Dispersion of large amounts of carbon fillers, such as graphene, mesocarbon microbeads, and multiwalled carbon nanotubes, in water provides a route to yield nanocomposites with superior mechanical properties and high conductivities for academic studies and practical applications. In this aspect, a self-healable polymer blend of poly(acrylic acid) (PAA) and poly(ethylene oxide) (PEO) is an excellent dispersant for carbon fillers, rendering nanocomposites with a large filler content (up to 90 wt %). As the carbon filler content increases from 10 to 90 wt %, the nanocomposites transfer from healable elastomers with a high fracture strain (up to 700%) into hard plastics with outstanding conductivities (up to 1.1 x 10(6) S m(-1)). Morphological investigations by scanning electron microscopy suggested the homogeneous dispersion of the carbon fillers in the PEO/PAA polymer blend. The experimental mechanical modulus and the conductivity of the nanocomposites as functions of the filler content can be approached by the theoretical Kolarik model and the scaling law, respectively, based on a co-continuous distribution of the carbon filler and the polymer blend. A theoretical evaluation provided in this study thereby lays the ground for future development in practical application fields.