147 ALASKA 2020 DIVISION 500 – STRUCTURES SECT ION 501
501-1.01 DESCRIPTION . Furnish, place, finish, and cure Portland cement concrete for structure
construction. Use the class of concrete noted on the Plans unless otherwise specified. CLASSES OF CONCRETE Class A: General us e concrete Class A -A: Concrete where improved strength and durability is required Class P : Concrete where strength in excess of 5000 psi is required Class DS: Concrete for drilled shaft foundations
501-1.02 Definitions .
ADMIXTURE. A material other than wat er, aggregate, hydraulic cement, pozzolan, and fiber reinforcement, added to the batch before or during mixing, used as an ingredient of a cementitious mixture to modify its freshly mixed, setting, or hardened properties. Air-Entraining Admixture. An admi xture causing the development of a system of microscopic air bubbles in concrete, mortar, or cementitious material paste during mixing, usually to improve its workability and resistance to damage by freezing and thawing. Set-Accelerating Admixture. An admi xture causing an increase in the rate of hydration of the hydraulic cement and shortens the time of setting, increases the rate of strength development, or both. Set-Retarding Admixture. An admixture causing a decrease in the rate of hydration of the hydra ulic cement and lengthens the time of setting, decreases the rate of strength development, or both. Water -Reducing Admixture. An admixture either increasing slump of freshly mixed mortar or concrete without increasing water content or maintaining slump wit h a reduced amount of water, due to factors other than air entrainment. AGITATION. The process of providing motion in mixed concrete just sufficient to prevent segregation or loss of plasticity. BLEED WATER. The autogenous flow of water emerging from newly placed concrete, and caused by the settlement of the solid materials within the mass. The relative quantity of mix water that will bleed can be estimated by AASHTO T 158. CAMBER. For prestressed concrete members, camber is the net upward deflection of an eccentrically prestressed concrete member due to the combined loads, shrinkage, creep, and eccentricity of the prestress force. For non- prestressed members, camber is a deflection intentionally built into a structural element or form to improve appearance or to nullify the deflection of the element under the effects of loads, shrinkage, and creep. CEMENT. A binding material that sets and hardens by hydration and is capable of doing so underwater, sometimes called hydraulic cements. CEMENTITIOUS MATERIA L. Hydraulic cements and pozzolans with cementing properties. CHAMFER. A beveled edge or corner formed into finished concrete. 148 ALASKA 2020 COMPRESSIVE STRENGTH TEST. The average strength test of concrete, from at least two 6.0 x 12.0 inch or at least three 4.0 x 8.0 inch c ompressive strength test cylinders sampled according to AASHTO T 141 or ATM 501, cured according to AASHTO R 39 or ATM 506, and tested according to AASHTO T 22 or sampled, cured, and tested to equivalent ASTM test methods. Or the average strength test of grout, from at least three specimens sampled and tested according to ATM 507, AASHTO T 106, or ASTM C 109. Unless otherwise noted, tested at an age of 28 days. COMPRESSIVE STRENGTH , (f’c). The measured maximum resistance of a concrete, grout, or mortar specimen to axial compressive loading; expressed as force per unit cross -sectional area; or the specified resistance used in design calculations. CONCRETE ANCHOR. Cast-in-place or post -installed fastening device installed in the concrete for the purpose of t ransferring loads to the concrete. See ASTM E2265 for standard terminology. CONSOLIDATION. The process of inducing a closer arrangement of the solid particles in freshly mixed concrete during placement by the reduction of voids, usually by vibration, roddi ng, tamping, or some combination of these actions. CONSTRUCTION JOINT. The surface where two successive placements of concrete meet. CURING COMPOUND. A liquid applied as a coating to the surface of newly placed concrete to retard the loss of water and, in the case of pigmented compounds, reflects heat to provide an opportunity for the concrete to develop its properties in a favorable temperature and moisture environment. CURING PERIOD. The length of time in which continuous curing operations are maintained thereby allowing the concrete to properly hydrate and develop its required strength and durability. CURING. Action taken to maintain moisture and temperature conditions in a freshly placed cementitious mixture to allow hydraulic cement hydration and (if applicable) pozzolanic reactions to occur so the desired properties of the mixture develop. DURABILITY. The ability of concrete to resist weathering action, chemical attack, abrasion, and other conditions of service. EVAPORATION RATE RED UCER. A material gen erating a continuous thin film when spread over water on the surface of fresh concrete to retard the evaporation of bleed water. FIELD TEST RECORD. A record of compressive strength test results from concrete used on prior projects and produced by the concr ete production facility. FINAL CURING PERIOD. The time period after the concrete achieves final set in which deliberate action is taken, without damaging or marring the concrete surface, to maintain satisfactory moisture content and temperature in concrete. FINAL SET. Attainment of significant rigidity in which rainfall, foot traffic, and curing materials contacting the concrete surface do not damage or mar the concrete surface and do not alter the properties of the finished surface. INFORMATIONAL FIELD TEST. A compressive strength test, determined by the Engineer, from field test cylinders cured on the site under temperature and moisture conditions similar to the concrete in the structure; except, the compressive strength test may consist of one 6.0 x 12.0 inch or one 4.0 x 8.0 inch compressive strength test cylinder. INITIAL CURING PERIO D. The time period between placement and implementation of final curing methods in which deliberate action is taken to reduce the loss of moisture from the surface of the concrete. 149 ALASKA 2020 INITIAL SET. The first stiffening of concrete. KEYWAY. A recess or groove in one lift or placement of concrete and filled with concrete of the next lift or grout, giving shear strength to the joint. LAITANCE. A layer of weak material derived from c ementitious material and aggregate fines either: 1) carried by bleeding to the surface or to internal cavities of freshly placed concrete; or 2) separated from the concrete and deposited on the concrete surface or internal cavities during placement of conc rete underwater. MORTAR. A mixture of cementitious material paste and fine aggregate occupying the space between particles of coarse aggregate. REQUIRED AVERAGE COM PRESSIVE STRENGTH, ( F’ cr). The 28- day compressive strength, used as the basis for selection of concrete proportions in the mix design process, sufficiently greater than the Specified Compressive Strength to ensure the acceptance criteria are met . RETEMPER. To add water and remix concrete or mortar to restore workability to a condition in which the mixture is placeable or usable. ROCK POCKET. A porous, mortar -deficient portion of hardened concrete consisting primarily of coarse aggregate and open voids. SCREED. To strike off concrete lying beyond the desired plane or shape. A tool for striking off the concrete surface, sometimes referred to as a strikeoff. SET. The condition reached by a cementitious material paste, mortar, or concrete that has lost plasticity to a degree of stiffening generally stated as the time in hours and minutes required for cementitious material paste to stiffen sufficiently to resist the penetration of a weighted test needle as prescribed by AASHTO T 197, SPECIFIED COMPRESSIVE STRENGTH, (F’ C). The 28- day compressive strength used in structural design and specified in the Cont ract documents . TREMIE. A pipe or tube with a hopper for filling at its upper end through which concrete is deposited.
501-2.01 MATERIALS. Use materials conforming to the following:
1.Cementitious Materials Portland Cement Subsection 701- 2.01 Blended Hydra ulic Cement Subsection 701- 2.02 Fly Ash Subsection 701- 2.04 Ground Granulated Blast -Furnace Slag Subsection 701- 2.05 Silica Fume Subsection 701- 2.06
2.Aggregate Materials Fine Aggregate Subsection 703- 2.01 Coarse Aggregate Subsection 703- 2.02 Aggregate for A brasive Finish Subsection 703- 2.14
3.Water, Admixtures and Curing Materials Curing Materials Subsection 711- 2.01 Chemical Admixtures Subsection 711- 2.02 Water and Ice Subsection 712- 2.01 150 ALASKA 2020 4. Anchors and Inserts Concrete Anchor Inserts and Bolts Subsection 712- 2.20 Utiliduct, HDPE Subsection 706- 2.08 Utiliduct, Steel Section 716 Structural Steel Section 716 Asphalt Felt ASTM D 226, Type I (No. 15 Asphalt Felt) Expanded Polyethylene Subsection 705- 2.06
5.Grout and Epoxy Grout Subsection 701- 2.03 Epoxy Adhesive for Crack Sealing AASHTO M 235, Type IV, Grade 3 Epoxy Adhesive for Crack Injection AASHTO M 235, Type IV, Grade 1 Low-Viscosity Resin Subsection 712- 2.19 Epoxy Bonding Agents AASHTO M235, Type V
501-2.02 COMPOSITION OF MIXTURE - JOB MI X DESIGN. Provide a Job Mix Design, for each
required class of concrete and Specified Compressive Strength (f' c), which meets the requirements of this Subsection and provides workability and consistency so the concrete can be worked readily into the forms and around reinforcement wi thout segregation or bleeding. Determine proportions using the absolute volume method according to ACI 211.1.
1.Water -Cement Ratio and Cementitious Materials . Provide a Job Mix Design meeting the water -cement ratio requirements in Table 501- 1. Calculate t he water -cement ratio based on the total weights of water and cementitious material. The weight of water includes all water as defined in Subsection 501- 3.01.2c. The following are considered cementitious materials: Portland cement, blended hydraulic cement, fly ash, ground granulated blast -furnace slag, and silica fume. Fly ash, ground granulated blast -furnace slag, silica fume, and combinations of these materials may be used as a substitute for Portland cement provided the quantity meets the limits of Tab le 501- 2 and the total quantity of combined fly ash, ground granulated blast - furnace slag, and silica fume does not exceed 40 percent of the total cementitious material by weight. Do not use Type III Portland cement for cast in place concrete decks and ap proach slabs. TABLE 501 -1 WATER -CEMENT RATIO R EQUIREMENTS Class of Concrete Water -Cement Ratio, maximum lbs/lbs A 0.45 A-A 0.40 P 0.35 DS 0.45 151 ALASKA 2020 TABLE 501 -2 SUPPLEMENTARY CEMENT ITIOUS MATERIAL LIMI TS Cementitious Material Percent of Total Cementitiou s Material by Weight1 Maximum Fly Ash 35% Ground Granulated Blast -Furnace Slag 40% Silica Fume 10% 1 The maximum percent includes initial quantities in blended hydraulic cement plus additional supplementary cementations materials.
