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And as the size of the openings increases, so should the con-


cern. As a rule of thumb, cracks “0.015 of an inch or larger” should be investigated, Barlow said. “The larger the width, the greater the likelihood you have


lost aggregate interlock,” he said. “But repairs can be done on cracks down to 0.005 of an inch.” Athird issue is location/orientation. Cracks in random direc-


tions are of lower priority than those in beams, columns or other load-bearing areas. “If one side of the fracture is offset from the other, that is


often a bad sign,” Barlow said. “Other warning signs are closely spaced cracks or repetition of cracking at the same locations on each floor.”


Epoxy in Concrete Repair In many cases, epoxy injection is used as the remedy for con-


crete cracks. Although there are many epoxy types and uses, high-performance epoxies manufactured for structural concrete bonding and crack repair are the focus here. Duntemann gave the example of cracking that appeared in a


cooling tower being constructed at a synthetic-fuel plant. Cracking developed at the ends of pre-stressed concrete beams. Demolish- ing the structure and starting over was not considered an option. Management brought in WJE to find an alternative. “The


beams were injected with epoxy and load-tested to verify their structural capacity,” Duntemann said. In another case, the firm was retained to investigate large


cracks in concrete caps that sat atop concrete pile foundations. “We developed a method of reinforcing the pile caps and injected an epoxy into the cracks to reconnect the fragmented caps,” Dun- temann said.


Water, however, presented a further challenge – the epoxy


had to deal with a saturated environment. WJE requested help from chemists at ChemCo Systems. They formulated an epoxy that could fill three-quarter-inch cracks and cure in the presence of water. “You often run into challenging environments such as cracks


full of water, cold temperatures or exceedingly wide cracks that require a customized solution,” Duntemann said. He pointed out that while many different types of epoxy are available, one size does not fit all. It requires the right combination of materials, chemistry and expertise, he said.


Summary Building owners or managers noticing cracks in the concrete,


are then advised to contact a structural engineer to assess the extent of the damage. He can help determine whether or not it is a significant issue. “As building owners and managers are typically not engi-


neers, they are advised to retain a licensed structural engineer who can evaluate concrete cracking,” Barlow said. He also advised against a do-it-yourself approach for all but


the most minor problems. In his view, too many factors are involved in the engineering and chemical formulation side to leave anything to chance. “When a problem is identified, it’s important to retain pro-


fessionals with experience solving these problems,” Duntemann said. “The correct solution requires a good understanding of the cause of that problem.”


For more information, contact ChemCo Systems VP John Bors at email@chemcosystems.com or visit www.chemcosystems.com.


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