Grout Joints

Structure Characteristics

The structure was constructed with reinforced concrete slab beams and columns. The in-fill between four exterior columns one at each corner of the tower and two intermediate is 8 inch concrete masonry units (CMU).  The exterior façade is comprised of a setting bed overlaid with ceramic tile.  The original building plans indicate that the tile setting bed should be 5/8 inches.  Test results using impact echo have found the setting bed varying from 1.7 to 2.7 inches. The total façade thickness varied due to the inconsistency in the setting bed thickness.

Problems that Prompted Repair

Significant areas of mosaic tile were un-bonded from the grout base. In limited and random sections tile fell leaving gaping holes in the façade.  Furthermore damage with regard to the structural integrity of the façade was evidenced by the loss of bond of the grout base to the CMU in-fill and the concrete columns.  This loss of grout bond resulted in profile protuberance throughout the entire face of the both tower mosaics.  In isolated areas the grout matrix was compromised and disintegrated causing a build up in the protruded areas making it impossible to reestablish a level surface profile.  Grout joints on both towers were severely weathered and on the greater portion of the surface area the grout was missing disintegrated and or friable.

The façade’s poor condition increased the probability that the tile and grout could loosen the mechanical bond and sections would shear from the face of the tower posing grave concern for public safety.

Inspection / Evaluation Methods

 The de-lamination survey was performed by sound with a rebound hammer.  The destructive testing entailed opening an area of the wall at the handrail anchorage and a hollow area on the north tower.  A 4 inch core was taken to evaluate the composite construction of the façade. Subsequently, testing team made a condition assessment specifically to evaluate the extent of damage and deterioration of the tile grout base and setting bed using non-destructive impact echo technology. 

Causes of Deterioration

 The mosaic tile façade was exposed to the harsh climate of winds rain and high temperature for nearly 50 years and the tile grout joints deteriorated.  This continuing process of deterioration and disintegration of the grout resulted in moisture intrusion leading to the loss of integrity of the grout base and eventually of the tile bond and grout base to the substrate.

Repair System Selection

Restoration of the tile façade required a combination of conventional and specialty techniques.  It was essential to the overall repair program to first replace damaged and missing tile and re-grout tile joints. Upon completion of the tile rehabilitation the façade was pinned with stainless steel anchors followed by the bonding of the tiles to the grout base along with the re-bonding of the grout base to the CMU and concrete column substrate. The tile and grout base were re-bonded with special resins and portland cement filler using the vacuum injection and impregnation process.

Repair Process Execution

Due to the numerous areas of damaged and missing tile all openings were grouted flush to the tile surface as a temporary means of sealing the surface to accommodate the vacuum process. Further missing and deteriorated grout in the tile joints was re-grouted to assist in providing a seal where the joints were porous or friable. Stainless steel mechanical anchors were installed on a two-foot grid pattern over the entire surface of both towers.  It was necessary to install the anchors after the damaged and missing tile areas were restored to secure the composite façade and realign the profile of the façade where possible. The vacuum process was then used to secure any questionably un-bonded original tiles fill de-lamination in the setting bed and fill and seal cracks.  Upon completion of the vacuum injection all previously repaired areas that exhibited damaged or missing tiles were removed and new tile was installed.  With the completion of the tile replacement and restoration the entire face of both mosaics was cleaned and hand polished with compounds and lamb’s wool buffers.