IMPLEMENTING NEW MATERIALS

Transcription

1 IMPLEMENTING NEW MATERIALS Corrosion Resistant Reinforcement

2 Table of contents 1 Steel Corrosion 3 2 TxDOT Corrosion Protection Measures Corrosion Resistant Reinforcement Materials

3 Steel Corrosion Carbon steel (black steel) Fresh concrete is a high-alkaline environment (ph > 13) Rebar won t oxidize as long as ph > 10 or 11 Moisture, Oxygen, and Chlorides arrive and ph Rebar corrodes Rust occupies 6-7 times more volume than the steel it replaces Tension cracks develop Faster access for more chlorides 3

4 TxDOT Corrosion Protection Measures TxDOT Corrosion 4

5 TxDOT Corrosion Protection Measures Increased Clear Cover for Bridge Slabs Top Clear Cover is now 2.5 for Standard Deck Slabs and Standard Composite Concrete Slabs (statewide). Substructures: case-by-case basis typically increase to 2½" no more than 3-3½" 5

6 TxDOT Corrosion Protection Measures High Performance Concrete (HPC) for Bridge Slabs & Rails High Performance Low Permeability (Class F Fly Ash) 6

7 TxDOT Corrosion Protection Measures Air Entrainment for Bridge Slab & Rails relieves pore pressures from freezing /thawing exposure limited application because air entrainment negatively Impacts the use of Class F Fly Ash (TxDOT Research Project ) 7

8 TxDOT Corrosion Protection Measures Epoxy Coated Reinforcement for Bridge Slabs & Rails...or other types of corrosion-resistant reinforcement......except - stainless steel is usually reserved for coastal / saltwater applications 8

9 ~ Cost Corrosion Resistant Reinforcement Materials Stainless Steel Dual Coated Low Carbon, Chromium Galvanized* Epoxy Coated (ECR) Carbon Steel Fiber Reinforced Polymer (FRP) Research Project Synthesis of Alternate Reinforcements for Enhanced Corrosion Resistance in TxDOT Bridges Performance 9

10 Corrosion Resistant Reinforcement Materials Epoxy Coated Developed in 1970s ASTM A775 (coated before fabrication) green ASTM A934 (coated after fabrication) grey or purple -- no bending after coating! Useful for Deck Reinforcing Holidays Bar Sizes Coating Thickness (mils) #3 - # #6 - # [1 mil = inch] CRSI [2015] 10

11 Item 440 Reinforcement for Concrete 11

12 Corrosion Resistant Reinforcement Materials Hot Dip Galvanized Reinforcement ASTM A767 Class I Heavier coating (5 6 mils) Class II Thinner, more ductile coating (3.4 mils)...steel reinforcing bars with protective zinc coatings applied by immersing the properly prepared reinforcing bars into a molten bath of zinc. Bend bars BEFORE hot-dipping Useful for Deck Reinforcing Domestic Availability 12

13 Item 440 Reinforcement for Concrete 13

14 Corrosion Resistant Reinforcement Materials Continuous Hot-Dip Galvanized Reinforcement ASTM A1094 The process of uninterrupted passage of long lengths of steel products through a molten bath of zinc or zincalloy Thinner, better-adhering than A767 Addition of Aluminum 2-mil Thickness Domestic Availability Bend AFTER Galvanizing Useful for Deck Reinforcing, or General Usage as Corrosion-Resistant Reinforcement 14

15 Item 440 Reinforcement for Concrete...coming soon! 15

16 Corrosion Resistant Reinforcement Materials CRSI [2015] Dual Coated ASTM A1055 Step 1: Metalizing Continuous HDG (ASTM A1094) Step 2: Fusion Bonding Apply outer epoxy powder coating Domestic Availability Issues Deck Reinforcing, or General Usage as Corrosion-Resistant Reinforcement 16

17 Corrosion Resistant Reinforcement Materials Glass Fiber-Reinforced Polymer (GFRP) Glass Fibers Carry Load Polymer Resin Protects Fibers AASHTO LRFD Bridge Design Specifications for GFRP-Reinforced Concrete Bridge Decks and Traffic Railings (2009) 2 nd Edition Currently in the Works Will Include Empirical Deck Design for GFRP Canadian Highway Bridge Design Code IGFRP 17