2.Aggregate Gradations . Provide a Job Mix Design meeting the fine aggregate gradation requirements in Subsection 703- 2.01 and the coarse aggregate gradation requirements in Table 501- 3. Alternative sizes of course aggregate, as shown in Table 1 of AASHTO M 43, may be used onl y when approved in writing. Combined aggregate gradations, shown in Table 1 of ATM 530, may be used for packing density mix designs (e.g. Shilstone) on the condition that the nominal maximum aggregate size specified remains unchanged and the concrete is proportioned according to ATM 530. TABLE 501 -3 COARSE AGGREGATE GRA DATION REQUIREMENTS Class of Concrete Coarse Aggregate Size Number AASHTO M 43 A No. 57 or 67 A-A No. 57 or 67 P No. 67 DS No. 7 or 8
3.Air Content . Provide a job mix design meeting the requirements of Table 501- 4 TABLE 501 -4 AIR CONTENT REQUIREMENTS Class of Concrete Air Content A 6.0% ±0.5% A-A 6.0% ±0.5% P 4.0% ±0.5%1 and Super Air Meter (SAM) number ≤0.201 DS Not required 1Not required for web and bottom flange of precast, prestressed decked bulb- tee girders.
4.Slump . Provide a Job Mix Design meeting the slump requirements in Table 501- 5.
5.Chloride Ion Content . Provide Job Mix Designs with water -soluble chloride ion contents determined by percent weight of cementitious material ac cording to ASTM C1218 for the concrete mixture aged between 28 and 42 days. For Class P and Class A -A Concrete the limit is 0.06 percent. For Class A and DS concrete the limit is 0.08 percent. 152 ALASKA 2020 6. Required Averaged Compressive Strength . Provide a Job Mix Des ign meeting a Required Average Compressive Strength (f'cr) established from either the Empirical Method or the Statistical Method. If the Specified Compressive Strength (f' c) is not designated on the Plans, use a Specified Compressive Strength listed in T able 501- 6. TABLE 501 -5 SLUMP REQUIREMENTS Condition Slump Concrete without a water -reducing admixture 4" max. Concrete with a Type A, D, or E water -reducing admixture 6" max. Concrete with a Type F or G high -range water - reducing admixture 9" max. Class DS concrete, wet -shaft process 7" min. 9" max. Class DS concrete, dry -shaft process 6" min. 9" max. TABLE 501 -6 COMPRESSIVE STRENGTH REQUIREMENTS
a.Empir ical Method. Establish the Required Average Compressive Strength from the following equations: f'cr = f'c + 1200 for f' c ≤ 5000 psi f'cr = 1.1f'c + 700 for f' c > 5000 psi Where: f'cr = Required Average Compressive Strength, psi f'c = Specified Compressive Strength, psi
b.Statistical Method . If the production facility has field test records of compressive strength tests, esta blish the Required Average Compressive Strength based on the calculated standard deviation of the field test records and using the largest result of the following equations: f'cr = f'c + 1.34ks for all f' c or, f'cr = f'c + 2.33ks – 500 for f' c ≤ 5000 psi, f'cr = 0.90f' c + 2.33ks for f' c > 5000 psi, Where: f'cr = Required Average Compressive Strength, psi f'c = Specified Compressive Strength, psi k = 1.16 if 15 total tests are considered Class of Concrete Specified Compressive Strength (f' c) (psi) A 4000 A-A 5000 P 8000 DS 4000 153 ALASKA 2020 1.08 if 20 total tests are considered 1.03 if 25 total tests are considered 1.00 if 30 or more total tests are considered s = standard deviation, psi Use linear interpolation to determine k for intermediate number of tests. Use field test records performed within the past 12 months and spanning a period of more than 60 days for a class of concrete within 1000 psi of the Specified Compressive Strength. Use field test records from concrete produced at the production facility, which represent materials, quality -control procedures, and climatic conditions similar to those expected in the work. Do not use field test records from concrete in which acceptance requirements for materials or concrete proportions were more closely restricted than those in the proposed work. Use field test records meeting one of the following:
1.One Group of Field Test Records . Use field test records representing a group of at least 15 consecutive compressive strength tests in which all concrete was produced using the same mixture proportions. Calculate the standard deviation using the following equation: Where: s = standard deviation, psi n = number of compressive strength test results considered Xi = individual compressive strength test result, psi = average of n compressive strength test results, psi
2.Two Groups of Field Test Records . Use field test records representing two groups of consecutive compressive strength tests totaling at least 30 tests. Ensure each group is comprised of at least 10 consecutive compressive strength tests, and all concrete in each group was produced using the same m ixture proportions. Calculate the standard deviation using the following equation: Where : s = standard deviation for the two groups combined, psi s1, s2 = standard deviation for groups 1 and 2, respectively, calculated according to Subsection 501- 2.02.6. b.(1), psi n1, n2 = number of test results in groups 1 and 2, respectively
7.Job Mix Design Verification .
a.Required Average Compressive Strength. Verify the Job Mix Design satisfies the Required Average Compressive Strength by meeting at least one of the fol lowing requirements:
1.Field Test Records . Use field test records that:
a.use materials of the same brand and type and from the same manufacturer as the materials used in the work; 154 ALASKA 2020 (b) were from concrete produced at the production facility;
c.use quality -control pr ocedures, and had climatic conditions similar to those expected in the work; and
d.encompass a period of not less than 60 days. Do not use field test records from concrete in which acceptance requirements for materials or concrete proportions were more closely restricted than those in the proposed work. For a single group of at least 10 consecutive compressive strength tests for one mixture, verify the average of the compressive strength tests equals or exceeds the Required Average Compressive Strength. For two groups, each having at least 10 consecutive compressive strength tests, for two mixtures representing classes of concrete within 1000 psi of the Specified Compressive Strength, plot the average strength of each group versus the water - cementitious mater ial ratio of the corresponding mixture proportions and interpolate between them to determine the compressive strength corresponding to the water - cementitious material ratio of the Job Mix Design. Verify the interpolated compressive strength equals or exceeds the Required Average Compressive Strength.
2.Laboratory Trial Mixtures . Use materials and material combinations for trial mixtures of the same brand and type and from the same manufacturer as the materials used in the work. Record the temperature of the f reshly mixed concrete according to ASTM C1064 and ensure the temperature is within 10°F of the intended maximum temperature of the concrete as mixed and delivered. For each trial mixture, make and cure at least two 6.0 x 12.0 inch or at least three 4.0 x 8.0 inch compressive strength test cylinders for each test age according to AASHTO R 39. Test for compressive strength according to AASHTO T 22 at test ages of 3, 7 and 28 days. For a single trial mixture, verify the compressive strength test equals or exceeds the Required Average Compressive Strength. For a group of trial mixtures, make at least three trial mixtures with each mixture having a different cementitious material content. Select water -cement ratios producing a range of compressive strengths encom passing the Required Average Compressive Strength. From the results of the 28- day compressive strength tests, plot a curve showing the relationship between water -cement ratio and compressive strength. From the curve of water -cement ratio versus compressive strength, determine the compressive strength corresponding to the water -cementitious material ratio of the Job Mix Design. Verify the compressive strength equals or exceeds the Required Average Compressive Strength.
b.Flowability Requirements for Class DS Concrete (Wet -Shaft Process). Verify the Job Mix Design satisfies the concrete flowability requirements of Subsection 501- 3.05.6.a.(1.) Develop a slump loss table showing the slump at 1 hour intervals since batching until the concrete takes initial set.
c.Plasticity Requirements for Class DS Concrete (Dry -Shaft Process). Verify the Job Mix Design satisfies the concrete plasticity requirements of Subsection 501- 3.05.6.b.(1.) Ensure initial set occurs after placement operations are complete. 155 ALASKA 2020 8. Job Mix Design Subm ittal. Submit a written mix design, signed and sealed by a Professional Engineer registered in the State of Alaska, for each specified class of concrete and for each Specified Compressive Strength, to the Engineer at least 45 days prior to scheduled produc tion. Submit the mix design on Form 25D -203. Include the following:
a.Job Mix Design Proportions and Test Results . Submit concrete mixture proportions per cubic yard and test results for the proposed Job Mix Design. Include the following information:
1.Weights of cementitious materials
2.Weights of aggregates in saturated surface dry condition
3.Volume or weight dosage range of each admixture.
4.Weight of water
5.Water -cement ratio
6.Percentage of air by volume
7.Total water soluble chloride ion content
8.Wet unit weight
9.Expected slump
10.Expected 3, 7 and 28- day compressive strength (Include 1- day compressive strength for Class P concrete.)
11.Slump loss table for Class DS concrete (if applicable)
12.Time of initial set for Class DS concrete (if applicable) and for other classes wh ere extending Time for Placement (Subsection 501- 3.02.2) will be requested
13.Compressive strength test results showing the Required Average Compressive Strength is met or exceeded.
b.Materials Documentation. Submit the following:
1.For each cementitious mater ial, include:
a.Type/Class
b.Brand
c.Producer
d.Plant location
e.Certified test reports confirming the cementitious material meets these Specifications.
2.For aggregates, include:
a.Pit or quarry location(s)
b.Bulk dry specific gravity, bulk saturated surface dry specific gravity, and apparent specific gravity 156 ALASKA 2020 (c) Absorption values
d.AASHTO size number for coarse aggregates
e.Gradations for aggregates
3.For each admixture, include:
a.Type
b.Manufacturer
c.Manufacturer's product data sheet giving the procedure for admixture use and confirm ing the admixture meets these Specifications.
d.The batching process step and mixing instructions when each admixture is added.
e.Manufacture’s certificates demonstrating admixture compatibility and manufacture’s recommended dosage range.
4.Include the source of supply for water and ice.
c.Materials Samples. The Engineer may require samples of aggregate, cementitious materials, and admixtures to verify the mix design. If requested, furnish representative samples (330 pounds each) of both coarse and fine aggregat es, 94 pounds of each cementitious material, and one- quart of each admixture to allow for Job Mix Design verification testing. Ensure the Department receives these samples at least 45 days before the mixture’s scheduled production for the project.
d.Basis of Required Average Compressive Strength. If the Statistical Method is used, submit the following for each field test record:
1.Compressive strength test results of the tested concrete.
2.Standard test method used for determining compressive strength.
3.Date the c ompressive strength tests were performed
4.Aggregate source used for the tested concrete.
5.Specified strength of the tested concrete.
6.Batched weights of constituent materials or the producer’s mix design identification number for the concrete used for each compressive strength test.
e.Documentation of Required Average Compressive Strength. Submit documentation indicating the proposed concrete proportions will produce an average compressive strength equal to or greater than the Required Average Compressive Strength meeting one of the following requirements:
1.Field Test Records. If field test records were used to verify the Required Average Compressive Strength, submit the following for each field test record:
a.Compressive strength test results of the tested concrete.
b.Standard test method used for determining compressive strength.
c.Date the compressive strength tests were performed 157 ALASKA 2020 (d) Aggregate source used for the tested concrete.
e.Specified strength of the tested concrete.
f.Batched weights of constituent materials or the producer’s mix design identification number for the concrete used for each compressive strength test.
