A combined viscoelastic/sintering model is incorporated in a sintering study of a ZrB2-SiC composite using the discrete element method. The sintering component of interacting particle forces arises from grain boundary and surface diffusion while the viscoelastic effect ensures adequate mass transport between interacting particles. The model includes a weighted transition between a Hertz-Mindlin type contact and the sintering model during heating of the discrete elements up to the sintering temperature. The model is verified by simulating pressureless sintering of zirconium diboride ceramic composites reinforced with multiple volume percentages of silicon carbide particulates. The model showed improvements in porosity, density and elastic modulus with increased particulate phase percentage up to 15 wt%. The model showed enhanced densification at higher temperatures with good correlation with experimental data.