Problem Solving Forum
May 21 - May 27, 2012
What tests should be run to determine if an existing concrete bridge pier needs rehabilitation or repair before cleaning and coating?
Jeremi Day of Allphaz Inspection Services on
May 22, 2012:
There are several non-des ...read more There are several non-destructive tests (NDT) that can be used to evaluate the strength of hardened concrete. Two of the most common NDT methods are the Schmidt rebound hammer and the Windsor probe, both of which measure the surface hardness of concrete as a quick indicator of relative compressive strength. The rebound hammer test (ASTM C 805) measures the rebound of a spring-loaded plunger pressed against a concrete surface. The harder the surface, the greater the extent of the rebound, which correlates to relatively greater strength. In the Windsor probe test (ASTM C 803), a powder-actuated gun drives hardened alloy probes into the concrete. The exposed length of the probe is measured, then related by a calibration table to the concrete's compressive strength. The results of these tests can be influenced by a variety of factors, including surface smoothness, type and hardness of aggregates, age and moisture condition of the concrete, and the degree of carbonation at the surface. Therefore, it's important that results be compared with those from cored or cast specimens, and interpreted by NDT specialists who understand the limitations of the tests.
Otto Drozd of J. Mori Painting, Inc on
May 23, 2012:
Conduct a visual ins ...read more Conduct a visual inspection of the surface to be coated to determine if any of the following are present: voids, bugholes, pop-outs, cracks, joints, spalls, fins/slivers, levelness , efflorescence, soundness, oil, grease,wetness/dryness, carbonation, chemical, ASR/AAR, transition areas below/above grade, age of concrete, blisters/other. Evaluate the severity of the damage detected and determine if it is critical that rehabilitation work be done.