2.Trial Mixtures. If a single or group of trial mixtures were used to verify the Required Average Compressive Strength, submit concrete mixture proportions per cubic yard and test results for each trial mixture. Include the following information:
a.Weights of cementitious materials
b.Weight of aggregates in saturated surface dry condition
c.Volume or weight of each admixture
d.Weight of water
e.Water -cement ratio
f.3-day, 7-day, and 28- day compressive strength test results (Include 1- day compressive strength test results for Class P concrete)
g.Percentage of air by volume
h.Wet unit weight
i.Slump
9.Approval. Obtain the Engineer’s approval of each mix design prior to use. Approval of the Job Mix Design does not constitute acceptance of produced concrete and will not obligate the Department to accept or pay for concrete that does not meet the mix acceptance requirements of Subsection 501- 3.03.
10.Changes. Provide a new Job Mix Design and obtain the Engineer’s approval according to Subsection 501- 2.02 for a change in approved Job Mix Design proportions, materials, aggregate gradation, aggregate quality, or admixtures. CONSTRUCTION REQUIREMENTS
501-3.01 BATCHING. Batch concrete, in pr oportioned amounts, according to the approved Job
Mix Design.
1.Certification and Calibration. Batch concrete using a certified batch plant. Use concrete batch plants certified according to the requirements of a. or b. of this subsection for cast -in-place concrete, and for precast or prestressed concrete where the concrete is supplied from a batch plant that is not located at the casting facility. Use concrete batch plants certified according to the requirements of a., b., or c. of this subsection for precast and prestressed concrete where the concrete is supplied from a batch plant located at the casting facility. Use concrete batch plants certified according to the requirements of a., b., or d. of this subsection for non- prestressed precast concrete where the concrete is supplied from a batch plant located at the casting facility. 158 ALASKA 2020 Use and maintain calibrated weighing and measuring devices for concrete batching and for adding material on- site, meeting the requirements of this Subsection..
a.Plant Certification b y the National Ready Mix Concrete Association. Certification may be obtained from the National Ready Mix Concrete Association (NRMCA). Information concerning NRMCA certification may be obtained from the NRMCA, 900 Spring Street, Silver Springs, MD 20910, or online at www.nrmca.org. The NRMCA certification is valid for 2 years from the date of inspection.
b.Plant Certification by a Professional Engineer . Certification may be obtained by independent inspection and evaluation by a Professional Engineer:
1.registered in the State of Alaska,
2.qualified by NRMCA for concrete plant certification, and
3.who uses and completes the NRMCA Plant Certification Check List. Correct deficiencies to the satisfaction of the Professional Engineer. The Professional Engineer must sign and seal the completed NRMCA Plant Certification Check List certifying all applicable items have been met. The certification by a Professional Engineer is valid for 2 years from the date of inspection.
c.Plant Certification by Precast/Prestressed Concrete Institute. Certification may be obtained from the Precast/Prestressed Concrete Institute (PCI) for fabrication of precast and prestressed concrete if the batching plant is located at the concrete casting facility. Information concerning PCI certification may be obtained from the Precast/Prestressed Concrete Institute, 200 W. Adams St. #2100, Chicago, IL 60606, or online at www.pci.org.
d.Plant Certification by National Precast Association. Certification may be obtained from the National Precast Association (NPCA) for fabrication of non- prestresed precast concrete if the batching plant is located at the concrete casting facility. Information concerning NPCA certification may be obtained from the National Precast Concrete Association, 1320 City Center Drive, S uite 200, Carmel, IN 46032, or on -line at http://precast.org.
e.Calibration of Weighing and Measuring Devices . Use weighing and measuring devices meeting the requirements of the NRMCA Plant Inspector’s Guide, calibrated by a commercial scale service, using e quipment traceable to the Alaska State Standards of Weight and Measure as adopted by AS 45.75.020. Verify calibration of all weighing and measuring devices used in concrete production:
1.no more than 6 months before commencing concrete work,
2.after each reloc ation,
3.at least once every 6 months until the work is completed, and
4.when, in the opinion of the Engineer, the accuracy or adequacy of the device is in question.
f.Certification and Calibration Submittals . Submit documentation required for plant certification and weighing and measuring device calibration meeting the requirements of this Subsection before commencing concrete work. 159 ALASKA 2020 If the Plant Certification is by NRMCA, PCI or NPCA submit a copy of the Certificate of Conformance. Include the most recent date of inspection and the calibrated accuracy for each weighing and measuring device. If the Plant Certification is by a Professional Engineer, submit a copy of the signed and sealed completed NRMCA Plant Certification Check List and calibration and/or verifi cation worksheets for each weighing and measuring device. Include the most recent date of inspection and the calibrated accuracy for each weighing and measuring device.
2.Measuring Materials .
c.Cementitious Materials . Use cementitious materials of the same brand, type, and from the same plant of manufacture as the cementitious materials used to verify the approved Job Mix Design according to Subsection 501- 2.02.7. Ensure the quantity of the Portland cement and the cumulative quantity of Portland cement plus other cementitious materials is proportioned in amounts required by the Job Mix Design and meets the mix acceptance requirements. Measure cementitious materials by weight. When other cementitious materials, including fly ash, ground granulated blast -furnac e slag, or silica fume, are specified in the concrete proportions, the material may be cumulatively weighed with the Portland cement. Weigh cementitious materials on a weighing device that is separate and distinct from those used for other materials. Weigh the Portland cement before other cementitious materials. Portland cement is permitted to be measured in bags of standard weight (94 pounds). Do not use a fraction of a bag of cementitious materials unless its weight has been determined by calibrated weig hting devices.
d.Aggregates . Use aggregates from the same sources and gradations as the aggregates used in the trial mixtures or field test records used to verify the required average compressive strength. Ensure the quantity of the aggregates is proportione d in amounts required by the Job Mix Design. Measure aggregates by weight. Establish batch weight measurements on dry materials and adjust the actual scaled weight for the required dry materials weight plus the total weight of moisture, both absorbed and s urface, contained in the aggregate.
e.Water . The total quantity of mixing water includes water added to the batch, ice added to the batch, and water occurring as surface moisture on the aggregates. Measure the added water by weight or volume. Measure added ice by weight. Discharge the flush water (wash water) prior to loading the next batch of concrete. Do not use flush water (wash water) as a portion of the mixing water.
f.Admixtures . Use concrete admixtures according to the manufacturer's instructions and as approved in the Job Mix Design. Measure powdered admixtures by weight. Measure paste or liquid admixtures by weight or volume.
3.Materials Storage and Handling.
a.Cementitious Materials . Keep cementitious materials dry and free from contaminants. Do not use cementitious materials which have become partially hydrated or which contain lumps of caked cementitious material.
b.Aggregates . Do not allow segregation of the aggregates or contamination with foreign materials. Separate aggregate to prevent intermixing of specified gradations. Drain aggregate so the moisture content is uniform and is accounted for during the batching process. 160 ALASKA 2020 Do not use aggregates that contain ice, are frozen, or have been heated directly by combustible materials. Use direct steam, steam -coil, or water -coil heating when heating aggregates. When direct steam is used to thaw aggregate piles, drain aggregates to uniform moisture content before batching.
c.Admixtures . Protect admixtures from contamination, evaporation, or damage. Store admixt ures according to the manufacturer’s instructions. Protect liquid admixtures from freezing and from temperature changes affecting the admixture’s performance.
501-3.02 MIXING AND DELIVERY. Mix concrete, in proportioned amounts, according to the
approved Job Mix Design. Mix ingredients into a thoroughly combined and uniform mixture. Do not retemper concrete mixtures. Do not use concrete that has developed initial set prior to placement
1.Addition of Water . Additional water may be added on- site provided the f ollowing are met:
a.The volume of concrete in the mixer after the additional water is added does not exceed the maximum mixing capacity.
b.The water measuring device is calibrated according to Subsection 501- 3.01.1.e.
c.The total quantity of mixing water, including wat er added according to Subsection 501- 3.02.1 is within the proportion requirements in Subsection 501- 3.03.4. Account for the actual volume of concrete remaining in the mixer.
d.Water additions are completed within 30 minutes after the introduction of the mixing water to the cementitious materials. The addition of water is not prohibited from being several distinct additions of water. Inject additional water into the mixer under pressure and direction of flow to allow for proper distribution within the mixer. Provide additional mixing to ensure a thoroughly combined and uniform mixture is attained.
2.Time for Placement . Discharge the concrete within 1.5 hours of the following:
a.after adding the mixing water to the cementitious materials, and
b.after adding t he cementitious materials to the aggregates. The time to complete discharging the concrete may be extended 2 minutes for every degree the concrete temperature is below 70°F, measured at the point of discharge, to a maximum total time of 2 hours. The Engineer may extend the Time for Placement if Time of Initial Set information is provided in the approved Job Mix Design submittal.
501-3.03 EVALUATION OF MATERIAL FOR ACCE PTANCE. All concrete in the work will be
evaluated for acceptance. The Engineer may rejec t a batch or load of concrete failing to meet the requirements for proportions, slump, total air content, or temperature. Prior to sampling, the Engineer may reject a batch or load of concrete that appears defective in composition.
1.Sampling . The Department will take all samples from the delivery truck discharge. Provide adequate and representative fresh concrete for sampling and testing as directed by the Engineer. The Engineer will sample the concrete after a minimum of 1/2 cubic yard of concrete has discharged from the delivery truck. Do not add water or admixtures to the mix after the concrete has been sampled for acceptance testing. 161 ALASKA 2020 The Engineer will determine aggregate gradation for acceptance based on random samples taken at the plant.
