse. Any modifications to the factory product will require approval by the Engineer. The portion of the deck adjacent to curbs will be neatly finished to a true surface with a wooden hand float. Before the concrete has attained its initial set the concrete will be given a final finish by transverse brooming or carpet drag to provide a surface microtexture. The surface of concrete bridge decks will be given a transverse metal-tine finish. Tining depth and spacing will be measured according to SD 418. The metal-tine finish will provide a groove width of 1/8 inch and a groove depth of 6/32 inch ±2/32 inch. The spacing between the individual grooves will be randomly spaced and will vary between 5/8 inches to 1-5/8 inches with 50% of the spaces being 1 inch or less. The repeating random pattern on the tining device will be avoided. Successive passes of the tining will not overlap. The 12 inch width of the deck next to curb will be left ungrooved. The surface of approach slabs and sleeper slab top surfaces poured with the approach slab will be given a metal-tine finish in accordance with the metal-tine finish for bridge decks or a longitudinal metal-tine finish in accordance with Section 380.3 J.6.b . After the concrete has hardened, the surface and joints will be tested for smoothness in accordance with SD 417. The permissible longitudinal and transverse surface deviation will be 1/8 inch in 10 feet. Any portion of the deck, approach slab, and sleeper slab top surface poured with the approach slab showing variation from the template of more than 1/8 inch will be either ground to an elevation that will be within the permissible deviation or be accepted without corrective action and will be subject to price reduction as determined by the Engineer under the provisions of Section 5.3. The Contractor will accomplish corrective grinding with specially prepared circular diamond blades mounted on a horizontal shaft. The Contractor will daylight corrective grinding to the outside edge. The Contractor will repair and replace joint sealant damaged by corrective grinding as directed by the Engineer and at no additional cost to the Department. The Contractor will not leave ground areas smooth or polished. The Contractor will ensure ground areas have a uniform texture equal in roughness to the surrounding unground concrete. The Contractor will reestablish the tining with a mechanical tining machine in all areas where the corrective grinding exceeds 75 square feet. The Contractor will remove and replace all joint sealant within the area where tining is replaced. M.Curing Concrete: Concrete surfaces, except bridge decks, approach slabs, and sleeper slab top surfaces poured with the approach slab will be cured in accordance with Section 460.3 M.1. Bridge decks, approach slabs, and sleeper slab top surfaces poured with the approach slab will be cured in accordance with Section 460.3 M.2. 1.Concrete surface, except bridge decks, approach slabs, and sleeper slab top surfaces poured with the approach slab will be cured as follows: 460 Page 329Concrete surfaces will be kept continuously wet by ponding, spraying, or covering with materials that are kept continuously and thoroughly wet. Such materials will consist of a double layer of a curing blanket or other materials, as approved by the Engineer, which does not discolor or damage the concrete. Forms will be considered as adequate cover for curing the formed surface as long as the forms remain in place without loosening. Curing will continue for not less than seven days after placing the concrete. Other precautions to ensure development of strength will be taken as the Engineer may direct. In lieu of the above method of curing, liquid membrane curing compound may be used. The compound will be uniformly applied immediately after the final finishing operations are completed and the free water has left the surface. The curing compound may be applied in one or two applications in accordance with the directions of the manufacturer. If applied in two applications, the second will be applied within 30 minutes of the first. Equipment, workmen, and materials will not be allowed on the surface for a minimum of seven days after application of the curing compound, unless the surface is adequately protected with an approved material. This protection will not be applied for at least eight hours after application of the curing compound. If the membrane film is broken or damaged within the seven day curing period, the areas affected will be given a duplicate treatment of the curing material, at the same application rate as the first treatment. Surfaces which are to receive a finish as per Section 460.3 L.1 and Section 460.3 L.2 will not be treated with curing compound, curing will be accomplished with a double layer of curing blankets and polyethylene sheeting. Membrane curing compound will not be allowed on any surface to which concrete is to be bonded. 