Comparison between the mechanical and dielectric strength distributions for hardened gypsum

Hardened gypsum is chosen as a simple model of hardened cement materials and an analogy between the mechanical and dielectric strength distributions is investigated. Both of the strengths are evaluated in terms of Weibull statistics and a two-parameter Weibull function is adopted for both of the strength distributions. Both plots show good coincidence which is independent of the water content used during the mixing of hemihydrate gypsum powder for hardening. The hardened gypsum sheets made with 70 wt % of water, have mechanical and dielectric strength distributions that show two different behaviours in the Weibull plots, however, both the plots agree with each other. From our results, it is concluded that the mechanical strength distribution of hardened gypsum can be evaluated in terms of the dielectric strength distribution, which can be easily measured from a breakdown test.