2.Sampling and Tes t Methods . The Department will sample and test according to the following: ATM 301 Sampling of Aggregates ATM 304 Sieve Analysis of Fine and Coarse Aggregates, and Materials Finer Than No. 200 Sieve in Mineral Aggregate by Washing ATM 501 Sampling Fresh ly Mixed Concrete ATM 502 Temperature of Freshly Mixed Portland Cement Concrete ATM 503 Slump of Hydraulic Cement Concrete ATM 504 Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete ATM 505 Air Content of Freshly Mixed Concrete by the Pressure Method ATM 506 Method of Making and Curing Concrete Test Specimens in the Field AASHTO T 231 Capping Cylindrical Concrete Specimens AASHTO T 22 Compressive Strength of Cylindrical Concrete Specimens ATM 507 Field Sampling and Fabrication o f 50-mm (2 - in) Cube Specimens using Grout (Non-Shrink) and or Mortar
3.Batch Tickets . Provide a printed ticket with each batch of concrete delivered to the project. Include the following information:
a.Manufacturer plant (batching facility)
b.Department contract number
c.Date
d.Batch number
e.Time batched
f.Time batch plant discharge is completed
g.Truck number
h.Quantity (quantity batched this load)
i.Type of concrete by class and producer’s mix design identification number
j.Weights of every type of cementitious material 162 ALASKA 2020 k. Weights of each aggregate type
l.Weight or volume of each admixture
m.Weight or volume of water added at the plant
n.Total moisture and absorption percentage for each aggregate
o.Volume or weight of any water added after batching
p.Signature of Contractor’s representative, affirming the accuracy of the information provided
4.Proportion Requirements . Meet the proportion requirements of the approved Job Mix Design within the proportion tolerances:
a.Total Cementitious Material, weight ±1%
b.Aggregates, weight ±2%
c.Total Water, weight or volume +3%
d.Admixtures, weight or volume, according to the dosage range in the approved Job Mix Design. If the total cementitious material weight is made up of different components, keep the component weights within the following tolerances:
1.Portland Cement ±1%
2.Fly Ash ±5%
3.Ground Granulated Blast -Furnace Slag ±5%
4.Silica Fume ±10% Proportion tolerance will be calculated using consistent units for M JMD and M A as follows: Where: P = Proportion tolerance, percentage MJMD = Weight or Volume of component according the approved Job Mix Design MA = Weight or Volume of actual batched component
5.Slump Requirements . Provide concrete with slump within 1 inch of target mix design slump.
6.Total Air Content Requirements . Provide concrete with total air content within +/ -1.5 percent of the approved Job Mix Design at delivery time.
7.Temperature Requirements . Unless otherwise noted, ensure the concrete temperature is between 50°F and 90°F when placed in the forms.
8.Compressive Strength Requirements . Meet the str ength requirements for the Specified Compressive Strength. Concrete of the approved Job Mix Design will be considered to meet 163 ALASKA 2020 the Specified Compressive Strength requirements when both of the following conditions are met:
a.The lowest individual compressive strength test result is not less than the Specified Compressive Strength minus 500 psi, or 90.0 percent of the Specified Compressive Strength, whichever is lower.
b.The lowest averaged result of three consecutive compressive strength tests meets or exceeds t he Specified Compressive Strength.
501-3.04 PREPARATION FOR CONCRETE PLACEM ENT. Allow time for inspection prior to
concrete placement. Remove debris, concrete splatter, oil, paint, and other foreign substances from the surfaces of forms and reinforcing st eel, against which the concrete is to be placed. Remove soil and other debris from pipe piles to the bottom of concrete elevation shown on the Plan. Prepare foundations according to Section 205. Moisten foundations and forms with water before the concret e is placed. Remove standing water on the foundation, in the pile, and in the forms before placing concrete.
501-3.05 PLACING CON CRETE. Do not begin concrete placement without the Engineer's
authorization. Place concrete conforming to the approved Job Mix Design. Place and consolidate each layer within 30 minutes and before the preceding layer takes initial set. If concrete placement operations are delayed so initial set occurs before placement of the succeeding section or layer, place a joint according to Subsection 501- 3.11. The resulting joint will be considered a construction joint. If, in the opinion of the Engineer, the location of the construction joint will affect the strength or durability of the concrete, the Engineer may reject the concrete, the structure, or a portion of the structure. Place concrete in a sequence to obtain a well -consolidated concrete and to prevent cracks. Place concrete as near as possible to final position. Prevent segregation of the mix, displacement of reinforcing steel, and spattering of mortar on the reinforcing steel and forms above the elevation of the layer being placed. Do not deposit a large quantity of concrete at any point and run or work the concrete along the forms. Do not allow concrete to slide down the sides of the forms. Regulate concrete placement so the pressures do not exceed the load capacity of the forms. Limit layer thickness to no more than 2.5 feet, or the capacity of the vibrators to consolidate and merge the concrete with the previous layer, whichev er is less. Unless otherwise specified, use a tremie, tube, or other such device to limit the free- fall height to less than 5.0 feet when placing operations would otherwise allow concrete to drop more than 5.0 feet. When using a tremie to place concrete, use a watertight tremie with an inside diameter of at least 10 inches. When using a concrete pump to place concrete, use concrete pump lines that are watertight with an inside diameter of at least 5 inches. Concrete placed in piles or in dry -shaft process may free -fall more than 5 feet without use of tremie, tube or other such device, provided the falling concrete does not contact rebar or other objects before reaching the top surface of the placed concrete. When free- falling concrete more than 5 feet, us e a drop chute at least 3 feet long. After initial set, prevent movement of forms, projecting ends of reinforcing steel, and other embedded items. 164 ALASKA 2020 Do not use aluminum components in contact with fresh concrete. Place concrete in the superstructure only aft er substructure forms are removed and the substructure has been inspected.
1.Concrete Placement Plan. Submit a concrete placement plan to the Engineer, for concrete decks and drilled shafts. Submit each concrete placement plan to the Engineer, at least 30 days before placing concrete. Do not place concrete until after the Engineer has approved the plan. Include the following in each concrete placement plan:
a.concrete placement sequence,
b.schedule of concrete placement and curing,
c.estimated concrete volume of each section,
d.placement rate and duration,
e.description of finishing equipment,
f.placement procedure,
g.name of the concrete foreman,
h.curing materials, equipment, and procedure.
2.Pre-concreting Conference . Hold a pre- concreting conference for concrete decks and Drilled Shafts, at least 5 working days before placing concrete. Include the Engineer, the Superintendent and foremen in charge of placing reinforcing steel, placing concrete, finishing concrete, and curing operations. Discuss construction procedures, personnel, and equipment to be used. If the project includes more than one concrete placement operation, and if key personnel change between concreting operations, hold additional conferences to include replacement personnel before placing successive concrete sections.
3.Pumping Concrete. Use a pump producing a continuous stream of concrete without air pockets. When pumping is completed, the concrete remaining in the pipeline, if used, must eject without contaminating the concrete or separating the ingredients . Discard concrete contaminated by priming or cleaning the pump.
4.Conveying Concrete. Concrete may be conveyed if the equipment will handle the class of concrete, with the slump and air content specified and without segregation of the aggregate, and no equi pment vibrations will damage freshly placed concrete or reinforcing steel. Limit the length of conveyor belts to prevent aggregate segregation or 300 feet, whichever is less. Cover the belt to protect the concrete from heat, evaporation, precipitation, or when the Engineer determines precipitation is likely.
5.Piles . Do not place concrete underwater in piles.
6.Drilled Shaft Foundations . Place concrete following either the wet -shaft process or dry -shaft process, as applicable. The dry -shaft process may be used where the ground water level and soil and rock conditions are suitable to permit construction of the shaft in a relatively dry excavation, and where the sides and bottom of the shaft can be visually inspected by the Engineer prior to placing the concrete. Relatively dry excavation conditions exist when excavation fluids have been removed from the shaft and the rate of water intrusion is less than 6 inches of water 165 ALASKA 2020 accumulating above the base in a 1- hour period without pumping or other methods to drain or remove water. Suitable soil and rock conditions exist when the sides and bottom of the hole remain stable without caving, sloughing, or swelling between completion of excavation and concrete placement; and loose material and water can be satisfactorily remo ved prior to inspection and concrete placement. Do not begin concrete placement if there is more than 1 inch of water in the bottom of the shaft excavation. Use wet -shaft process if the requirements for dry -shaft process cannot be satisfied. Provide proces s control testing during concrete placement. Test slump and air content before placing each batch of concrete in the drilled shaft. Perform sampling and testing according to Subsection 501- 3.03.2 using a WAQTC qualified concrete testing technician or ACI c ertified concrete field testing technician. Test every batch of concrete before placement. Record the time when each sample is collected. Submit test results in writing to the Engineer immediately after completing each test.
a.Wet-Shaft Process . Place concrete using a tremie or concrete pump. Place concrete continuously until good quality concrete, as determined by the Engineer, is evident at top of the shaft or nearest construction joint. Good quality concrete is considered concrete of the same consistency, appearance, and quality as the concrete being delivered and meeting the applicable mix acceptance requirements. Remove a sufficient volume of concrete to ensure elimination of contaminated concrete at the top of shaft before continuing with subsequent cons truction operations. Remove concrete laitance during or immediately after concrete placement operations have ended. Do not allow water, fluids, drilling aids, or concrete from the top of the shaft to enter streams or other waterways. Construct the dischar ge end of the tremie or pump line to prevent water intrusion and permit the free flow of concrete during concrete placement. Use caps, bottom plates, pigs, or other such devices inserted into or attached to discharge pipe to separate the concrete from the excavation fluid during initial charging of the discharge pipe. Ensure the discharge pipe has sufficient length and weight to rest on the shaft base before starting concrete placement. When using a tremie, provide adequate support so the tremie can be rai sed to increase the discharge of concrete and lowered to reduce the discharge of concrete. Do not shake, vibrate, or rapidly raise or lower the tremie to increase the discharge of the concrete. Maintain a positive head of concrete inside the tremie or pump line relative to the excavation fluid level. Position the discharge orifice within one pipe diameter of the shaft base. Do not re- position the discharge pipe until the orifice is at least 8 feet below the concrete surface. Maintain at least 8 feet of conc rete above the discharge orifice during concrete placement. Monitor the concrete level during placement to ensure the tremie or pump line discharge orifice remains at least 8 feet below the concrete surface throughout placement. If the discharge orifice r ises above the concrete surface before concrete placement is complete, the shaft will be considered defective. Immediately terminate concrete placement operations and notify the Engineer.
1.Concrete Flowability Requirements . Ensure concrete placed in the shaft remains flowable throughout placement operations by maintaining a slump of at least 6 inches until placement is completed. Collect samples from the first batch of concrete. Test slump from the first batch of concrete at the beginning of the concrete placement 166 ALASKA 2020 operations and immediately after concrete placement operations are complete. Record the time when samples are collected and when tests are performed. Submit test results in writing to the Engineer immediately after completing each test.
b.Dry-Shaft Pr ocess. Place concrete continuously until concrete is evident at top of the shaft or nearest construction joint. Concrete may be permitted to free- fall into place if the concrete does not contact the sides of the shaft, reinforcing steel, or other objects w hile free falling. Remove concrete laitance during or immediately after concrete placement operations have ended.
