We discuss the sensitivity of a 100 TeV pp collider to heavy particles decaying to top-antitop (tt¯) final states. This center-of-mass energy, together with an integrated luminosity of 10ab-1, can produce heavy particles in the mass range of several tens of teraelectronvolts (TeV). A Monte Carlo study is performed using boosted-top techniques to reduce QCD background for the reconstruction of heavy particles with masses in the range of 8-20 TeV, and various widths. In particular, we study two models that predict heavy states, a model with an extra gauge boson (Z0′) and with a Kaluza-Klein (KK) excitation of the gluon (gKK). We estimate the sensitive values of σ×Br of about 2 (4) fb for Z0′ (gKK), with a corresponding mass reach of 13 (20) TeV.