Over the years varying degrees of success have attended efforts to design concrete mixes capable of conducting electricity for various applications such as grounding, protecting against lightning, eliminating static electricity, environmental heating, and radio frequency interference screening. The term concrete is used here to include not only conventional Portland cement concretes and mortars but also those made with polyesters or epoxies.
There are many problems to be overcome in designing conductive concretes. The electrical characteristics of the finished product must be made suitable for the particular application without degrading the mechanical properties of the concrete. This article discusses the concept of using a conductive aggregate in place of conventional aggregates specifically, a carbonaceous aggregate that is more effective than carbon powders because it does not cause excessive water-cement ratios.
Unlike conventional aggregates, the water absorption of the carbonaceous aggregate is instantaneous and, in a surface-dry condition, is about 15 percent water by weight. The aggregate is normally in a moisture-free state less than 0.2 percent prior to mixing which makes control of water-cement ratio easier when designing for compressive strength. However, it should be noted that the 15 percent water absorption slightly reduces the workability for a given water-cement ratio and that mixes appear to be harsher than ordinary concretes. It therefore is recommended that trials be carried out before large quantities are placed.
