However, they also may indicate excessive shear loads.Įxcessive deflection, such as sagging cantilevers, should raise a red flag. On columns, beams, or other vertical surfaces, diagonal cracks may be the result of shrinkage. Telltale crack patterns, such as what may be observed on the upper surface of a parking deck around a column, can indicate potential punching shear failure or reinforcement that is too low. Clues for the trained eyeĪn experienced investigator can learn a great deal about what's going on with various structural elements by observation. Additionally, ACI 564R-04 outlines general considerations for undertaking concrete repair as well as specific information about methods and materials. This will ensure that the proper cause of the concrete deficiency is identified and that the repair plan will have the intended effect. Note the interesting steel reinforcement.įor anything more than minor repairs, the contractor needs to work with engineering support. Repairing the crumbling around the edges of this concrete cap atop a stone pier would extend its functional life as one of the primary supports for a multi-track railroad bridge.
But these also may affect long-term structural integrity, such as when surface repairs are made to replace or renew the concrete cover protecting steel reinforcement. A structural repair, as defined in ACI 564R-04, “Concrete Repair Guide,” is one that “reestablishes or enhances the structural capacity of a member.” Other repairs that are deemed nonstructural often are made for aesthetic reasons. Some concrete repairs are primarily structural while others are primarily cosmetic. Repairs may be needed to improve appearance of the concrete member or structure, to provide better protection of the embedded reinforcement, to meet load carrying requirements, or all three. The first step in developing a concrete repair plan is determining why the repair is necessary. Other types of concrete deterioration can be the result of exposure to severe weather or chemicals, impact, overloading, or under design. Typically this is the result of inadequate cover, cracking construction joints, or permeable concrete. (See sidebar, “Some Cracking is Normal.”) In reinforced concrete such cracking and spalling are caused most often by the expansive forces created as rebar corrodes. The appearance of unexpected cracking, spalling, or other deterioration of the concrete is often the first sign that repairs are needed. But the key to successful concrete repair lies in understanding why it became necessary, then being sure to address the root cause of the problem. Proper repair techniques and materials are important to taking advantage of that attribute. One of the advantages of building with structural concrete is its repairability. Located in Wisconsin, it may have been affected by water saturating the concrete then freezing. Although this ragged split concrete obviously should be repaired, it is likely at this point more cosmetic than structural.