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Publication Number: FHWA-HRT-09-044
Date: October 2009

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CHAPTER 2. RESEARCH COMPONENT #1: 2304 SS REINFORCING BARS IN CHLORIDE-CONTAMINATED ENVIRONMENTS

OBJECTIVE

The objective of this component of the study was to expand the scope of the companion FHWA/Florida Department of Transportation (FDOT)-sponsored research project by investigating the possible susceptibility of stainless alloy 2304 SS (UNS-S32304) to stress corrosion cracking under conditions relevant to reinforcing steel in concrete (task 1.1) and conducting both accelerated and long-term corrosion experiments on stainless alloy 2304 reinforcement (task 1.2).

MATERIAL

The microstructure of duplex SS such as 2304 is comprised of approximately equal amounts of ferrite and austenite phases. Table 1 lists information for this alloy including the supplier, the as-received surface condition, and the pitting resistance equivalent number (PREN, also referred to as PRE), as defined by the following equation:

Equation 1. PREN. Uppercase PREN equals weight percent chromium (Cr) plus 3.3 times weight percent molybdenum (Mo) plus 16 times weight percent nitrogen (N)


Table 1. Listing of information for 2304 SS.
Designation Common
Designation
As-Received
Condition
PREN Supplier
UNS-S32304 2304 SS Pickled 25 UGITECH

Likewise, table 2 lists the composition of this alloy. In general, duplex SS exhibits relatively high strength and ductility as well as beneficial corrosion properties including resistance to sensitization-induced intergranular corrosion, and high resistance to stress corrosion cracking. All experiments were performed using #5 (16-mm-diameter) bars.

Table 2. Composition for 2304 SS.
Alloy C Mn P S Si Cr Ni
Type 2304 SS 0.03 1.16 0.026 0.002 0.45 22.33 4.16

Note: C = carbon, Mn = manganese, P = phosphorus, S = sulfur, Si = silicon, Cr = chromium, and Ni = nickel.

 

 

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