Norcure® Re-Alkalization
Electrochemical Treatments
Electrochemical treatment for carbonated concrete structures.
Alamo Cenotaph Monument
San Antonio, Texas, United States
Preserving an iconic Texas monument through advanced electrochemical restoration.
Owner: Texas General Land Office
Consultant: EChem Consultants
Contractor: Clark-Guido, Vector Construction
The Alamo Cenotaph, built in 1939 to honour the defenders of the 1836 Battle of the Alamo, is a historic monument of great cultural significance. After more than eight decades of exposure, carbonation had reached the depth of its reinforcing steel, threatening both its appearance and structural integrity. A specialized re-alkalization treatment was designed to restore the concrete’s pH and protect the embedded steel, preserving the monument’s original fabric for generations to come.
The Problem
The Alamo Cenotaph, a monument at the Alamo built in 1939, showed signs of deterioration due to carbonation of its concrete frame. This historic monument, built to honor the defenders who died during the Battle of the Alamo in 1836, is a culturally significant structure, so its original fabric and aesthetic had to be preserved.
As part of the comprehensive evaluation performed by Echem Consultants, it was discovered that carbonation had reached the depth of the reinforcing steel and beyond. Carbonation is a known deterioration mechanism that can negatively affect aged, reinforced concrete. The carbonation process lowers the concrete's pH to a point where corrosion of embedded reinforcing steel is initiated, causing concrete damage and steel section loss. Given the state of the eighty-six-year-old structure, an intervention was necessary to repair the visible damage, prevent future damage, and extend its service life.
The Solution
To address the carbonation problem and restore the monument's structural integrity, the consultant recommended and designed a comprehensive realkalization solution integrated with the concrete repairs. Vector Corrosion utilized the Norcure® Re-alkalization process to comply with the design.
The re-alkalization process, a temporary treatment that provides long-term durability, is non-destructive, which was crucial for preserving the historic monument. The treatment involves temporarily applying a low-voltage electric field between the steel reinforcement within the concrete and an external anode mesh. An alkaline electrolyte solution is then transported into the concrete, raising its pH and restoring the passive layer, creating a non-corroding state around the steel. This approach allowed the entire structural frame to be protected without extensive concrete removal, minimizing disturbance to the historic fabric of the monument.
The work was also able to be performed from a single side of the structure, ensuring protection of all reinforcing steel. This approach allowed for the monumental marble statuary to remain in place, a preservation requirement set by Architexas due to the immense weight and impracticality of removing all the sculpture.
The Result
The Norcure® Re-alkalization treatment successfully restored the alkalinity of the Alamo Cenotaph's concrete, bringing the environment around the reinforcing steel back to its original passive state. The higher pH and reinstated passivity of the steel will greatly increase the monument's service life, ensuring its preservation for future generations. This solution provided a long-term, low-impact repair that maintained the historic and aesthetic integrity of the Alamo Cenotaph while effectively addressing the root cause of its deterioration.
Technology Used
These innovative products and technologies were used on this project.