for Highway Construction Page 301 of 71 5 SECTION 502 – CONCRETE
502.01 Description.
Provide portland cement concrete . Separate bids may be taken on Schedule no. 1 concrete placed in the substructure and Schedule no. 2 concreted placed in the superstruc ture.
A.Classification . Provide the classes of concrete specified in Table 502.01-1 . Table 502.01- 1 – Basic Mix Design Parameters Concrete Class in (100 psi) (28 day) (a) Minimu m Cementitious Content lb/yd3 (b) (c) Maximum Cementitious Content lb/yd3 Maximum Water Cement Ratio Air Content Percent 65 and greater, Self - consolidated concrete (d)(e)(f)(g) 660 NA 0.42 0-6.0 45 to less than 65 (d)(e)(f)(g) 560 710 0.44 0-6.0 35 to less than 45 (d)(e)(f)(g) 470 615 0.44 0-6.0 30 470 570 0.50 6.5±1.5 Seal Concrete 660 N/A 0.60 0 - 6.0 Mass Concrete(d)(e)(g)(h) 560 N/A 0.44 0-6.0 (a) Numerical part of class designation is the specified compressive strength when using the applicable tests as specified in 502.02. (b) Cementitious is cement and secondary cementitious materials (SCM). (c) It may not always be possible to produce concrete using the minimum SCM content that will ensure mortar bar expansion does not exceed the standard limit when tested in accordance with CRD C 662 or ASTM C 1293. If additional SCM is needed to meet mortar bar expansion requirements, the Contractor may add it to the mix without a corresponding increase in cement provided the strength requirements are met. Obtain approval to add lithium or other mitigating measures to meet the mortar bar expansion requirement. A separate payment will not be made by the Department for additional cementitious material required to meet the specified compressive strength. The alkali content of the concrete must be kept below 3.0 lb/yd3 Na2Oe. (d) Concrete designated as Class A will have an air content of 6.5 plus or minus 1.5 percent. (e) Concrete designated as Class C will have a maximum water cement ratio of 0.40, water reducer required, and air content of 6.5 plus or minus 1.5 percent. (f) Concrete designated as Class F will contain SCM. Minimum SCM content varies by product; for fly ash and slag cement (slag) minimum content is 20% by weight of total cementiti ous material. Fly ash will not exceed 25% of total cementitious material. Slag will not exceed 35% of the total cementitious material. For silica fume, minimum content is 7.5% by weight of total cementitious material. Silica fume will n ot exceed 10% of the total cementitious material. Ternary and quaternary blends will contain at least 20% SCM. Total SCM content will not exceed 50%. (g) Provide SCM meeting the requirements of 714. (h) Use only Type I, II, IL, IP or IS cements. An y combination of slag or Class F fly ash. Class C may be used with a maximum substitution of 20%. Maximum total substitution of SCM must not exceed 50%, including the amount of blended cement. Water reducing or retarding adm ixtures may be used to aid in air entrainment . Non -chlorine accelerators are allowed. for Highway Construction Page 302 of 71 5 Self-consolidated concrete must meet the requirements in Ta ble 502.01- 2 for mix design approval and field acceptance testing . Table 502.01- 2 – Self-Consolidating Concrete Flow, in (AASHTO T 347) Visual Stability Index (AASHTO T 351) J-Ring Test Value (J), in (AASHTO T 345) Static Segregati on Index (ASTM C1610) 20-30 1.5 maximum J ≤ 0.75 10% maximum Field Test Field Test Mix Design Mix Design Provide Class 30 concrete and use Nos. 2a, 2b, or 3 size coarse aggregate or combined gradation Nos. 2c or 3c aggregate gradations, except for Class 40, and above concrete and prestressed girders. Use Nos. 2a or 2b size coarse aggregate or No. 2c combined aggregate gradation for Class 40 concrete and above and prestressed girders. Minimum cementitious material content may be reduced 20 percent by the Contractor when using a combined gradation. Ensure the slump does not vary more than 1 inch or that flow does not vary by more than 2 inches during placement . Ensure the flow and the J -Ring flow do not vary by more than 2 inches. Should an increase or decrease in the slump or flow be desirable for the concrete as batched, the aggregate blend or the additive dosages may be adjusted. Maintain the ratio of the weight of water to weight of cement. The Department will not require AASHTO T 303 mitigation testing as part of the mix design and wi ll not require the use of ASR mitigation measures for Class 22, Class 15, and seal concrete, except when used in structural foundation and bridge applications.
B.Acceptance. The Department will base acceptance of concrete on parameters specified for the gi ven concrete class. The Department will base acceptance of strength from the results of 28- day compressive strength tests performed as specified in 502.02 on cylinders made from concrete samples being placed. The Department will consider average strength from 3 companion cylinders as one test. Precast, Prestressed, and Cast -In-Place Post -Tensioned Concrete. Provide precast, prestressed, and cast - in-place post -tensioned concrete meeting the release strength and 28- day strength as specified. Conventionally Reinforced Concrete. The Engineer may accept conventionally reinforced concrete provided the strength is no more than 10 percent below the specified strength. Replace unacceptable concrete at no additional cost to the Department. The Engineer will use the price adjustment for concrete that does not meet the intended strength, but is allowed to remain in place according to Table 502.01-3: for Highway Construction Page 303 of 71 5 Table 502.01- 3 – Pay Factor Summary Percent of Specified Strength Pay Factor ≥ 100 1.00 ≥ 95 < 100 0.90 ≥ 90 < 95 0.80 < 90 Subject to rejection (a) (a) If allowed to remain in place, as determined by the Engineer, the pay factor will be 0.50. The Department will pay for the acceptable concrete quantities at the contract unit price multiplied by the applicable pay factor. The Contractor may core drill concrete subject to price adjustment or rejection as an alternative test for acceptance at no additional cost to the Department. The Engineer will determine the core locations and how many and witness coring and testing. Limit the coring to 1 set of 3 if the Engineer determines that taking multiple cores will be detrimental to the integrity and quality of the work. Repair holes left by the coring operation at no additional cost to the Department. Obtain approval of repair methods and materials before beginni ng repairs . The Department will consider cores obtained within 42 calendar days of placement as representing the 28- day strength. Cores obtained after 42 calendar days will only be accepted when the Contractor submits a correlation curve, developed by a Department -approved independent testing laboratory, to relate strength at the actual test age to 28- day strength for the particular class and design mix represented by the cores. The Engineer and the Contractor will accept the test results of the drilled cores instead of the test cylinders results when the Contractor elects to submit acceptable drilled cores. Obtain and test cores in accordance with AASHTO T 24, except protect the cores from moisture gain or loss and test as soon as possible without further conditioning other than preparing the ends, if needed. Take at least 3 representative cores from each member or area of concrete in place that is considered potentially deficient. If, befor e testing , 1 or more of the cores shows evidence of having been damaged subsequent to or during removal, replace with a new core. Tests by the Contractor may include compressive strength, cement content determined by ASTM C1084, and petrographic analysis determined by AS TM C856, including water cement ratio and air content. If the average strength of the cores from conventionally reinforced concrete is less than the specified strength for the area represented, the Engineer will require the concrete be removed or accept at a reduced price, as specified in this section . The Engineer may reject the member and require replacement at no cost to the Department if the average core strength is less than the required strength. In some cases, the Engineer may perform additional analysis to determine if the concrete may be allowed to remain in place and accepted at a reduced price. Tests by the Engineer may include compressive strength, cement content determined by ASTM C1084, and petrographic analysi s determined by ASTM C856, including water cement ratio and air content. Make corrective changes in the materials mix portions, concrete fabrication procedures, or other c orrective action before continuing, at no cost to the Department if the concrete used in the work does not meet the for Highway Construction Page 304 of 71 5 specified compressive strength. Make approved corrective changes if 7- day strength test results are low or show a downward trend predicting concrete may not meet the specified 28- day strength. The Engineer may accept concrete with spe cified strength of 3,000 psi or less, including seal concrete, from qualified aggregate material suppliers by certification. The Department requires conc rete mix designs, including strength test data for acceptance by certification. For each concrete mix design regardless of the pay item in the contract, test the first load, then again before reaching 50 cubic yards. Test again before reaching 100 cubic yards and again within every 100 cubic yards thereafter. Include test results for slump, unit weight, air content, and compressive strength to verify the certification. For precast concrete products, test once within every 40 cubic yards of concrete used. Include test results for slump, unit weight, air content, and compressive strength to verify the certification. Use only manufacturers that provide precast concrete products that hold current certification under the NPCA Plant Certification Program, the ACPA QCast Plant Certification Program, or PCI Plant Certification Program.