2.Bridge decks will be cured in accordance with Section 460.3 M.2.a unless otherwise specified in the plans. a.Immediately after concrete finishing, a fog will be applied to the exposed concrete surfaces until such time that wet curing blanket or other materials, as approved by the Engineer, is in place in such a way as to prevent drying of the concrete surface. Maintain the fogging to produce a “gloss to semi-gloss water sheen” on the concrete surface until the wet curing blanket is applied. The bridge deck surface will not be treated with curing compound. Fogging equipment will be capable of applying a fine fog mist in sufficient quantity to curb the effects of rapid evaporation of mixing water from the concrete resulting from wind, high temperature, or low humidity, or a combination of these factors. The fogging equipment will be capable of being turned off and on as necessary, or as directed by the Engineer. Only equipment capable of producing a fog or mist will be used. Moisture from the fog applicators under pressure will not be applied directly upon the concrete and cannot accumulate on the surface in a quantity sufficient to cause a flow or wash the surface. Fog misting will not be used to apply water to the surface of the concrete to facilitate lubrication for finishing purposes. Water on top of the fogged concrete surface will not be worked into the surface of the concrete. 460 Page 330Fogging equipment will be such that the fog spray is produced from nozzles that atomize the droplets and are capable of keeping a large area damp without depositing excess water. Use high pressure equipment that generates at least 1200 psi at 2.2 gallons per minute or low pressure equipment having nozzles capable of supplying a maximum flow rate of 1.6 gallons per minute. Handheld weed sprayers are not allowed. Water will not be allowed to drip, flow, or puddle on the concrete surface during fog misting. The Contractor will demonstrate the fog mist system at the bridge deck prepour inspection to verify that sufficient volume and coverage will be attained. A fogging system will not be used until approved by the Engineer. Apply fog spray upwind of the concrete placement during finishing, texturing, and until the concrete is covered by wet curing blanket. A single layer of wet curing blanket will be placed as soon as possible and within a distance of 25 feet behind the finish machine. In the case the placement of the wet curing blanket within 25 feet is not practical, the Contractor will keep the surface wet by fogging. In the event of a delay in concrete placement or finishing, the wet curing blanket will be placed on as much of the exposed concrete behind the finish machine as is practical. The curing blanket will be pre-wetted by soaking in water for a minimum of 4 hours and then draining the soaked curing blanket such that the free water is removed prior to placement. If non- woven polypropylene geotextile is used, pre-wetting may be done immediately prior to placement. Caution will be used when placing wet curing blanket so that no damage occurs to the surface. Placement of dry curing blanket and then wetting the curing blanket once it is in place is not allowed. The curing blanket will be kept continuously wet by misting with water until such time that the concrete can support soaker hoses without causing deformation to the concrete. At that time, soaker hoses will be placed on top of the curing blanket and the curing blanket and soaker hoses covered with polyethylene sheeting. In lieu of the preceding paragraph, the Contractor may immediately cover the wet curing blanket with polyethylene sheeting. Once the concrete can be walked on without damaging it, the Contractor will then pull back the polyethylene sheeting and place the soaker hoses between the curing blanket and polyethylene sheeting. The curing blanket will not be exposed for such duration that it dries prior to being recovered with the polyethylene sheeting. The soaker hoses must be placed and recovered within 24 hours of completion of the deck pour. Water will be run through the soaker hoses periodically as required to keep the curing blanket continuously wet, but at a minimum of once per day. These wet cure procedures will be continued for a period of 7 days after completion of the deck pour. b.Approach slabs and sleeper slabs top surfaces poured with the approach slab will be cured as follows: As soon as the concrete surface has received the final surface finish, linseed oil base emulsion curing compound will be uniformly applied at the specified rate. This 460 Page 331application is not a substitute for curing with curing blankets and polyethylene sheeting but is required for moisture retention until the curing blankets and polyethylene curing materials can be placed. The curing blankets and polyethylene sheeting curing materials will be in place not later than 4 hours after completion of concrete surface finishing. The concrete surfaces which are to have superimposed concrete placed upon or against them will be protected from the curing compound and will be cured with curing blankets and white polyethylene sheeting. All reinforcing steel will be protected from the compound application. 3.Application of Curing Compound: Application of linseed oil base emulsion curing compound will conform to the following requirements: a.Prior to and during application, the material will be mixed to a uniform consistency without the use of air, violent agitation, or thinning. b.The material will be maintained above 50°F during application. c.The material will be applied with a spray applicator of sufficient capacity and with spray nozzles of proper size and design to provide a uniform application at the specified rate, immediately after the concrete has received the final finish. d.The minimum application rate will be as follows: 1)Carpet drag or broom finish - 1 gallon per 150 square feet. 2)Groove finish - 1 gallon per 125 square feet. 4.Curing Blankets and Polyethylene: Surfaces cured with curing blankets and polyethylene sheeting will be cured in the following manner: a.The surface to be cured will be entirely covered with a double layer of curing blankets. The curing blankets will cover the entire surface with sufficient material beyond the