High Performance Concrete Specifications and Practices for Bridges (2013) / Chapter Skim
Currently Skimming:
Pages 48-72
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 48... ...
48 Appendix B Summary of Responses to Survey Questionnaire This appendix contains a summary of the responses to the questionnaire. Only those agencies that submitted comments to the questions are listed.
|
From page 49... ...
49 Michigan Concrete that will perform better for a given application than a "standard" mix design would have. Nebraska We try to follow AASHTO definition.
|
From page 50... ...
50 Are your agency's special provisions for HPC prescriptive, performance-based, or a combination? Not applicable: 8 agencies Prescriptive: 11 agencies Performance: 2 agencies Combination: 17 agencies In general, how is your agency's HPC performing compared to conventional concrete?
|
From page 51... ...
51 New Jersey Deck cracking -- -- New Mexico ASR, shrinkage, heat of hydration, cracking ASR, shrinkage, heat of hydration, cracking, creep ASR, shrinkage, heat of hydration, cracking, creep New York We still see some cracking but believe it is related to the numerous variables of deck construction -- not always specific to HPC although there are still concerns w/autogenous shrinkage. -- No concerns with the panels themselves and HPC use Ohio Cracking -- -- Oklahoma -- Buggy textured surface susceptible to minor cracking -- Oregon Shrinkage cracking has increased.
|
From page 52... ...
52 Florida Our latest revision to Section 346 requires the use of fly ash or slag cement in all concrete. Where high strength and durability are required for a particular environmental classification, silica fume, metakaolin, or ultra fine fly ash may be required as well.
|
From page 53... ...
53 Pennsylvania Some key aspects to improved performance are: 1. Limiting rate of strength gain, keeping 28-day/7-day strength to 1.20 maximum 2.
|
From page 54... ...
54 New Hampshire We originally had no lower limit on our permeability specification and the contractors were getting numbers below 800 coulombs by adding cement to get the bonus. We adjusted the specification and increased the lower limit.
|
From page 55... ...
55 Agency Response Alabama One requirement in our Special Provision for this project was that the contractor would be required to perform a test pour of the HPC. We did not specify the conditions under which the test pour should be performed.
|
From page 56... ...
56 South Carolina HPC mix was hard to handle in the field. The mix was very rich and sticky and needed experienced contractors.
|
From page 57... ...
57 Compressive strength: 23 agencies Modulus of elasticity: 2 agencies Creep: 1 agency Shrinkage: 6 agencies Other: 8 agencies Other characteristics included restrained shrinkage cracking, surface resistivity, air content, corrosion resistance, w/c ratio, and strength gain such that the 7-day compressive strength can be no greater than 80% of the 28-day strength, and the 56-day compressive strength must be at least 108% of the 28-day compressive strength. In your agency's prescriptive specifications, which of the following characteristics are currently considered in developing the specifications for cast-in-place concrete bridge decks?
|
From page 58... ...
58 Require fogging during placement when evaporation rates are high 27 8 Other 12 5 If other, please list. Agency Other Strategies Alabama Note: wind breaks are only required when evaporation rate is too high.
|
From page 59... ...
59 Agency Most Effective Strategies to Minimize Concrete Deck Cracking Alabama Use of nomographs, wind breaks, and fogging Arizona Good curing plan and good protection plan as in other above California Curing Colorado Wet curing District of Columbia Reduction of total cement Florida Effective and adequate curing in a timely manner is the best means of minimizing cracking. Georgia Proper curing and controlling the concrete temperature Hawaii Use of shrinkage-reducing admixture Iowa Early wet cure, reduction in portland cement content, evaporation rate control, limit on maximum concrete temperature at time of placement Kansas Fogging, 14-day wet cure, SCMs, reduced cement and water content Louisiana Prompt and proper construction methods Maine Extra steel in areas subject to movement, minimize delays in applying wet curing Maryland Wet curing and fibers Massachusetts Wet curing Michigan Nighttime concrete placements, 7-day wet cure Minnesota University of Kansas mix designs, limited cement content, shrinkage testing, performance-based specifications based on meetings with industry Nebraska Increased the curing from 5 days to 7 days Nevada Wet curing New Hampshire Placing wet burlap on the deck as soon as possible after placement and keeping it wet for 7 days New Mexico Mix modifications to minimize characteristic shrinkage potential, controlling batch weights and water, proper curing New York Maintaining reasonable w/c and water content controls appear to impact performance.
|
From page 60... ...
60 Utah Proper curing and placing sequence Wisconsin Limiting cement content, wet cure What strategies to minimize cracking in cast-in-place concrete bridge decks have been least effective? Agency Least Effective Strategies to Minimize Concrete Deck Cracking Alabama Maximum slump Colorado Prescriptive mix designs Florida Normally the contractor wants to wait until he gets the entire deck concrete placed before he starts to cure the concrete.
|
From page 61... ...
