Stainless Steel Reinforcement as a Replacement for Epoxy Coated Steel in Bridge Decks ODOT-OkTC Transportation Research Day Oklahoma City, OK October 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 Phase I Phase II Cracking of Concrete

Measurements and observations Voltage drop to measure corrosion rate Corrosion potential Mat-to-mat resistance Linear Polarization to measure microcell and macrocell corrosion Cl – content at corrosion initiation Cracking and staining of concrete Corrosion on bars following tests Evaluate disbondment of epoxy coating

Bench-Scale Tests

Southern Exposure Test

Cracked Beam Test

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/yd 3 ) Conventional Conv./ Conv./SSClad ECR SSClad-4h SSClad /Conv

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 Steel Designation Initiation Initiation to Cracking Cracking to Repair First Repair Conventional ECR p-- 10> 100 SSClad-- 10> 100

Costs per yd 2 Present worth for 2% discount rate Steel Designation Initial Cost Total costs 75 years 100 years Conventional$163$1048$1265 ECR$198$ $275 $ p$275 SSClad$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-SCR TM 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 Chair Dept. of Civil, Environmental & Architectural Engineering 2150 Learned Hall Lawrence, Kansas, (785) Fax: (785)