  We study the rheology of bidisperse non-Brownian suspensions using
particle-based simulation, mapping the viscosity as a function of the size
ratio of the species, their relative abundance, and the overall solid content.
The variation of the viscosity with applied stress exhibits shear thickening
phenomenology irrespective of composition, though the stress-dependent limiting
solids fraction governing the viscosity and its divergence point are
non-monotonic in the mixing ratio. Contact force data demonstrate an asymmetric
exchange in dominant stress contribution from large-large to small-small
particle contacts as the mixing ratio of the species evolves. Combining a prior
model for shear thickening with one for composition-dependent jamming, we
obtain a full description of the rheology of bidisperse non-Brownian
suspensions capable of predicting effects such as the viscosity reduction
observed upon adding small particle fines to a suspension of large particles.
