TECH NOTES | Not Just Another Day at the Beach
Coastal structures have increased susceptibility to corrosion, concrete distress, leaks and safety hazards due to moisture and airborne salts from the ocean. Restoration projects at beach front condominiums can be complex, often necessitating intricate repairs and advanced preservation techniques for meaningfully extending the life of the building. These projects typically require specialty engineers and contractors for addressing materials distress; concrete contamination with ongoing corrosion activity; deficient or deteriorated fenestration and cladding; waterproofing and specialty structural issues (including guardrails, wall systems, deficient original construction and corrosion). They also generally require completion within compressed off-rental season time frames or while the building remains open and accessible to tenants.
Corrosion distress at hollow-core panel
Thermal spray cathodic protection being applied to walkway hollow-core panels with contamination but limited distress
Case Study: Shipyard Village
Shipyard Village Buildings A and B are five story, forty unit beach front condominiums located in Pawleys Island, SC. Repairs totaling approximately $8.5 million were undertaken at both buildings, including concrete repair and replacement, cathodic protection (CP), coatings and fenestration replacement. The structural system includes prestressed hollow-core panels (PHCP) supported by load bearing concrete masonry walls and reinforced concrete beams. Corrosion-related distress was observed at portions of the exterior PHCP and beams supporting the panels, and reinforced concrete slab edges supporting windows. A study was conducted to determine the contamination levels and distress of representative components with respect to the different areas of the building to select the economical repair methods. Corrosion of embedded reinforcing and prestressing steel was the result of elevated chloride levels in the concrete. Ocean-front slab edges were replaced with pre-packaged repair materials prior to new window installation. Land-side PHCP and ocean-side reinforced concrete haunches supporting ocean-side masonry walls with minimal outward distress were protected with thermal spray CP and a breathable aesthetic topcoat. CP monitoring stations were installed at representative locations. Ocean-front PHCP and land-side PHCP with increased oceanic wind exposure, contamination and distress, and associated cantilever beams were removed and replaced with a high-performance lightweight concrete mixture. The mixture was designed with weight similar to the replaced PHCP, and resistance to chloride ingress, cracking and other deterioration mechanisms. New slabs were keyed into the existing masonry walls or supported on cantilever beams on the ocean-side balconies, depending on existing configuration. The land-side walkway sections were cast integrally with replaced cantilever beams without control joints. Because some existing beams did not meet current live load requirements, supplemental reinforcing or pilasters were installed to increase capacity. Cathodic prevention point anodes were installed at interfaces to deter incipient corrosion. Most concrete and repair work was conducted in winter, requiring close attention to placement and curing. Slabs were sloped to promote drainage and components were coated.
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