THE APPLICATION OF ELECTROCHEMICAL CHLORIDE EXTRACTION ON CORRODED BRIDGES BY JOHN TERCHA AND CONNOR WILSON
AMERICAN INFRASTRUCTURE: A PROBLEM AMERICAN SOCIETY OF CIVIL ENGINEERS (ASCE) REPORTS ISSUES WITH: • AGE • COSTS • STABILITY/DURABILITY • FUNCTIONALITY
BRIDGES AND CORROSION • MATERIAL DETERIORATION • IRON AND STEEL • EXPOSURE TO ELEMENTS IN THE ATMOSPHERE • DANGEROUS • COSTLY $$
The oxygen gets reduced and acts as a cathode. The iron oxidizes and acts as an anode. Both combining to form rust.
WHAT IS ELECTROCHEMICAL CHLORIDE EXTRACTION (ECE) ? • ECE IS A REHABILITATION METHOD FOR DETERIORATING REINFORCED CONCRETE TYPICALLY FOUND ON BRIDGES ABOVE WATER • CONCRETE: PROTECTS • PENETRATION CHLORIDE IONS FROM THE SALT IN THE ENVIRONMENT - WEAKENS PROTECTIVE LAYER FROM CONCRETE - EXPOSING STEEL • ECE: USE OF ELECTRICAL CURRENT TO EXTRACT CHLORIDE IONS FURTHER STRENGTHENING THE MATERIAL
PROCESS • ROOTS IN ELECTRICITY STUDIES AND ELECTROCHEMISTRY • STEEL OR TITANIUM MESH: ACTS AS THE ANODE (POSITIVELY CHARGED SURFACE) • WIRE CONNECTED TO STEEL REBAR MAKING IT THE CATHODE (NEGATIVELY CHARGED SURFACE) • CONNECTED TO A RECTIFIER (BATTERY) FORMING AN ELECTRICAL CIRCUIT • CURRENT FLOW: FORMING REPULSIVE AND ATTRACTIVE BEHAVIORS W/ IONS • COLLECTED/EXTRACTED AND RELEASED IN A GASEOUS STATE • LEFT WITH MATERIAL STRENGTHENING ANIONS
TECHNIQUES AND INSTALLATION • STEEL OR TITANIUM MESH IS LAID ON THE EFFECTED AREA • MULTIPLE RECTIFIERS: 900-1000 FT^2 PER RECTIFIER - ACCOUNTING FOR THE ENTIRE SURFACED • 50V VOLTAGE SOURCE AND CURRENT DENSITY OF 1A/M^2 • PLASTIC FILM AND SAND PLACED : ALLOW FOR CONSTANT MONITORING AND RECORDING • EXTRACTED AND RELEASED • 4-12 WEEK PROCESS
LAB RESEARCH AND TESTING • HAS BEEN RESEARCHED SINCE 1973 • RESEARCH HAS PROVED THE EFFECTIVENESS OF ECE • NECESSARY TO IMPROVE • HARBIN INSTITUTE OF TECHNOLOGY STUDY • NEGATIVE EFFECT DISCOVERED: SMALL AMOUNTS OF ALKALI SILICA GEL FOUND Graph showing chloride concentrations decreasing, depending the current levels
HISTORY AND FIRST USES • FIRST INTRODUCED IN 1973 • FIRST REAL USE IN 1989 ON BURLINGTON BAY SKYWAY BRIDGE, ONTARIO CA • PROVED VERY EFFECTIVE • SIGNIFICANT DROPS IN DANGEROUS CORROSION LEVELS • 1995- 26 USES THROUGHOUT NORTH AMERICA
MODERN APPLICATIONS • MANY STATES ACROSS THE COUNTRY HAVE USED ECE ON HIGHWAYS AND BRIDGES • MOST PROMINENT: PENNSYLVANIA, VIRGINIA AND IOWA • BRIDGES ON I-95 Pictures of ECE being applied to 34 th street and 5 th street extended Bridges in Virginia. Provided by Virginia Department of Transportation.
OTHER APPLICATIONS IN ENGINEERING • AFACE- AUTOMATED FEASIBILITY ANALYSIS OF CATHODIC PROTECTION OR ELECTROCHEMICAL CHLORIDE EXTRACTION • MODERN ENGINEERING TOOL • MOST EFFICIENT METHOD OF REPAIR • COMPUTER PROGRAM DECIDES • BASED OFF OF CIRCUMSTANCES
Flow chart of selection process
ECE: THE SUPERIOR METHOD • OTHER METHODS: CATHODIC PROTECTION (CP) AND PATCH REPAIRS • CP- STRENGTHENS STEEL AND CONCRETE - AVERAGE COST IS LOWER THAN ECE • PATCH REPAIRS- SMALL VERSIONS OF CP • ECE USES TITANIUM: MORE SUSTAINABLE • ECE COVERS MORE AREA- MORE EFFICIENT • EXTRACTS MORE CHLORINE THAN CP
EFFICIENCY AND ECONOMIC IMPACTS • DURATION: 4-8 WEEKS • DYNAMIC EXTRACTION PROCESS • UP TO 70% CHLORINE IONS EXTRACTED • STANDARD TREATMENT: $11.90-$12.50/FT^2 • DOES NOT STOP TRAFFIC • BETTER ALTERNATIVE TO BRIDGE DEMO- SUSTAINABLE - PREVENTS SIGNIFICANT BRIDGE WASTE
CASE STUDIES • DE LA CONCORDE OVERPASS BRIDGE 9/30/2006 - KILLING 5 PEOPLE, INJURING 6 • LOWES MOTOR SPEEDWAY BRIDGE 5/20/2000 - 107 PEOPLE INJURED • CORROSION FAILURES/ LACK OF INSPECTION • ECE: COULD HAVE PREVENTED
CONCLUSION • AMERICA’S BRIDGES: REQUIRE SIGNIFICANT IMPROVEMENT • CORROSION: NATURAL BUT DANGEROUS PROCESS • ECE: SUCCESSFUL METHOD OF BRIDGE REPAIR - COULD SAVE UP TO MILLIONS OF DOLLARS - SUSTAINABLE - EFFICIENT - CONSTANT IMPROVEMENT- STAY RELEVANT
THANK YOU
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