Section 568 — Service Life Design Concrete
Description
568.01This work consists of constructing Service Life Design Concrete (SLDC) for structural elements to meet the requirements of a stated service life in conditions subject to exposure to chloride ions.
Material
568.02Conform to the following Section and Subsections: Coarse aggregate for concrete 703.02 Concrete curing material and additives 711 Fine aggregate for concrete 703.01 Hydraulic cement 701.01 Pozzolans 701.03 Structural steel 717.01 Water for cementitious materials 725.01(a)
Construction Requirements
568.03Service Life Analysis to Determine Adequacy of Submitted Concrete Mixture. Provide concrete for service life design that is free of repairs from chloride intrusion and damage caused by corrosion of reinforcing steel for the stated service life of the structure. Use approved service life modelling software that models the ingress of chlorides into the structure. Use software that indicates the initiation of corrosion based on inputs of estimated chloride exposure, environmental conditions, steel type used, concrete cover depth, and element geometry, and provides the years from corrosion initiation to concrete damage caused by steel corrosion that requires repair to the structure. Provide results of modelling and the life cycle cost to meet the stated service life requirement for the structure. Fabricate trial batches of concrete to verify that the mixture proposed for SLDC meets the requirements of the model. Fabricate and test specimens according to AS TM C1556 to determine apparent D28 chloride diffusion rate for the mixture. Input the D28 value into the model to confirm service life performance. If a corrosion inhibitor is selected to meet service life requirements use a calcium nitrite based Corrosion Inhibiting (CI) admixture. Report addition rate required to meet service life requirements. For prestressed concrete elements that contain 270 kilopound per square inch low relaxation carbon steel strand provide a concrete mixture with minimum addition ra te of 3 gallons per cubic yard of CI admixture regardless of level of chloride exposure. If necessary, increase the addition rate of CI to meet the service life requirements of the prestress ed element based on exposure risk to chlorides. Provide documentation that calcium nitrite addition rates have been evaluated for the exposure risk for the concrete element with the use of the approved service life modeling software. If a proposed design alternative uses stainless steel secondary reinforcement and stainless steel prestressing strand, the inclusion of CI is not required unless warranted by the service life analysis.
568.04Composition (Concrete Mix Design). Design and produce concrete mixtures that conform to Tables 568-1 and 568-2. Table 568-1 Performance Characteristics and Plastic Properties of Service Life Design Concrete
Property Specification
Concrete resistivity , no corrosion inhibitor in mixture , AASHTO T 358, except as modified in Subsection 568.04(c) 25 kΩ -cm minimum Concrete resistivity, corrosion inhibitor in mixture, AASHTO T 358, except as modified in Subsection 568.04(c) 18 kΩ -cm minimum Drying shrinkage, ASTM C157, except as modified in Subs ection 568.04(g) 400 microstrains maximum Apparent chloride diffusion Rate D28, as determined according to ASTM C1556 Subsection 568.03 Compressive strength, AASHTO T 22 4500 psi minimum at 56 days Approved shrinkage reducing admixture 1.5 gal/yd3 addition rate Water to cementitious material ratio 0.45 maximum Plastic air content AASHTO T 152 5.5% to 8% Super air meter ( SAM ) value AASHTO TP 118 0.20 minimum Aggregate size(7) 1.5 in maximum Total cementitious content(1) 750 lb/yd3 maximum Slump,(2) AASHTO T 119 2 to 8 in Sulfate resistance AASHTO M 240, Type IP(MS) or Type IS(< 70)(MS) (use Type II cement per AASHTO M 85)(4),(5)
Water -soluble chloride ion content,
ASTM C1218(6) 0.15% by mass of cement maximum for reinforced concrete 0.06% by mass of cement maximum for prestressed concrete
(1)The total cementitious content includes portland cement and all pozzolans added to the concrete mixture (such as ground granulated blast furnace slag, fly ash, and silica fume).
(2)Slump can be adjusted using a high- range water reducer (superplasticizer) if the maximum water to cementitious material ratio is not exceeded. Include the water contained in the aggregates above the amount of absorbed water in the calculation of the water to cementitious material ratio.
(3)If the plastic air content is low when the concrete arrives on site, additional air -entraining agent may be added to the concrete and mixed pr ovided that 300 revolutions of the mixer has not been exceeded.
(4)For seawater exposure, other portland cement types are allowed if the tricalcium aluminate (C 3A) content is 10 percent or less and the water to cementitious material ratio is 0.40 or less.
(5)Other cement types are allowed if the C 3A content is less than 8 percent.