502.02 Materials.
Provide material as specified in: Portland Cement ........................................................................................................................... 701 Aggregate ..................................................................................................................................... 703 Permanent Metal forms ........................................................................................................... 708.31 Membrane- Forming Curing Compounds ................................................................................. 709.01 Air-Entraining Admixtures ........................................................................................................ 709.03 Set Retarding Admixtures ........................................................................................................ 709.04 Water -Reducing Admixtures .................................................................................................... 709.05 Lithium Nitrate Admixtures ....................................................................................................... 709.06 Water ....................................................................................................................................... 720.01 Secondary Cementitious Materials ............................................................................................... 714 If it is determined that concrete aggregate is reactive for ASR according to 703.02, test the concrete mix for effectiveness of mitigation measures using CRD C662 (Table 502.02- 1) or ASTM C1293 (Table 502.02- 2). All results must be provided with the mix design submittal . Table 502.02- 1 - Characterizing Effectiveness of Mitigation in Concrete (CRD C 662) Expansion at 28 days (%) Charac terization Min Max 0 0.09 Acceptable
0.10 0.14 Uncertaina
0.15 N/A Not effectivea
a: Redesign until concrete mix meets acceptable expansion limits for Highway Construction Page 305 of 71 5 Table 502.02- 2 - Characterizing Effectiveness of Mitigation in Concrete (ASTM C 1293) Expansion at 2 years (%) Characterization Min Max 0 0.039 Acceptable
0.040 N/A Not effective
Obtain approval of admixtures before use. Determine an aggregate correction factor for the concrete aggregate for each mix design in accordance with AASHTO T 152. Conduct testing in accordance with the following standard methods: Compressive Strength of Cylindrical Concrete Specimens .......................................... AASHTO T 22 Making and Curing Concrete Test Specimens in the Field (except cylinders will be molded only in single use molds made of plastic.) ...................... AASHTO T 23 Standard Method of Test for Surface Resistivity Indication of Concrete 's Ability to Resist Chloride Ion Penetration. ......................................... AASHTO T 358 Obtaining and Testing Drilled Cores and Sawed Beams of Concrete (Provisions of AASHTO T 24 relating to ASTM and ACI references do not apply) .................. AASHTO T 24 Slump of Hydraulic Cement Concrete ........................................................................ AASHTO T 119 Mass Per Cubic Meter (Cubic Foot), Yield, and Air Content (Gravimetric) of Concrete including cement content ................................................................. AASHTO T 121 Making and Curing Concrete Test Specimens in the Laboratory (except cylinders will be molded only in single use molds made of plastic.) ...................... AASHTO R 39 Measuring Length of Drilled Concrete Cores ............................................................. AASHTO T 148 Air Content of Freshly Mixed Concrete by the Pressure Method ............................... AASHTO T 152 Measuring Texture Depth of Portland Cement Concrete Using a Tire Tread Depth Gauge ............................................................................ Idaho IT 147 Pavement Straightedge Procedures ................................................................................. Idaho IT 87 Determination of the Rate of Evaporation of Subsurface Moisture from Concrete ......................................................................... Idaho IT 133 Determining the Percentage of Fracture of Coarse Aggregate ................ AASHTO TP 61 (Method 1) for Highway Construction Page 306 of 71 5 Sampling Freshly Mixed Concrete ................................................................................ WAQTC TM -2 Provi de a safe and accessible platform for sampling the fresh concrete in close proximity and elevation to the final point of placement . When concrete is delivered by means of a concrete pump, obtain samples f rom the truck chute. Accelerated Detection of Potentially Deleterious Expansion of Mortar Bars Due to Alkali -Silica Reaction ...................................... AASHTO T 303 Temperature of Freshly Mixed Portland Cement Concrete ........................................ AASHTO T 309 Petrographic Examination of Aggregates for Concrete .................................................... ASTM C295 Determinin g the Potential Alkali -Silica Reactivity of Combinations of Cementitious Materials, Lithium Nitrate Admixture and Aggregate (Accelerated Mortar -Bar Method) ..................................................... CRD- C 662 Standard Method of Test for Potential Alkali Reactivity of Aggregates and Effectiveness of ASR Mitigation Measures ................................................... AASHTO T 380 Standard Practice for Static Segregation of Hardened Self -Consolidating Concrete Cylinders ............................................................................................................... AASHTO R 81 Standard Method of Test for Passing Ability of Self -Consolidating Concrete Concrete by J- Ring ............................................................................................. AASHTO T 345 Standard Method of Test for Visual Stability Index of Self -Consolidating Concrete ............................................................................................................. AASHTO T 351
502.03 Constructi on Requirements.
A.Proportioning. Submit a concrete mix design and include compressive strength data from the Contractor’s laboratory or an approved independent laboratory. Uniquely identify each submitted mix design. Submit the proportion of the ingredients for each mix design for Engineer review. Submit the theoretical maximum density and "final set" time with the mix design. Measure final set using AASHTO T 197M / T 197. Proportion each batch as specified in 502.03. Test the proposed mix design in accordance with applicable listed test procedures and AASHTO T 126. Submit the mix design on the ITD -916 form along with the following documentation:
1.Proposed mix design.
2.Copies of test reports.
3.Aggregate gradations.
4.Final set time.
5.ASR determination. for Highway Construction Page 307 of 71 5 6. Slump.
7.Water source.
8.Aggregate size number.
9.Design air cont ent.
10.Basic mix design strength.
11.Design mix strength.
12.Laboratory qualification.
13.Tester qualification. Ensure basic mix strength equals or exceeds the design mix strength calculated for the specified class of concrete . Determine the basic mix strength by one of the following methods:
1.Average of at least 15 consecutive field production tests using the proposed mix design, provided the tests cover a period of at least 45 calendar days and during the last 12 months.
2.Average strength of 3 test cylinders from a laboratory prepared trial mix based on the proposed mix design and prepared during the last 12 months. In addition to strength, report the air content for each test. Strength data obtained by either method is valid only if air content tests are within required limits for the specified mix class. Determine design mix strength by one of the following methods:
a.Method 1. Product of the specified strength (class) of concrete multiplied by the appropriate factor obtained from Table 502.03- 1. Calculate coefficient of variation from at least 15 consecutive field production tests using the proposed mix design, or a s imilar mix design, provided the tests cover a period at least 45 calendar days and during the last 12 months. The mathematical definition of coefficient of variation appears in the ACI Manual of Concrete Practice section 214. The Department allows interpol ation. Table 502.03 -1 – Strength Factor Similar Mix, percent 5 10 15 Factor for concrete except cast -in-place girders 1.07 1.15 1.24 Factor for cast -in-place girders 1.09 1.20 1.33 Coefficient of variation is a statistical measure of the variation in strength among specimens fr om a given plant. If coefficient of variation is above 15 percent, review plant operations and develop an appropriate factor. If fewer than 30 test results are available, multiply the calculated coefficient of variation by the following factor in Table 502.03 -2 before using the Table 502.03- 1. The Department allows interpolation. for Highway Construction Page 308 of 71 5 Table 502.03 -2 – Coefficient of Variation Strength Factor No. of Tests 30 or More 25 20 15 Less than 15 Factor for Modified C.V. 1.00 1.03 1.08 1.16 Use Method 2
b.Method 2. Sum of the specified strength (class) of concrete plus the value obtained from Table 502.03- 3. Table 502.03 -3 – Strength Value Concrete Class Location Design Mix Strength Specified strength 3,000 psi thru 5,000 psi Concret e, except cast in -place girders Specified strength +1,200 psi — Cast-in-place girders Specified strength + 1,600 psi Specified strength over 5,000 psi Concrete Specified strength + 2,000 psi Ensure the fly ash used in the concrete mix for ASR mitigation does not have a calcium oxide (CaO) content more than 2 percent above the CaO content of the fly ash used for AASHTO T 380 testing. If the fly ash used in the concrete mix for ASR mitigation has CaO content greater than 2 percent above the fly ash used for testing, the Department will require additional AASHTO T 380 testing at the higher CaO content. If fly ash is used only as a mineral admixture, determine the dosage of lithium nitrate based on CRD- C 662 testing without fly ash. Whenever SCM is used, provide the same SCM source, cement source (mill), and cement type throughout the work in an individual mix design. The Engineer will only approve a change on submission of laboratory test reports by the Contractor to verify the revised mix design meets specification requirements. The Contractor may use high- range water reducers (superplasticizers) meeting ASTM C494, subject to the followin g additional requirements:
1.Do not exceed water/cementitious materials ratio design parameters in e xcluding water contained in the admixtures. Cementitious materials are the sum of cement, fly ash, silica fume , ground slag, or other pozzolans.
2.When segregation is evident, stop placement and take corrective action. Do not allow slump to exceed 8 ½ inches. Superplasticizer redosing to maintain slump may be completed up to 2 times. Slump, concrete temperatures, and air content must remain within the specification limits after redosing. The Engineer may allow additional drum revolutions beyond the limit in a redosing situation. When c oncrete is pumped to the point of placement , adjustments to basic mix proportions may be required to ensure concrete meets specifications at the placement end. Be responsible for such adjustments, at no additional cost to the Department. Notify the Engineer in writing before implementing such adjustments. The for Highway Construction Page 309 of 715 Department requires laboratory verification as a new mix design for changes other than admixture dosage adjustm ents.