periphery of the area to assure adequate curing of the edges. The curing blankets will be thoroughly saturated with water and will be placed with the wettest side down. Combination burlap-polyethylene sheets may be substituted for one layer of curing blanket and the polyethylene film with the Engineer’s approval. b.Immediately after placement, the curing blankets will be entirely covered with white polyethylene sheeting. Adjacent sheets will be lapped at least 18 inches. The sheeting will be placed and weighted down to ensure contact with the surface. c.Curing will be maintained for seven days. The curing blankets will be kept moist by periodic applications of water. N.Protection of Concrete : The following requirements are in addition to the requirements for curing contained in Section 460.3 M. Vibrations caused by any work activities that may be detrimental to the freshly placed concrete will not be allowed for at least 72 hours after placement or until the concrete has 460 Page 332attained a minimum compressive strength of 1500 psi. If the Engineer suspects that construction activities may be causing excessive vibration, a 2 x 4 inch stake will be driven solidly into the ground adjacent to the freshly placed concrete. A small container of water will then be placed on top of the stake. If the water surface remains calm, the construction activity will be allowed to continue. When the water surface shows any movement, vibrations are reaching the freshly placed concrete and the construction activities will be either stopped or altered such that vibrations at the freshly placed concrete are eliminated. Appropriate measures will be taken to ensure one of the following requirements are met between October 15th and May 1st and when directed by the Engineer during periods of cold weather: 1.Concrete for sidewalks, curb and gutter, drop inlets, manholes, ditch checks, pipe headwalls, sleeper slabs, approach slabs, pavement, etc. will be maintained at a temperature of 35°F or above until it has attained 1500 psi compressive strength. In addition, when the air temperature is forecast to be below 32°F for more than 4 hours, the Contractor will protect the concrete surface. 2.Concrete for bridges, box culverts, retaining walls, anchor blocks, median barriers, light and signal footings, and other structures will be maintained at a temperature of 50°F or above for the first 72 hours after the concrete has been placed. The concrete will be maintained at a temperature of 40°F or above for the next 48 hour period. If low temperatures are recorded during this protection period, one extra day of protection time above 40°F will be added to the original five days of protection for each day that the minimum concrete temperature falls below the specified temperature. Alternatively, the concrete will be maintained at a temperature of 65°F or above for at least 72 hours. If temperatures less than 65°F are recorded during this protection period, the protection time required will revert back to that in the preceding paragraph with its provision for low temperatures also being applicable. Until one of the protection periods have been satisfied, cold weather protection will continue, falsework will remain in place, live loads will not be applied, and the concrete temperature will be maintained above 35°F. 3.Any work may be protected by flooding concrete with water for 7 calendar days after the concrete is placed. The water temperature must be maintained to prevent freezing of the water in contact with the concrete. At the end of the protection period, the concrete temperature will not be permitted to fall more than 40°F in each subsequent 24 hour period. The surface temperature of concrete protected by housing and heating or insulated forms will not exceed 100°F during the protection period. Enclosures for protection of concrete will be capable of maintaining the temperature specified and permit free circulation of artificial heat. Open flame type heating units are prohibited except when the entire concrete surface is covered by forms. 460 Page 333Form insulation will be bats of fiberglass, rockwool, balsam wool, or similar commercial insulation material. Insulation will remain in place for the full protection period. If deemed necessary by the Engineer, the Contractor will provide thermometer wells 1/2 inch to 1 inch in depth at locations established by the Engineer. This may require the Contractor to drill holes in the forms to determine the temperature of the concrete. O.Removal of Temporary Works and Construction of Superimposed Elements : Methods of removal of temporary works likely to cause overstressing of the concrete will not be used. Temporary works will be removed such that the concrete gradually and uniformly takes stresses due to its own weight. Falsework, forms and other temporary works will not be removed and superimposed elements will not be placed without the approval of the Engineer. Falsework and forms may be removed from the affected concrete and placement of superimposed elements may proceed when the concrete reaches the strength specified in Table 2. Concrete compressive strength will be used as the basis for falsework removal, form removal, and placement of superimposed elements whenever possible. Falsework removal, form removal, and superimposed element placement may be allowed on the basis of time only when concrete compressive strength is notable to be determined and will be exclusive of periods of time when the temperature is below 40°F. Table 2 Formwork/Form RemovalPlacement of Superimposed Elements Structural ElementsConcrete