Sacred Heart Chapel and Bell Tower had several locations where original pre-cast decorative elements needed intervention and preservation.
As with many older structures, the decay was traceable to the rusting and decay ("ironjacking") of interior reinforcing and structural steel components. Previous attempts at repairs (not at all unusual for this type of damage) were evident in the obvious grey Portland cement smeared on the original surface in an effort to stop the ongoing moisture penetration.
The decorative grills flanking the Chapel entry displayed the same type of decay on a regular grid-like basis, and made it easy to guess where the internal reinforcement lay.
A similar decay process was taking place on horizontal concrete deck surfaces at the entry doors and perimeter.
Even from a distance, this type of failure could be observed on the decorative finials of the bell tower. Notice the crack and its linear orientation, a likely sign of interior failure.
Simple use of a screwdriver was all that was needed to selectively pry off the sections of iron-jacked cast stone for reuse.
Careful hand preparation included chiseling out decayed and rusted steel embedded in the column to prevent future failure.
Where the original steel reinforcement was only rusted on the surface but still structurally sound, we used power tools with steel brushes to clean the steel surface.
The exposed and cleaned steel could then be coated with a rust-resistant polymer treatment, designed to protect against future oxidation.
The previously removed sections of the cast stone column could then be reattached to the body using epoxy adhesive and stainless steel pins.
Meanwhile, at the cast stone finials above the entry, we prepared for the removal of the decorative elements. Even though there was no surface evidence of the same interior corrosion, we determined that the prudent response would be to carefully remove the finials and core out the iron that we knew was present.
Diamond-tipped chainsaws were used to cut at the joint line of the pre-cast finials and the structural concrete supporting wall.
Careful coordination is required when the process involves lifting a quarter-ton decorative trim piece without damaging the historic fabric. Here, we are using a mobile crane to lift the previously cut finial from the building veneer.
Since the original construction had the decorative elements installed in a composite fashion (sections), we removed the original material in the same fashion, reversed.
Once isolated and safely on the ground, we could begin the process of removing the ferrous reinforcement that posed a potential problem.
When each decorative component was laid over on a horizontal axis, the internal steel that was our quarry was exposed and ready for treatment.
Diamond-equipped tooling again proved useful, in this case core bits that could core at least 12-18 inches into the cast stone body of the decorative piece, and around the steel reinforcement.
Concurrent with this activity, our crews were preparing the stairs and landing of the chapel entry, by cutting the failed original surface to assist in the controlled removal of original surface material.
Once all original material was removed to a depth of approximately 3/4", the corroded steel reinforcement of the original construction was wire-brushed and then coated with an anti-corrosion protective coating.
After all preparations were completed, we began installation of the specialty repair mortar, in this case Jahn M90, color-matched to the cleaned original surface.
This proprietary repair mortar is useful in its ability to match color and material properties for restoration purposes.
This finish shot shows the same area after all mortar and grout installation have been completed.
The same deterioration of internal steel was taking place at the bell tower, as evidenced by this image taken from closer quarters. As noted from ground level, the cracks were likely indicators of internal decay, and the residual caulk of previous repairs confirmed that others had, in the past, tried to keep moisture from penetrating to the interior of the decorative precast surface.
Since use of a crane would have been difficult and intrusive at this height, we elected to use special scaffolding erection techniques to give access to these work areas, all of which were at a height of over 100 feet above ground level.
Multiple applications of tape helped keep the fractured pieces together during the cutting and removal process.
As with so many other examples of this type of decay mechanism, the axis of fracture usually corresponded with the placement of the original steel reinforcement.
In some cases, the original decorative element was removed, only later to be reduced to several component parts, all of which were saved for later reassembly.
Many of these pieces retained a rust-stained image of the original steel anchoring.
Tape and straps were used to hold the component pieces in place until epoxy adhesive could cure and finish the reassembly of deteriorated precast pieces.
Here, a reassembled three-part finial has been set onto new stainless steel anchor pins and awaits final surface repair and rendering.
Flexible scaffolding plans allowed for support of hoisting equipment to ensure the safe reinstallation of these half-ton decorative elements.
After reinstallation, each finial was coated (rendered) with the same Jahn M90 repair mortar to a depth of approximately 3/16" and after curing treated with a penetrating application of a water-repellent sealer.
By treating each repaired precast element in this manner, we have removed the potential cause of material failure. Application of a water-repellent sealer enhances this prevention of possible future damage.
Our repairs will increase the life-cycle of this structure, and improve the life-safety of the facade.