B.Equipment.
1.Mixers and Agitators. Mixers may be stationary or truck mounted. Agitators may be truck mixers or truck agitators. Equip truck mixers and agitators with a means of counting of the drum, blades, or paddle revolutions and can be readily v erified. Ensure each mixer and agitator has a metal plate or plates attached that plainly identifies the various uses the equipment is designed for, the drum volume, the drum capacity or container in terms of the mixed concrete volume, and the rotation speed of the mixing drum or blades. Ensure plates meet NRMCA standards. Equip stationary mixers with timing device that will no t allow discharge until the specified mixing time has elapsed. Equip truck mixers with a calibra ted water flow meter or other approved measuring device to control the quantity of mixing water added in the field.
2.Provide mixers. When loaded to the rated mixing capacity and the concrete mixed for the tim e or revolutions prescribed, combine the concrete ingredients into a thoroughly mixed and uniform mass and discharge the concrete with satisfactory uniformity as specified in 502.03.D.
3.Provide agitators. When loaded to rated capacity, maintain the mixed concrete in a thoroughly mixed and uniform mass and discharge the concrete with satisfactory uniformity as specified in 502.03.D.
C.Handling, Measuring, and Batching Materials . Produce concrete that meets the approved mix design . Submit the proportion of the ingredients for each batch to the Engineer at the time of batching. Prepare a batch ticket on an acceptable form for each batch of concrete delivered. Show on the ticket the project name, project number, supplier name, mix design number, date and time batched, load number, truck number, percent moisture in aggregate , volume batched, and the weight measurement of each individual component of the mix added to the batch. Deliver the batch ticket to the Engineer at the point of discharge before incorporating the concrete into the work. Submit changes to the mix design for approval. Minor adjustment s due to varying moisture in the aggregates and minor adjustments of approved admixtures are not considered changes in the mix design and will not require approval of a new mix des ign. Repor t minor adjustments to the Engineer before batching.
1.Measure cement by weight. Weigh cement in an individual hopper, when measuring by weight, and keep separate from the aggregates until released for discharge. Attach the cement hopper to a separate scale for individual weighing or to the aggregate scale for cumulative weighing. If cement is weighed cumulatively, weigh it before the other ingredients. Ensure the scale and weigh hopper for cement is separate and distinct from agg regate wei ghing equipment. Provide cement batchers with a dust seal between the charging mechanism and hopper, installed in such a way as to not affect the weighing accuracy and vented to allow the escape of air. Ensure the hopper is self - cleaning and fitt ed with means to ensure complete discharge. Provide sufficient wind protection to prevent interference with batching accuracy. Ensure the cement, as measured, is within 1 percent of the design weight.
2.Measure aggregates by weight. Weigh aggregate within 2 percent of the required weights and the total weight of the aggregate within 2 percent of the total required weight. Handle aggregates from stockpiles or other sources to the batching plant so uniform grading and stable moisture content i s for Highway Construction Page 310 of 715 maintained. Stockpile or bin aggregates for draining at least 12 hours before being batched when produced or handled by hydraulic methods or washed.
3.Measure water by volume or by weight. Arrange the measuring device so the measurements will not be affected by variable pressures in the water supply line. Do not use wash water as a portion of the mixing water. Weigh or measure water within 1 percent of the required quantity .
4.Measure SCM by weight. Weigh the SCM within 1 percent of the design weight.
5.Measure dry admixtures by weight, and paste or liquid admixtures by weight or volume. Dispense admixtures used in small quantities in proportion to the cement, as air -entraini ng admixtu res, with the mixing water. Adjust the quantity of admixtures used in accordance with manufacturer’s written instructions. Ensure admixtures used meet 709.
6.If batches must be transported to the mixer , transport cement and aggregates from the batching plant to the mixer in batch boxes, vehicle bodies, or other containers of adequate capacity and construction to properly carry the volume required.
D.Mixing and Delivery.
1.Mix and deliver concrete by any of the following means:
a.Central mixed concrete . Mixed completely in a stationary mixer and the mixed concrete transported to the point of delivery in agitating equipment or in approved nonagitating equipment.
b.Transit mixed concrete. Mixed completely in a truck mixer at the batching plant or while in transit.
c.Truck mixed concrete. Mixed completely in a truck mixer at the point of delivery following the addition of mixing water.
d.Shrink mixed concrete. Mixed partially in a stationary mixer , and the mixing completed in a truck mixer.
e.Mixed in an a pproved mixer that volumetrically measures the concrete ingredients and continuously produces concrete that meets ASTM C685.
2.Operate truck mixers and truck agitators within the rated capacity and at a speed of r otation for mixing or agitating as designated by the equipment manufacturer.
3.The minimum mixing time for mixers of 10 cubic yards or less is 50 seconds for central mixed concrete . Mixing time for mixers of more than 10 cubic yards capacity requires approval. Measure mixing time from when the cement and aggregates are in the drum. Charge the batch into the mixer so some water will enter before cement and aggregates and al l water is in the drum by the end of the first ¼ of the specified mixing time.
4.For shrink -mixed concrete, the Contractor may reduce mixing time in the stationary mixer to at least 30 seconds. Complete mixing in a truck mixer with 50 to 100 revolutions of the drum or blades at mixing speed. Do not exceed a batch volume of 70 percent of the drum gross volume.
5.When a truck mixer is used for complete mixing, mix each batch of concrete with 50 to 100 revolutions of the drum or blades at mixing speed. Use agitating speed for additional mixing.
6.When a truck mixer or agitator is used for transporting concrete that has been completely mixed in a stationary mixer, use agitating speed for mixing during transport.
7.When a truck mixer or agi tator is used for transporting concrete , apply the following: for Highway Construction Page 311 of 715 a. Deliver the concrete and complete discharge within 1.5 hours after the introduction of the cement to the aggregates or before the drum has revolved 300 revolutions, whichever comes first. If a set stabilizer meeting ASTM C494 is used, the Contractor may extend the discharge time and revolution count in accordance with the manufacturer’s rec ommendations. Submit this information with the mix design for approval.
b.In hot weather, or under conditions contributing to quick stiffening of the concrete , a time less than 1.5 hours may be directed.
c.Begin mixing operation within 30 minutes after the cement has been intermingled with the aggregates when a truck mixer is used for the complete mixing of the conc rete.
d.If additional mixing water is approved, at least 30 additional revolutions of the truck mixer drum at mixing speed are required before discharge of concrete. The Engineer may allow additi onal mixing water 1 time during the discharge of the concrete.
8.Transport cent ral mixed concrete in suitable nonagitating equipment. Provide covers when required. Equip bodies with smooth, mortar -tight metal containers capabl e of discharging the concrete at a controlled rate without segregation. Completely discharge concrete within 45 minutes after the introduction of the cement to the aggregates.
9.Do not use aluminum pipe to co nvey concrete .
10.Provide concrete at a temper ature between 50°F and 80°F at the time of placing.
E.Falsework and Forms .
1.General. Submit to the Engineer working drawings, loading assumptions, allowable material stresses used in design, and final design calculations for proposed falsework and formwork. Working drawings and approval for footings or walls are not required, unless either is more than 4 feet high. The Engineer will measure the wall height from the top of footing. Ensure the working drawings and design calculations are sealed and signed by an Idaho licensed professional engineer. Submit plan sheets to the railroad for review an d approval showing railroad falsework clearances, if required. When falsework crosses or is adjacent to traffic, the Department requires the design to include a positive barrier between the construction and traffic to prev ent the possibility of dropping construction items into the roadway. The approval of the falsework or formwork working drawings or Engineer inspections will not relieve the Contractor of responsibility for the falsework and forms . Do not start the construction of falsework or formwork until the drawings for that unit are reviewed and approved. Field -verify ground elevations at the proposed falsework footing locations for fals ework design.
2.Plans. Submit falsework or formwork drawings and design calculations. Include on each drawing and calculation sheet the key number and contract drawing number. Ensure working drawings identify materials used, including grades of lumber, in sufficient d etail to allow accurate checking. The Contractor may revise the working drawings provided at least 4 weeks are allowed for Engineer review before construction is started on the revised por tions. for Highway Construction Page 312 of 71 5 The Department requires working drawings to include a placing diagram showing the concrete placing sequence, rate of pour, and construction joint locations. When a schedule for placing concrete is specifie d, deviations will not be allowed. Submit, with the working drawings, the manufacturer’s catalog data listing the weight of construction equipment that will be supported by the falsework . When footing type foundations are to be used, determine the bearing value of the soil and show the values assumed in the falsework design on the falsework drawings. Show assumed values for wet and dry soil conditions. Show anticipated total settlements and/or deflections of falsework and forms on the w orking drawings, including falsework footing settlement, joint take up, and deflection of beams or girders. Settlement and deflection of falsework greater than 1 inch will not be accepted. Design falsework and forms supporting deck slab and overhangs on girder bridges so there is no differential settlement between the girders and the deck forms during of deck concrete placement .