(6)Determine the water -soluble chloride ion content contributed from the ingredients including water, aggregates, cementitious material, and admixtures between ages 28 and 4 2 days.
(7)Meet size number gradation and requirements from AASHTO M 43 for coarse aggregates. Blending of standard sizes to optimize gradation is allowed. Table 568-2 Cementitious Material Requirements for Concrete Cementitious Material Maximum Percent of Total
Cementitious Material by Mass
Fly ash or other pozzolans, AASHTO M 295 25 Slag, AASHTO M 302 50 Silica fume, AASHTO M 307 10 Total fly ash or other pozzolans, slag, and silica fume 50(1) Total fly ash or other pozzolans and silica fume 35(1)
(1)Limit fly ash or other pozzolans to no more than 2 5 percent of the total mass of cementitious material and limit silica fume to no more than 10 percent of the total mass of cementitious material. Determine design strength values according to S ection 4 of ACI 301, Specifications for Concrete Construction. Verify mixture design with trial mixes prepared according to S ection 4 of ACI 301 from proposed sources or with previous concrete production data for the mixture design submitted from proposed sources. Verify the performance characteristics and plastic properties in Table 568-1. Submit written concrete mix designs for approval at least 3 6 days before production. Submit SLDC mix designs on Form FHWA 1608, 552 Structural Concrete Mix Design Submittal . Include the following in each mix design submittal:
(a)Mix design information. Information listed in Subs ections 552.03(a) except for Subsections 552.03(a) (23) and 552.03(a) (24).
(b)Shrinkage reducing admixture. Provide a shrinkage reducing admixture that conforms to the requirements of ASTM C494 Type S.
(c)Corrosion inhibiting admixtur e. If required for meeting service life requirements, provide a calcium nitrite corrosion inhibiting admixture that conforms to ASTM C494 Type S. (d) Design strength. Specified design strength ( f' c) and required average strength ( f'cr) for the concrete mixture at 56 days as determined by the process described in S ection 4 of ACI 301. This process and associated calculations are outlined on Form FHWA 1608, pages 4 and 5. Pending 56- day strength results, a mix design may be approved on the basis that 14 -day compressive strength results meet or exceed 8 5 percent of the required average strength ( f'cr) at 5 6 days.
(e)Compressive strength. Compressive strengths test results at 1, 3, 7, 14, 28, and 56 days according to Table 552-10, Note (3) .
(f)Concrete resistivity. Report concrete resistivity according to AASHTO T 358 at 56 days of curing.
(g)Drying shrinkage of concrete. Initial lime water curing is according to ASTM C157 for 1 4 days. Report Drying Shrinkage of Concrete after 28 days of air drying, that is 4 2 days from fabrication of test samples.
(h)Internally cured concrete (ICC). If used as part of the SLDC design , produce concrete mixtures that conform to Tables 568 -1 and 552 -2. Provide aggregate for the class specified, except substitute a portion of the normal weight fine aggregate (on a cubic yard basis) for Lightweight Fine Aggregate (LWFA) conforming to AASHTO M 195. Determine the quantity of LWFA (pounds per cubic yard) by the following calculations: Cementitious Factor = Cementitious Content ( lb/yd3)/100 where: Cementitious Content is the inclusion of portland cement and any supplementary cementitious materials in the submitted co ncrete mixture; 𝑈𝑈𝑊𝑊𝑃𝑃𝑆𝑆 𝑞𝑞𝑃𝑃𝐼𝐼𝑛𝑛𝑓𝑓𝐼𝐼𝑓𝑓𝑞𝑞 =𝑐𝑐𝑀𝑀𝑐𝑐𝑀𝑀𝑛𝑛𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑐𝑐𝑐𝑐𝑠𝑠 𝑓𝑓𝑀𝑀𝑐𝑐𝑀𝑀𝑐𝑐𝑀𝑀 × 7.0 � 𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑝𝑝𝑝𝑝𝑝𝑝𝑎𝑎𝑎𝑎𝑝𝑝 𝑎𝑎𝑜𝑜 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 �1 + �𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝𝑝 𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑎𝑝𝑝𝑝𝑝𝑝𝑝𝑎𝑎𝑎𝑎𝑝𝑝 𝑎𝑎𝑜𝑜 𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 100��� ; and Round calculated LWFA quantity to nearest pound per cubic yard. Adjust the concrete mix design normal weight fine aggregate quantity after determining the saturated surface dry (SSD) volume of the LWFA. Subtract the SSD LWFA volume from the original volume of normal weight fine aggregate. Calculate new adjust ed SSD weight of normal weight fine aggregate on a pound per cubic yard basis. Start production only after the mix design is approved. Provide a new mix design for approval if there is a change in a source of material source or when the fineness modulus of the fine aggregate changes by more than 0.20.
