> Cement in an uncontrolled environment is not going to work as a capacitor, even if it works in a controlled environment. Some water will get in. Concrete alw

> Cement in an uncontrolled environment is not going to work as a capacitor, even if it works in a controlled environment. Some water will get in. Concrete always has water. It's part of it's composition. What exactly led you to believe it doesn't? Also, there's a technology that can turn concrete waterproof which is called paint. In harsh environments it's also mundate to coat rebar with epoxy paints to protect against corrosion. > There's expansion and contraction as temperature changes, which causes cracking. Thermal stress in monolithic structures does not cause cracking. At best, it can happen in hyper static structures when thermal strain imposes displacements beyond design limits. This is countered by using technologies such as prestress. What can cause cracking in concrete is delamination from frosting, where water penetrating through pores expands and detaches concrete blades at the surface. This is prevented by applying a technology called paint. I saw nothing in your comment that put into question the usage of concrete-based super capacitors. You pointed to known failure modes that are addressed in a very mundane way.