3.Design.
a.General. Design falsework and formwork that meets AASHTO Guide Design Specifications for Bridge Temporary Works and incorporate the following exceptions: (1) If in conflict with the contract specifications, the cont ract specifications will govern. (2) Where other codes and standards are referenced in the guide, use the most current edition of that code or standard. (3) Show the falsework and formwork design calculations for the stresses and deflections of load supporting members. (4) Design, provide, and install camber strips to account for beam deflection, vertical alignment, and anticipated structure deflection if necessary. (5) Falsework and forms supporting concrete work on steel structures . (a) Loading of Girder Webs. Construct falsework and forms supporting the concrete work on steel structures so loads applied to girder webs are within 6 inches of a flange or stiffener and distributed so no local distortion is produced. (b) Lateral Loading of Girder Flanges. Provide temporary struts and ties as necessary to resist lateral loads applied to the girder flanges and to prevent relative vertical movement (1/8 inch maximum) between the edge of deck form and the adjacent steel girder. (6) Add the following procedure for determining the lateral pressure of fluid concrete, if pozzolans or admixtures are used, in the concrete mix: For concrete made with pozzolans or admixtures and placed wi th normal internal vibration to a depth of 4 feet or less, formwork can be designed for a lateral pressure as follows: p = lateral pressure, psf R = rate of placement, foot/hour T = temperature of concrete during placing, °F C c = chemistry coefficient: for Highway Construction Page 313 of 71 5 1.2 for cement type I and III with a retarder 1 .2 for blends containing fly ash without a retarder
1.4 for blends containing fly ash with a retarder,
Where: retarders include admixtures that delay setting of concrete. For columns: p = C c [ 150 + 9000 R / T ] with a p between 600 and a maximum of (3,000)(C c) psf, at least 600 psf, but in no case greater than (w) x (h), where w is density of concrete times in pound per cubic foot and h is total height of concrete placem ent in foot. For walls: p = C c [ 150 + 43,400 / T + 2800 R / T ] with a p between 600 and a maximum of (2,000)(C c) psf, at least 600 psf, but in no case greater than (w) x (h), where w is density of concrete in pound per cubic foot and h is total height of concrete placement in foot. For applying the lateral pressure formulas, columns are defined as elements with no plan dimension exceeding 6.5 feet. Walls are defined as vertical elements with at least 1 plan dimension greater than 6.5 feet. Note: This specification is a modification of the Manual of Concrete section 347 section 2.2.2 Lateral Pressure of Concrete published by ACI.
b.Permanent Metal Concrete Forms. Do not use permanent metal forms for decks. Ensure materials meet 708.31. Design permanent metal forms to meet the following criteria and the loads specified in this section. (1) The unit working stress in the steel sh eet is 0.725 or less of the specified minimum yield strength of the material provided, but not to exceed 36,000 psi. (2) The maximum deflection under the weight of the forms , plastic concrete , and reinforcement or a load of 120 pounds per square foot, whichever is greater, will not exceed 1/180 of the form span or ½ inch, whichever is less. (3) Ensure the form span for computation of stress and deflection is at least the clear span of the corrugated form material plus 2 inches. (4) Compute physical design properties in accordance with the edition of AISI Specifications for the Design of Cold Formed Steel Structural Members published at bid opening. (5) Ensure reinforcement has a minimum concrete cover of 1 inch. Center bars in the bottom layer of the main reinforcement over the valleys of the forms when necessary to achieve the minimum 1 -inch concrete cover. (6) Provide positive lateral support by the use of concrete haunches formed against the top flanges of steel beams or girders except where shear connectors are provided. for Highway Construction Page 314 of 71 5 (7) Do not locate longitudinal deck construction joints between stringers where permanent metal forms are used. (8) Cut off support angle legs extending into the deck concrete in excess of ½ inch. Install forms in accordance with approved detailed fabrication plans. Ensure the fabrication plans meet 502.03.E.2 and include the grade of steel used and the moment of inertia calculations for the form. Do not rest form sheets directly on the tops of the stringer or floor beam flanges. Securely fasten sheets to form supports and provide a minimum bearing length of 1 inch at each end. Place form supports in direct contact with the stringer flange or floor beam. Attachments are to be made by bolts , clips, or other approved means. Submit the method of attachment fo r approval with the fabrication plan. Thoroughly clean, wire brush, and then paint damaged galvanized coating on exposed form metal with 2 coats of zinc oxide zinc dust primer, federal specification TT -P-64ld Type II. Locate transverse construction joints at the bottom of a flute with ¼ inch weep holes field drilled at least 12 inches on center along the line of the joint. Remove at least 1 section of the forms at a location and tim e selected for each concrete placement on each span as directed. Remove forms for inspection as soon after placing the concrete as practical to provide visual evidence the concrete mix and the Contractor’s procedures are obtaining the desired results. Remove an additional section each time the concrete mix or the Contractor’s procedures are changed, if directed. After the deck concrete has been in pl ace for at least 2 calendar days, test the concrete for soundness and bonding of the forms by sounding with a hammer. If areas of doubtful soundness are disclosed, remove the forms from such areas for visual inspection after the concrete has attained adequate strength, at no additional cost to the Department. At locations where sections of the forms are removed, the Department will not require replacement of forms, but will require repair of the adjacent metal forms and supports to present a neat appearance and ensure their satisfactory retention. Remove unsatisfactory concrete or repair as directed.
4.Construction.
a.General. Provide tell -tales attached to the soffit forms that are readable from the ground in enough systematically placed locations to determine the total settlement of the entire portion of the structure where concrete is being placed. If unanticipated events occur, including set tlements that deviate more than plus or minus 3/8 inch from those shown on the falsework drawings, stop placing concrete until corrective measures are provided. When directed to suspend placing concrete, cons truct a temporary bulkhead at a location determined by the Engineer. Remove unacceptable concrete at no additional cost to the Department.
b.Bracing. Provide temporary bracing as necessary to withstand imposed loads during erection, construction , and removal of falsework whose height exceeds its clear distance to the edge of sidewalk or shoulder of roadway open to the public. Show provisions on the falsework drawing for temporary bracing or methods to be u sed to meet this requirement during each phase of for Highway Construction Page 315 of 71 5 erection and removal. Include wind loads in the design of temporary bracing methods. Set the falsework to give the finished structure the camber specified. In addition to the specified camber , make allowance for settlement of the falsework using 1/8 inch for each contact of timbers.
c.Expansion Joints. At the ends of bridge deck expansion joints, securely fasten joint material (or the armor angles of compression seals) to the overhang forms to prevent relative movement during concrete placement . On deck rehabilitation work, the Department may require shimming and/or tack welding new steel joint elements to existing armor angles or parts.
d.Bridge Rail, Curbs, and Parapets. Cast the concrete portions of bridge rails, curbs, and parapets in place using conventional fixed formwork.
e.Form Fasteners. Use form fasteners consisting of form bol ts, clamps, or other devices as necessary to prevent spreading of the forms during concrete placement . Do not use ties consisting of twisted wire loops to hold forms in position.
f.Anchor Devices. The Contractor may use anchor devices cast into concrete for supporting forms or for lifting precast members. Do not use driven types of anchorages for fastening forms or form supports to concrete. Use the type of form fasteners and anchors that can be removed without chipping, spalling, heating, or otherwise damaging the concrete surface. Remove form bolts , metal ties or anchors, or other metal placed for the Contractor’s conveni ence to a depth of at least 1 inch below the surface of the concrete. Clean and fill the resulting holes or depressions with mortar. Remove form bolts projecting into the cells of box girders flush with the surface of the concrete.
