Award of Merit: High-Rise Category
Renovation of Exterior Façade and Structure
Submitted by Gale Associates, Inc.
University of Massachusetts, Amherst
Gale Associates, Inc.
Chapman Waterproofing Company
Lyndhurst, New Jersey
The Lederle Graduate Research Center (LGRC) is a multi-building project site that includes a three-story computer/ library wing, and three 17-story classroom research towers. The multi-building facility was constructed in two phases (1967 and 1971).
The façade consists of precast concrete panels, each 8 ft (2.4 m) wide x 13 ft (4 m) tall. These panels serve as the outside face of the structure and were used as the exterior form for the inner cast-in-place (CIP) concrete wall. Between the exterior precast wall and inner CIP wall, a layer of extended poly-styrene insulation was installed. The precast panels were secured to the CIP wall using heavy-gauge wire rods.
The LGRC was experiencing moisture intrusion at multiple locations. An initial review revealed that most of the precast concrete panel sealant joints had failed. Concrete defects such as surface crazing, spalls, and cracking were present through out the façade. Panel discoloration was evident throughout the elevations. Bowed and deflected panels were noted at corners. Concerns about precast panel securement were a major driving force in determining the type and extent of exterior façade deficiencies.
Testing data concluded that the surface crazing of the concrete was due to expansive alkali-carbonate reactivity. The deflection and displacement of the panels resulted from panels being stacked on one another with no shims or dowels present to reduce the upper/lower limits from movement. Though the structural calculations indicated that existing anchors should have had sufficient strength to support the units, some displacement occurred. This caused displacement of the sealant joints as well as concrete cracks and spalls at the edge of the panels.
Special features of the project:
- Unique exterior wall construction presented challenges in determining the cause and origin of observed deficiencies;
- Various nondestructive test methods (that is, a ground-penetrating radar) assisted in quantifying type and location of anchors; and
- Specialized procedures and operations were required to remove polychlorinated biphenyl (PCB) contaminants.