Investigating the effects of corrosion protection coatings on the ductility of welded wire reinforcement
CAIT project no.: CAIT-UTC-NC36
Fiscal Year: 2015/2016
Principal investigator(s): Marc Maguire, Ph.D.
Performing organization(s): Utah State University
Managing organization: Rutgers CAIT
In cooperation with: Insteel Wire Products
Partner project manager: Paul Aubee, Engineering Manager
Supported by: USDOT OST-R
UTC, grant, or agreement no.: DTRT13-G-UTC28
This study demonstrated that epoxy coated and galvanized WWR affects mechanical properties along with the known enhanced corrosion resistance.
Tensile tests were performed on a total of 108 wire samples and 18 hot rolled reinforcement samples. These samples consisted of black (non-coated), epoxy coated, and galvanized WWR. Each coating was tested on three different sized wires: D11, D20, and D31. The tensile tests showed that coating the wire had an obvious effect on some mechanical properties, but had a less pronounced effect on others. The rupture location was also found to have a significant effect. These properties were then simulated using Response 2000 to estimate their effect at the member level. Large variability (material property CVs ranged from 0.1% to 67.2% for wire) was observed in all wire samples (coated and uncoated), especially the D31 samples in all sizes’ percent area reduction, as compared to a series of hot rolled reinforcement (CVs ranged from 3.3 to 5.0).
Rupture location played a significant role in all material properties. Rupture at the cross weld location negatively affected all measured properties and also negatively affected the benefits observed from coating. However, the small sample sizes for the D11 and D20 wires that ruptured at a weld affects this conclusion. Additional testing is needed to confirm whether larger diameter wire is affected more by the welding process than smaller wires, but this seems to be indicated by the data. Galvanizing the wire increased the mean percent elongation from 3.7% to 6.5% and increased the standard deviation from 0.63 to 1.1. Epoxy coating the wire marginally increased the percent of elongation from 3.7% to 4.3%, but only small differences in standard deviation were observed (0.82 to 0.78). The yield stress and ultimate stress for smaller wire sizes (D11 and D20) increased when the epoxy and galvanized coating was applied. However, the coatings had the least effect on the highly variable D31 wires. Galvanizing wire resulted in a slight increasing in the elastic modulus for smaller diameter wires (D11 and D20), while galvanizing did not have any impact on the elastic modulus for D31 wires.
Designers can expect an increase in deformation capacity and ductility ratio for structural members reinforced with galvanized wire, considering the average properties observed in this report: up to 11% and 25%, respectively when design for slabs and up to 76% and 55%, respectively, for beams.