g.Mortar. Provide and place mortar in recesses and holes, on surfaces, under structural members, and at other locations as specified. Provide mortar composed of portland cement , sand , and water. Use a 1 to 2 ratio for the proportion of cement to sand, measured by volume. Provide material that meets 701.01. Ensure the maximum size of sand is not larger than ½ the size of the recess, hole, or space where the mortar is to be placed. Use only enough water in the mortar to allow placing and packing. Clean concrete areas to be in contact with the mortar of loose or foreign material that would prevent bond between the mortar and the concrete surfaces. Flush with water and allow to dry to a surface dry condition immediately before placing the mortar. Completely fill and tightly pack the mortar into recesses, holes, on surfaces, under structural members, and at other locations as specified. After placing, cure surfaces of mortar by the water method as specified in 502.03.J for at least 3 days. Ensure keyways, spaces between structural members, holes, spaces under structural members, and other locations where mortar could escape are mortar tight before placing mortar. Do not allow loads on mortar within 72 hours. Remove improperly cured or defective mortar and replace at no additional cost to the Department. For exposed surfaces, add white cement to the mortar in a quantity sufficient to result in a patch that matches the surrounding concrete when dry. for Highway Construction Page 316 of 71 5 h. Forms . Clean the form ’s inside surfaces of dirt, mortar, and foreign material. Thoroughly coat forms that will later be removed, with form oil before use. Use commercial quality form oil or other equivalent coating that will allow the ready release of the forms and not discolor the concrete . Ensure concrete forms are mortar tight, true to the dimensions, lines , and grades of the structure, and of sufficient strength to prevent deflection during the placing of the concrete. Do not discharge concrete into the forms until work connected with constructing the forms has been completed, materials required to be embedded in the concrete have been placed for the unit to be poured, and the Engineer has inspected the forms and materials. This work includes the removal of dirt, chips, sawdust, water, and other foreign material from the forms. Control the rate of depositing concrete in forms to prevent deflections of the forms or form panels in excess of the deflections specified. The Department requires forms for concrete surfaces that are not completely enclosed, or hidden below the permanent ground surface, meet the same requirements as forms for exposed surfaces. Interior surfaces of underground drainage structures are to be completely enclosed surfaces. Form exposed surfaces of each element of a concrete structure with the same forming material or with materials that produce similar concrete surface textures, color, and appearance. Face forms for exposed surfaces with form panels. A form panel is the continuous section of form facing material, unbroken by joint marks, against which the concrete is placed. Provide and place form panels for exposed surfaces in uniform widths of at least 3 feet and in uniform lengths of at least 6 feet, except where the width of the member formed is less than 3 feet. When the width of the panels is less than 3 feet, provide and place panels that are the width of the member. Arrange panels in symmetrical patterns conforming to the general lines of the structure. Place panels for vertical surfaces with the long dimension horizontal and with horizontal joints level and continuous. Place panels with the long dimension parallel to the footi ng for walls with sloping footings that do not abut other walls. Precisely align form panels on each side of the panel joint, by means of supports or fasteners common to both panels, to result in a continuous, unbroken concrete plane surface. Construct forms for exposed surfaces with triangular fillets at least ¾ inch by ¾ inch attached to prevent mortar runs and to produce smooth, straight chamfers at sharp edges of the concrete. Do not stamp concrete (e.g., with company logo, dates, patterns).
5.Removal of Falsework and Forms . Do not remove forms and falsework without approval. This approval does not relieve the Contractor of responsibility for the safety of the work. Remove blocks and bracing at the time the forms are removed, including the wood forms left in the concrete. Include falsework removal procedures for continuous or cantilevered structures with the working d rawings. If the Contractor intends to remove falsework and forms before 28 calendar days, proportion and design the concrete mix to provide the minimum strengths required at the proposed removal time, as specified. Do not remove the falsework and forms before the minimum number of days and minimum strength for the applicable structural element. Comply with 502.03.F. for Highway Construction Page 317 of 71 5 Perform maturity testing in accordance with ASTM C1074 to determine compressive strength for form removal and loading. Validate maturity -strength relationship with the first placement and every 1,000 cubic yards thereafter. Develop the maturity -strength relationship and submit maturity curves along with supporti ng data and field procedures for monitoring maturity for approval at least 10 calendar days before use. Provide equipment, including thermo or maturity meters, thermocouples, wire, and qualified personnel to monitor maturity and submit information. Ensure maturity testing represents the concrete in the most unfavorable field conditions. When using maturity testing, validate the first field placement and every 1,000 cubic yards thereafter. Cure cylinders used for validation testing using the same procedures as used in developing the initial maturity -strength relationship. When initially validating the maturity curve, validate at least 2 points, 1 of which must be at a period of less than 7 calendar days for subsequent validation. A maturity curve will be considered valid if the validation points are within 10 percent of the original maturity curve. Loading of a member is defined as additional horizontal or vertical loads applied other than loads from formwork and reinforcing steel of further concrete placements. For post -tensioned concrete bridges, release the falsework supports that might continue to remain engaged after structure units are prestressed, to allow the concrete to accept its own weight and distribution of stresses uniformly and gradually. Sequence disengagements so fixed connections at tops of piers will not be subjected to damaging forces. Sequence falsework support disengagement as specified on falsework drawings. The stressing operation in prestressed units must be completed and approved before removing supporting false work. Apply a membrane- forming curing compound or a water cure as specified in 502.03.J to exposed surfaces, except for construction joints if forms are removed before 7 calendar days have elapsed. Cure construction joints using a water cure as specified in 502.03. Leave t he forms in place for footings constructed within cofferdams or cribs, if their removal would endanger the safety of the cofferdam or crib, and where the forms left in place will not be exposed to view in the fini shed structure. Remove forms whether above or below the ground line or water level. Remove forms from the cells of box girders. Remove forms and falsework in a manner to allow the concrete to uniformly and gradually take the stresses due to its own mass. The Contractor may remove forms and falsework or place subsequent loads when both condit ions in Table 502.03- 5 for the activity involved are met. Table 502.03- 5 – Form and Fal sework Removal and Loading of Concrete
Part 1 — :
Minimum Days (a) (b) Percent of Design Side forms for: footings, abutment caps, pier caps, 1 — Columns, abutment backwalls, and retaining walls 3 50 for Highway Construction Page 318 of 71 5 Cantilever bridge deck sidewalks 7 — Bridge decks, top slabs of concrete box culverts or 10 80 Crossbeams, caps, box girders, T -beam Girder s, 7 80 Signal, Luminair e, and Sign Support Foundations 7 80
Part 2 — :
Minimum Days (a) (f) Percent of Design Footings and abutments 3 80 Approach slabs, and b ottom slabs of box girders 5 80 Columns and walls 5 100 Bridge decks, top slabs of concrete box culverts or 10 100 Signal, Luminair e, and Sign Support Foundations 7 100 Erecting girders on pier caps 7 100 (a) From the time of the last placement in the forms or falsework supports and excluding the days when the surrounding temperature is below 40°F for a total of 4 hours or more. Requirements in 502.03.G still apply. The Contractor will monitor the temperature during curing time by continuous recording thermometers. (b) Do not remove forms until the concrete has sufficient strength to prevent damage to the surface or cause over stressing of the concrete. (c) Where continuous spans are involved, the time for spans will be determined by the last concrete placed. (d) Except loads from formwork and reinforcing steel of further concrete placements. (e) Standard concrete mix designs may not achieve strength in the minimum days shown. (f) 1 day is 24 hours.
F.Placing Concrete .
1.General. Do not place concrete until forms and metal reinforcement have been inspected. Cl ean the forms of debris and foreign material before concrete is placed. Avoid segregation of the concrete and displacement of the reinforcement . When placing operations involve dropping the concrete more than 5 feet, deposit concrete through sheet metal or other approved tubes. Keep tubes full of concrete during placing and their lower ends buried in the newly placed concrete, as much as practical. Control the rate of depositing concrete in forms to prevent deflections of the forms or form panels in excess of the deflections specified. Place concrete in the forms as soon as possible after mixing. Keep the concrete plastic and workable. The concrete placement is to be continuous, with no interruption longer than 30 minutes between adjoining layers. Fill each part of the form carefully by depositing the concrete as near the final position as possible. Place and consolidate each layer before the preceding layer takes initial set. Do not jar the forms or allow strain to be placed on the ends of projecting reinforcement after initial set of the concrete. Do not place bridge decks and other concrete flatwork when the evaporation rate is greater than
0.15 pounds per square foot per hour when tested in accordance with Idaho IT 133. Flatwork is a surface not cured in contact with a form and that is not part of a construction joint. Surfaces essentially vertical are excluded from the definition.
for Highway Construction Page 319 of 715 Use the proper mix design and combination of low shrink materials, low temperature concrete, proper curing techniques, or other procedures necessary t o eliminate or minimize the development of cracks. The Engineer will determine surface crack intensity after completion of concrete cure and before prestressing or releasing of forms or falsework . The surfac e crack intensity of concrete bridge deck s is determined by the number and size of cracks in the top surface of the concrete. Remove equipment and material from the deck and clean the surface as necessary for the Engineer to measure the crack intensity. Fill cracks in any 60 square yard portion of deck when there are more than 50 feet of cracks whose width exceeds 0.02 inch with a 2 component modified methacrylate penetrating sealer or equal, as approved. Fill the cracks in accordance w ith the penetrating sealer manufacturer’s written instructions at no additional cost to the Department. Decks that have excessive cracking or cracking that jeopardizes the structural integrity of the deck may be determined unacceptable and require removal. Work after the placement is incidental and the cost included in the contract unit price for concrete .
2.Vibrating. Consolidate the concrete with suitable vibrators oper ating within the concrete. Supplement vibrating by hand- spading with suitable tools to ensure proper and adequate consolidation, especially around obstructions. Use vibrators that operate at frequencies of at le ast 5,000 impulses per minute. Use vibrators in concrete containing epoxy -coated reinforcement that have a resilient covering to prevent damage to the epoxy coating. Vibrate deck concrete with internal vibrat ors turning at least 10,800 revolutions per minute in air and are fully submerged. Space the vibrator i n the concrete mix approximately 18 to 24 inches measured in longitudinal and transverse directions. Work the concrete thoroughly aroun d the reinforcement , embedded fixtures, and into corners and angles of the forms with vibrators. Do not use vibrators to cause the concrete to flow or run into position instead of placing. Ensure vibrati on is sufficient to accomplish thorough consolidation, but not prolonged to the point where segregation occurs. The vibrators are not required for seal concrete or concrete in shell piles .
