Paver Joint Mortar Evaluation at Woodrow Wilson Plaza

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The open-air Woodrow Wilson Plaza at the Ronald Reagan Building and International Trade Center covers approximately three acres and is constructed atop a concrete-framed parking garage and occupied space. The plaza is used predominately for pedestrian traffic and transporting materials into the building. The plaza construction was completed in April of 1998. After one winter, deterioration of mortar joints was reported in 35 to 40 percent of the plaza area. Many mortar joints were reported to be soft with the appearance of damp sand and could be easily scraped with hand tools. CTLGroup was retained to observe and document existing conditions, evaluate the cause of the mortar deterioration, and provide conceptual repair recommendations.

CTLGroup performed the following scope of work:

  • Reviewed available project documents.
  • Performed field investigation work including condition surveys, inspection openings, and removal of samples for laboratory testing.
  • Performed laboratory examinations and tests including petrographic examinations and chemical analysis of mortar and concrete samples.
  • Analyzed field, laboratory and project document data and prepared report indicating findings, conclusions, and recommendations.

Based on CTLGroup’s observations, the following conclusions were made:

  • The paver system lacked proper surface and subsurface drainage.
  • The paver joint mortar was severely deteriorated due to poor initial compaction and insufficient hydration.

A major rehabilitation of the plaza paver system was recommended to provide for a reasonable service life. CTLGroup provided short-term and longterm repair recommendations. For short-term maintenance and repair of the plaza mortar joints, CTLGroup recommended that a mortar joint replacement program be established to repair deteriorated mortar joints on the plaza on an ongoing basis. Recommended program strategies included: Removal of granite pavers and setting bed, cleaning of existing granite pavers of all
mortar, reinstallation of the pavers in a cementitious setting bed, and filling of paver joints with a high quality mortar and tool for proper compaction.

For long-term repairs, CTLGroup recommended an open paver system. The design provides for narrower joints to minimize trip hazards and for a better drainage system. Water management systems may include a layer of free draining fill such as sand and crushed stone, or a free space created by a pedestal paver system. A pedestal paver system places the pavers on a series of pedestals, providing a free space below the pavers for passage of water to the drains.