1.Concrete Plasticity Requirements . Ensure concrete placed in the shaft remains plastic throughout placement operations by completing placement operations before initial set occurs.
7.Concrete Decks and Approach Slabs . Before placing concrete, operate the finishing machine over the entire length of the deck to check screed deflection, reinforcing steel clearance, and concrete thickness. Limit the rate of placing concrete to what can be finished before initial set.
a.Placement Sequence. Place the concrete deck in the sequence shown on the Plans. The Engineer may approve a revised placement sequence for casting the concrete deck continuously from one end to the other provided the following:
1.Stockpile the materials necessary to complete the placement and have the equipment, incidentals, and workers on the site before beginning concrete placement operations.
2.Ensure the continuous concrete placement an d finishing operation proceeds at a minimum rate of 30 feet per hour, measured longitudinally along the axis of the span.
3.The Engineer determines the revised placement sequence will not reduce the stability during construction and will not reduce the qual ity, capacity, or durability of the completed structure. If the Engineer approves the proposal for a continuous concrete placement operation, the Department will observe and evaluate performance to the first planned construction joint in the sequence. At this point, the Engineer may authorize you to proceed with the continuous concrete placement operation or suspend the placement and install a construction joint. The Engineer's decision will be based on whether the concrete can be produced, delivered, and finished at a continuous rate permitting the structure to accommodate final dead load deflections while the concrete is plastic. If the Engineer suspends the continuous concrete placement operations after the first sequential placement, submit modifications for improving the continuous concrete placement operations, beginning at the other end of the deck. If a second attempt at continuous concrete placement is authorized, the placement will be evaluated and allowed or terminated based on the same criteria as the first sequential placement. If the Engineer suspends the continuous concrete placement operation after the second attempt, additional attempts will not be permitted. Follow the deck placing sequence shown on the Plans.
501-3.06 CONSOLIDATI ON OF CONCRETE. Consolidate concrete to make a dense
homogeneous mass free of voids and rock pockets. Consolidate each layer to leave a compact, 167 ALASKA 2020 dense, and impervious concrete with smooth faces on exposed surfaces with no visible line of separation between adjoining layers. Consolidate concrete, except underwater or other exempted placements, by mechanical vibration at the point of deposit. Use vibrators capable of visibly affecting concrete with a 1- inch slump for a distance of at least 18 inches from the vibrator. Use vibrators and regulate placement in order to consolidate the fresh concrete within 15 minutes of placement and before initial set . Effectively vibrate the full depth of each layer. For immersion- type vibrators, insert vibrators vertically to a depth penetrating into the previous layer. Withdraw vibrators slowly to avoid segregation or grout pockets. Vibrate in a uniform pattern spaced less than 1.5 times the radius of visible effectiveness. Avoid vibration of initially set layers and reinforcing steel below the succeeding placement. Do not hold vibrators against reinforcing steel or use them to flow or spread the concrete into place. Manipulate vibrators to produce concrete free of voids, with proper texture on exposed faces, and maximum consolidatio n. Do not allow the concrete to segregate, form pools of mortar, or form laitance on the surface. When immersion- type vibrators are used to consolidate concrete around epoxy -coated reinforcing steel, use rubber or nonmetallic vibrator heads that will not damage epoxy coatings. Concrete may be placed directly into drilled shaft foundations and piles without mechanical vibration; except, vibrate the top 5 feet of concrete. For drilled shaft foundations, consolidate the top 5 feet of concrete after good quali ty concrete is evident at the top of the shaft and after water, slurry, drilling aids, and other materials other than concrete have been removed.
501-3.07 FINISHING C ONCRETE SURFACES. After the concrete is consolidated and prior to
the application of curing materials, strike off unformed concrete surfaces to the required elevation and slope. Finish the surface by floating the surface to remove local irregularities and leave sufficient mortar to seal the concrete surface. Do not use mortar topping for concrete surfaces. Do not use aluminum finishing equipment. Complete initial floating operations before bleed water or excess moisture is present on the surface and before the concrete takes initial set. Complete final finishing before final set occurs. Do not use finishing aids or additional water to assist in finishing concrete surfaces. Do not finish concrete surfaces if bleed water, excess moisture, or curing materials are present. Provide formed concrete surfaces with an ordinary finish unless otherwise noted.
1.Ordinary Finish . An ordinary finish is the finish left on a surface after removing the forms, filling the holes left by the form ties, and repairing defects. Ensure the surface is true and even and free from rock pockets and depressions or projections. Immediately after removing the forms, remove the metal devices holding the forms in place and passing through the body of the concrete, or cut them back at least 1 inch beneath the surface of the concrete. Remove fins of mortar and irregularities caused by form joints. Patch cavities produced by form ties, depressions, holes, and voids greater than 1/4 inch. Fill the cavity with stiff mortar composed of one part of Portland cement to two parts of fine aggregate. Proportion the mortar by loose volume with only enough water to form a small ball when squeezed gently by hand. Clean the cavity and saturate the concrete with water before filling the cavity. Thoroughly tamp the mixture into place. Float the surface of the mortar before initial set to make the sur face neat in appearance. Cure the patch according to Subsection 501- 3.08. 168 ALASKA 2020 Do not repair concrete with rock pockets, cracks, or other defects until the concrete is inspected by the Engineer. Concrete repaired prior to inspection by the Engineer may be rejec ted. If, in the opinion of the Engineer, the defect will affect the strength or durability of the concrete, the Engineer may reject the concrete, the structure, or portion of the structure. If the defect is greater than 3/4 inch in depth, submit a repair plan including complete details of the method, materials, and equipment proposed for use in repairing the concrete. Obtain the Engineer's approval of the repair plan before repairing the defect. A repair plan is not required if the defect is less than 3/4 i nch in depth. Repair broken corners and edges, rock pockets, and other defects. If the defect is greater than 3/4 inch in depth, repair the defect according to the approved repair plan. If the defect is less than 3/4 inch in depth, chip away coarse or brok en material according to Subsection
501-3.16 to obtain a dense, uniform surface of concrete exposing solid coarse aggregate. Cut
feathered edges to form faces perpendicular to the surface. Apply an epoxy bonding agent to the concrete mating surfaces according the manufacturer's instructions. Patch the repaired area with stiff mortar composed of one part of Portland cement to two parts of fine aggregate. Proportion the mortar by loose volume with only enough water to form a small ball when squeezed gently by hand. Perform repairs prior to releasing falsework, prestressing, or applying additional loads to the concrete.
2.Rubbed Finish. Provide a rubbed finish at locations shown on the Plans. When forms can be removed, wet the surface and then rub with a wooden f loat until irregularities and form marks are removed and the surface is covered with a lather composed of cement and water. A thin grout composed of one part Portland cement and one part fine aggregate may be used. Allow this lather to set for at least 5 days. Then, smooth the surface by lightly rubbing with a fine carborundum stone. If the concrete has hardened before being rubbed, use a medium coarse carborundum stone to finish the surface at least 4 days after placing the concrete. Spread a thin grout c omposed of one part Portland cement and one part fine aggregate over a small area of the surface. Immediately rub the surface with the stone until form marks and irregularities are removed and the surface is covered with a lather. Allow this lather to set for at least 5 days. Then, smooth the surface by rubbing lightly with a fine carborundum stone. Complete ordinary finish work before applying the rubbed finish.
3.Concrete Decks and Approach Slabs . Obtain a smooth riding surface of uniform texture, true to the required grade and cross section. Use a self -propelled mechanical finishing machine
a.capable of forward and reverse movement,
b.with a rotating cylindrical single or double drum screed,
c.with necessary adjustments to produce the required cross -section, li ne, and grade,
d.allowing screeds to be raised and lowered, and
e.with an upper vertical limit of screed travel permitting the screed to clear the finished concrete surface. When placing concrete abutting previously placed concrete, equip the finishing machine to travel on the existing concrete. 169 ALASKA 2020 The Engineer may approve hand- operated motorized roller screeds (friction screeds) where jobsite conditions prohibit the use of conventional configuration finishing machines described above, for small areas less than 12 feet wide, and on approach slabs in which conventional configuration finishing machines are not used to finish the concrete deck. Do not use vibratory screeds. Use equipment capable of striking off the full placement width without intermediate supports or rails. Use rails resting on adjustable supports that can be removed with the least disturbance to the concrete. Place the supports on structural members or on forms rigid enough to resist deflection. Use supports that are removable to at least 2 inches below the finished surface. If possible, place rails outside the finishing area. If not possible, place them above the finished surface. Use rails (with their supports) that are strong and stiff enough for operation of the equipment without excessive deflection. Place and secure rails for the full length of the deck before placing concrete. Set the rails to the proper grade and elevations to ensure the required profile is provided. After placing and consolidating the concrete, carefully strike off the conc rete surface. Correct imperfections left on the deck. Provide a float finish to surfaces receiving a waterproof membrane. Texture other surfaces with a heavy -broom finish perpendicular to the direction of traffic. Do not place finishing machines or other loads on the screed rail supports or on features supporting fresh concrete after the concrete has initially set and before the concrete attains at least 80 percent of the Specified Compressive Strength. Do not release falsework or wedges supporting concret e on either side of a joint until each side has cured as specified.
4.Curb, Sidewalk, and Concrete Barrier Surfaces . Finish exposed faces of curbs, sidewalks, and concrete barriers to true surfaces and provide a broom finish. Broom finish sidewalks perpendic ular to the direction of traffic.
5.Sandblasted Finish. Sandblast the cured concrete surface with hard, sharp abrasive media to produce an even fine- grained surface in which the mortar has been cut away, leaving the aggregate exposed.
6.Trowel Finish . Trowel t he surface smooth and free of trowel marks.
501-3.08 CURING CONCRETE. Maintain a satisfactory moisture content and temperature in the
concrete immediately after finishing operations are completed.
1.Initial Curing Period . Before final curing, ensure the surface of the concrete is kept moist. Concrete surface is beginning to dry when no bleed water is present and the surface color changes. If the concrete surface begins to dry before the final curing method can be applied, prevent further loss of moisture by one or more of the following methods:
a.Fog Spray . Use equipment producing a fog spray from an atomizing nozzle with sufficient velocity to cover the entire concrete surface. Direct the atomized water spray above the concrete surface to allow the fog to drift down to the concrete surface. Do not apply the discharge of the atomized water spray directly at the concrete surface. Continue fogging to maintain the reflective appearance of the damp concrete. Do not allow the surface to dry, or to undergo cycles o f drying and wetting. Keep the concrete surface damp, but do not accumulate water until after final set has occurred. Use water meeting the requirements of Subsection 712- 2.01. 170 ALASKA 2020 b. Evaporation Rate Reducer . Apply a monomolecular film intended specifically as an evaporation rate reducer to entrap bleed water or excess moisture on the concrete surface. Apply the evaporation rate reducer according to the manufacturer’s written instructions. Do not use the evaporation rate reducer during finishing operations or as a finishing aid. Do not use evaporation rate reducers on concrete surfaces receiving a waterproofing membrane such as concrete decks, approach slabs, end diaphragms and decked precast concrete members.