3.Underwater Concrete. Use seal concrete in or under water. Carefully place concrete in a compact mass, in its final position, by means of a tremie, a bottom dump bucket, or other approved method to prevent segregation. Do not disturb concrete after being deposited. Do not place concrete in running water. Construct the forms for underwater concrete to provide still water inside the forms. Continuously place the concrete until the required depth is reached and keep the surface of the concrete as nearly level as possible. Comply with the following requirements for placing if a tremie is used:
a.Use a watertight tube having a diameter of at least 10 inches with a hopper at the top.
b.Provide a device that will prev ent water from entering while charging the tube with concrete .
c.Support the tremie to allow free movement of the discharge end over the entire top surface and to allow r apid lowering when necessary to slow down or stop the flow of concrete. for Highway Construction Page 320 of 71 5 d. Use a method to fill the tremie that will prevent washing of the concrete.
e.Completely submerge the discharge end in concrete and maintain sufficient concrete in the tremie tube to prevent water entry.
f.When concrete is dumped into the hopper, induce the flow of concrete by slightly raising the discharge end, always keeping it in the deposited concrete.
4.Massive Placement . Concrete placements with the least dimension greater than 4.5 feet are considered mass concrete placements. The Engineer will indicate mass placements in the Contract documents. This specification does not apply to drilled shafts unless otherwise specified . The Contractor must produce a mass concrete placement free of cracks caus ed or worsened by concrete heat of hydration. Accomplish this through appropriate concrete mix design and control of concrete temperatures and temperature differences. Use of concrete pre- cooling, concrete post - cooling, application of insulation or external heat, and or selection of reduced heat of hydration concrete mix may be appropriate for this purpose. Compliance with this specification may result in long durations of temperature control which could impact the sequenc e and schedule of planned work. The Contractor must implement procedures to control concrete temperatures that are compatible with the work plan and project schedule. The Contractor must provide a thermal control plan signed and stamped by an Idaho licensed engineer . Unless otherwise specified, the following temperature limits apply:
a.Maximum temperature in concrete after placement cannot exceed 160°F.
b.Maximum temperature difference between center and any surface of placement , and with ambient temperature, must not exceed 35°F. (1) The surface is 2 to 6 inches internal to the outer dimension of the placement and can include the upper surface and the sides. (2) The center is the vertical centerline horizontally centered with the element where mass concrete is being placed. Submit a thermal control plan for each mass concrete placement that includes:
a.Concrete materials , mixture proportions, and ranges of chemical admixture dosages using ITD - 0916.
b.Permissible changes to concrete materials and mixture proportions that do not require the thermal control plan to be updated.
c.Calculated and measured adiabatic temperature rise of concrete ;
d.Upper limit for concrete temperature at time of placement ;
e.Description of specific measures and equipment that will be used to ensure maximum temperature in placement will not exceed the specified maximum temperature;
f.Calcula ted maximum temperature difference in placement based on expected conditions at time of placement and use of proposed measures to control temperature differences;
g.Description of equipment and procedures that will be used to monitor and l og temperatures and temperature differences; for Highway Construction Page 321 of 71 5 h. Drawings of locations for temperature sensors in placement ;
i.Description of format and frequency of reporting temperature data;
j.Description of measures to address and reduces excessive temperat ures and temperature differences if they occur;
k.Description of curing procedures, including materials and methods, and curing duration;
l.Description of formwork removal procedures to ensure temperature difference at temporarily exposed surface will not exceed temperature difference limit, and how curing will be maintained. Update thermal control plan if changes in concrete materials or mixture proportions affect compliance with temper ature limits. Unless otherwise specified, preserve moisture by maintaining forms in place. For surfaces not in contact with forms either apply water -retention sheeting material without holes or gaps, or apply membrane- forming curing compound. Control concrete temperature and temperature difference within the concrete from the time concrete is placed until internal temperature has cooled from its maximum so that the difference between average daily ambient temperature and internal temperatures at time of protec tion removal is less than the specified temperature difference limit. Do not use ice in the concrete mix. Place two temperature sensors (one redundant backup) at the center of the largest portion of placement , two temperature sensors (one redundant backup) at a depth 2 to 3 inches from the edge of exterior surface that is nearest to the vertical center of the placement, and two temperature sensors (one redundant backup) at a depth 3 to 4 inches from the upper surface nearest the horizontal center of the placement. In addition, place two temperature sensors (one redundant backup) in a shaded location for monitoring ambient onsite temperature. Monitor temperatures hourly using electronic sensors capable of measuring temperatures from 0 to 212°F to an accuracy of 2°F . Ensure temperature sensors are operational before placing concrete . Provide temperature monitoring data daily to the Engineer until the internal temperature has cooled from maximum so that the difference between the average daily ambient temperature and the internal temperature at the time of protection removal is less than 35°F. Do no place fresh concrete between hardened concrete placed within the previous four weeks . If unavoidabl e, obtain approval from the Engineer. If temperatures are nearing the maximum temperature or maximum difference in temperature, take immediate action as described in the thermal control plan. Do not place additional concrete until the cause of excessive temperatures or temperature difference has been identified and corrections are accepted. Care must be taken to avoid construction j oints where they are not specified. If unavoidable, obtain approval from the Engineer. If the temperature difference limit is exceeded, the Engineer may require additional testing at no cost to the Department to determine if a pay deduction or removal of material is required. If there is no apparent damage with the concrete, the material may remain in place. If the maximum temperature limit is exceeded, strengths may be reduced and internal expansion and cracking of concrete may not be apparent for several years after the placement ; therefore, the material must be removed and replaced at the discretion of the Engineer. for Highway Construction Page 322 of 715 G. Cold Weather Concreting.
1.Heating and Placing Concrete. Obtain approval for a cold- weather concreting and curing plan detailing the methods and equipment to ensure the required concrete temperatures are maintained before placing concrete when ther e is a probability of air temperatures below 40°F during the placing and curing periods. Meet the following cold- weather concreting operation requirements when the ambient temperature falls below 40°F:
a.Compl etely remove ice, snow, and frost before placing concrete .
b.Provide concrete that will have a temperature of at least 50°F and less than 80°F at the time of placing.
c.Do not place concrete against material with a temperature of 32°F or less.
d.Heat the mix water and/or the aggregates when necessary, before batching to produce concrete of the specified temperature. Heat in a manner that is not detrimental to the mix and does not prevent the entrainment of the required amount of air. Heat the materials uniformly.
e.Do not heat aggregates directly by gas or oil flame or on sheet metal over fire.
f.Do not heat aggregates or water to over 150°F. If either is heated to over 100°F, mix together before adding the cement so the cement does not come into contact with materials that are in excess of 100°F.
2.Protection of Concrete. Maintain a concrete temperature of at least 50°F for 7 calendar days or 70°F for 3 calendar days after placement except when steam curing is used. When SCM is used, increase the time to 10 calendar days for 50°F and 5 calendar days for 70°F. Maintain the temperature of uniform surfaces of concrete (e.g., decks) at the temper atures and the times shown. Do not allow the water to freeze during the curing period when water cure is required for concrete as specified in 502.03.J. Protecting and curing concrete under water is allowed provided the temperature of the w ater does not fall below 35°F and at least 6 inches of water is maintained over the concrete for at least 10 calendar days. Block up combustion heaters off the surface of the concrete and vent to the outside of the enclosure. Do not allow the maximum temperature within the enclosure to exceed 120°F when the concrete is protected by means other than steam. The maximum drop in temperature of the concrete throughout the first 24 hours after the end of protection will be 50°F for protection methods other than the use of steam. Meet the requirements of 502.03.J when steam is used in the protection of the concrete. Provide calibrated temperature recording devices with a range of 20°F to 212°F for steam -cured concrete and a range of 20°F to 160°F for other concrete. Continuously record temperatures for at least 24 hours. Provide a sufficient number of recording devices to keep adequate records of temperatures. On s mall quantities used in minor structures , sign foundations, and other nonstructural placement (e.g., sidewalks, curb and gutter ), protect the concrete from freeze dam age by covering the for Highway Construction Page 323 of 71 5 concrete with suitable blanketing material. Maintain protective covering for at least 5 calendar days. Use recording thermometers to show that concrete used in minor structures was not expos ed to freezing temperatures .
H.Hot Weather Concreting. Do not allow the temperature of concrete to exceed 80°F at time of placement. Take measures (e.g., erecting sunshades, placing at ni ght or early morning) to slow evaporation to tolerable limits when the combination of ambient air temperature, concrete temperature, humidity, and wind promotes rapid evaporation of moisture from the concrete surface. Ice may be used as a part of the mixing water if it has completely melted by the time mixing is completed. Ensure the temperature of the surface to be covered by concrete does not exceed 90°F.
