Propagation of Corrosion in Reinforced Mortar Samples by Anodic Current Application
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Propagation of Corrosion in Reinforced Mortar Samples by Anodic Current Application Reid Richardson Florida Atlantic University BACKGROUND EXPERIMENTAL DETAILS It is known that concrete is a porous material and can be permeated by chlorides •Chloride transport process can be accelerated by applying an electric field •Steel reinforcing members are then corroded once chlorides exceed the chloride threshold at the rebar surface and corrosion can propagate at a fast rate if current continues to be applied •Different concrete mix composition affects the rate of chloride permeation and the time needed for surface cracks to form from corrosion products •The rebar exposed area to chlorides is also a factor Concrete group Cemen t (kg) FA (kg) Water (kg) Fine agg. SSD (kg) w/c s/c MD1 14 3.36 6.6 48 0.38 2.76 MD2 18 - 6.8 50 0.38 2.76 • Six mortar samples of each mix were made according to the table below with one steel reinforcing rebar in each (9.525 mm diameter) RESULTS ‐600 ‐500 ‐400 ‐300 ‐200 ‐100 0 0 5 10 15 20 Ecorr(mV) Days Since Polarization MD2‐3 Ecorr Measurements MD2‐3‐01 MD2‐3‐02 MD2‐3‐03 ‐600 ‐500 ‐400 ‐300 ‐200 ‐100 0 0 2 4 6 8 Ecorr (mV) Days Since Polarization MD1‐7 Ecorr Measurements MD1‐7‐01 MD1‐7‐02 MD1‐7‐03 CRACK & MASS MEASUREMENTS Sample Crack Length (cm) Corrosion Length (cm) MD1‐3‐01 2.5 3 MD1‐3‐02 2 3 MD1‐3‐03 1.75 1.5 MD2‐3‐01 6.5 4.5 MD2‐3‐02 2 2.25 MD2‐3‐03 7.5 6.5 MD1‐7‐01 10 13 MD1‐7‐02 10 11 MD1‐7‐03 10 10.5 MD2‐7‐01 N/A N/A MD2‐7‐02 2 11 MD2‐7‐03 N/A N/A Sample Length (inch) Length (cm) Initial (g) After Cleaning (g) Delta Mass (g) MD1‐3‐ 01 16.09 40.88 223.50 221.50 2.00 MD1‐3‐ 02 16.00 40.63 212.00 210.40 1.60 MD1‐3‐ 03 16.04 40.74 216.70 214.90 1.80 MD2‐3‐ 01 16.02 40.70 216.80 215.20 1.60 MD2‐3‐ 02 16.01 40.66 227.20 225.90 1.30 MD2‐3‐ 03 16.00 40.64 230.50 228.80 1.70 1+C/Lhalf xcrit‐calc‐L C/ xcrit_L/(c/) S011 1.77 0.245 1.26 0.195 S08 1.08 0.276 1.26 0.219 MD1‐00‐P 1.15 0.115 0.84 0.137 MD2‐P25 1.55 0.274 1.26 0.217 MD1‐37 1.19 0.219 0.84 0.261 MD2‐36 1.30 0.283 1.26 0.224 MD1‐36 1.33 0.018 0.84 0.021 MD1‐10‐01 1.68 0.395 0.84 0.470 MD1‐10‐02 1.67 0.744 0.84 0.886 MD1‐10‐03 9.00 4.252 0.84 5.062 MD2‐10‐02 1.92 0.491 1.26 0.389 MD1‐40 1.22 0.291 0.84 0.346 MD1‐48 1.22 0.262 0.84 0.312 MD1‐3‐01 2.14 1.215 0.84 1.446 MD1‐3‐02 3.67 2.268 0.84 2.700 MD1‐3‐03 7.40 6.122 0.84 7.290 MD2‐3‐01 2.88 1.067 1.26 0.847 MD2‐3‐02 3.74 1.263 1.26 1.003 MD2‐3‐03 2.60 0.964 1.26 0.765 • Plastic reservoirs of differing sizes (10 cm or 3 cm long) were attached to the top of each samples and were filled with a chloride solution • An electric field was applied. Stainless steel mesh was placed in the reservoir and the reinforcing rebar was the working electrode. The applied potential ranged from 3 to 12 V. A smaller current was applied upon corrosion initiation (via small applied potential < 1V). • Rebar Electrical potential and impedance as well as polarization resistance measurements were taken throughout the process (after 24 hr off) • Once surface cracks were found, the applied current was removed and the samples were terminated for further analysis ACKNOWLEDGEMENTS CONCLUSIONS 1. After corrosion began, the electrical potential stabilized around ‐450mV 2. In the MD1‐3 and MD2‐3 samples, the minimum mass loss required for cracking was 1.3 grams 3. Mass loss required for surface cracking would increase with an increased reservoir size. But the mass loss per unit length is larger for shorter exposed rebar area. 4. MD1 concrete mix is better at preventing chloride permeation in small reservoirs and therefore sees less corrosion and smaller cracks I would like to acknowledge the technical assistance of: Professor Francisco Presuel‐Moreno. And to FAU‐ Broward for Travel assistance X crit fromCORROSION PRODUCTS MD1 and MD2 Mortar Specimens, most with small L Examples of surface cracks can be seen here both before and after the reservoir was removed The L values used to calculate x crit were obtained by determining the percent surface area that experience corrosion and adjusted to a L where corrosion would cover all around the rebar. Eqs. 1,2,3 Proposed by Sagues and collaborators. C = 8 mm on MD1 specimens and 12 mm on MD2 specimens Rebars were cleaned per ASTM G‐01 Crack and corrosion length before cleaning the rebars Rebar segment length and mass before and after cleaning
description
Concrete corrosion research presented at a corrosion conference.