2.Final Curing Period. Unless otherwise noted, employ t he final curing method immediately following finishing operations. Use wet curing on construction joints, concrete with a mix design water -cement ratio less than 0.40, concrete decks, approach slabs, and other concrete surfaces subject to tire contact in the completed structure. For other concrete, use wet curing, liquid membrane-forming curing, forms -in-place curing, or a combination of these curing methods. Do not use liquid membrane- forming curing compounds on concrete surfaces to which other materials will be cast against or bonded such as concrete and waterproofing membranes. In addition to the requirements in this section, precast concrete members may use accelerated curing.
a.Wet Curing. Until the end of the curing period, provide continuous moisture by:
1.watering a covering of heavy burlap blankets or quilted cotton mats,
2.keeping concrete surfaces wet with water continuously,
3.wetting the outside surfaces of wood forms. Wait to install curing materials until the concrete has sufficiently hardened to permit such operations without damaging the concrete or marring the finish. While waiting to employ curing materials, maintain the concrete surface moisture as specified for the initial curing period. Uniformly distribute absorbent materials across the ent ire concrete surface. Apply water in a manner that will not displace the curing materials or erode the concrete surface. Keep the concrete surfaces continuously wet. Do not allow concrete surfaces to dry or alternate with wetting and drying cycles. Cover t he concrete, wooden forms and absorbent material with impermeable sheeting. Use white reflective impermeable sheeting if direct sunlight is present, or if the Engineer determines direct sunlight may be present during the curing period. Do not use absorbent materials containing harmful substances such as sugar or fertilizer, or materials that may discolor the concrete.
b.Liquid Membrane- Forming Curing Compounds . Apply liquid membrane- forming compounds immediately after final finishing and as soon as the free water has disappeared, no water sheen is visible, and bleeding has essentially ceased. Apply two coats of liquid membrane- forming compound with the second coat at right angles to the first. Apply both coats of liquid membrane- forming compounds uniformly until the original color of the concrete is obscured. Apply liquid membrane- forming compound according to the manufacturer’s instructions. Do not apply the liquid membrane- forming compound to dry concrete surfaces. Moisten the concrete surface, without standing water, before applying the liquid membrane-forming compound. Protect the membrane from damage for the duration of the curing period. Re- apply the liquid membrane- forming compound if the membrane is cracked or damaged during the curing period. 171 ALASKA 2020 c. Forms -In-Place Curing. Formed concrete surfaces may be cured by retaining the forms in place for the entire curing period. Keep the forms moisture tight. Do not loosen forms. For wooden forms, keep the forms wet as required for wet curing. If gaps develop between the forms or between the forms and concrete:
1.remove the forms and implement another curing method
2.keep the gaps continuously filled with water for the remainder of the curing period.
d.Accelerated Curing. Accelerated curing may be used only for precast conc rete members with Class P Concrete. During the curing period, keep the concrete in a saturated curing atmosphere until the concrete achieves the required release strength. The curing period may be accelerated by using saturated low -pressure steam, convect ion-heat, or radiant -heat in a suitable curing chamber to contain the live steam or heat. Provide at least 3 inches of clearance between the enclosure and forms to allow adequate circulation. If accelerated curing methods are used, embed at least one temperature- recording device in the concrete to verify concrete temperatures are within the specified limits. Install one temperature- recording device, accurate to ±5°F, near the member’s midpoint, 6 to 8 inches from the top or bottom, and along the member’s centerline. Monitor the concrete temperature with the temperature- recording device sensor arranged and calibrated to continuously record, date, and identify the concrete temperature throughout the heating cycle. Begin recording temperatures once concrete is placed in the forms. Stop recording temperatures after the heating cycle is complete and when the concrete temperature is within 20°F of the air temperature to which the concrete will be exposed. Upon request, submit the temperature record to the Engineer for each precast concrete member. While waiting to begin the heating cycle, maintain the concrete temperature between 50°F and 90°F and maintain concrete surface moisture as specified for the initial curing period. Do not apply steam, convection- heat or radiant -heat prior to initial set except to maintain the concrete temperature. Determine the time of initial set according to AASHTO T 197. Begin the heating cycle immediately after the initial set. Prevent hot air and steam from blowing directly onto the c oncrete or forms. Increase the concrete temperature at an average rate not exceeding 40°F per hour until the curing temperature is reached. Limit curing temperature within the concrete to 175°F maximum. Decrease the concrete temperature not more than 40°F per hour until reaching a temperature 20°F above the temperature of the air to which the concrete will be exposed. Apply radiant heat by pipes circulating steam, hot oil, or hot water, or by electric heating elements.
3.Curing Temperature. Maintain concrete temperature at or above 50°F for the first 6 days after placement. After 6 days you may choose to maintain concrete temperature between 32°F and 50°F with the addition of curing time as specified under 501- 3.08.4a.
4.Ending Curing Operations . Continue curi ng operations uninterrupted until the required concrete properties, strength, and durability have developed or until there is reasonable assurance these properties will be achieved after the curing operations have been terminated. 172 ALASKA 2020 Curing operations may be terminated after both 501- 3.08.4.a and 501- 3.08.4.b are satisfied:
a.The concrete has cured for:
1.at least 7 days.
2.at least 10 days when fly ash or ground granulated blast furnace slag in excess of 10 percent by weight of the Portland cement are used in the mix. Add one additional day of curing to the requirements of 501- 3.08.4.a.(1) and 501- 3.08.4.a.(2), for each day or portion of a day the concrete temperature falls below 50°F during the curing period.
b.The compressive strength from informational field tests reaches the following:
1.70 percent of the Specified Compressive Strength if post curing concrete temperature is expected to remain at or above 50°F until 100 percent of the Specified Compressive Strength is attained.
2.100 percent of the Specified Compressiv e Strength, if post curing conditions are expected to allow the concrete temperature to fall below 50°F before 100 percent of the Specified Compressive Strength is attained.
501-3.09 PROTECTION OF CONCRETE. Protect concrete from damage. Do not apply loads to
the concrete until the end of the curing period and until the Engineer determines the concrete has attained sufficient strength to safely carry the applied loads without damage. Unless otherwise noted, sufficient strength is attained when the concrete has attained a compressive strength, determined from informational field tests, of at least 80 percent of the Specified Compressive Strength. Release forms and falsework according to Section 512. During the curing period, protect concrete from damaging mechanical disturbances. Protect concrete surfaces from damage by construction traffic, equipment, materials, rain or running water, and Cold Weather Conditions, and other adverse weather conditions. Meet the vibration limits during pile driving of Section 505. Do not backfill against concrete structures until the end of the curing period and until the concrete has attained a compressive strength, determined from informational field tests, of at least 80 percent of the Specified Compressive Strength. Obtain aut horization from the Engineer before driving vehicles or equipment, or storing materials on the structure. Keep the structure closed to traffic until the end of the curing period and until the concrete has attained a compressive strength determined from inf ormational field tests, of at least 100 percent of the Specified Compressive Strength. Obtain authorization from the Engineer before opening the structure to traffic.
1.Rain Protection. Provide materials and equipment on site to protect concrete until final set. During precipitation, or when the Engineer determines precipitation is likely before final set, employ materials and equipment to protect the concrete until final set occurs. Do not expose the concrete to rain or flowing water before final set occur s.
2.Cold Temperature Protection. Place and cure concrete according to an approved cold temperature concreting plan whenever the air temperature in the shade, away from artificial heat, is expected to be below 40° F during placement or curing, or in the opi nion of the Engineer, the air temperature in the shade, away from artificial heat, is likely to be below 40°F during placement or curing. 173 ALASKA 2020 Prevent damage to concrete throughout the curing period. Prevent concrete from freezing, rapid cooling of concrete surfaces, or from large temperature differences within the concrete. Have materials and equipment ready to protect concrete from exposure to cold during placement and throughout the curing period. Maintain the concrete temperature with methods such as insulated forms, enclosures, and indirect heat. Vent flue gases to the outside of the enclosure when using combustion heaters. Prevent overheating areas or drying of concrete during the curing period by directing heaters and ducts away from the concrete surfac e. Do not heat the curing concrete to a temperature more than 90°F except as permitted in Subsection 501- 3.08.2.d. Measure and record air temperature in the work area, away from sunlight and artificial heat, at approximate 12 hour intervals, at least twice each 24- hour period. Air temperature measurement is not required when air temperature is expected to remain above 40°F throughout concrete placement and the curing period.
a.Cold temperature concreting plan submittals . Submit cold temperature concreting plan to the Engineer at least 5 days before beginning concrete placement when Cold Weather Conditions are present or expected. For each concrete placement include:
1.Procedures for the production, transport and placement
2.Considerations for section size and outside air temperature during the pour
3.Concrete placement temperatures
4.Methods that ensure adequate curing conditions are maintained as required in Subsection 501- 3.08
5.Procedures for measuring and reporting concrete temperatures
6.Procedures for abrupt changes in weather conditions and equipment failures
7.Methods for verification of in- place strength
b.Temperature of Concrete During Batching and Placement . Obtain concrete batching and placement temperatures by heating the mixing water and/or aggregates. Avoid overheating aggregates so spot temperatures of aggregates do not exceed 212°F and average temperature of aggregates does not exceed 150°F when added to the batch. Ensure temperature of combined ingredients does not exceed 8 5°F when cementitious materials an d admixtures are added. Ensure concrete is between 50 °F and 90°F during placement.
c.Preparation. Remove snow, ice, and frost from all surfaces that will touch fresh concrete. Thaw the subgrade to at least 2 feet below the concrete to be placed before beginning concrete placement. Preheat surfaces that will be in contact with placed concrete. Maintain these temperatures to no more than 10°F greater or 15°F less than that of the concrete during placement.