Strength psiTimeConcrete Strength psiTime Footings/Sleeper Slabs 800 24 hrs. 1600 72 hrs. Columns 800 24 hrs. 2000 12 days Pier Walls 800 24 hrs. 2000 12 days Abutment/Sills 800 24 hrs. 3000 20 days Bent Caps/Pier Caps 2400 15 days 3000 20 days Grout Pads 800 24 hrs. 2000 12 days Concrete Diaphragms 800 24 hrs. 2000 12 days Bridge Decks: Girder Bridges Continuous Conc. Bridges Rigid Frame Bridges Other Deck Slabs2000 2400 2400 200012 days 15 days 15 days 12 days1200 1200 1200 120048 hrs. 48 hrs. 48 hrs. 48 hrs. Box Culvert: Floor, Wing Wall Footings Walls Top Slab800 800 200024 hrs. 24 hrs. 12 days1600 3000 120072 hrs. 20 days 48 hrs. Other Vertical Surfaces not Carrying Load800 24 hrs. 460 Page 334P.Backfilling and Application of Liveload: All concrete will attain full design strength and all falsework will be removed prior to backfilling and applying highway live loads to the structure. Construction vehicles, materials, and equipment weighing less than 4,000 pounds in total will be allowed on any span, provided the most recently placed concrete has attained a compressive strength of 2,400 psi. Loads over 4,000 pounds will not be allowed until the concrete has attained design strength and all falsework has been removed. The only exceptions are that footings, columns, curb and gutter, and sidewalks (sidewalks on bridge decks are not included) will not be backfilled until permission has been given by the Engineer. The approach slabs may be opened to traffic when they have attained a compressive strength of 4000 psi. Backfill material will be placed in accordance with Section 420.3 G. Luminaires, sign poles, signals, and sign bridges will not be installed on their footings until the concrete has reached full design strength. Q.Joints: Surfaces of fresh concrete at horizontal joints will be rough floated sufficiently to consolidate the surface. All construction joints will be cleaned of surface laitance, curing compound, and other foreign materials prior to placing fresh concrete against the joint. Drainage fabric will be placed around construction joints on cast in place box culverts in accordance with Section 422.
460.4METHOD OF MEASUREMENT
Structural concrete will be measured in accordance with the neat line dimensions shown on the plans to the nearest 0.1 cubic yard, unless changes are ordered in writing. Deductions will not be made for the volume of concrete occupied by utility conduits, 6 inch or smaller drainage pipe, reinforcing steel, encased structural steel, pile heads, anchors, sleeves and encased grillage, or for volume of concrete displaced by weep holes, joints, drains and scuppers or for fillets, chamfers or scorings, 1 square inch or less in cross section. Concrete approach and sleeper slabs will be measured to the nearest 0.1 square yard. Concrete used for foundation seals will not be measured for payment. Commercial texture finish will not be measured for payment. The special surface finish will be measured along the neat line dimensions shown in the plans for the surfaces designated. The special surface finish will be computed to the nearest square foot. Concrete curing will not be measured.
460.5BASIS OF PAYMENT
The accepted quantities of concrete will be paid for at the contract unit price per cubic yard. 460 Page 335Concrete approach and sleeper slabs will be paid for at the contract unit price per square yard. Payment will be full compensation for labor, equipment, tools, materials and all other items of work required in furnishing, forming, placing, finishing, curing, protecting, and all other items incidental to the structural concrete. Reinforcing and structural steel will be paid for separately. When a bid item for concrete is provided, it will be considered full compensation for excavation necessary to construct the structure, unless a separate item is provided for such excavation. Commercial texture finish will be incidental to the contract unit price per cubic yard for structural concrete. Special surface finish will be paid for at the contract unit price per square foot. 462 Page 336462 CONCRETE FOR INCIDENTAL CONSTRUCTION – CLASS M
462.1DESCRIPTION
This work consists of site preparation, form construction, and the furnishing, handling, placing, curing, and finishing of concrete for minor structures and incidental construction.
462.2MATERIALS
Material will conform to the following Sections: A.Cement: Section 750. Type II cement will be used, unless otherwise specified. B.Fine Aggregate: Section 800. C.Coarse Aggregate: Section 820. D.Water: Section 790. E.Admixtures: Section 751 and Section 752. F.Reinforcing Steel: Section 1010 . G.Curing Materials: Section 821. H.Preformed Expansion Joint Filler: Section 860. I.Joint Sealer: Section 870. J.Fly Ash: Section 605 and Section 753. K.Grout: Section 460.2 K.
462.3CONSTRUCTION REQUIREMENTS
The supplier of Class M concrete will be required to furnish a written statement certifying the concrete furnished meets the applicable requirements of Section 462 for Class M concrete. With the exception of Section 462.3 A, the requirements of Section 462.3 will not apply to Class M concrete produced at a commercial precast facility regularly producing other precast items under Section 560. Class M concrete produced at a commercial precast facility will conform to Section 560 and Section 462.3 A. A.Concrete Quality and Proportion: The concrete specified in this section will be designated as Class M6 concrete. 1.The following requirements will apply for Class M6 concrete:
a.The concrete aggregate mixture will contain a minimum of 50% coarse aggregate by weight.