61 Ground-granulated blastfurnace slag 10 12 6 7 Other 9 0 0 0 No other supplementary cementitious materials were listed. What is the frequency of use of the following admixtures for cast-in-place concrete bridge decks?
|
From page 62... ...
62 Illinois Slump, air content, and strength Iowa Trial batch strength and permeability Kansas Approval of the mix by testing permeability using permeable voids or rapid chloride permeability and ACI statistical strength analysis Louisiana Trial batch Maine Permeability trial batch for new concrete plants or new mix from existing plants Maryland Trial batch Massachusetts Trial batch testing (temperature, air, slump) 28-day compressive strength Michigan Must meet specification requirements for material content/proportioning, coarseness and workability factors, and compressive strength Minnesota Laboratory testing of those properties indicated in Question No.
|
From page 63... ...
63 Does your agency conduct tests of the hardened cast-in-place concrete to check end-product performance other than compressive strength? Routinely: 5 agencies Sometimes: 12 agencies Never: 20 agencies If routinely or sometimes, what tests are performed?
|
From page 64... ...
64 Arizona Monitoring HPC report, see Jaber 2007. California Monitor Maintenance Reports Colorado None, other than the required routine bridge deck inspections District of Columbia None at this time except rapid chloride permeability and compressive strength Florida Our bridge inspectors assess our non-movable bridges every 2 years and the movable ones every year.
|
From page 65... ...
65 Idaho Haven't seen the advantage in doing so Illinois Illinois DOT has not seen a compelling reason to have low permeability concrete beams. Kansas Due to the low water-cement ratios and controlled environment of the precast plants we have not been as involved.
|
From page 66... ...
66 Characteristic Precast Beams Precast Panels Not applicable 7 13 Permeability 11 3 Freeze-thaw resistance 11 8 Deicer scaling 2 2 Abrasion resistance 1 1 Workability 11 2 ASR resistance 10 6 Sulfate resistance 4 4 Compressive strength > 6.0 ksi 19 4 Modulus of elasticity 3 2 Creep 2 2 Shrinkage 4 3 Other 2 1 The one other characteristic was flexural strength. What is the frequency of use of the following supplementary cementitious materials in your agency's precast, prestressed concrete beams?
|
From page 67... ...
67 Ground-granulated blastfurnace slag 18 3 3 1 Other 14 0 0 0 What is the frequency of use of the following admixtures for precast, prestressed concrete bridge beams? Admixture Extent of Use as a Percentage of All Bridges None 1 to 33 34 to 67 68 to 100 AASHTO M 194 Type A -- Water-reducing admixtures 8 6 5 8 AASHTO M 194 Type B -- Retarding admixtures 14 5 5 1 AASHTO M 194 Type C -- Accelerating admixtures 18 3 4 0 AASHTO M 194 Type D -- Water-reducing and retarding admixtures 12 7 4 2 AASHTO M 194 Type E -- Water-reducing and accelerating admixtures 18 4 2 1 AASHTO M 194 Type F -- High range water-reducing admixtures 3 3 7 15 AASHTO M 194 Type G -- High range water-reducing and retarding admixtures 14 5 3 4 Corrosion inhibitors 14 7 2 4 Shrinkage reducing admixtures 20 4 0 1 Expansive components 24 0 0 0 What is the frequency of use of the following admixtures for precast, prestressed concrete deck panels?
|
From page 68... ...
68 Agency Curing Method Alabama Either wet cure for a minimum of 3 days, or steam cure for minimum of 24 hrs. This is all prior to detensioning.
|
From page 69... ...
69 Georgia Strength data, permeability data, concrete test data (slump, air entrainment, temperature, etc.) Hawaii Same tests as non-HPC mixtures Iowa Strength and permeability Louisiana Trial batch Maine Mix design review Massachusetts Air, slump, temperature, finish/color, compressive strength Michigan Compressive strength Minnesota Compressive strength Nebraska Trial batches Nevada Same as deck concrete New Hampshire Test results for strength, permeability, air, and slump/spread on the mix, and ASR on the aggregates/mix New Jersey Verification testing of new mix design New Mexico Same as cast-in-place concrete except we do not require a controlled strength gain curve due to nature of precasting operations.
|
From page 70... ...
70 Iowa Permeability Louisiana Surface resistivity Maine Verification of permeability if applicable (very rare) Nebraska Modulus of elasticity New Hampshire Permeability New Mexico Plastic properties and compressive strength tests New York Acceptance testing performed per the PCCM found at https://www.dot.ny.gov/divisions/engineering/structures/manuals/pccm North Carolina Permeability Virginia Permeability 30.
|
From page 71... ...
71 Florida We are investigating the use of a field device that can perform several NDT evaluations in one pass. We have a prototype that can be attached to the side of a prestressed girder.
|
From page 72... ...
72 Florida Effective means to evaluate concrete in all applications so that we can move towards performance specifications. To me this is the one facet of the performance specification puzzle that has not been completed.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.