I.Finishing Concrete . Provide an ordinar y surface finish for all formed surfaces that are not exposed. Provide a rubbed surface finish on exposed surfaces, except the soffits of superstructures and the interior faces and bottoms of concrete girders. Concrete surfaces are define d as follows:
1.Ordinary Surface Finish. Remove form bolts and tie wires immediately after the forms have been removed. If rock pockets materially affect the strength of the structure or endanger the life of the steel reinforcemen t, the Engineer may declare the concrete defective and require the removal and replacement of that portion of the structure affected. Clean, thoroughly wet, and fill holes and depressions with a cement mortar composed of 1 part of cement and 2 parts of sand. The Department may require an approved bonding agent. Remove fins caused by form joints and other projections above the ground line. Ensure the resulting surface is reasonably smooth and uniform in texture and color.
2.Rubbed Surface Finish. Thoroughly wet and rub the entire surface with a carborundum stone or other approved method after the pointing has set sufficiently. The Department may require an approved bonding agent. Spread the paste by rubbing uniformly over the surface and finish by floating or rubbing to attain a uniform color and texture. Thoroughly clean concrete that has been discolored by the drip from the abrasi ve by using a dilute solution of muriatic acid, and then washing thoroughly with clean water. The Engineer may waive the requirement for a rubbed surface finish if the uniformity of color and texture obtained wit h ordinary surface finish are essentially the equal of a rubbed surface finish when metal forms, fiber forms, lined forms, or plywood forms in good condition are used. Grinding with powered disc grinders or light sandblasting with fine sand or other approved means may be used in conjunction with ordinary surface finish.
3.Slab Finish. Finish and straightedge deck slabs and wearing surfaces as follows: Finish deck slabs greater than 40 feet in length and other wearing surfaces subject to highway traffic that are greater than 40 feet in length by the machine method. Finish other deck slabs and wearing surfaces using machine or hand methods. Do not use additional water on the concrete surface during machine or hand- finish ing operations. Straightedge the concrete surface, broom finish, and meet the completed surface requirements of the following in paragraphs c, d, and e after finishing by machine or hand methods. for Highway Construction Page 324 of 71 5 a. Equipment. Use an Engineer -approved, power -driven finishing machine complying with the following requirements for finishing all areas of work with a width of at least 14 feet. Have at least 2 hand- operated, spud type internal vibrators available at all times for use as directed. Submit equipment ap proval re quests a t least 15 calendar days before the start of the work. Do not begin placing deck concrete until the screed and placing procedure is approved. Provide a self-propelled finishing machine capable of forward and reverse movement under positive control for placing, striking off and finishing the bridge deck surface, with provisions for raising screeds to clear the surface. Equip the machine with vibrating screeds designed to consolidate the modified composition. The Department requires the vibration frequency be variable with positive control between 3,000 and 11,000 vpm and the bottom face of the screeds be at least 4 inches wide and be metal covered. Provide screeds with positive control of the vertical position. Equip the finishing machine with one or more rollers, augers, and 1,500 or 2,500 vpm vibratory pans. Provide a Bid- Well 2450, or equivalent finishing machine. Modification to the Bid-W ell 2450 or equivalent is subject to Engineer approval. Texas, Allen, or Bunyan type screeds will only be allowed for small and/or irregular areas if approved. Before beginning concreting operations, operate the finishing machine over the full length of the bridge segment to be finished. Make this test run with the screed adjusted to its finishing position. Check the screed rails for deflection and proper adjustment , the cover on slab reinforcement , and form alignment while operating the finishing machine in this test. Make necessary corrections before placing concrete. Ensure the concrete carried ahead of t he screed does not cause slipping of the finishing machine wheels on the rails. Orient the transverse axis of the finishing machine parallel to the bearing centerline on prestress and steel girder spans. Ensure the concrete placement heading and the strike- off heading are parallel so equal loads are produced on each girder.
b.Hand Method. Strike the concrete off with a template or a vibrating screed after it is placed. Finish concrete to an even surface by means of longitudinal and transverse floats. Do not use a power tr owel.
c.Straightedging. Test the surface of the concrete for trueness while the concrete is still plastic. Use an approved 10- foot straightedge. Hold the straightedge in contact with the surface in successive positions parallel to the centerline and go over the whole area from 1 side of the slab to the other. Advance along the surface in successive stages of less than ½ the length of the straightedge. Immediately fill depressions found with freshly mixed concrete, strike off, consolidate, and refinish. Cut down high areas and refinish. Ensure the concrete surface across joints meets the requirements for smoothness. Perform straightedging and surface correction from foot bridges resting on the side forms and spanning, but not touching, the concrete. Continue straightedge testing and surface corrections until the entire surface is without observable departures from the straightedge and the slab conforms to the required grade and cross- section.
d.Final F inish. Float the deck slab after screeding to produce a uniform surface without porosity. Give the surface a steel tine finish if necessary. Use tines 1/8 inch wide, spaced at ½ to ¾ inch intervals, and producing grooves 5/32 inch ± 1/32 inch deep. Check groove depth in accordance for Highway Construction Page 325 of 71 5 with Idaho IT 147. If more than 3 readings in a set of 10 are outside the intended depth range, make adjustments to the tining operation. Minim ize surface tearing or aggregate removal when t ining. Tine-stroke transverse to the roadway centerline and the full width of the roadway except for troweled smooth strips 12 inches wide along curb faces. Do not overlap adjacent strokes. Finish the surface without porous spots, irregularities, depressions, small pockets, or rough spots. The Contractor may saw cut grooves instead of the steel tine finish, if approved. Use a width and spacing of the grooves 1/8 to ¼ inch. Do not perform saw cut grooving until after the curing duration. Continuously and completely remove residue from the grooving operation. Screed or float finish structures that will receive a deck membrane and asphalt overlay. Complete surface without porous spots, irregularities, depressions, small pockets, or rough spots.
e.Surface Smoothness. The Engineer will test the slab surface for smoothness in accordance with Idaho IT 87, at the end of the curing period. Ensure the surface does not vary more than ¼ inch in 10 feet from the lower edge of the straightedge and 90 percent of the readings do not exceed 1/8 inch in 10 feet. Grind concrete surfaces that do not meet surface smoothness requirements or replace as directed at no additional cost to the Department.
J.Curing Concrete . Keep concrete surfaces completely and continuously moist until a curing method is applied. Do not apply membrane- forming curing compound to concrete surfaces before the finishing has been accepted. Do not apply m embrane- forming curing compound to construction joints or to the inside faces of joints to be sealed. Cure concrete as specified in Tables 502.03- 6 and 502.03- 7. Table 502.03- 6 – Concrete Placement Type Placement No. 1 Bridge decks, including sidewalks on bridges, bridge curbs, or parapets. Placement No. 2 Sidewalks, urban approaches , curbs, or curb and gutter . Approach slabs and concrete slope paving. Placement No. 3 Prestressed girders. Concrete placements (e.g., beams, caps, columns, fo otings, catch basins, manholes, median barrier , median curbs, box girders excluding the deck portion, signal, luminaries, sign support foundations). Concrete g uardrail Sound walls for Highway Construction Page 326 of 71 5 Table 502.03- 7 – Cure Methods Placement Number Method A: Water Cure Method B: Membrane -Forming Curing Compound Method C: Form Cure Method D: Steam Cure 1 X — — — 2 X X-System 1 — — 3 X X-System 1 X X Cure concrete by one of the following methods:
1.Method A: Water Cure. Make a single application of a membrane- forming curing compou nd immediately after surface finishing is completed on each individual portion of the placement . Apply the membrane- forming curing compound under pressure at a rate of at least 1 gallon per 150 square feet. Use System 1 membrane- forming curing compound on placement numbers 2 and 3. Use System 2 membrane- forming curing compound on placement number 1. Start water curing after the concrete surface has set up enough so it will not be damaged, but not later than 4 hours following application of the curing compound. Keep the concrete surfaces in placement 1 continuously wet for at least 10 calendar days. Keep the concrete surfaces in placement 2 and 3 continuously wet for at least calendar 5 days. Parapet finishing may be performed during the wet cure period. The Contractor may have the burlap removed for finishing small, isolated areas of the parapet provided the surface of the concrete is not allowed to dry out. Keep the concrete surface wet using cotton mats, rugs, carpets, burlap, laminated moisture- retaining cover, or other approved coverings as a reservoir medium. Saturate the reservoir medium before placement on the concrete surface. Ensure the reservoir medium is in a saturated state, drained of free water, when initially placed. Add water as necessary to keep it from drying out during the curing period. Cover the reservoir medium with white plastic sheeting to reduce evaporation. Do not use plastic sheeting alone as a reservoir medium. Clear the surface of reservoir mediums at the end of the curing period. Show ability to provide the water cure as specified before placing concrete . The Engineer will immediately suspend the concrete placing operations for failure to provide sufficient cover material or sufficient water to adequately take care of water curing and other associated requirements.
