Compact and lightweight” graphene-based mortars were produced and their piezo-resistive behavior was analyzed. Such property is exploitable in the production of functional building materials, which could work as stress–strain sensors. First, graphene-isopropyl alcohol dispersionwas synthesized through Liquid Phase Exfoliation and the few layered structure was evidenced via Raman spectroscopy. Afterward, “compact and lightweight” mortars-graphene based composites were produced by using, respectively, cement and cement/diatomite as matrix, the previously mentioned graphene dispersion and a suitable amount of water. The morphological, structural, thermal and electro-mechanical properties of the obtained materials were analyzed. The mix-design here discussed can pave the way for a new kind of eco-friendly, multi-applicative, multi-responsive building material.