568.05Test Section for Cast -in-Place Bridge Deck and Cast -in-Place Structural Elements. For bridge decks, approach slabs, and other flatwork, construct a 9- foot by 9- foot by 8- inch test section. For other structural elements, construct a 3 - by 3 - by 3-foot test section. Use the approved concrete mix design and the same methods of handling, placing, monitoring, finishing, curing, and cleaning as intended for production placement. Sample and test according to Table 568-1. Monitor temperatures of the test placements according to Subs ectio n 552.07.Start production only after the test section is approved.
568.06Delivery. Conform to Subs ection 552.05 .
568.07Quality Control of Mix. Conform to Subs ection 552.06.
568.08Tempe rature, Weather, and Mass Concrete Conditions. Conform to Subs ection 552.07.
568.09Handling and Placing Concrete. Conform to Subs ection 552.08. Remove and replace concrete represented by cylinders having a compressive strength less than 90 percent of the minimum 56 -day compressive strength ( f'c).
568.10Construction Joints. Conform to Subs ection 552.09.
568.11Expansion and Contraction Joints. Conform to Subs ection s 552.10 and 552.11.
568.12Finishing Plastic Concrete. Conform to Subs ection 552.12.
568.13Concrete Curing. For cast -in-place structural elements, start curing immediately after the free surface water has evaporated and the finishing is complete. If the surface of the concrete starts to dry before the selected cure method can be implemented, keep concrete surface moist using a fog spray without damaging the surface. As soon as possible after completion of finishing operations, start selected curing method. Keep surfaces to be rubbed moist after forms are removed. Cure immediately following the first rub. Cure cast -in-place elements at least 14 days and until the summation of the product of concrete temperature (°F) and curing time (hours) for all the temperature sensors placed in the structural element meets a minimum value of 7000 degree -hours, as calculated using the Nurse Saul Method of ASTM C1074, with a datum temperature of 32 °F.
(a)Flatwork and bridge decks. Cure the top surfaces of bridge decks using the water method. Apply the water cure as soon as all finishing operations have been completed. Use water method for flatwork placements. Keep the concrete surface continuously wet by ponding, spraying, or covering with material that is kept continuously and thoroughly wet. Covering material may consist of cotton mats, multiple layers of burlap, o r other approved material that does not discolor or otherwise damage the concrete. Cover the covering material with a waterproof sheet material that prevents moisture loss from the concrete. Use the widest sheets practical. Lap adjacent sheets at least 6 inches, and tightly seal seams with pressure sensitive tape, mastic, glue, or other approved methods. Secure material so that wind does not displace it. Immediately repair sheets that are broken or damaged.
(b)Cast -in-place structural elements. Use a combinati on of the forms in -place method according to Subs ection 552.13(a) and the water method according to Subs ection 552.13(b) . If forms are stripped or loosened before the end of the curing period, complet e the remainder of the curing using the water method. (c) Prestressed elements. Cure according to Subs ection 553.06 . If directed after curing, clean staining or efflorescence to provide a uniform color to the concrete surface.
568.14Finishing Cured Formed Structural Elements and Concrete Bridge Decks. Finish according to Subs ection 552.14.
568.15Acceptance. See Table 568-4 for sampling, testing, and acceptance requirements. Material for SLDC will be evaluated under Subsections 106.02 and 106.03. Submit a production certification with each shipment of cementitious material. The concrete mixture’s slump, air content, density, and temperature will be evaluated under Subsections 106.02 and 106.04. Concrete compressive strength will be evaluated under Subs ection 106.05. The lower specification limit is the minimum required compressive strength ( f'c) at 5 6 days shown in Table 568-1. Concrete r esistivity will be evaluated under Subs ection 106.04 . Refer to Table 568-1 for Resistivity Lower Specification Limits. Drying shrinkage will be evaluated under Subs ection 106.04. Construction of SLDC structures will be evaluated under Subsections 106.02 and 106.04.
Measurement
568.16Measure the Section 568 pay items listed in the bid schedule according to Subs ection 109.02 and the following as applicable: When measuring SLDC by the cubic yard, measure in the structure.