2.Method B: Membrane- Forming Curing Compounds. Apply membrane- forming curing compounds, as specified in 709.01, to the finished concrete immediately after the bleed water or free water sheen leaves the surface of the finished concrete surface. for Highway Construction Page 327 of 715 Thoroughly mix membrane- forming curing compounds before using and agitate it during application to prevent settling or separation. Uniformly apply the membrane. Apply the second coat of membrane at right angles to the first coat when 2 coats are used, if possible. Immediately apply the same type of membrane material to membrane surfaces that are marred or damaged by scuffing or wearing before completion of the curing period, or water cure the area for the remaining cure period. Each manufacturer’s identified lot of curing compound is required to be sampled, tested, and approved before use. Allow 3 weeks for laboratory testing of the curing compound once it has been receiv ed by the Central Materials Laboratory . Quantities of curing compound over 1,000 gallons may be inspected and sampled by the Department at the manufacturer’s plant for acceptance testing. Request inspection from the Engineer and the Central Materials Laboratory in writing 30 calendar days before ordering material.
a.System 1 : AASHTO C309 Type 1 D Class B with Fugitive Dye. Prepare the concrete surface before painting if System 1 is used. Refer to 627.03.E. Provide 2 applications of the curing compound for a total coverage of 1 gallon per 150 square feet to co ncrete cured by this method. Apply each application of the curing compound under pressure at a rate of at least 1 gallon per 300 square feet. If the surface under the forms has dried, thoroughly wet the concret e with water and apply the curing compound just as the surface film of water disappears. Apply the first coat immediately after stripping the forms and before acceptance of the concrete finish. Apply t he second application immediately af ter the first application has set. Keep unsprayed exposed surfaces wet with water during curing operations.
b.System 2: AASHTO C309 , Type 2, Class B, White Pigmented. Apply curing compounds under pressure at a rate of at least 1 gallon per 150 square feet on surfaces.
3.Method C: Form Method. Protect concrete with forms for at least 7 calendar days. Intermittently moisten and protect forms from the sun during daytime periods of hot weather. Cure exposed surfaces b y water or approved membrane cure.
4.Method D: Steam Curing. When steam curing is used, protect the concrete for a minimum 2 -hour period when the temperature is 50°F to 100°F. Following thi s initial period, increase the temperature at a maximum rate of 40°F per hour to a temperature between 100°F and 175°F. Continue curing at this temperature until cylinder strengths are above the release strength for prestressed reinforced concrete or above 80 percent of the intended 28- day strength, whichever is greater. Cool the beam gradually by decreasing its temperature at a rate of 40°F per hour or less until the temperature differential between the beam and outside air is 25°F or less at the end of the cure cycle, when ambient air temperatures are below 40°F. Do not expose member to below freezing temperatures until at least 6 calendar days after fabrication or until the 28 -day strength has been achieved. for Highway Construction Page 328 of 71 5 502.04 Method of Measurement. The Engineer will measure acceptably completed work as follows:
1.Precast stringers, prestressed stringers, and concrete parapets by the foot.
2.Approach slabs by the square yard, including the exposed finished surface of the concrete deadman.
3.Other concrete by the cubic yard with the dimensions specified or ordered, except the volume of concrete placed under water and formed Class 15 concrete may be based on batch design volumes. The volume occupied by the reinforcing steel , anchors , conduits, weep holes, H piling, or chamfers will not be deducted. The volume of concrete displaced by culverts or piles, other than H piling, will be deducted.
4.Deck concrete by the square yard or cubic yard to the dimensions specified.
5.Thermal Control Plan will be paid by the lump sum including the thermal control plan, temperature monitoring and thermal control measures .
502.05 Basis of Payment .
The Department will pay for accepted quantities as follows: Pay Item Pay Unit Concrete Class ____ .............................................................................. CY Concrete Class ____ Schedule No. ____ ............................................... CY or SY Seal Co ncrete ......................................................................................... CY Precast Stringers ____ (Beam) ............................................................. FT Prestressed Stringers ____ (Beam) ...................................................... FT Concrete Parapet ................................................................................... FT Approach Slab ........................................................................................ SY Prestressed Slabs (w___ x d____) ......................................................... FT Prestressed T Beam (w___ x d____) ..................................................... FT Prestressed Box Beam (w___ x d____) ................................................. FT Thermal Control Plan .............................................................................. LS
1.Concrete. At the contract price per cubic yard or square yard for concrete of the class and schedule specified. Pay for concrete placed in the superstructure as concrete Class __ Schedule No. 2 by plan quan tity as specified in 109.01. The Engineer will use the price adjustment for concrete that does not meet the intended strength, but is allowed to remain in place, as follows:
502.05 -1 – Pay Facto r Summary
Percent of Specified Strength Pay Factor for Highway Construction Page 329 of 71 5 ≥ 100 1.00 ≥ 95 < 100 0.90 ≥ 90 < 95 0.80 < 90 Subject to rejection (a) (a) If allowed to remain in place, as determined by the Engineer, the pay factor will be 0.50. The Department will pay for the acceptable concrete quantities at the contract unit price multiplied by the applicable pay factor.
2.Precast and Prestressed Stringers, Slabs, and T Beams. At the contract price per foot. The contract price includes reinforcing steel, epoxy coating of steel entirely or partially embedded in the precast elements, prestressing, and structural steel that is cast in and includ ed with precast elements. Payment will be made on plan quantities, except for authorized additions.
3.Concrete Parapet. At the contract unit price per foot and include reinforcing st eel and epoxy coating that is cast within the parapets in whole or in part.
4.Approach Slabs. At the contract unit price per square yard, including site preparation (e.g., excavation or other shaping), reinforcing steel, joint sealers, sleeper beams, concrete deadman, and curbs.
5.Price Adjustment. The Department will adjust the contract unit prices for strength deficiency as specified in 502.01.B. The Engineer will apply a price adjustment to the unit price of the concret e class if required for the quantity represented by the individual strength tests. The Department will apply this price adjustment provision to the contract unit price of other items of work by their respective units of measurement and payment that incorporate concrete under 502. If concrete is at incidental cost or included in the overall cost of an item, the Engineer will establish a value of the concrete proportional to the total contract price for purposes of establishing a price reduction on the concrete that does not meet specified strength, but is allowed to remain in place.
6.Surface Resistivity Price Adjustment . The Department will make the following price adjustment to the contract unit price for each lot of Schedule No. 2 concrete meeting the following surface resistivity requirements when measured using AASHTO T 358 at 28 calendar days. Table 502.05 -1 – Surface Resistivity Price Adjustment Price/yd3 Surface Resistivity, kΩ-cm (4X8) Surface Resistivity, kΩ-cm(6X12) $2.50 > 21.0, < 37.0 > 16.5, < 29.0 $5.00 > 37.0 > 29.0
7.Thermal Control Plan. Concrete, forming, stripping and placement are not included in the contract unit price. for Highway Construction Page 330 of 71 5 SECTION 503 – METAL REINFORCEMENT
503.01 Description.
Provide and install reinforcing steel . The metal reinforcement, Schedule no. 1 pay item includes metal reinforcements placed in subst ructures. The metal reinforcement, Schedule no. 2 pay item includes metal reinforcement placed in superstructures. The Department will show the schedules in the plans for the structures involved.
503.02 Materials.
Provide materials as specified in: Reinforcing Steel ..................................................................................................................... 708.02 Epoxy -Coated Metal Reinforcement ........................................................................................ 708.02 Dowel Bars .............................................................................................................................. 708.03 Tie Bars ................................................................................................................................... 708.04 Splices ..................................................................................................................................... 708.32 Order additional bars to account for the field sampling. Do not cut and splice bars to obtain samples. Com plete fabricated bars are to be sampled and replaced. Order additional mechanical splices to account for field sampling. Provide reinfor cing steel spirals with additional length to accommodate sampling. Do not cut and splice material to obtain samples. Replace bar from failing heat numbers at no additional cost to the Department.
503.03 Construction Requirements.
A.Bar List and Bending Schedule . The plans will show the bar list and bending sc hedule to arrive at an estimate of quantities . Verify the quantity , size, and shape of the bar reinforcement against the structure drawings and make necessary corrections before ordering. The Department will not adjust the contract unit price because of errors in the bar list and bending schedule.
B.Protection of Material . Protect steel reinforcement from damage. When placed, ensure the steel reinforcement does not have dirt, detrimental scale, paint , oil, or other foreign substance. Do not store epoxy -coated reinforcing steel outdoors for more than 2 months. When stored outdoors, cover the bars to protect them against the elements and against condensation forming on the bars.
C.Bending. Field bend reinforcing bars only when the bars conflict with prestressing ducts , are within anchorage recesses, or as specified. Do not field bend:
1.Bar sizes larger than No. 7.
Source: Idaho Standard Specifications for Highway Construction, 2023 Edition. Pages 337–365 of 768.