Stainless Steel Reinforcement as a Replacement for Epoxy Coated Steel in Bridge Decks

ODOT-OkTC

Transportation Research Day

Oklahoma City, OKOctober 12, 2013

Outline

Objectives

Reinforcement

Test methods and Results

Life expectancy and Cost-effectiveness

Conclusions and Recommendations

Determine the corrosion resistance of 2304 duplex stainless steel reinforcement and NX-SCR™ stainless steel clad bars compared to conventional and epoxy-coated reinforcement in reinforced concrete bridge decks

Estimate the life expectancy and cost effectiveness of 2304 duplex stainless steel, NX-SCR™ stainless steel clad reinforcement, epoxy-coated reinforcement, and mild steel reinforcement in bridge decks in Oklahoma

Objectives

Reinforcement

Conv.

ECR

2304

SS Clad

2304

Pickled a second time

As delivered

Test Methods

Rapid Macrocell test

Southern Exposure test

Cracked Beam test

Chloride Induced Corrosion

Two phase process:

Phase I – initiation– Time to reach the

critical chloride corrosion threshold

Phase II – corrosion– Corrosion products

build up around reinforcement

Time

Co

rro

sio

n L

oss

Phase I Phase II

Cracking of Concrete

Measurements and observations

Voltage drop to measure corrosion rateCorrosion potentialMat-to-mat resistanceLinear Polarization to measure microcell and macrocell corrosionCl– content at corrosion initiationCracking and staining of concreteCorrosion on bars following testsEvaluate disbondment of epoxy coating

Bench-Scale Tests

Southern Exposure Test

10 ohm

Terminal Box

Voltmeter

15% NaCl solution

12.0 in.

2.25 in.2.5 in.2.5 in.2.5 in.2.25 in.

1.0 in.

1.0 in.

7.0 in.

V

Cracked Beam Test

VVoltmeter

Terminal Box

10 ohm

6.0 in.

1.0 in.

1.0 in.

7.0 in.

All bars – Southern Exposure

Corrosion resistant bars – Southern Exposure, different scale

Critical Chloride Corrosion Threshold

Reinforcement No. of Samples

Avg. Initiation

Age(weeks)

Avg. Chloride Content(lb/yd3)

Conventional 34 12.5 1.78

Conv./2304 18 8.0 1.76

Conv./SSClad 26 9.3 1.59

ECR 36 16.5 4.59

SSClad-4h 54 26.7 7.62

SSClad -- -- --

2304 35 99.8 20.5

2304/Conv. 14 75.0 20.5

All bars – Cracked Beam

Corrosion resistant bars – Cracked Beam, different scale

2304– Cracked Beam

2304 (pickled a second time) – Cracked beam

SS Clad– Cracked Beam

Cracked beams

Conv. ECR 2304 SS clad

Comparisons based on:

150 ft span, 42 ft width, 8 in. deck

75 and 100-year economic lives

ODOT costs

Time to first repair (years)2 ½-in. cover

SteelDesignation Initiation

Initiation to

Cracking

Cracking to Repair

First Repair

Conventional 2.1 7 10 19

ECR 8.4 35 10 53

2304 44 26 10 80

2304-p -- -- 10 > 100

SSClad -- -- 10 > 100

Costs per yd2 Present worth for 2% discount rate

SteelDesignation

InitialCost

Total costs

75 years 100 years

Conventional $163 $1048 $1265

ECR $198 $422 $422

2304 $275 $275 $423

2304-p $275 $275 $275

SSClad $240 $240 $240

Conclusions and Recommendations

Corrosion resistant steels, even when damaged, provide significant advantages over conventional reinforcement

Lack of proper pickling reduces corrosion resistance of stainless steel

Conclusions and Recommendations

Some problems with NX-SCRTM

stainless steel clad reinforcement – the bars are not currently available

Stainless steel reinforcement should be pickled to a bright or uniformly light surface to ensure proper performance

The University of Kansas

David Darwin, Ph.D., P.E.

Deane E. Ackers Distinguished Professor and ChairDept. of Civil, Environmental & Architectural

Engineering2150 Learned HallLawrence, Kansas, 66045-7609(785) 864-3827 Fax: (785) 864-5631

daved@ku.edu