d.Ending Cold Temperature Protection. Cold temperature protection may be terminated when the air temperature in the shade, away from artificial heat, is rising, above 40°F, and is expected to remain above 40°F until the end of the curing period. At the end of the protection period, remove the protection so the concrete surface drops in temperature gradually at a rate not more than 1.25°F per hour until the concrete temperature is within 20°F of the air temperature in the shade, away from artificial heat. If water curing is used, terminate the addition of wat er to the surface and allow the concrete surface to dry prior to exposure of the concrete to freezing temperatures. 174 ALASKA 2020 3. Hot Temperature Protection. Do not begin concrete placement when air temperatures are expected to exceed 90°F during concrete placement wit hout an approved hot temperature concreting plan. When air temperatures are expected to, have materials and equipment in place to prevent the concrete temperature from exceeding 90°F before final set and exceeding 150°F during the final curing period. Implement the hot temperature concreting plan when the air temperature in direct sunlight is greater than 90°F.
a.Submittals . Submit a hot temperature concreting plan to the Engineer at least 5 days before placing concrete when the air temperature is expected to exceed 90°F during the concrete placement. Submit detailed procedures for the production, transport, placement, protection, curing, and temperature monitoring of concrete during hot temperatures for each concrete placement. Include procedures for abrupt changes in temperature conditions or equipment failures.
b.Preparation. Prior to placing concrete, plan to minimize the exposure of the concrete to hot temperatures and direct sunlight. Cool surfaces that will touch the concrete to less than 90°F. Do not s prinkle fine aggregate piles with water. If sprinkling coarse aggregates, monitor the moisture content and adjust the mixing water for the free water in the aggregate. If replacing all or part of the mixing water with crushed ice, then ensure the ice is completely melted and thoroughly mixed with the other concrete materials before beginning concrete placement.
c.Temperature of Concrete Before Placement . Ensure concrete being placed in forms is between 50°F and 90°F. Obtain these temperatures by cooling the m ixing water and/or aggregate.
d.Temperature of In- place Concrete. Protect the concrete from damage due to hot weather immediately after concrete placement and ensure adequate curing conditions are maintained as required in Subsection 501- 3.08. Provide extra protection in areas especially vulnerable to temperatures above 90°F such as exposed top surfaces, corners and edges, thin sections, and concrete placed against steel. Protection may be terminated when the air temperature in direct sunlight drops below 90°F and is expected to remain below 90°F for at least 24 hours.
501-3.10 TOLERANCES. Produce concrete elements conforming to the following tolerances:
1.Length: ±3/4 inch for members 100’ and shorter. ±1 inch for members longer than 100’
2.Cross -sectional D imensions :
a.For dimensions 6 inches or less: - 1/8 inch to +1/4 inch.
b.For dimensions over 6 inches but not over 18 inches: - 1/8 inch to +3/8 inch.
c.For dimensions over 18 inches: - 1/4 inch to +3/8 inch.
3.Distortion of Cross -section: Limit the slope with respect to the specified surface, plane, or line to less than ±1/16 inch per foot, but not to exceed ±1/4 inch measured perpendicular to the long axis of member.
4.Surface Irregularities (deviation from a 10- foot straight edge): 175 ALASKA 2020 a. For surfaces receiving a topping or are buried: ±1/4 inch.
b.For surfaces not receiving a topping or are visible in the completed work: ±1/8 inch.
5.Camber : Do not vary from the approved camber more than ±1/8 inch per 10 feet of length, but not to exceed 1 inch. In addition, the camber of each girder may not differ from the camber or the other girders by more than 1 inch.
6.Lateral Sweep (deviation from a straight line parallel to centerline of member):
a.For member length 40 feet or less: ±1/4 inch.
b.For member length over 40 feet but not over 60 feet: ±3/8 inch.
c.For member length over 60 feet: ±1/2 inch.
7.Deck Width (measured out -to-out): Zero to +2 inches, except not more than +1/2 inch where more precision is dictated by the substructure details such as anchor bolts, parallel wing walls, etc.
8.Position and Alignment :
a.Bottom of footing elevation: ±0.1 feet.
b.Profile grade: ±0.05 feet.
c.Lateral position: ±0.1 feet.
d.Skew: ±0.05 degrees.
9.Bearing Seats :
a.Elevation: ±0.01 feet
b.Variation between bearing seats: Do not vary from a straight line coincident with the centerline of bearings and parallel to the surface of the bottom flanges more than 0.01 feet.
c.Grade and cross slope: ±0.005 feet per foot.
10.Openings :
a.Size of opening: ±1/4 inch.
b.Location of centerline of opening: ±1/2 inch.
11.Embedded Items :
a.Bolts: ±1/4 inch.
b.Utility hangers: ±1/2 inch.
c.Weld Plates: ±1/2 inch measured along the length of the member, ±1/8 inch measured perpendicular to the length of the member.
d.Inserts: ±1 inch.
e.Rail post anchor plates: ±1/4 inch. 176 ALASKA 2020 f. Expansion joints: ±1/8 inch.
g.Electrical conduits: ±1/2 inch.
h.Deck drains: ±1/2 inch.
i.Other embedded items: ±1/2 inch.
501-3.11 CONSTRUCTIO N JOINTS. Unless otherwise noted, locate construction joints where
specified in the Contract documents. Obtain approval before adding, deleting, or rel ocating construction joints specified in the Contract documents. Make requests for such changes in writing, accompanied by a drawing depicting the joint. The Engineer will evaluate the proposed construction joint to determine if the joint will affect the s trength or durability of the concrete. Joints noted as "permissible" do not need the Engineer's approval before deleting. When permitted, place the joints where they will not be exposed to view in the finished structure. At horizontal construction joints, place gage strips 1 -1/2 inches thick inside the forms along exposed faces to give the joints straight lines. Do not use wire mesh forming material. If the Plans require a roughened surface on the joint, create grooves at right angles to the length of the member. Make grooves that are 1/2 to 1 inch wide, 1/4 to 1/2 inch deep, and spaced equally at twice the width of the groove. Terminate the grooves within 1- 1/2 to 2 inches from the edges of the joint. If the Plans require a smooth surface on the joint, pr ovide a trowel finish. Include shear keys at the joint when the Contract documents do not require a roughened surface or a smooth surface. Make shear keys of formed depressions with slight beveling to ensure ready form removal. Do not use raised shear keys . Make shear keys that meet the following:
1.For tops of beams, at the tops and bottoms of boxed girder webs, in diaphragms, and in crossbeams, use shear keys 1- 1/2 inches deep, 8 inches long, and spaced at 16 inches.
2.In other locations, use shear keys at l east 1- 1/2 inches deep and 1/3 of the joint width. Terminate the shear keys within 1- 1/2 to 2 inches of the joint edge. Clean construction joints of surface laitance and other foreign materials before fresh concrete is placed against the surface of the joint. Flush construction joints with water and allow the joint to dry to a surface- dry condition immediately prior to placing concrete.
501-3.12 FORMS AND F ALSEWORK. Use forms and falsework designed and constructed
according to Section 512.
501-3.13 PRECAST CONCRETE MEMBERS. In addition to the requirements listed in this
Section, conform to Section 502 when fabricating prestressed concrete members.
1.Shop Drawings . Provide shop drawings for precast concrete members. Include details not provided in the Plans for the construction and erection of the members. Cast members only after shop drawings are approved. Use precast methods for cast -in-place elements when approved. Submit shop drawings, showing construction joint details and other required information.
2.Manufacture. Prestress concrete according to Section 502. Fabricate and install reinforcing steel according to Section 503. 177 ALASKA 2020 a. Unless otherwise noted, use Class P concrete for precast concrete members meeting the Specified Compressive Strength noted on the Plans.
3.Storage and Handling . Handle and move precast concrete members without damage. Store and transport precast concrete members in an upright position with the directions of the support reactions on the member during storage or transport as if in the final position. Locate support points during transport and storage within 30 inches of their final position, or as shown on approved shop drawings. Ship only after the member has cured at least 7 days and has a compressive strength not less than 100 percent of the Specified Compressive Strength.
4.Erection . Maintain member stability during transport, lifting, and erection operations. Limit concrete tension stresses due to transport, lifting, and erection operations to less than 500 psi. Set interchangeable precast concrete members so the initial difference between the top surfaces of the edges of adjacent precast concrete members is no more than 1/2 inch at midspan and no more than 1/4 inch at the bearings. Set and securely brace precast concrete members within a s pan before making shear connections. Secure the member to the structure, and provide temporary braces necessary to resist wind or other loads immediately after erecting each precast concrete member. Provide and use forcing devices as shown in the Plans or as recommended by the precast concrete member manufacturer. Use devices maintaining the top edges of adjacent members at the same elevation while casting or welding diaphragms, welding shear connector plates, and while placing and curing grout in the shear keys. Make field welds according to Section 503 and Section 504. Install cast -in-place diaphragms within 2 weeks after setting precast concrete members on their bearings. If cast -in-place diaphragms cannot be placed within the prescribed time limit, ens ure the members are adequately braced to resist movement and rotation. Submit a bracing plan including complete details and substantiating calculations, sealed by a Professional Engineer registered in the State of Alaska. Erect and place precast deck panel s so the mating surfaces do not allow grout leakage. Seal joints where grout leakage may occur. When the Plans require filling keyways between adjacent concrete members with grout, place grout according to the manufacturer's written instructions. Clean joints of surface laitance and other foreign material before placing grout. Do not place loads on the grouted members until the grout compressive strength has reached 5000 psi. Tightly pack and rod the grout in the keys and spaces. Keep the grout surface smooth and neat. Ensure the grout surface meets the member edges throughout their lengths and matches the surface elevation of the members with a tolerance of ±1/8 inch.
501-3.14 PLACING ANC HOR BOLTS. Secure anchor bolt assemblies where shown on the
Plans. When casting anchor bolts in concrete, secure anchor bolts before placing concrete in the forms. Do not disturb anchor bolts after concrete has been placed. When installing anchor bolts in pipe sleeves, pre- cast holes, cored holes, or drilled holes, complet ely fill the cavity with grout. Do not allow water to freeze in the cavity. Do not allow foreign material in the cavity. 178 ALASKA 2020 501-3.15 UTILIDUCTS, PIPES, CONDUITS, DU CTS, AND UTILITY HOL ES. When utiliducts, pipes, conduits, and ducts will be encased in concrete , install them in the forms before placing the concrete. Support the utiliducts, pipes, conduits, and ducts to prevent displacement during concrete placement. Install utiliducts and utility holes parallel to the roadway centerline unless noted otherwise. Prevent bond between the utiliducts and concrete by tightly wrapping the utiliducts with at least two layers of asphalt felt.
