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Testing Concrete

The concrete testing process garners little attention from the construction industry – until a problem occurs. At that point, everyone is intensely interested and all the parties involved become, for the most part, adversaries.

Here’s a true example from a personal experience. A commercial project with a lot of structural concrete allowed the general contractor to do the concrete testing. Subsequently, the GC assigned this responsibility to a laborer who had not received the proper training (and who was not ACI certified). Not surprisingly, several cylinders were not prepared according to the specification, resulting in some cylinders that displayed extensive honeycombs (voids) when the molds were removed. Instead of rejecting these cylinders due to their obvious lack of proper consolidation, the engineering firm allowed the cylinders to be broken, and then held up the job when the cylinders failed to make the required strength. The burden of proving that the inplace concrete met the strength specification now fell on me (the ready mix producer), in spite of the very obvious fact that this responsibility was being transferred to me on the basis of defective, non-standard cylinders. Subsequent coring demonstrated the in-place concrete strength to be fine, and GC had to foot the bill for several thousand dollars of coring expense, plus the delay to the job.

Procedures and specifications for concrete testing are well defined and generally accepted by all parties as fair and reasonable – the problem occurs when these well-defined specifications are not followed throughout the testing process. Unfortunately, failure to follow the mandated specifications is often more common than compliance. This problem is exacerbated when non-standard cylinders are allowed to be tested instead of being immediately rejected.

The following story highlights some of the most common problems encountered at various stages in the process. Armed with this important information, resolve to eliminate these specification violations from your next (or even your existing) projects – everyone will benefit.

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Concrete FACTS, a publication of the Concrete Foundations Association, is THE voice for residential concrete industry news, market intelligence, business strategies, technical solutions, product information, and other resources for professionals in the cast-in-place concrete industry. Subscriptions to Concrete FACTS is available to anyone involved or interested in the residential concrete industry as a service to your industry. Please contact CFA Headquarters to find out more about your free subscription or Email Us