Payment
568.17The accepted quantities will be paid at the contract price per unit of measurement for the Section 568 pay items listed in the bid schedule, except the SLDC contract price will be adjusted according to Subs ection 106.05. Payment will be full compensation for the work prescribed in this Section. See Subs ection 109.05. Payment for SLDC will be made at a price determined by multiplying the contract price by the lower of the two pay factors determined for compressive strength or chloride permeability. Table 568-4 Sampling, Testing, and Acceptance Requirements
Material or
Product
(Subsection) Type of
Acceptance
(Subsection) Characteristic Category Test Methods
Specifications Sampling
Frequency Point of
Sampling Split
Sample Reporting
Time Remarks
Source
Aggregate
(fine & coarse ) Measured & tested for conformance (106.04 & 105) Quality − Subsections
703.01& 703.02 including ASR requirements 1 per material type Source of material Yes Before producing −
Mix Design
Concrete
composition Measured & tested for conformance (106.04) All − Subsection
568.041 per mix design " Yes " − Production Start -up (Test Section)
SLDC Measured &
tested for conformance (106.04)(1) Concrete resistivity(2) − AASHTO T 358 1 set per test sextion Discharge stream at point of placement Yes Upon completing tests − " Compressive strength(3) AASHTO T 23 & 22 " " " " − " Plastic air content − AASHTO T 152 " " No " −
For
Informational
Purposes SAM value − AASHTO TP 118 " " No " – Table 568-4 (continued) Sampling, Testing, and Acceptance Requirements
Material or
Product
(Subsection) Type of
Acceptance
(Subsection) Characteristic Category Test Methods
Specifications Sampling
Frequency Point of
Sampling Split
Sample Reporting
Time Remarks
Production
Produced
aggregate (fine & coarse) Measured & tested for conformance (106.04 ) Gradation − AASHTO T 27 & T 11 1 per day Flowing aggregate stream (bin, belt, discharge conveyor belt, or stockpile) Yes Before batching −
Fineness
modulus − AASHTO T 27 " " " " − Moisture test − AASHTO T255 " " " " −
SLDC Measured &
tested for conformance (106.04 ) Density − AASHTO T 121 1 per load Point of discharge No Upon completing tests − Air content − AASHTO T 152 or
AASHTO
T 196 " " No " − Slump(5) − AASHTO T 119 " " No " − Temperature − ASTM C1064 " " No " −
Drying
shrinkage(4) −
ASTM
C157 As directed " No " −
Concrete
resistivity −
AASHTO
T 358 1 set per 30 yd3 but not less than 1 per day " Yes " Table 568-4 (continued)
Sampling and Testing Requirements
Material or
Product
(Subsection) Type of
Acceptance
(Subsection) Characteristic Category Test Methods
Specifications Sampling
Frequency Point of
Sampling Split
Sample Reporting
Time Remarks
Production (continued)
SLDC Statistical
(106.05) Compressive strength(6) II AASHTO T 23 & T 22 1 set per 30 yd3, but not less than 1 per day Discharge stream at point of placement Yes Upon completing tests −
SLDC For
informational purposes SAM value – AASHTO TP 118 1 test per 30 yd3, but not less than 1 per day Discharge stream at point of placement No Upon completing tests −
(1)Sample according to AASHTO R 60, except composite samples are not required.
(2)Cast at least three 4 - by 8- inch for AASHT O T 358 testing cylinders per set and carefully transport the cylinders to the job site curing facility. Have the testing done at 5 6 days in an independent laboratory that is qualified to perform the testing and is approved. The set test result is the average of the measurements on three cylinders cast from the same load.
(3)Cast at least eighteen 4 - by 8- inch compressive strength cylinders per set and carefully transport the cylinders to the job site curing facility. Have the testing done at 1, 7, 14, 28, and 5 6 days in an independent laboratory that is qualified to perform the testing and is approved. A single compressive strength test result is the average result from three cylinders cast from the same load.
(4)If testing is directed, use 3 - by 3- by 11 -inch prisms for drying shrinkage specimens. Cast at least thr ee drying shrinkage prisms per set and carefully transport the prisms to the job site curing facility. Moist the prisms for the duration of the specified moist curing period for SLDC elements. Have the testing done in an independent laboratory that is qualified to perform the testing and is approved. The zero measurement for percent drying shrinkage is the initial measurement taken at demolding of the specimens at 23½±½ hours after introduction of mixing water to the concr ete mixture. Measure percent drying shrinkage at the end of specified moist curing period for the structural elements, 1, 4, 7, 14, 28, and 5 6 days after the end of the specified field moist curing period.
(5)If reinforcing fibers are used at an addition rate greater than 0. 3 percent by volume, measure slump at the batch plant before the addition of fibers.
(6)Cast at least six 4 - by 8-inch compressive strength cylinders per set and carefully transport the cylinders to the job site curing facility. Test three cylinders at 5 6 days. Use the remainder of cylinders as designated by the CO.