It was with great interest that I read your recent article, "What Does Cylinder Strength Mean?" Followed by the numerous responses. About 20 years ago, we worked with Frank Kozeliski and others in New Mexico on the first real test program to see what actually happened to mishandled cylinders in the field during the first 24 to 48 hours and the results of using various curing methods.
There seems to be a lot of confusion about the purpose of these cylinders versus in-place results. They are meant to be an insurance policy that the concrete that was delivered to the jobsite, with no alterations or field placement changes, meets what was actually specified. It is truly step one and a starting point in the process and nothing more. All the other cylinder uses, such as strength-to-strip formwork or shoring, work only if step one is accomplished and verified. For years, ready-mix concrete companies have been adding extra cement (at considerable cost) to increase strength and overcome what was actually an incorrect field test cylinder curing problem. This has driven up concrete prices throughout the country.
We think this is a great topic and years ago the National Ready Mix Concrete Association identified the improper handling of test cylinders in the field as their membership's number one technical issue. I think continuing down this investigative path will be of tremendous benefit to the concrete industry as a whole.
Bob Edwards, Construction Innovations Co.