Posted By Jane Blunt Dear Steve As I am sure you now know, post tensioning is a way of producing concrete floors and other structures whereby the concrete is cast with cables or rods embedded in it, which are placed under tension after the concrete has set. This holds the concrete in compression, which is desirable since concrete does not perform well in tension. You don't say what aspect is of interest. There is the fabrication, which involves concrete pouring. An article in a recent issue of SHP about an unfortunate worker who had to have his leg amputated showed that concrete contains hazardous substances. There is the tensioning, which involves large forces, and I believe is done using jacks. In service, there is the problem of corrosion of the tensioning elements, which can weaken the structure and could lead to premature failure. Finally, when demolishing the structure there is a lot of stored elastic energy in it from the tensioning elements and this must be released safely while at the same time not allowing the whole thing to collapse. Jane