Cabrillo Bridge
San Diego, SD County, California
Restoration and Stabilization of the Concrete-Span Bridge constructed for the 1915 California Exhibition
The Cabrillo Bridge was constructed for the 1915 California Exhibition and had the usual issues with rusting and decay of internal steel reinforcing bars. When chunks of concrete began falling on the Cabrillo Freeway below, a restoration and stabilization project was immediately started.
Wikipedia Reference: http://en.wikipedia.org/wiki/Cabrillo_Bridge
Click on images below to view at larger size.
The Cabrillo Bridge was a local landmark in need of restoration and repairs due to the spalling and failure of the concrete where iron-jacking was forcing surface away. |
Over the years, staining from internal sources of moisture and organic material on the exterior had stained and discolored the surface as well. Careful tests were performed to ascertain the most effective cleaning method using the least agressive methods to avoid damaging the historic surface of the concrete. |
In addition to the normal range of spalled locations from ironjacking, there were numerous 'pockets' where the original concrete had not been properly vibrated in the form during construction. |
Typical problems included the placement of reinforcing steel too close to the surface, and all areas around this type of damage had to be prepared. |
Note here the straight cut on the right side of the patch area, to deliniate where the cutting process will stop. This horizontal and vertical emphasis on the cut borders of patch areas is critical to producing a patch that will be less visible to the untrained eye. |
Here the loose concrete around the pocket has been removed, the cuts made to delinieate the repair area, and the chipping process will come next. |
Small chipping hammers were used in most cases to prepare the patch areas, to control the possible damage to adjacent undamaged concrete. |
Chipping was executed to a depth of approximately 3/4" in most cases, unless unsound material went deeper. |
Old meets New: Note here the junction of older, twisted rebar and newer, formed steel. |
After all chipping was completed, the exposed reinforcing steel bars were all sandblasted to remove all traces of rust and prepare for the application of a rust-preventive coating. |
Deeper areas of repair were formed and cast using a special concrete designed for this purpose. The cast material was held back about 1/2" from the finish surface to leave room for the color-matched patching mortar. |
Only after direct access to the damaged area could we determine the amount of concrete to be prepared and patched. |
Stainless steel wire and anchor pins were also installed in all patch areas to provide the mechanical anchor necessary to ensure a long-lasting repair. |
Skilled craftspeople were employed to install the patch material, which was carefully formulated to match the cleaned appearance of the original concrete. Care was taken after application to tool in the board-formed joint marks, in order to make new repairs less evident after curing. |
A final post-construction cleaning just before scaffold removal took care of whitish efflorescence deposits, normal after the installation of cementitious mortars. |
The bridge is not totally complete, but this first phase will undoubtedly provide the impetus for the final completion of restoration on this notable structure from California's history. |