18 Corrosion Resistant Reinforcement Materials Glass Fiber-Reinforced Polymer (GFRP) One Huge Benefit Galvanic Corrosion Not Possible (no expansive corrosion product) Points to Consider Low Compressive Strength, Modulus Long-term Tensile Capacity Elastic through Failure Bends Must Be Incorporated during Bar Manufacture Empirical Deck Design Not Yet Applicable AASHTO LRFD Bridge Design Specifications for GFRP-Reinforced Concrete Bridge Decks and Traffic Railings (2009) Concrete Exposure Condition not exposed to earth and weather exposed to earth and weather Table Environmental Reduction Factor, C E See also: Gooranorimi et al. (2016) FRP Reinforcement for Concrete: Performance Assessment and New Construction Vol I: Sierrita De La Cruz Creek Bridge 18

19 Item 440 Reinforcement for Concrete 19

20 Corrosion Resistance Corrosion Resistant Reinforcement Materials Low Carbon, Chromium Steel ASTM A1035 High Yield Strength Available Grades are 100, 120 Alloys based on Chromium Content CL ( % Cr) CM ( % Cr) CS ( % Cr) [see SP to Item 440] No Special Handling Requirements 4 < f c < 12 ksi Domestic Availability CL CM CS Chromium (Cr) % SS Useful for Deck Reinforcing, or for General Usage as Corrosion-Resistant Reinforcement 20

21 Item 440 Reinforcement for Concrete 21

22 Corrosion Resistant Reinforcement Materials Stainless Steel Reinforcement ASTM A955 CR or SS markings indicate compliance Austenitic Usual choice for reinforcing steel Chromium and Nickel Non-magnetic Duplex Superior strength and corrosion resistance Austenite and Ferrite Magnetic These alloys are all available as reinforcing bars in the US and permitted in TxDOT Standard Specifications. Specify all allowable alloys in plan specifications. UNS Designation Type Cr % Austenitic S LN S24100 XM Duplex (Austenitic Ferritic) S S32304 * * ASTM A240 22

23 Corrosion Resistant Reinforcement Materials Stainless Steel Reinforcement Solid Stainless Steel (preferred) Can be shipped, handled, and bent without damage Deck Reinforcing, or General Usage as Corrosion-Resistant Reinforcement Useful in Corrosive Coastal Environments TxDOT Does Not Permit the Use of Stainless Steel-Clad Carbon Steel Fusing process is expensive Bar ends require coating Limited Domestic Availability 23

24 Item 440 Reinforcement for Concrete This is size 20 font 24

25 Item 440 Reinforcement for Concrete 25

26 Questions?

27 Additional References Concrete Reinforcing Steel Institute CRSI [2012], Frequently Asked Questions (FAQ) about Stainless Steel Reinforcing Bars, CRSI Technical Note ETN-M-2-12, Schaumburg, IL, 8 pp. Concrete Reinforcing Steel Institute CRSI [2013], Specialty & Corrosion-Resistant Steel Reinforcement: Product Guide, 28 pp. Concrete Reinforcing Steel Institute CRSI [2015], Frequently Asked Questions (FAQ) about Dual-Coated Steel Reinforcing Bars, CRSI Technical Note ETN-M-7-15, Schaumburg, IL, 5 pp. Concrete Reinforcing Steel Institute CRSI [2017], Frequently Asked Questions (FAQ) about Low-Carbon, Chromium ASTM A1035 Type CS, CM and CL Steel Reinforcing Bar, CRSI Technical Note ETN-M-11-17, Schaumburg, IL, 6 pp. Concrete Reinforcing Steel Institute CRSI [2015], Frequently Asked Questions (FAQ) about Epoxy-Coated Steel Reinforcing Bars, CRSI Technical Note ETN-M-6-15, Schaumburg, IL, 5 pp. Concrete Reinforcing Steel Institute CRSI [2016], Frequently Asked Questions (Faq) about Hot-Dip Galvanized Reinforcing Bars, CRSI Technical Note ETN-M-10-16, Schaumburg, IL, 6 pp. Gooranorimi et al. [2016], FRP Reinforcement for Concrete: Performance Assessment and New Construction, Volume I: Sierrita De La Cruz Creek Bridge, Final Report, RECAST UTC # A, 36 pp. 27

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