Pressure stimulated electrical emissions from cement mortar used as failure predictors

The electrical signals emitted during the application of uniaxial compressive mechanical stress upon cement mortar specimens are observed and discussed in this paper. This work discusses the electrical signals that are detected when the specimens are excited by a stepwise uniaxial stress increase from a low level (σ _L ) to a higher level (σ _H ) at a fast or slow rate and consequently remain at a high pressure regime for a long time. When maintaining constant mechanical stress for a long time, creep phenomena are evident in the specimen and the corresponding electrical emissions are recorded and analyzed. The characteristics of the electrical signal give clear information regarding the breaking stress (σ _F ) of the material. The electrical emission recordings are of great interest when the applied σ _H is located in the vicinity of the failure stress; the emitted electrical current increases greatly due to the sequential formation and propagation of cracks that occurs in this stress region. Thus, by correlating the strain rate variations to the electrical emissions this methodology can be used to predict failure due to compressive stress in cement mortars.