Concrete Pixels

Most of the construction projects big or small are estimating the in-place compressive strength of the newly cast structures using the cubes or cylinder specimens taken at the time of casting. It is “widely believed” that the specimens taken on the same casting have the same strength as the structure cast. This is extremely important for a contractor to know when he can proceed with other construction activities such as stripping the formwork or removal of scaffolds, end of curing, partial or full stressing of tendons, lifting of precast elements, etc. Some are storing the specimens in the curing tanks and or/fog rooms which is not correct as it does not represent the actual site condition and there is a danger that the strength is overestimated. While others are doing it right by storing the specimens at site close to where the structure in question is cast, this system has become more cumbersome especially if they are concreting many parts in a say high-rise buildings or other large projects. It becomes impractical bringing in cubes molds at the pouring area, storing and then taking the cubes thereafter to the Laboratory for crushing. There is always the possibility of mishandling the cubes especially at early ages that will impair the strength. With the advancement of technology, we can now get rid of these cubes or cylinders as specimens at site. What we need are just thermocouples embeded at critical points of the structure that monitors the temperature development. This temperature combined with age (hours or days) can then be used to calculate the strength of the concrete in the structure using the concept of “concrete maturity” which I will discuss separately. It is also possible that the temperature readings can even be transferred remotely to your personal computer or laptop in the office so that you can see the real time concrete strength of the structure. Interesting, isn’t it? I’m sure this is a big relief to everyone in the construction be it owner, contractor or independent consultant as it gives a very reliable esimate of compressive strength.