In this paper we present a nondestructive evaluation technique based on the propagation of highly nonlinear solitary waves (HNSWs) to monitor the hydration of cement. HNSWs are mechanical waves that can form and travel in highly nonlinear systems, such as one-dimensional chains of contacting spherical particles (i.e., granular crystals). In the present study, we use a granular crystal-based actuator/sensor to observe the solitary waves propagating to and from the mechanical interface between the transducer and a fresh gypsum cement sample. We hypothesize that the reflected HNSWs traveling along the crystal-based transducer are affected by the hydration process of the cement, and we assess the elastic modulus of the specimen in the localized region of the granular crystal contact. To verify the experimental results, we perform numerical simulations based on a simplified finite element model. The elastic properties of the cement specimen measured by the granular crystal transducer are compared with the compressive strength and the elastic modulus measurements obtained from destructive tests, conducted according to the ASTM C109. We observe good agreement between experiments and numerical simulations.