501-3.16 REMOVING CO NCRETE. Do not damage other portions of the structure remaining in
place when removing concrete. Determine an d delineate the extent of removal area. Outline the area with a 3/4- inch deep saw cut to form faces perpendicular to the surface prior to the removal of concrete. Do not cut or damage existing reinforcing steel or prestressing steel. During the course of r emoval, the Engineer may suspend removal or may require additional removal and outline saw cut. Use any combination of mechanical methods, water -blast cleaning, or abrasive- blast cleaning to remove coarse or broken concrete until a dense, uniform surface of concrete exposing solid coarse aggregate is obtained. When using mechanical methods for removal of concrete, meet the following:
1.Use impact tools weighing less than 15 lbs.
2.Operate impact tools at an angle less than 45 degrees relative to the surface of the concrete being removed.
3.Use hand tools such as hammers and chisels or small air chisels, water blast cleaning, or abrasive blast cleaning to remove final particles of unsound concrete. During the removal operation do not damage existing reinforcing st eel, prestressing steel, or concrete to remain in place. Before applying the repair material, clean the surface according to ASTM D4258 within 24 hours of applying the repair material. Use water meeting the requirements of Subsection 712- 2.01 for removal operations.
501-3.17 CRACK EVALU ATION. The Engineer will evaluate concrete that is cracked during
execution of the Contract. Measure cracks at their widest point. For concrete decks and approach slabs, allow the Engineer to inspect any surface cracking immediately after termination of concrete curing operations, before prestressing (if applicable), and before releasing falsework. If any 500 square foot portion of the concrete deck or approach slab has cracks, whose width exceeds 0.020 inches and combined l engths total more than 16 feet, treat the surface by performing low -viscosity resin crack repair. For other concrete, cracks will be evaluated based on the crack width.
1.For crack widths equal to and greater than 0.060 inches, the concrete will be considered unacceptable.
2.For cracks widths equal to and greater than 0.013 inches but less than 0.060 inches, the Engineer will evaluate the cracked concrete for structural adequacy and durability. If the Engineer determines the crack may affect structural adequacy or durability, the Engineer may reject the concrete, the structure, or a portion of the structure. If the Engineer determines the cracked concrete is acceptable, repair the crack by performing low -pressure crack repair according to Subsection 501- 3.18. 179 ALASKA 2020 3. For cracks widths less than 0.013 inches wide, the crack will be considered acceptable with no additional evaluation or repairs required.
501-3.18 CRACK REPAI R. Perform crack repairs and replace unacceptable concrete at no cost
to the Department. No contrac t time extension will be given for repairing, removing, and replacing unacceptable material.
1.Low-Pressure Crack Repair . Repair cracked concrete according to the following requirements:
a.Crack Repair Plan. Submit a crack repair plan to the Engineer. Do not repair the crack until the Engineer has approved the crack repair plan. Include the following in the crack repair plan:
1.Experience of the injection equipment technicians
2.Evaluation of the crack width and the recommended epoxy viscosity allowing the epoxy to achieve and maintain the penetration requirements
3.Material information including manufacturer's product data sheets
4.Equipment
5.Crack preparation, injection procedures, and injection sequence
6.Cleanup procedures
b.Experience. Provide epoxy injection technic ians who have a minimum of 2 years experience in performing repairs using the methods and materials of the selected system.
c.Materials . Use epoxy adhesive for crack injection with viscosity capable of filling at least 90 percent of the crack volume. Use epoxy adhesive for crack sealing capable of containing the epoxy adhesive for crack injection.
d.Equipment . Use positive displacement plural component pumps, specifically designed to meter, mix, and to inject epoxy, and capable of filling at least 90 percent of the crack volume.
e.Surface and Crack Preparation. Remove contaminants and other foreign material reducing the effectiveness of the surface seal and repaired crack. Allow adequate time for drying. If cleaning solutions are used, perform trial tests to verify the contaminants can be removed. Prepare the surface and crack according to the epoxy manufacturer’s instructions.
f.Entry and Venting Ports . Install entry/venting ports spaced equal to the thickness of the concrete member along one face of the crack. A cceptable types of entry/venting ports are fittings inserted into drilled holes, bonded flush fittings, and gasket devices covering unsealed portions of interrupted seals, allowing injection of epoxy directly into the crack without leaking epoxy.
g.Mixing Ep oxy for Crack Sealing. Mix the epoxy adhesive for crack sealing to the volume ratio prescribed by the manufacturer.
h.Surface Sealing . Seal the surface of the crack with epoxy adhesive for crack sealing.
i.Mixing Epoxy for Crack Injection. Mix the epoxy adhesive for crack injection to the volume ratio prescribed by the manufacturer. 180 ALASKA 2020 j. Epoxy Injection. Assure the crack seal is cured and capable of containing the crack injection epoxy. Inject the epoxy according to the epoxy manufacturer’s instructions. Do not i nject epoxy until the air, substrate, and epoxy are within the manufacturer's application temperature range. Limit injection pressure to prevent propagation of the crack, prevent additional damage, and injection pressure in excess of 50 psi.
1.Inject the epoxy in the sequence noted in the approved crack repair plan. Ensure at least 90 percent of the crack volume is filled.
2.Maintain the epoxy temperature within the manufacturer's application temperature range during injection operations and until the epoxy is cured.
k.Finishing and Cleanup. After the injected epoxy is cured, remove ports and surface seal flush with the concrete surface. Do not damage the injected epoxy and do not heat the surface seal to aid in removal.
2.Low-Viscosity Resin Crack Repair . When concrete deck or approach slab crack repair is required, the Engineer will define the repair area with the following boundary limits:
a.Beginning and ending on straight lines perpendicular to the direction of traffic and extending across the entire width of the concrete deck or approach slab, between the concrete barriers or curbs.
b.Beginning and ending at least 5 feet beyond the furthest opposing cracks, measured from where the crack widths exceeds 0.020 inches If grinding is required, treat the concrete before grinding. Before treatment, ensure the concrete surface is clean, sound and free of foreign materials that may reduce the effectiveness of the repaired cracks. If the concrete surface becomes contaminated before placing the resin, repeat the cleaning process. Apply low -viscosity resin to the repair area. Protect barriers, railing, joints, and drainage facilities to prevent contamination by the treatment material. Completely cover the deck surface with resin so the resin penetrates and fills cracks. Ensure the relative humidity is less than 80 percent, the prepared area is dry, and the surface temperature is at least 50°F and not more than 90°F when the resin is applied. Apply the resin and distribute excess material within the manufacturer's listed pot lif e. For textured surfaces, including grooved surfaces, remove excess material from the texture indentations. For concrete decks and approach slabs not receiving a waterproofing membrane, apply aggregate for abrasive finish within 20 minutes of resin application and before setting occurs. Broadcast the aggregate for abrasive finish evenly over the entire treated area at a rate of 1.5 to 2.5 pounds per square yard.
501-3.19 CLEANUP. Remove concrete splatter, paint marks, laitance, rust staining, chamfer
strips , and other material not providing a uniform texture and color to the concrete surface.
501-4.01 METHOD OF M EASUREMENT. See Section 109 and the following:
1.Cubic Yard. The lesser of the actual volume or neat line volume of each class of concrete accepted i n place in the finished structure.
2.Class DS Concrete. The sum of the lengths of drilled shafts complete in place, measured along the centerline of the drilled shaft from the bottom to the top.
3.Precast Concrete Members . Measured per unit, complete in place. 181 ALASKA 2020 Crack repair for unacceptable concrete will not be measured for payment.
501-5.01 Basis of Pa Yment.
Material not appearing in the Bid Schedule and contained within, embedded, or attached to concrete elements is subsidiary. Crack repair for unacceptable concrete is subsidiary. Precast Concrete Member . Payment for precast concrete member includes materials and work for the following items: Class P concrete, reinforcing steel contained in the member, prestressing steel, plates, nuts, inserts contained withi n the concrete member, bolts, studs, anchor bars, blockouts, elastomeric bearing pads, grout, drains, and other miscellaneous steel embedded in or attached to the precast concrete member. Payment will be made under: PAY ITEM Item Number Item Description Unit 501.0001.____ Class A Concrete LS 501.0002.____ Class A -A Concrete LS 501.0004.____ Class A Concrete CY 501.0007.____ Precast Concrete Member, (Identification) EACH 501.0009.____ Class DS Concrete, (Identification) LF 182 ALASKA 2020 SECTION 502 PRESTRESSING CONCRETE
502-1.01 DESCRIPTION . Prestress precast or cast -in-place concrete by furnishing, placing,
tensioning, and bonding prestressing steel by using either pretensioning or post -tensioning methods or a combination of the two methods according to the Contract documents. For pretensioning, this work also includes furnishing and installing the materials and equipment necessary to prestress concrete as designated in the Contract documents. For post -tensioning, t his work includes furnishing and installing all post -tensioning systems and other pertinent items necessary for the particular prestressing system used, including but not limited to ducts, anchorage assemblies, supplementary reinforcement, and grout used for pressure grouting ducts.
502-1.02 Defin Itions.
ANCHORAGE. An assembly of various hardware components that secure a tendon at its ends after it has been stressed imparting the tendon force into the concrete. ANTICIPATED SET. The set that was assumed to occur in the design calculation of the post - tensioning forces immediately after load transfer. BEARING PLATE. Hardware that transfers the prestressing force directly into concrete. BLEED. The autogenous flow of mixing water within or its emergence from newly placed grout caused by the settlement of the solid materials within the mass and filtering action of strands. DUCT. Material forming a conduit to accommodate prestressing steel installation and provide an annular space for the grout that protects the prestressing steel. FLUIDITY. A measure of ti me, expressed in seconds, necessary for a stated quantity of grout to pass through the orifice of a flow cone. GROUT. A mixture of cementitious materials and water with or without admixtures proportioned to produce a pumpable consistency without segregatio n of the constituents when injected into the duct to fill the space around the prestressing steel. GROUT CAP. A device that contains the grout and forms a protective cover sealing the post - tensioning steel at the anchorage. POST -TENSIONING. A method of prestressing in which the tendons are tensioned after the concrete has reached a specified strength. POST -TENSIONING SCHE ME OR LAYOUT. The pattern, size and locations of post -tensioning tendons. POST -TENSIONING SYST EM. An assembly of proprietary post -tensioni ng hardware, including but not limited to anchorage assembly, local zone reinforcement, wedge plate, wedges, bearing plate, prestressing steel, duct, duct connections, vents and grout cap, used to construct a tendon of a particular size and type. PRESTRES SING STEEL. The steel element of a post -tensioning tendon, which is elongated and anchored to provide the necessary permanent prestressing force. SET ( Also Anchor Set Or Wedge Set ). The total movement of a point on the strand outside the anchoring wedges d uring load transfer from the jack to the permanent anchorages. Set
Source: Alaska Standard Specifications for Highway Construction, 2020 Edition. Pages 175–209 of 584.