Transcript of Propagation of Corrosion in Reinforced Mortar Samples by Anodic Current Application
Propagation of Corrosion in Reinforced MortarSamples by Anodic Current Application
Reid RichardsonFlorida Atlantic University
BACKGROUND
EXPERIMENTAL DETAILS
It is known that concrete is a porous material and can be permeated by chlorides•Chloride transport process can be accelerated by applying an electric field•Steel reinforcing members are then corroded once chlorides exceed the chloride threshold at the rebar surface and corrosion can propagate at a fast rate if current continues to be applied
•Different concrete mix composition affects the rate of chloride permeation and the time needed for surface cracks to form from corrosion products•The rebar exposed area to chlorides is also a factor
Concrete group
Cement (kg)
FA(kg)
Water(kg)
Fine agg. SSD(kg)
w/c s/c
MD1 14 3.36 6.6 48 0.38 2.76MD2 18 - 6.8 50 0.38 2.76
• Six mortar samples of each mix were made according to the table below with one steel reinforcing rebar in each (9.525 mm diameter)
RESULTS
‐600
‐500
‐400
‐300
‐200
‐100
00 5 10 15 20
Ecorr(mV)
Days Since Polarization
MD2‐3 Ecorr Measurements
MD2‐3‐01MD2‐3‐02MD2‐3‐03
‐600
‐500
‐400
‐300
‐200
‐100
00 2 4 6 8
Ecorr (mV)
Days Since Polarization
MD1‐7 Ecorr Measurements
MD1‐7‐01MD1‐7‐02MD1‐7‐03
CRACK & MASS MEASUREMENTSSample Crack Length (cm) Corrosion Length
(cm)
MD1‐3‐01 2.5 3MD1‐3‐02 2 3MD1‐3‐03 1.75 1.5MD2‐3‐01 6.5 4.5MD2‐3‐02 2 2.25MD2‐3‐03 7.5 6.5MD1‐7‐01 10 13MD1‐7‐02 10 11MD1‐7‐03 10 10.5MD2‐7‐01 N/A N/AMD2‐7‐02 2 11MD2‐7‐03 N/A N/A
Sample Length (inch)
Length (cm)
Initial (g)
After Cleaning (g)
Delta Mass (g)
MD1‐3‐01 16.09 40.88 223.50 221.50 2.00MD1‐3‐02 16.00 40.63 212.00 210.40 1.60MD1‐3‐03 16.04 40.74 216.70 214.90 1.80MD2‐3‐01 16.02 40.70 216.80 215.20 1.60MD2‐3‐02 16.01 40.66 227.20 225.90 1.30MD2‐3‐03 16.00 40.64 230.50 228.80 1.70
1+C/Lhalf xcrit‐calc‐L C/ xcrit_L/(c/)S011 1.77 0.245 1.26 0.195S08 1.08 0.276 1.26 0.219MD1‐00‐P 1.15 0.115 0.84 0.137MD2‐P25 1.55 0.274 1.26 0.217MD1‐37 1.19 0.219 0.84 0.261MD2‐36 1.30 0.283 1.26 0.224MD1‐36 1.33 0.018 0.84 0.021MD1‐10‐01 1.68 0.395 0.84 0.470MD1‐10‐02 1.67 0.744 0.84 0.886MD1‐10‐03 9.00 4.252 0.84 5.062MD2‐10‐02 1.92 0.491 1.26 0.389MD1‐40 1.22 0.291 0.84 0.346MD1‐48 1.22 0.262 0.84 0.312MD1‐3‐01 2.14 1.215 0.84 1.446MD1‐3‐02 3.67 2.268 0.84 2.700MD1‐3‐03 7.40 6.122 0.84 7.290MD2‐3‐01 2.88 1.067 1.26 0.847MD2‐3‐02 3.74 1.263 1.26 1.003MD2‐3‐03 2.60 0.964 1.26 0.765
• Plastic reservoirs of differing sizes (10 cm or 3 cm long) were attached to the top of each samples and were filled with a chloride solution
• An electric field was applied. Stainless steel mesh was placed in the reservoir and the reinforcing rebar was the working electrode. The applied potential ranged from 3 to 12 V. A smaller current was applied upon corrosion initiation (via small applied potential < 1V).
• Rebar Electrical potential and impedance as well as polarization resistance measurements were taken throughout the process (after 24 hr off)
• Once surface cracks were found, the applied current was removed and the samples were terminated for further analysis
ACKNOWLEDGEMENTS
CONCLUSIONS1. After corrosion began, the electrical potential
stabilized around ‐450mV2. In the MD1‐3 and MD2‐3 samples, the
minimum mass loss required for cracking was 1.3 grams
3. Mass loss required for surface cracking would increase with an increased reservoir size. But the mass loss per unit length is larger for shorter exposed rebar area.
4. MD1 concrete mix is better at preventing chloride permeation in small reservoirs and therefore sees less corrosion and smaller cracks
I would like to acknowledge the technical assistance of:Professor Francisco Presuel‐Moreno. And to FAU‐Broward for Travel assistance
Xcrit fromCORROSION PRODUCTSMD1 and MD2 Mortar Specimens, most with small L
Examples of surface cracks can be seen here both before and after the reservoir was removed
The L values used to calculate xcrit were obtained by determining the percent surface area that experience corrosion and adjusted to a L where corrosion would cover all around the rebar. Eqs. 1,2,3 Proposed by Sagues and collaborators.
C = 8 mm on MD1 specimens and 12 mm on MD2 specimens
Rebars were cleaned per ASTM G‐01
Crack and corrosion length before cleaning the rebars
Rebar segment length and mass before and after cleaning
