Condo Media - April 2010 - (Page 40)

MAINTENANCE by Michael Norman Solid Upkeep oncrete is among the most durable building materials available. However, concrete can deteriorate if it is not applied and maintained properly especially in New England’s ever-changing weather conditions. Care and Maintenance of Concrete Structures another are usually a clue that the reinforcing cage may be improperly positioned. Premature removal of shoring may cause excessive deflection in beams. Deflection can cause distorted window frames, problems with window spalls, or popouts, may occur at edges where bar ends terminate near the concrete surface or at other localized areas of shallow concrete cover. Spalling also can be promoted when electrical conduit is placed too close to the surface. Larger spalls may occur near embedments and where long sections of reinforcing steel, with insufficient cover, run parallel to the concrete surface. For example, in a recent restoration at Primus Court Condominiums in Boston’s historic Beacon Hill section, Abbot found that the concrete band over street floor windows was severely deteriorated. In the process of renovating the concrete band, a structural steel beam was exposed and determined to be in need of repair. The steel beam was repaired and a new concrete surface was applied to match its original color and texture in compliance with the Beacon Hill Architectural Commission. Delaminations are areas where the concrete has lost bond with the reinforcing steel. The resulting planar cracks that run parallel to the surface are due to corrosion of rebar near the top surface or below embedments. Delaminations can be detected by tapping the concrete with a hammer. A hollow sound indicates a delaminated area. Spalls and delaminations on the building facade may be only warnings of more extensive structural damage extending into the building. Repairs inside the building are more expensive, often requiring shoring and bracing of windows or walls, and protection of interior spaces from dust and weather. C Concrete Deterioration Concrete deterioration is typically caused by one or more of the following conditions: Poor Quality Materials. Poor quality concrete may manifest itself when the ingredients of the mix are improperly calculated. To determine concrete quality, core samples should be taken from various locations for evaluation. It is a good idea to take core samples from both deteriorated areas and those that appear to be undamaged. Differences in the concrete may provide clues to the reason for the deterioration. Knowing the quality of the concrete can provide an indication of the expected life of the building, and it can help the owner plan and budget immediate and future repairs. Construction and Design Errors. Construction errors occur when what is actually built deviates from the original specifications or prevailing standards. Although construction defects typically can’t be completely corrected, efforts must be made to alleviate their detrimental effects. Insufficient concrete cover over the reinforcing bars is among the most common construction errors. This condition is often revealed by rust stains on spandrels or columns. Misaligned columns from one level to 40 CONDO MEDIA • APRIL 2010 Cross section of structurally built concrete column with reinforcing steel rods. seals and cracked masonry. Honeycombing or segregation of the aggregate results from concrete placement problems in small or substantially reinforced columns. Design errors occur when mistakes are made in the original specification. Design errors also may include an absence of drip edges at the underside of the slab, or expansion and control joints that are spaced too far apart. Spalling and Delamination. Spalls and delaminations are usually the result of internal pressure caused by corroding reinforcing steel. Spalls are areas where concrete has broken away from the wall. Small

Table of Contents for the Digital Edition of Condo Media - April 2010

Condo Media - April 2010
Table of Contents
From the CED’s Desk
President’s Message
CAI News
CAI Regional News
Asked & Answered
Homeowner’s Corner
Risk Management
Rising Fears
Vendor Spotlight
Industry Perspective
CAI National Law Conference Was Tops … Now for the Bottom Line
.2010 CAI-NE Insurance & Restoration Directory
Advertisers Index
Classified Service Directory

Condo Media - April 2010